Missing Matter... Still Missing

squidfrog writes "Nature.com, PhysicsWeb, and the BBC all report on the latest results from the Cryogenic Dark Matter Search. 'The most powerful search yet for the Universe's missing matter has come up empty handed, contradicting an earlier study that claimed to have seen new particles.' 'A favoured theory is that the dark matter consists of Wimps (weakly interacting massive particles) about a thousand times more massive than a proton, one of the particles found in an atom's nucleus... on the rare occasions a Wimp strikes an ordinary atom, the effect should be noticeable.' 'Writing in the Physical Review Letters, the team says that while a detection has yet to occur, there is now a better idea of how much dark matter must exist.' They 'hope to improve the sensitivity of the experiment by another factor of 20 over the next few years.' What's 20 times 0? And don't tell me zero!"

Comments

I "detect" a grant money detector at work...

[erick99]

That the sensor has never detected something doesn't tell you that it's working or not working - or am I am missing something here?

....Researchers from the Cryogenic Dark Matter Search II (CDMSII) say they are pleased with their first results, which show that their detector is working.

However since it started running in November last year, the detector has not seen a single WIMP.

Then they decide to make a more sensitive detector so that they can "not" detect at an even higher level?

Physicists with the CDMSII experiment say they will now add another 24 crystals to the detector, increasing its sensitivity tenfold.

Okay, maybe I am being a bit silly, but, I still don't see how they can know the detector is working. I don't even know how the WIMP can make the thing "ring" once it, itself, is subject to the 1/10 degree above absolute Zero conditions. And then, somehow, with no data, they can extrapolate more accurately how much dark matter is in the universe. Well, they would say the lack of WIMPS is data but I'm not buying it. Enough /. folks have worked in research to know better than to buy into those kinds of statistical games (you can prove almost anything with non-parametric statistics).

Happy Trails!

Erick

Re:I "detect" a grant money detector at work...

[Xandu]

No, they don't extrapolate how much dark matter is in the universe. They say, if dark matter is of the 'WIMP' variety, we know that the mass and cross section (aka how easily they interact with other particles, namely the germainium nuclei in their detectors) of of these WIMPS is not in a certain range.

Re:I "detect" a grant money detector at work...

[reidbold]

A possible explanation:

The detector can measure interactions between protons and strong interactions (collisions with photons or what have you). But is not sensitive enough to detect interaction with WIMPs.

Re:I "detect" a grant money detector at work...

[confused one]

when we built a detector, we put in a mechanism for testing and calibration. So, we could apply artificial pulses to verify everything was working properly; and, because we knew the amplitude of the pulses we applied, we could calibrate the instrumentation.

I'm sure this is part of thier validation that the detector is working.

Re:I "detect" a grant money detector at work...

[iminplaya]

However since it started running in November last year, the detector has not seen a single WIMP.

If they ran it five or six years ago, they would have found one in the White House. :-)

Re:I "detect" a grant money detector at work...

[iminplaya]

Damn new math...Try fifteen or sixteen years ago.

Re:I "detect" a grant money detector at work...

[Anonymous Coward]

The lack of WIMPs is data. If they reported "zero" WIMP events, the actual report would have been within some error, zero +/- some amount. Using that, you can set an upper limit to the actual amount of WIMP activity; you can say that the WIMP level must be below a certain amount (if the data is to be trusted).

You can tell a piece of equipment is working if it sees things you expect and if it behaves the way you expect it to from the theory. Getting "nothing" is not no data. You're being way too cynical.

Love,
A Published (albiet undergraduate) Physicist

Re:I "detect" a grant money detector at work...

[TMB]

That the sensor has never detected something doesn't tell you that it's working or not working - or am I am missing something here?

Yes, you're missing something. :-)

The statement "the sensor has never detected something" is patently false. Figure 1 of the paper shows all of their detections - and there are lots of them! WIMPs aren't the only things that interact with Germanium. ;-) However, once you exclude all of the events which are consistent with being cosmic-ray produced interactions with the shielding, you get Figure 4... all of the detections in the red region (which is where the WIMPs would show up) are gone.

So the detector works great and detects lots of things! But no WIMPs yet.

[TMB]

Re:I "detect" a grant money detector at work...

[blair1q]

Tell you what.

You go stand in the middle of the freeway.

Just by looking at this setup, I can tell that my automobile detector is now working.

And, as long as it never detects an automobile, so can you.

Re:I "detect" a grant money detector at work...

[Anonymous Coward]

GWB: "This missing matter has to be here somewhere..."

(background noise of ten thousand nuclei dying of radioactive decay)

( http://www.alternet.org/waroniraq/2004/03/001819.h tml )

Re:I "detect" a grant money detector at work...

[Anonymous Coward]

They know it works because other neutral particles (but not dark matter) interact with their detectors and are picked up. It's just a matter of isolating the events which are caused by particles we don't know about - which for now translates into none.

Re:I "detect" a grant money detector at work...

[Ya Bolshoi!]

I'll bet it's easy to tell if equipment is running or not. A simple diagnostic--artificially creating what they're looking for--would tell them if the thing is working or not.

Then they decide to make a more sensitive detector so that they can "not" detect at an even higher level?

Basically, yeah, that's exactly what they're doing. If they can establish some kind of upper limit on the number of WIMPs, then that is a very important result that allows physicists to see what theories worked and which were just crap.

And then, somehow, with no data, they can extrapolate more accurately how much dark matter is in the universe.

They do have data. They know that there cannot be more that a certain number of WIMPs per unit volume, because otherwise they would have detected them. To use a vaguely similar analogy, if I'm trying to find out how many people are in a building, and I look in the first floor and see no one in it, that observation is data about the number of people in the building and it tells me things about how many people I can possibly expect to find.

At any rate, failed experiments are very important to physics. For instance, the Michelson-Morley experiments failed to detect anything, thus giving strength to the wave-particle theory of light. It would really have sucked for physics if after the first time, Michelson had said, "Oh, well, our equipment must be bogus, this is a waste of money."

Re:I "detect" a grant money detector at work...

[Goldsmith]

You're missing some physics, allow me to fill you in:

Particle detectors of these kinds detect all weakly interacting particles. Weakly interacting means that it will generally go strait through matter without "touching" it at all. Thermal equilibrium (temperature) is a non-issue in that weakly interacting particles don't contact enough with "normal" matter to ever come to thermal equilibrium. They cool it down so that stray vibrations don't give a false positive reading. A good example of a weakly interacting particle is a neutrino. You probably know that most neutrinos go strait through the earth, other stars, and a whole lot of the universe without even knowing that anything else exits. These guys probably pick up all sorts of neutrinos, and they use that measurement to calibrate their instrument. Neutrinos have a very low mass, and their energy spectrum on earth is pretty well mapped out now. If these guys get anything out of the ordinary, they'll jump on it and call that a WIMP.

So we get to the statistical part. Now, on /., it's very popular to put down statistics, but in real life, scientests use statistics for nearly everything. My theory is that most people hate statistical mechanics, so they don't realize the power and accuracy which it has, and don't trust it in general. Marketers and politicians, on the other hand, know little to nothing about statistical mechanics and abuse the math of statistics for personal gain. This further poisons people's minds against the elegance of statistics.

These guys aren't playing statistical games. They're calculating the probability that they get no measurement of WIMPS with the parameter being how easily they interact with the normal matter that makes up their instrument. They then use that to put an upper bound on how often they interact with matter. That bound is defined by the probabilities in their calculations (which you can probably trust since just about every theoretical particle physicist in the world has checked them). The exact level, be it 90%, 99%, 99.999999% or whatever is something the guys in the field have decided on, and it's in some paper somewhere.

The end result that these guys are looking for is how much dark matter interacts with the rest of the universe. Being able to say, "It interacts less than X with 99% accuracy" is pretty nice. At some point that "X" is going to get so low, the theorists will throw the idea out and move on. Unless, of course, the holy grail is found and someone detects dark matter interactions.

I hope that helps.

Where you are directly on target is to critisize these guys for doing all this research and gathering all this money for something that is so far unmeasurable and theoretically not much more than the "aether" of 150 years ago (I've met theorists who will admit to as much). The bottom line is that it hasn't been disproven yet either (people are trying to do that too). As long as that's the case, people probably should still be out there looking for this stuff.

Re:I "detect" a grant money detector at work...

[redwyrm]

So apparently they had a way of producing these WIMPS for calibration purposes? Sounds like BS to me.

Re:I "detect" a grant money detector at work...

[Erratio]

another possible explanation: Did they check in the couch cushions? That's where I always lose stuff like remote controls and change, both of which are chock full of matter.

Re:I "detect" a grant money detector at work...

[nateb]

I'll bet it's easy to tell if equipment is running or not. A simple diagnostic--artificially creating what they're looking for--would tell them if the thing is working or not.

So.. go create some WIMPs and you'll be first in line for their maintenence contract, Hoss...

Good luck.

Re:I "detect" a grant money detector at work...

[jandersen]

"Okay, maybe I am being a bit silly, but, I still don't see how they can know the detector is working. I don't even know how the WIMP can make the thing "ring" once it, itself, is subject to the 1/10 degree above absolute Zero conditions."

Yes, Erick, you are being silly ;-)

Temperature is a statistical measure - ie. a measure that is valid only for a large number of objects. A single particle doesn't have a temperature - and apart from that, there is no reason why a few particles out of 10^23 couldn't have a fairly high energy, even if the ensemble as a whole has a very low temperature.

Far too often do we see this kind of attitude, that a superficial glance is enough to dismiss something, and I think it is a very dangerous way to go about things. That attitude is what lies behind pollution ('Oh come on, it's not that bad ...'), deforestation ('Oh come one, we do plant new trees'), terrorism ('Oh come on, people are just poor because they are lazy'), and it has also led the US into a stupid and easily avoidable war in Iraq ('Oh come on, of course he has WMDs or something').

What distinguishes us humans from the other animals, if not our ability to think critically? Let's at least try.

Check the actual webpage...

[Xandu]

For much more info, head to the CDMS homepage, which includes links to preprints of the mentioned Phys. Rev. Letters article (note, the paper hasn't been published yet), as well as other (published and unpublished) papers, as well as general info.

Chilled out

[rd4tech]

The new detector is four times more sensitive than any previous experiment. To shield it from high-energy particles from outer space, the machine is based 700 metres underground in an abandoned iron mine in Soudan, Minnesota. The detector is also chilled to within a tenth of a degree of absolute zero to reduce vibrations from surrounding molecules.

How do they do it?

Re:Chilled out

[citdude]

Cooling is done in tiers (over a distance of many meters). I would assume that the outermost is cooled to 76K with LN2 since that is dirt cheap. And then inside that LHe cools it down to a couple Kelvin or so, maybe less if they use superfluidic Helium. This much is pretty standard by now. As far as the last degree or so, I would guess they mess with the pressure a bit to get the temperature as low as possible.

Re:Chilled out

[r_j_prahad]

The detector is also chilled to within a tenth of a degree of absolute zero [...]

How do they do it?

Ever been to Minnesota? In the winter? You wouldn't have to ask.

Re:Chilled out

[Neil Blender]

How do they do it?

with lasers

Re:Chilled out

[b4rtm4n]

Lack of detection could be down to the size of the final detector.

If it's in a layered cooling system it must be significantly smaller than neutrino detectors which are vast vats of heavy water. Even then they detect relatively few neutrino interactions.

If WIMPS are much less commonplace than neutrinos (which we get bathed in) then detecting them in a smaller container is going to be difficult.

Re:Chilled out

[Anonymous Coward]

I should probably RTFA before posting, but hey, this is /. So, my guess is they have an outer vessel with LN2 surrounding a bath of Liquid Helium 4 which in turn is surrounding the rest of the refrigeration equipment. This most likely has a He4 pre-cooling stage (works just like any other refrigeration cycle...reduce pressure over a given amount of liquid and the temp drops). Next stage is most likely a dilution refrigeration cycle, which uses a mixture of He4/He3. Not going into details here, but this will get you to tens of millikelvin or so. To get lower temps, use adiabatic demagnetization of a large copper block and you can get into the micro-kelvin range...assuming no heat leaks...tada!

Re:Chilled out

[Anonymous Coward]

Ooops...put this reply in the wrong place a bit ago..

I should probably RTFA before posting, but hey, this is /. So, my guess is they have an outer vessel with LN2 surrounding a bath of Liquid Helium 4 which in turn is surrounding the rest of the refrigeration equipment. This most likely has a He4 pre-cooling stage (works just like any other refrigeration cycle...reduce pressure over a given amount of liquid and the temp drops). Next stage is most likely a dilution refrigeration cycle, which uses a mixture of He4/He3. Not going into details here, but this will get you to tens of millikelvin or so. To get lower temps, use adiabatic demagnetization of a large copper block and you can get into the micro-kelvin range...assuming no heat leaks...tada!

Re:Chilled out

[painandgreed]

How do they do it?

I assume you mean how do they cool it that low rather than how they found an abonadoned mine in Minnesota.

First, I imagene you have a series of refrigerators. If you've seen the movie Akira you have an idea what I'm talkign about. You put various types of refrigerators inside of eachother to limit the heat coming in from outside.

Take Helium (He) and put under pressure till it is in liquid form. If you let it boil, it will cool down to about 4K at atmospheric pressure. if you lower the atmospheric pressure by pumping out all the atmosphere, it will cool lower. This will take you to about 1K.

To get lower you can use a mixture of He3 and He4 (Helium atoms with different atomic weights) and cool it to make a dilution refrigerator. The lighter He3 will spearate from the He4. The He4 works to absorb the He3. You pump off He3 out of the He4 at the othe end of the tube and it cooles the remaining He3 as it is disolved into the He4. This should take you to the temperatures needed for this experiment. Simply put your experiment inside of the cold He3.

You can get even lower with various magnetic traps that allow fast atoms to "evoprorate" out of the traps but this tends to be for a small amount of atoms.

Re:Chilled out

[Anonymous Coward]

But the real question is how far can they overclock this puppy?

Re:Chilled out

[Nakkel]

Friggin sharks with fridging laser beams on their frigging heads. Cool.

Re:Chilled out

[wass]

Some other posts describe this a little, here's some more info.

They use a "dilution refrigerator" to get that cold. Dilution refrigeration uses a mixture of He3/He4 (mash) and cycles between two phases of the mixture (a He3 rich phase and a He3 dilute phase). The He3 and He4 are both liquids at this point.

Here's a basic overview of cryogenics. Liquid Nitrogen (LN2) liquifies at 77 K in 1 atmosphere. N2 is abundant, and LN2 is priced cheaper than milk. LHe4 liquifies at 4.2 K, and costs (here in the USA) about $4 per liter. I think it's much more expensive elsewhere in the world, but helium is mined w/ natural gas companies, so is more plentiful here than elsewhere. LHe3 is a rare isotope of Helium and vastly more expensive. It liquifies (I think) around 3K, and costs several hundred dollars for a few gaseous liters (here in USA).

So one can easily get to 4.2 K by dipping something in LHe4. One can employ evaporative cooling, and 'pump' on the LHe4 dewar, and get down to temperatures of about 1.5K. Perhaps slightly lower for bigger pumps. This cooling is quite easy and cheap to do, but often doesn't get low enough in temperature. If one has LHe3, that can be pumped on to get down to about 200 mK. But this is difficult because LHe3 is so expensive, and closed-cycle pumps are needed so as not to waste the cryogen.

Dilution fridges can get to lower temperatures. We just got one of these fridges in our lab, and using that I've cooled some samples down to about 20 mK. Dilution fridges have fundamental limits around 6 mK or so, but physical limits usually kick in earlier than that due to equilibrium between cooling 'power' and heating (mostly due to radiation and vibration). The basic thermodynamics are actually quite similar to your standard fridge, and you can think of it as He3 'evaporating' out of the mash, absorbing energy as they do so. And later the He3 is condensed back into the mash.

Fridge operation basically has a mixing chamber, which is the 'cold' point of the system. One hopes to create the phase boundary between the two phases here. The mixture absorbs heat from the sample, and the dilute phase travels up to the still, where it's pumped on by some big-ass pumping lines. The liquid is effectively warmed up, gets circulated around and re-condensed by a cold block at about 1.5 K. [This block is called the 1-K pot and is only pumped LHe4]. There's a flow impedance put in (to calibrate the pumping power with the circulation to get the phase separation at the right place). Then it's back into the mixing chamber. Meanwhile there are many heat exchangers along the way, exchanging heat from the incoming rich phase and outgoing dilute phase. The cooling power of the fridge is greatly increased depending on these heat exchangers. The effective sample size in our fridge is a cylinder about 1 inch diameter and 10 inches long. The dewar itself is about 7 feet tall and 3 feet diameter, and there's a rack of electronics and four pumps to go with it. So it's a big unit for a relatively small cooling volume.

Dewers are designed using stainless steel and other components to minimize thermal conductance to room temperature as much as possible. Radiative heating, however, is a problem. The dewar is evacuated between the 'cold' part and the outside, to minimize conductance. Radiation goes as T^4, and this power law is greatly exploited in dewar design. If one surrounds the 'cold' part of the dewar with a LN2 shroud, the cold part sees radiation at 77K instead of 300K. This factor of ~1/4 translates to a drop in radiative heating power of about 1/250.

Beyond this dewars use superinsulation, whereby aluminized mylar is wrapped around many times (with spacers), so each successive layer sees a colder temperature. So the 20mK part of the dewar might only be surrounded by an effective layer of a few K. These methods cut radiative heating down by factors of millions or more.

Re:Chilled out

[Muttley]

Laser cooling as in forming Bose-Einstein Condensates?

Re:Chilled out

[shadowbearer]

Should have been in the Sunscreen song:

"Live in Northern Minnesota once, but leave before you are cold enough that you will your body to research physicists to make liquid hydrogen."

Been there, done that. More than a year later I'm still trying to get the cold out of my bones...

SB

Re:Chilled out

[citdude]

I don't believe that laser cooling works on something this big, but I could be wrong. The second reply to my post likely hit the nail on the head; it sounds right, but I couldn't remember the details on my own.

Re:Chilled out

[Anonymous Coward]

I assume you mean how do they cool it that low rather than how they found an abonadoned mine in Minnesota.

The mine isn't strictly speaking abandoned. They don't mine iron any more, as deep iron mining is no longer economical (the ore at Soudan is very pure, but with "modern" methods, we can refine crappy surface ore, which is cheap to extract), but the mine is owned by the Minnesota DNR, and run as a tourist attraction.

The physics experiments underground (currently CDMS, MINOS and Soudan 2) lease the space, cage accesses etc. from the DNR.

Re:Chilled out

[Anonymous Coward]

He3/He4 Dilution Refrigerator. Made by oxford instruments.

That explains it

[Anonymous Coward]

I wondered what that strange picture on my milk carton was.

Re:That explains it

[infinite9]

Well as far as I'm concerned, it doesn't matter.

(sorry, i couldn't resist)

Good news.

[Retep Vosnul]

No Omega particles yet. That will spare our alpha quadrant for a couple of years.

But it's obvious...

[R2.0]

Anyone in high school knows that if a wimp hits anything, no one notices. If someone did notice, he wouldn't be a wimp.

Re:But it's obvious...

[Anonymous Coward]

Anyone in high school knows that if a wimp hits anything, no one notices. If someone did notice, he wouldn't be a wimp.

Unless that "anything" is a "someone", in which
case the wimp may no longer be considered a wimp.

Wimp?!

[Kjuib]

If a Wimp is about a thousand times more massive than a proton - what does that make a proton? a Wuss? or a Nerd?

Re:Wimp?!

[Anonymous Coward]

Thank you for making the most obvious joke I could think of when seeing that acronym on the first page. Your IQ must be at -least- in the double digits!

Re:Wimp?!

[NegativeK]

If a Wimp is about a thousand times more massive than a proton - what does that make a proton? a Wuss? or a Nerd?

A little bitch.

Re:Wimp?!

[shaitand]

Now now, if you go on like that he'll get a big head. You should have said his IQ -COULD- be in the teens! ;)

The Real Dark Matter

[Nom du Keyboard]

The real dark matter in the universe is the massive SCO intellectual property rights that no one else has yet seen.

Re:The Real Dark Matter

[Anonymous Coward]

Yay! A SCO joke. How creative.

Re:The Real Dark Matter

[LousyPhreak]

maybe someone should tell them that their search is pointless and doomed to fail

Re:The Real Dark Matter

[pseudochaotic]

Only if your current theories depend on their existence...oh, hi Darl.

Re:The Real Dark Matter

[nizo]

Maybe Iraq's hidden WMD account for all that missing matter?

Gravity is wrong

[Ckwop]

I think the answer to the dark matter problem and the quantum theory of gravity is one in the same. Our description of gravity is wrong. It has recently been discovered that dark matter is 'missing' from three elliptic galaxies. One would think that on the scale of something as big as a galaxy and with WIMPs being so massive that you ought to detect some quite major effect..

Add that to the fact that the universe's acceleration is getting quicker rather than slowing down and I think we have a strong case for our description of gravity being incorrect.

Simon.

Re:Gravity is wrong

[blincoln]

I think the answer to the dark matter problem and the quantum theory of gravity is one in the same.

I agree.

A friend and I read The Elegant Universe and both came to the same conclusion - "dark matter" doesn't exist. The gravitational effects are due to gravitons entering our universe either from another brane, or from our own brane folded over in a higher dimension.

For those who haven't read it, according to string theory all particles except the graviton are bound to their "home" brane. Gravitons may move freely between branes. A brane is a "slice" of a larger, hyperdimensional structure called "the bulk." Our universe occupies one brane out of the bulk.

Re:Gravity is wrong

[forand]

You can always tweak gravity to give ANY answer you want, BUT whenever you do it tends to break other things or look really strange. Case in point, if we change gravity to account for the missing mass we "see"(we notice that things don't rotate as they should given the light we see) then you can break other systems, like black holes, or the acceleration of the universe. Which brings us to your statement about the accleration of the universe: Einstein's theories predict solutions with an accelerating expanding universe so your statement doesn't help your idea. Also if dark matter is not seen in some galaxies there could be other reasons for this, like they don't produce whatever the dark matter is, the universe tends to hold all possiblities, being infinite and all, so not seeing something that we see elsewhere doesn't mean we didn't see it.

Re:Gravity is wrong

[Ckwop]

GR is perhaps the most well-tested physical theory yet developed and, as such, you can't say that it's "wrong". It plainly isn't once you remain within its field of reference.

You miss the point.. I'm citing the effects as evidence the theory is incorrect.

Simon.

Re:Gravity is wrong

[Abcd1234]

Uhh, did you read that article? That article only showed that three elliptical galaxies didn't have as much dark matter in them as expected. It did this by showing that these galaxies rotated in the exact fashion they should *in the absence of dark matter*. So, this study does not deny the existence of dark matter. It only poses the question "why do some galaxies have dark matter and others don't?"

As for cosmic acceleration, there's no particular reason to believe that that phenomenon has anything at all to do with the nature of gravity. It very well could be related to how our universe formed (see some of the alternative theories to inflation that involve pre-big-bang states).

Re:Gravity is wrong

[citdude]

The fact that dark matter is "missing" in eliptical galaxies means nothing. The amount of gravitational mass in young (or close) spiral galaxies is much higher than the visible mass that makes up the stars and the dust clouds around the galaxy. At some point, whenever my project gets approved, I will conduct similar research on older, farther away spiral galaxies that may give us some insight as to how spiral galaxies and the dark matter in them evolved together.
In other words, it a bit early to say that everything we know is wrong and that the "quantum theory of gravity" is right. No physicist is so arrogant to claim that they know what IS correct. Everything that we have is but a model. Hawking, Thorne, Preskill, Kamionkowski, Phinney, all realize this but the truth is that our current model of gravity works well most of the time and many people are working on finding a better one but notice that in the meantime, no on is abandoning our current model. It is still the best thing that we have.
You are also forgetting that while WIMPs may be big, they are neutral (like neutrinos) and interact very little with matter, making them difficult to detect. Give physists more time (or money) and they will get there. By the way, you are also forgetting gravitational lensing with things a big as galatic clusters. That is a major effect that cannot be explained by the mass that we can see too. And those galaxies incude all types of galaxies.

I'm done rambling now.
Scott

Re:Gravity is wrong

[bigg_nate]

I think he's referring to the fact that current gravitational theories don't seem to match observations over extremely small distances (I seem to remember ~10^-30m). So strictly speaking the current theory is "wrong", even though it matches observations extremely well at any reasonable scale.

Re:Gravity is wrong

[trentblase]

You can always tweak gravity to give ANY answer you want

Teacher: Bobby, what's 5 times 4?
Bobby: Ummm, 10?
Teacher: That's wrong, it's 20
Bobby: Oh yeah, you just have to apply a constant factor of L where L=2

Re:Gravity is wrong

[Henry V .009]

GR is perhaps the most well-tested physical theory yet developed...

It just doesn't pass the Galaxy-Shape test. Oops. Well, maybe there is a bunch of imaginary matter out there that no one can see.

Re:Gravity is wrong

[b4rtm4n]

Try an alternative theory.

Young galaxys may be formed around the black hole nucleus of ancient dispersed super massive objects (quasars, collapsed galaxys, gamma ray bursters, who knows?!?)

This may give them sufficient mass to appear to invalidate current galaxy formation theory.

Also this theory could be the result of too much beer.

Re:Gravity is wrong

[Lemmeoutada Collecti]

The galaxies. Dark Matter. Dark Energy. There, there's three. They are mathematical kludges to attempt to fit the observed universe into GR.

Of course, I think that it's just the cream filling from all the twinkies, after all, we never can seem to find it!

Re:Gravity is wrong

[algae]

give me one example of an experimentally observed physical process which violates general relativity. Just one.

Well, haven't we observed galaxies whose outer arms are spinning faster than they should, given their observable mass? And haven't we been unable to detect the additional matter that is needed to keep those galaxies from flying apart given our current understanding of gravity? I don't know that this violates relativity, but it's certainly causing some problems for cosmologists and physicists.

Re:Gravity is wrong

[EvilTwinSkippy]

I prefer the holographic theory of the Universe, namely that what we observe as the universe is not really there. It is an interference pattern of several underlying signals.

Ever wonder why coastlines and clouds are easily modeled with fractals?

Re:Gravity is wrong

[Anonymous Coward]

If you think it is, give me one example of an experimentally observed physical process which violates general relativity.

"Mathematical fudge factor X" is not a synonym for "observed physical process."

Your statement is as enlightened as Newton claiming that he knew everything about gravity and dynamics.

Re:Gravity is wrong

[TMB]

But then you'd have all the mass at the center, and the velocities would have a Keplerian fall off with radius (ie. like in the solar system, where most of the mass is in the sun). But rotation curves tell us that the matter is distributed in a much more extended way (the rotation curves don't fall off so fast, so as you go farther out there must be more and more mass inside your radius).

[TMB]

Re:Gravity is wrong

[EvilTwinSkippy]

Well when I drop my keyboard it still goes "crash" on the floor. Maybe it's some incan monkey god that pulls everything toward the center of large masses.

Re:Gravity is wrong

[Anonymous Coward]

If you think it is, give me one example of an experimentally observed physical process which violates general relativity. Just one.

Cheap shot: The rotation curve of spiral galaxies. Given the presumed distribution of mass, GR does not predict the star orbits. Either we aren't perceiving mass that's there, or GR is wrong.

Expensive shot: Gravity in the presence of delocalization. One can, in principle, convert huge amounts of mass-energy (gigagrams) into photons, and diffract those photons over large distances (hundreds of meters). GR predicts that those photons will create a substantial gravity field, one that is "trivially" measurable with a spatial resolution of meters. GR does not predict the values of those measurements. Ergo, GR does not describe the universe. It is easy to devise other quantized systems for which GR predicts a particular average result, but makes no predictions about the distribution of results.

I'm not saying that GR isn't a useful approximation when you have vast numbers of localized particles, but it ain't the Truth. This has implications for neutron stars in particular, as they may contain on the order of a solar mass of Bose-Einstein condensate (superfluid neutrons and such).

-- dn

Re:Gravity is wrong

[ifwm]

"Trust me on this"

I love this. No, sir, I will not trust you. You are some guy on a web board that most probably has no grater understanding of the topic than many others here. You certainly don't know all there is to know about it, and by vigorously defending something (General Relativity) that should be tested at every opportunity, you have displayed a clear lack of understanding of scientific method. Others have given you examples of why GR may be incorrect as it relates to gravity. The correct thing to do here (as a scientist) is to accept the challenge to an established idea and prove your point with evidence, not by saying "trust me"

Re:Gravity is wrong

[gnuman99]

GR description of gravity is not wrong. :) You see, if you are going to say that it is wrong, you have to provide a better model, or an experimental observation that shows GR is wrong.

As to the "cosmological constant", well, WTF does that have to do with gravity? AFAIK, there could be no relationship between that and gravity at all. The point there is that we do not know what is going on, true, but it does not mean everything is wrong. You explanation is like:

Since no one can account for formation of object A in rock sample B, then evolution and science must we wrong and only my holy book (insert book's name here) tells the truth

No explanation for event A from theory B does not mean that B is wrong. It means there is no explanation for A. Theory B would only be wrong if A contradicts predictions of B.

Re:Gravity is wrong

[shaitand]

Or maybe there is something other than relativity. Give me a puzzle, I'll come up with solutions that "ALMOST" solve it all day long.

Since GR was first introduced we've been making adjustments here and there, adding a constant here or there, adding new rules. Basically cooking the science to make it fit or establishing our facts based on it's principles. If our facts are only facts because they are proven by GR then they are not facts at all. And us using GR to prove them does qualify as proof of GR 20mins or 20yrs after the fact.

Most of what we've built on assumes GR is correct and testing against it. If you want to test GR, you have to throw away everything that determined within the GR system and compare observations of RAW data against the unmodifed, unadjusted, unconstant thrown in and correction factor GR.

We've been assuming GR is how things work for so long I doubt we can untwist it all.

Re:Gravity is wrong

[Dyslexicon]

i'm agreeing with the above(and the poster who has also replied to this same post) in that yes you have missed the point. All of this Dark Whatever nonesense stems from the seperation between how GR tells us the universe should behave and how the universe actually does behave.

There was a day when Newton's gravity was overthrown by GR, which was a more general theory that was correct in the limits in which it was originally conceived. Is it so hard to believe that just perhaps it's possible that GR is correct only in some other limit and that some other theory which is more general yet will supersede it?

Re:Gravity is wrong

[cyril3]

That might have been the wrong phrase for him to use as it does leave him open to riposts such as yours. But is it true that that vigourous defence of a position is not acceptable in the scientific method. This is after all only a discussion forum. Other posts have already suggested reasons why the data referred to may not destroy the GR/Gravity links.

Others have given you examples of why GR may be incorrect as it relates to gravity

But that doesn't mean their interpretation of the data is correct. If the accumulated evidence against GR as it relates to gravity was so clear this would be a discussion between scientists and the GR equivalent of the flat earth fringe who keep pushing the old GR/gravity line. But it hasn't come to that yet so discussion is still valid.

Is this the first time ever that data has suggested that GR may be incorrect as it relates to gravity. If not, what was the outcome.

prove your point with evidence

I thought the scientific method was to disprove your point with evidence. If you fail to do that you strengthen your view that the point you have is less likely to be incorrect than any alternative. As far as I can tell he merely suggests that the state of current observations are insufficient to show GR AIRT gravity to be unsustainable.

.I'm not a scientist either but this isn't a scientific forum. So it's onl a laymans view of how it works.

Re:Gravity is wrong

[Muttley]

GR is perhaps the most well-tested physical theory yet developed and, as such, you can't say that it's "wrong".

This seems patently false. Quantum mechanics is ugly as all hell, but has a lot of observable physical evidence that verifies it. General Relativity is mathematically quite elegant, yet there is little physical observable evidence to verify it. We have the precession of Mercury, and some other small things, but nowhere near the wealth of experimental data we have that verifies quantum mechanics.

I think GR is very much a correct theory, but things like pre-inflation cosmology, and string theory, which are more based on the elegance and beauty of the mathematics involved, I have a harder time considering proved, or even to some extent considering if we will ever have the experimental capacity to prove them.

I don't think many people, especially in the field of GR, would disagree with your statement that GR is "the most well-tested physical theory yet developed". One only has to look at it's brother, Special Relativity, to see a theory which has been much more thoroughly tested.

Re:Gravity is wrong

[Anonymous Coward]

GR is perhaps the most well-tested physical theory yet developed and, as such, you can't say that it's "wrong".

Well, except that it blatantly fails to explain a number of observed astronomical phenomena.

Sure, you can make the numbers work out if you assume that there's invisible, intangible matter floating around. But one could explain the precession of Mercury in Newtonian terms simply by assuming an invisble, intangible planet Vulcan.

Sure, that wouldn't explain other GR phenomena, but dark matter doesn't reconcile GR with QM, either. As long as we're making special explanations and assuming invisible matter, I'm sure we can make a few more, and show that Newton's gravity was a sufficient explanation of the universe . . .

Re:Gravity is wrong

[forgotmypassword]

I think the answer to the dark matter problem and the quantum theory of gravity is one in the same. Our description of gravity is wrong.

Do you realise that you can couple a theory of exotic mater or energy together with our current theory of gravity?

What you are saying could be analogous to "GR can't explain accretion, therefore GR is wrong". (You have to add E&M to the mix)

Toying with the stress-energy-momentum tensor and the cosmological constant would not really be changing the theory of GR.

Re:Gravity is wrong

[forgotmypassword]

Expensive shot: Gravity in the presence of delocalization. One can, in principle, convert huge amounts of mass-energy (gigagrams) into photons, and diffract those photons over large distances (hundreds of meters). GR predicts that those photons will create a substantial gravity field, one that is "trivially" measurable with a spatial resolution of meters. GR does not predict the values of those measurements. Ergo, GR does not describe the universe. It is easy to devise other quantized systems for which GR predicts a particular average result, but makes no predictions about the distribution of results.


Did you use classical gravity with the expectation value of the stress-momentum tensor, or did you use semiclassical gravity to make this calculation.

It's not fair to mix classical with quantum in any manner.

Re:Gravity is wrong

[beeplet]

General Relativity is mathematically quite elegant, yet there is little physical observable evidence to verify it.

I beg to differ... In addition to the precession of Mercury, which you mention, there is a huge amount of physical evidence in agreement with the predictions of GR. For example:

1. Measurement of time dilation (gravitational redshift) in the Earth's gravitational field, and in light from the sun, other stars, white dwarfs, and neutron stars. The accuracy of GPS depends on taking this effect into account.
2. Gravitational lensing of stars in line with the sun, of galaxies in line with one another, of galaxies lensed by the gravitational field of extended foreground clusters, etc.
3. Orbital decay of binary pulsars, such as PSR 1913+16, due to gravitational radiation. The slowdown rate can be measured very precisely and corresponds exactly to what GR predicts. In addition, LIGO will hopefully be sensitive enough to detect gravitational waves directly within the next few years.

In every instance where measurements are accurate enough to confirm the predictions of the theory, they match. The question of which scientific theory is the "most" well-tested is probably a matter of opinion, but I wouldn't be too quick to dismiss GR on the basis of lack of hard evidence.

Re:Gravity is wrong

[canadian_right]

We are looking for dark matter because we think GR is CORRECT. Dark matter must be there because GR says some mass is missing. If GR is incorrect maybe we don't need to look for 'dark matter'.

Re:Gravity is wrong

[Grayswan]

I think I understand what you are saying. One of the following is true:

1) The Cosmological Constant is real.

2) Dark matter is real.

Both cannot exist? Either implies something that has not been experimentally observed (like God. Neat, huh?). ...because there is compelling evidence for the existence of dark matter, there must be something wrong with general relativity...

They both kind of explain each other, no?

Re:Gravity is wrong

[doctorfaustus]

I call BS

A scientist too in love with his thesis becomes a politician.

Re:Gravity is wrong

[Muttley]

Where did I fail to demonstrate a basic knowledge of GR?

The first poster has the right tack - list experiments verifying GR - all correct, all informative.

What google search should I have done?
this one

This lists, like the above post, gravitational lensing, gravitational timeshift, shapiro time delay, and precession.

I probably shouldn't have said 'little', perhaps I meant less, that is, less than the experimental evidence for quantum tunnelling, wave-particle duality, the second law of thermodynamics, but as the parent said quite correctly, that is entirely a matter of opinion, and I appreciate that comment. After all, what is the relevance of a 'lot' of proof, or a 'little' proof, if something is proven.

I 'invoke' string theory, because I think it holds too high a place in TOE study, and within mathematical physics in general. People have to spend many years gaining competence in all the areas which string theory covers, and are unable to specialise in any one of these areas. I probably shouldn't have mentioned it, as it was irrelevant - what I was trying to say was that there are certainly some branches of physics, or more precisely mathematics, that are very hard to find observable evidence for.

What factory should I go back to? Are you a gifted and talented chest-beating theoretical physicist? are you trying to be the creator of GUT? In my experience cosmology and GR attract a lot of arrogant physics undergraduates, who think their problem of universe origin is the most important problem of all.

Then again, physics students in general could be said to be arrogant, and it helps to study something that you think is genuinely important, so what's the loss?

take home message: first poster - left me informed, humbled, you - left me thinking you are a physics major worth little salt.

Re:Gravity is wrong

[Anonymous Coward]

You can't say it's right either. You should know that scientists can never prove that something is right... only wrong. And it's a safe bet that all our theories today are simply and approximation of what is the actual "true theory". Otherwise it'll puts scientists out of work so they wont accept it! :)

No gravity waves have been detected, indirectly albiet but not directly. Does this mean that gravity waves don't exist? Also personally, I am working with fellow scientists on an experiment to test the lorentz invariance of space. If lorentz invariance is broken, then you can pretty much throw out both SR and GR, because it will show that a prefered frame exists! Though you can replace it with the Standard Model Extension (http://physics.indiana.edu/~kostelec/faq.html) or the Mansouri-Sexl kinematical theory. (which basically preturbs the values of a taylor series if my understanding is correct)

You sure?

[sameerdesai]

In 20 years, as we all know the universe will have expanded and definitely the numbers will be off again.

Re:What is next...

[bersl2]

Somehow, I think the search for WIMPs will be more successful than the search for WMDs.

Maybe -

[Black Parrot]

What if software bugs emit gravitons? Wouldn't that explain the apparent extra mass in the universe?

Re:Maybe -

[DrLudicrous]

LOL. I get it.

Re:Maybe -

[Patrik_AKA_RedX]

What if software bugs emit gravitons?

Windows. Solar system still exists. nuff said.

Re:Maybe -

[Grayswan]

What if software bugs emit gravitons?

If that were true, there would be a black hole located at Redmond, Washington.

The Answer

[theraccoon]

What's 20 times 0? And don't tell me zero!

Zero.

Opps. I meant, seven.

Re:The Answer

[Nom du Keyboard]

Zero.
Opps. I meant, seven.

How about 42?

Re:The Answer

[Anonymous Coward]

I think the question is: Is the time clock on their detector flashing 12:00 .. 12:00 .. 12:00 ..?

Re:The Answer

[infinite9]

Opps. I meant, seven.

IBM may agree with you! Try this code on AIX:

#include"stdio.h"

int x,y,z;

int main() {

x=1;

y=0;

z=x/y;
printf("%d", z);

}

On most unix implementations you get floating point exception since the divide operator takes floating point operands. On AIX, when the denominator is cast to a float, it's a zero approximation rather than the official floating point zero. The result is that instead of a core dump, you get... 15.

Re:The Answer

[pseudochaotic]

No, that's six by nine.

Re:The Answer

[Anonymous Coward]

GCC can do this too:

#include"stdio.h"
int x,y,z;
int main() {
x=1;
y=0;
z=x/(float)y;
printf("%d", z);
}

2147483647, which is maxint and not unreasonable. I just had to force the same cast you mentioned.

Re:The Answer

[Anonymous Coward]

I tried this on AIX 5.2, gcc 2.95, xlc 6. Code compiled with both compilers returns.. 0. (not segfault !)

Re:The Answer

[essreenim]

aka naught aka nada aka nothin

Forgive my ignorance

[jm92956n]

A favoured theory is that the dark matter consists of Wimps (weakly interacting massive particles) about a thousand times more massive than a proton

My training in physics is quite elementary, but I was led to believe the proton is relatively massive on the atomic level, especially when compared to an electron. How could a wimp be so large and yet unnoticed?

Re:Forgive my ignorance

[beady]

Because it interacts weakly perhaps?

Re:Forgive my ignorance

[Anonymous Coward]

For two reasons:
1) Because it is weakly interacting. A particle can be as large or energetic as you like, but if it doesn't interact with most things, chances to see it are going to be few and far between, and
2) if its mass is a thousand times that of the proton, that means it takes about 1 TeV to make one. This is around, although within, the limits of moden accelerators (the Fermilab Tevatron gets between 1 and 2 TeV depending on what beamline you're talking about). Although, once you've made a WIMP, see part 1 about detecting it.

Also, though protons are decently large, they are outweighed by a lot of other particles.

Re:Forgive my ignorance

[Mr. Bad Example]

> How could a wimp be so large and yet unnoticed?

You just described my entire high school career.

Re:Forgive my ignorance

[stox]

The Top quark was only discovered in 1995, and it is around 200 times the size of a proton.

Re:Forgive my ignorance

[bigg_nate]

I also don't have much of a physics background, but I believe we notice protons because they have strong interactions with other particles, not because of their mass. Nuclear forces cause protons and neutrons to cluster together, and electromagnetic forces cause atoms, molecules, and larger objects to form. If WIMPs only interact with (relatively much weaker) gravitational forces, they could easily go unnoticed. Similarly, it's easier to detect electrons than neutrons, even though neutrons are 1000 times as massive.

Re:Forgive my ignorance

[jmtpi]

> > A favoured theory is that the dark matter
> > consists of Wimps (weakly interacting massive
> > particles) about a thousand times more massive
> > than a proton

> My training in physics is quite elementary, but
> I was led to believe the proton is relatively
> massive on the atomic level, especially when
> compared to an electron. How could a wimp be so
> large and yet unnoticed?

The key is the "weakly interacting" in the name. At the microscopic level, these particles (if they exist) can only interact via the weak force, which is both weak and short-range.

In particle physics the size of a particle has no relation to a physical size or a particle's mass. It is defined in terms of how strongly a particle interacts with other matter. (See the definition of cross section at PhysicsWorld.) So since the WIMP particle interacts only weakly, it is by definition "small," even if it is massive.

If the WIMP hypothesis is correct, then the WIMPs have hardly been "unnoticed." One of the chief motivations for looking for them is to explain the rotation of various galaxies which appear to be much more massive than can be calculated by adding up the mass of all the stars and dust in them. So if this missing mass does consist of WIMPs, then they have already been noticed!

Re:Forgive my ignorance

[UnknowingFool]

Part of the issue is that some of these particles are extremely short-lived. Combined with their weak interactions, it is hard to determine that they exist. For example, the Higgs Boson is theorized to be the most massive. It has yet to be actually observed.

Re:Forgive my ignorance

[radtea]

Size, mass and interaction strength are unrelated. For example, imagine trying to detect clouds by throwing rocks at them. Clouds are big, but they only interact with rocks very weakly.

--Tom

Re:Forgive my ignorance

[Anonymous Coward]

Ah - that explains it.

The massive wimp is hiding behind the quark.

Re:Forgive my ignorance

[Roger W Moore]

How could a wimp be so large and yet unnoticed?

Ever seen the film "The Hollow Man" where they turn Kevin Bacon invisible? Essentially they prevent his body from interacting with photons, i.e. light, so that he turns invisible and nobody can see him.

It's exactly the same principle with WIMPs. If they hardly ever interact you will never see any effect of them being there.

Of course being invisible raises the point of how can he actually see anything since his retinas can no longer interact with any photons thus making him blind....so in terms of physics the film is more like a road runner cartoon with fancy CGI but you get the idea.

Re:Forgive my ignorance

[Ruie]

How could a wimp be so large and yet unnoticed?

Because we cannot directly observe mass. What we can observe is an influence of a particle on other matter which we can track.

For example, proton that is flying by will influence other particles by its electromagnetic field and also with strong force - if its bumps into another particle.

Thus in a babble chamber you will see a track from the photon since it will ionize other particles during its fly-by and they will serve as starting points for bubbles.

Also if one makes a big block lead and cools it down one would be able to observe the increase in temperature if the proton hits a lead nucleus. (this assumes that the proton is fast enough..)

WIMP means weakly interacting massive particle. Since it interacts very weakly with matter (like neutrino) it is very hard to observe.

Re:Forgive my ignorance

[servognome]

So we should use rocks to detect WIMPs. We can throw them at people and if they run away crying, they can be classified as WIMPS. Then again it could get ugly if the rock detects MaCHOs

Re:Forgive my ignorance

[darkfire5252]

While I would agree with you that size doesn't matter, when talking about how dark matter affects normal matter via gravitry, I would tend to argue that mass is very very important.

The analogy with rocks and clouds is a bit of a stretch, because a cloud is a collection of molecules, not a particle.

I'd say it would be more like trying to detect a large ball with a rock. Even if you can't see the ball, you'd notice that the rocks change path for no apparent reason.

Re:Forgive my ignorance

[dustmite]

"Beginner" question: the evidence in favour of the notion of the existence of Dark Matter (via WIMPs or otherwise): does it suggest if the additional mass is distributed more or less evenly throughout the Universe, or does it specifically suggest that the dark matter is not distributed evenly throughout the Universe but rather that there would be "patches" of higher densities in certain places?

Re:Forgive my ignorance

[dustmite]

Ha, I was thinking the same thing the other day, that an invisible person would need to be blind. If not, you would probably be able to see some weird sort of "floating shadows" where the person's eyes are, at least if you were standing behind them. Hmm .. actually, you'd probably see a shape the size of their eyeballs, because the entire usually opaque part of the eyeball would have to continue blocking photons, otherwise the person's retina would be flooded by light coming through the side of their eyeballs (instead of just the aperture/lens as per normal sight).

Re:Forgive my ignorance

[dustmite]

Is it possible that WIMPs (or whatever dark matter is) is so weakly interacting that it literally cannot be detected on a microscopic scale? I.e. that the mass effectively doesn't even interact at all, and that the effects of the existence of large amounts of this stuff might only ever be evident by their large-scale interactions (e.g. gravity affect on galaxies)?

Re:Forgive my ignorance

[TMB]

It is clumpy. The initial deviations from completely-smooth come from inflation. Some areas have very slightly higher density than average. Because gravity is attractive, areas with higher density attract matter from lower density regions, so the density increases further. Soon those tiny little fluctuations grow into large structures, with "halos" (roundish virialized clumps of dark matter in which galaxies form) are stretched along filaments and sheets that fill space.

Take a look at some of the Virgo consortium pictures and movies for an idea of what this looks like.

The detailed distribution of matter within halos is a matter of some debate, but it's clumpy (even within any one halo) and falls off with radius with a slope (in log-log plots... ie log(density) vs log(radius)) that ranges from about -1 (there is considerable debate about this number... depending who you ask, you'll get answers ranging from 0, ie. a central constant-density core, to -1.5) in the center to -3 in the outer parts of the halo.

Because there is much more dark matter than baryonic (normal) matter, the baryons are also concentrated in the halos. That's where they cool and form galaxies.

[TMB]

Re:Forgive my ignorance

[Ruie]

It could be.

What happens is that there are several theories (supersymmetry for one) that predict WIMPs, but those particles are similar to neutrinos - they interact, but very rarely (for example, one of the candidates is a supersymmetric double of neutrinos).

The good thing about those theories is that they can be tested with present technologies.

So the experiment we are discussing will allow to rule out or at least constrain parameters in such theories.

Great Location

[sssmashy]

The Cryogenic Dark Matter Search uses equipment at the bottom of a Minnesota mine to filter out all interference.

The underground observatory is some 1,000m beneath the surface. It is only from such an isolated place that scientists believe they have a chance of catching their quarry.

Excellent location choice! Even if they don't find any dark matter, at that depth they at least have a chance at locating the remnants of ex-Gov. Jesse Ventura's political career.

Hidden outside the horn of the universe

[Ra5pu7in]

Horn, funnel, whatever shape it was. Maybe the dark matter is really the "nothingness" that exists beyond the shape of the universe.

Re:Hidden outside the horn of the universe

[benchbri]

IAKAP, but I do have access to a dictionary, and the universe, as defined, is EVERYTHING. Nothing exists outside the universe, by definition.

From dictionary.com:

universe (yn-vûrs)
n.

1. All matter and energy, including the earth, the galaxies, and the contents of intergalactic space, regarded as a whole.
2. 1. The earth together with all its inhabitants and created things.
   2. The human race.
3. The sphere or realm in which something exists or takes place.

If WIMPS were outside the universe, I'd think the physisists would have a much, much larger problem. Either that or we'd have to redefine "universe"

Re:Hidden outside the horn of the universe

[DaZedAdAm]

Alright, maybe I'm just behind the times or a bit confused, but for the life of me I can't figure out IAKAP. Perhaps it was meant to be IANAP (I am not a physicist)?

The only other thing I can come up with is "I ain't knowledgeable about physics," and I'm just hoping that a statement like that wouldn't be abbreviated.

Re:Hidden outside the horn of the universe

[Mindwarp]

Maybe it was "I am knot a Physicist" and had an implicit IANAEM postpended to it (I am not an English Major)

Dark Matter

[dustmote]

I don't know, even though science has a track record of proving (at the time) absurd claims, dark matter just seems.....silly. (I typed darl matter here as a typo, that would have led to yet another SCO thread I'm sure) What are the other theories about the missing mass? I'd like to shop around and see if I can find one a little more reasonable-sounding. :)

Re:Dark Matter

[Anonymous Coward]

>What are the other theories about the missing mass?

I think Douglas Adams has a great theory about this.

Massive wimps?

[WCityMike]

Massive wimps, huh? Never knew there was dark matter at my high school ...

Missing Matter

[Detritus]

I thought the usual rule in science was, if your theory conflicts with your observations, there is something wrong with your theory. Maybe there is no "missing matter", just an incomplete or defective theory of gravity.

Re:Missing Matter

[k98sven]

Well, for one: It's the only theory of gravity we've got really. If you can come up with one from as few (or fewer) postulates, which fits as well into the what we already know, and make the same predictions, I'm certain people will listen.

It's not as if everyone here has 'decided' that dark matter simply exists. There are plenty of people at work with alternative explanations.

However: If the theory is correct, and dark matter does exist, how are you supposed to find it without looking?

Re:Missing Matter

[Anonymous Coward]

And when something is wrong with your theory, you have to adjust it or come up with a new one that explains your observations.

And thus we have the theory of the existence of dark matter.

Re:Missing Matter

[Anonymous Coward]

That's what dark matter/dark energy always sounds like at first glance. However, it's not quite so simple, and cosmologists are not quite so stupid.

Actually, the "dark matter" hypothesis agrees with practically every observation you can think of: x-rays from galaxy clusters, the rate of formation of large-scale structure, the formation of deuterium/helium/lithium in the Big Bag, the cosmic microwave background, gravitational lensing by large clusters, AND (of course) the familiar argument that 'the outer parts of galaxies rotate too fast)'. The only odd thing about the hypothesis, is the fact that the dark matter apparently interacts only very weakly: with photons, not at all, thus 'dark'; with gas, stars and planets hardly at all, thus the extended shapes of galactic halos; and with CDMS, too weakly to have been detected so far, apparently.
Weakly interacting particles shouldn't surprise us - think of neutrinos, no? - and indeed a very powerful theory called SUSY predicts the existence of dark matter, based on elementary particle physics constraints.

The idea that you can fix the 'dark matter problem' by modifying gravity is interesting, and it has been thought about a lot. It's hard to make any sort of theory agree with all of the measurements I mentioned. Google for "MOND" (Modified Newtonian Gravity" to learn more.

Re:Missing Matter

[Anonymous Coward]

We'll see in time I suppose, however we already knew our theory of gravity was incomplete, or otherwise it would work properly at qauntum scales, which it doesn't.

There are several new theories trying to cover that though. So maybe some of these measurements might validate one of them. Be interesting times.

Quickshot

Re:Missing Matter

[citdude]

Yes, but only if you can see everything.

In this case, we have the visible mass (stars and dust clouds) and calculated gravitational mass (calculated either with spiral galaxies rotation curves or with gravitational lensing effects) that are off by a factor of 9 or 10. It is unlikely (though possible) that all we need to add is a small term that is usually negligble except in this case. It is far more probable that there is some mass that is invisible (ie. not emitting or absorbing light) to make up the difference.

The word defective should probably not preceed the phrase "theory of gravity" becase the theory of gravity is very good (right on as far as we can currently tell). Incomplete is much more probable; like I said above, it could just be missing a ususally small term....some day we may find out.

Re:Missing Matter

[Henry V .009]

from as few (or fewer) postulates

Unless GR is an oversimplification (read: hack). Can't say that would be a first as theories of gravity go.

Re:Missing Matter

[k98sven]

I think you may have confused the concept of basing something on a few postulates with simplification.

A theory is not necessarily simple just because it derives from a few postulates. Heck, all of math and logic does, and they can be far from simple.

Anyway, the point is that Relativity and Quantum theory both derive as a logical consequence of a number of postulates.
For special relativity, the two are:
1) Laws of physics remain unchanged regardless of the frame of motion. (Or: 'Why the earth seems to be standing still' )

2) Speed of light is constant regardless of frame of motion. (Weird! Yet in accordance with 100 years of observation)

The older theories, of gravity etc, are far more ad hoc than these modern ones. Newton never explained why his law of gravity was proportional to the square of the distance. Why the square and not, say, the cube? 'Because it works', would've been his answer.

Today, the answer is: 'Because we believe this-and-this-and-this is true, and therefore this must follow'.

Obvious, but ...

[nicodaemos]

Missing Matter ... still missing

Did anyone check under the cushions on the couch?

Why do dark matter found

[Anonymous Coward]

because there isn't any.

The astronomers have been seeing something they do not understand, and so they assume it is dark matter. The same result could be gotten by a decaying speed of light.

Unfortunately, that requires another rewrite of physics, from the ground up. However, looking for something understood gets more grant money.

Re:Why do dark matter found

[Profane MuthaFucka]

Nice with the conspiracy theory, AC. Too bad that you're wrong. The first tip-off that there's dark matter is the rotational speed of galaxies. Your decaying speed of light won't explain that.

Re:Why do dark matter found

[gewalker]

OK, so you don't like decaying lightspeed as an explanation (and I agree, though it could explain some other issues and is given serious consideration by real scientists).

There is a thery that there is little or no dark matter, and the difference is accounted for by the assumption that the inverse square law for gravity fails at large distances -- based on a theoretical model of graviton particle exchanges that would not follow inverse square -- This just happens to match the observed data pretty well without need for dark matter.

A second alternative is combines light speed decay along with big change in assumed age of universe, so that spiral galaxies look the way they do because they are quite young compared to the standard model.

I'll bet there are other non-darm matter models that are explain observed data as well as the dark matter model too.

Re:Why do dark matter found

[Profane MuthaFucka]

No, I like all those theories, including decaying lightspeed as explanations equally well. That is to say, I have no preference for any of them, except the one that will eventually have the most evidence. Decaying lightspeed is off to a spectacularly bad start...

But, I don't think that scientists are staying away from that theory because they don't want to rewrite the Physics textbooks.

Look at the last guy who rewrite the Physics textbooks. He's got one of the most recognizable faces in the world. Everyone considers him to be wonderful, despite the fact that he doesn't comb his hair. His name is considered to be the definition of intelligence. His ideas helped to invent the Atomic Bomb yet the Einstein Peace Prize is named after him.

Now tell me who in the world wouldn't want to be considered the Albert Einstein of the 21st century? The conspiracy theory proposed was just ludicrous.

Re:Why do dark matter found

[BlueJay465]

I expect the scientists responses, if questioned about what this closed-box dark-matter detector detects and how it detects it will be:

"Move along, nothing to see here"

Soon after, the MiB will come rolling in your driveway and

NO CARRIER

Re:Why do dark matter found

[forgotmypassword]

The decaying light theory introduces a dozen new flaws for every existing flaw it fixes.

Re:Why do dark matter found

[TMB]

There seems to be a common sense here that all of the evidence for dark matter could be equivalently explained by changing the force law.

However, that isn't true. One unique test of dark matter is that it is dynamical; it can move. And there are a bunch of tests that have started to be made that show evidence for dynamical dark matter:

- in order to explain rotation curves without dark matter, models like MOND require force laws that would make the derived "shape" of the dark matter halo spherical at large radius. You can test this by looking at the shapes of clusters using X-ray emitting gas (eg. Buote et al. 2002, ApJ, 577, 183; Lee & Suto 2003, ApJ, 585, 151; Lee & Suto 2004, ApJ, 601, 599) or the Sunyaev-Zeldovich effect (LS03,LS04). You can also look at the shapes of dark matter halos around galaxies using weak gravitational lensing (Hoekstra et al. 2004, ApJ, 606, 67). So far all of the tests indicate that dark matter halos are not spherical, but flattened exactly as predicted by cold dark matter.

- the bars in barred spiral galaxies should slow down and disperse quickly in a spherical static halo potential, like you'd get from modifying the force law, but they can be maintained for long periods of time if they can exchange angular momentum with the dark matter (Athanassoula 2002, ApJ, 569, L83; Valenzuela & Klypin 2003, MNRAS, 234, 459).

- there's a weak gravitational lensing observation of a group that is falling into a cluster, where the mass of the infalling group is offset from the light - the gas is moving slower because it's interacting with the cluster gas, while the dark matter has kept moving (Clowe et al. 2004, ApJ, 604, 596).

[TMB]

Re:Why do dark matter found

[Thing 1]

I like the idea that, once we develop nanotechnology a goal should be to begin to develop Dyson Spheres, so we can capture 100% of each star's output and save it in batteries to be rationed later. We can make the universe last longer that way (a year or two ago it was determined that we won't contract: we were sentenced to a heat death. So we might as well conserve as much as possible; think big.

So if that's a goal of ours, perhaps it's a goal of another race's. And perhaps they got a head start on us, and that large percentage of "dark matter" actually consists of Dyson Spheres which capture everything, so are "undetectable" by us. That's pretty scary, to think that we just lost that much playground, and will eventually have to deal with the bully--on his own terms perhaps.

I mentioned this a year ago or so, and someone pointed me in the direction of Matrioshka Brains, so I will include some links for that as well. And an excellent discussion.

I would add to the last part that the larger planets could be taken apart by space elevators as well. They'd just start with the upper atmosphere; then work their way down. All the time the mass is getting smaller, and the elevators are pulling mass out so they can make themselves bigger in order to reach deeper. I think it's workable, and appears to be the most efficient way to do it--get the mass all out into "orbit" first. Actually, when you're about halfway done you can then start shipping what you mine off to other locations, and taking that amount of mass out of the elevators as well since they won't need to counterbalance as the planet's now smaller. (I don't know what the mathematical "middle point" where you start dismantling the elevators actually is--it could be something other than 50%.)

We could have "planet splitter seeds" which we shoot off to other stars, and they start with a tiny, correctly-placed elevator and build more of them as fast as is physically possible; the seed would be smart enough to calculate all the masses and start with the most effective one that would lead to the earliest date at which the entire mass of the star system is being used for computation.

The only problem is if we encounter life. Will our machines just assimilate it? Are the ones out there programmed to preserve us? Have they already done so?

Re:Why do dark matter found

[BlackHawk-666]

Perhaps Michaelson and Morley can give them a hand with this experiment, after all, their ether search went so well.

Re:Why do dark matter found

[BlackHawk-666]

The only problem is if we encounter life. Will our machines just assimilate it? Are the ones out there programmed to preserve us? Have they already done so?

What do you think happened to the dinosaurs?

Re:Why do dark matter found

[Anonymous Coward]

all of the evidence for dark matter could be equivalently explained by changing the force law.

Today is your lucky day! Today, Thomas, your brain gets to overload and possibly melt down because there is a third opinion! Hint: ZPE ain't necessarily constant, and that has quantum consequences on a large scale.

Re:Why do dark matter found

[iii_rjm]

Dyson spheres do not collect everything. There is still gravity and gravity is what this whole thing is about.

Re:Why do dark matter found

[Anonymous Coward]

I'm in agreeance with this guy, dark matter is dynamical

Re:Why do dark matter found

[Christopher Thomas]

And perhaps they got a head start on us, and that large percentage of "dark matter" actually consists of Dyson Spheres which capture everything, so are "undetectable" by us.

Two problems with this scenario:

• The spheres would be detectable in non-visible bands. Even a Matrioshka style nested dyson sphere would have an outer temperature above the microwave background level (and would in fact stick out like a sore thumb in the microwave background surveys). In practice, you quickly run into diminishing returns with mass vs. power flux, so a Matrioshka's outer shell would be somewhere in the intermediate IR range. So, you'd get what looked like a red supergiant, only more so (IR super-duper-giant).
  
  
• Most of the dark matter is "non-baryonic". While the astrophysics version of the term has a different meaning than the particle physics version, it still means that whatever dark matter is, most of it is _not_ the kind of matter we're familiar with. It has to be something that doesn't interact via the EM force (hence the focus on EM-neutral particles that interact via the weak nuclear force, mainly because that's the easiest type to detect once EM is ruled out).
  

I hope this clears things up.

Re:Why do dark matter found

[Thing 1]

Is it possible that advanced civilizations might produce something similar to superconductors but on an EM basis? In other words, the outer shell of their Dyson spheres might mop up the rest of the emissions so that there is nothing for us to detect?

The other response mentioned gravity. We are currently doing experiments with gravity. Perhaps in the future we'll figure out how to contain it?

Yes, I'm appealing to essentially the same forces that religious folk appeal to when they attempt to explain God to you. And I definitely do not understand all the physics and maths involved. However, I stand by my potential correctness(?). More things than Horatio and all that.

Re:Why do dark matter found

[Christopher Thomas]

Is it possible that advanced civilizations might produce something similar to superconductors but on an EM basis? In other words, the outer shell of their Dyson spheres might mop up the rest of the emissions so that there is nothing for us to detect?

The problem is that no matter what you do, power that is produced inside the sphere ends up as heat eventually. If it flows out through the outermost sphere, the sphere radiates in a detectable band. If you somehow prevent radiation from the outermost sphere, the inside of the system heats up (and keeps heating up, as the central star keeps pumping out energy).

In practice, there is no known way to keep the sphere from radiating in a steady-state system. You could dump all of your emissions as a narrow beam in one direction, but that would only make you _less_ detectable, not invisible. You could keep a pet black hole and dump thermal emissions into it, but a black hole with an event horizon large enough to be useful for this task would weigh as much as the galaxy.

So, if a dyson existed, it would be visible, unless currently-known physics is grossly incorrect.

(And if you're proposing changing physics, it's easier just to propose a change that removes the need for dark matter :)).

The other response mentioned gravity. We are currently doing experiments with gravity. Perhaps in the future we'll figure out how to contain it?

Gravity does not appear to be something that can be contained, even in principle. One of the particle physics professors in the audience can give you a more detailed explanation of why than I can. Short version is that it's just the nature of the kind of field we think gravity is.

A shell of negative mass around the system (of magnitude equal to the system's mass) would remove its gravitational effects, but negative mass is almost certainly not compatible with the universe as we know it. This falls into the "changing physics" category :).

To sum up, while it's possible to make dyson spheres that are _difficult_ to detect, they'd still be detectable, especially if present in great enough number to explain the baryonic component of dark matter (non-baryonic component can't be explained by dyson spheres, detectable or not).

I hope this helps.

Re:Why do dark matter found

[Thing 1]

Thanks for the response. I like the idea of sending emissions in a narrow beam, perhaps they're all dumping emissions toward the outside of the galaxy? Then it'd be difficult for galactic citizens to detect, and intergalactic citizens would take a while to get here. ;-)

Of course, those stars near the core would have to dump emissions toward some part of this galaxy, so that's perhaps not as effective an argument. Although they could dump "up" and "down" as it's much narrower, and since we're out on one of the unfashionable arms we wouldn't be able to detect it.

Again, thanks for enlightening me!

20 times 0...

[aaribaud]

... would be the efficiency of the experiment (assuming it would fail the same way as this one), not the sensitivity of the equipment used.

20 times Zero?

[kortex]

In this case I'm willing to bet the answer is................42

Thanks

[Anonymous Coward]

I was wondering how this story was going to be tied into SCO or Microsoft.

The obvious solution

[fiannaFailMan]

All they have to do is reverse the polarity of the anti-proton injectors in the warp core, re-route the resulting subspace pulse through the plasma conduits, synchronise the comm-system to transmit the frequency of the subspace distortion field to the deflector dish and emit a sub-tachyon particle scan over a wide area. That'd surely reveal what they're looking for!

Re:The obvious solution

[JaxGator75]

Pshaw... Like they didn't already try THAT ...

Re:The obvious solution

[Anonymous Coward]

That's just going to emit a Crimson Shield.

He is smart. He can make it go.

Re:The obvious solution

[iggymanz]

yup, the 3 tv generation have learned all of lifes problems can be solved by technology in 60 minutes less commercial interruptions & station identification.

Re:The obvious solution

[Barryke]

No, its like this.

For real. Learned it from thé Men in Black (MIB)... see:
----------
EDWARDS

So who pays for all this?
KAY

Oh, we hold a few patents on gadgets we confiscated from our out-of-state visitors.

Velcro. Microwave Ovens. Liposuction.
----------

Re:The obvious solution

[G-funk]

"Mista Spock ser! It jest might werk!"

"Shit worked last week motherfucker!"

I "detect" someone jumping to conclusions

[Vellmont]

That the sensor has never detected something doesn't tell you that it's working or not working - or am I am missing something here?


Yah, you're missing the scientific paper. This is a one page write-up written by a journalist. The one page write up doesn't describe how they know the detector works, but I'm sure they have _some_ means of testing that it does. Blame the article, but at this point you can't really accuse anyone of doing shoddy science for grant money.

Re:I "detect" someone jumping to conclusions

[Uber Banker]

The one page write up doesn't describe how they know the detector works, but I'm sure they have _some_ means of testing that it does.

Sure they do... the system has a green light on. If the red light were on it would be on standby and no light may mean there is no power, or the light is broken. But as long s the green light is on they know it's working.

Surely everyone knows that. Now please increase my grant.

Re:I "detect" someone jumping to conclusions

[Tackhead]

> Sure they do... the system has a green light on. If the red light were on it would be on standby and no light may mean there is no power, or the light is broken. But as long s the green light is on they know it's working.
>
>Surely everyone knows that. Now please increase my grant

You forgot the third possibility. Suppose the power indicator LED is orange: it's hard to tell if we're in a superposition of states or merely oscillating very rapidly.

Or I just want a high-speed digital camera for Christmas.

Re:I "detect" someone jumping to conclusions

[Dun Malg]

You forgot the third possibility. Suppose the power indicator LED is orange: it's hard to tell if we're in a superposition of states or merely oscillating very rapidly.

...or that some bonehead wired the unit up to 24VAC instead of DC....

Re:I "detect" someone jumping to conclusions

[Tackhead]

> > You forgot the third possibility. Suppose the power indicator LED is orange: it's hard to tell if we're in a superposition of states or merely oscillating very rapidly.
>
> ...or that some bonehead wired the unit up to 24VAC instead of DC....

Fifth possibility. How about 24VDC and no current-limiting resistor? It may not be observed for very long, but it will be observed as orange...

Re:I "detect" someone jumping to conclusions

[darkonc]

.... you can't really accuse anyone of doing shoddy science for grant money.

Sure I can! I do it all the time.
Sometimes, I'm even right!

Re:I "detect" someone jumping to conclusions

[lord merlin]

Do you also have a machine that goes 'Bing'??

It makes it a ...

[Anonymous Coward]

/.'er!

Some thought...

[Anonymous Coward]

Does mass exists because of gravity or gravity exists because of masses?
I think gravity is the single fundamental force, it's just someone needs to explain this statement well enough.

Does space bends or does light bends?
I think light bends, not space, as in concordance to gravity doing its stuff due to its nature as the more fundamental existance.
Maybe Einstein is right about that one constant he is keeping..

-an EE gradstudent...

What's 20 times 0?

[Animus Howard]

Dunno. But 20 divided by zero is &)%*$%*_))[LOST CARRIER]

Re:What's 20 times 0?

[Barryke]

It took me a while but i found it, its halfway down.
2writer: You freak! you actualy looked up the episode # cq webpage?

[snip] Bart: But I have 52 million shares! What's 52 million times zero? AND DON'T TELL ME IT'S ZERO! [snap]

Re:What's 20 times 0?

[duggy_92127]

I'm completely serious here, this joke with NEVER get old, not as long as there are those of us who remain who have ever actually seen a "NO CARRIER" message. I salute you, sir!

Doug

The search Continues

[Anonymous Coward]

Maybe the search for missing matter should be included to add Iraqi Weapons of "Mass" Destruction...

Mod down

[Anonymous Coward]

Don't give known-trollers karma

ObBart

[sharkey]

1:00 - Still just a potato.
2:00 - "
3:00 - "

Maybe....

[AviLazar]

the wimp is hiding in fear?

-A

Comment removed

[account_deleted]

Comment removed based on user account deletion

Not completely zero

[kyoko21]

I am not a physics/math expert, but assuming that dark matter does exist, it only proves that the equipment currently used has a sensitivity that is approaching zero, but not zero. But anyone who has seen a graph of an asymptope, it is not very promising especially if you push x approaching infinity. Even if you were to multiply x by 20, while you are out to infinity, by not knowning where exactly they are relative to the origin on the graph, a factor of 20 may not be all that significant... :-/

But at least they are still trying... and trying... and trying some more.

Re:Not completely zero

[Mikeface]

Hmmm... interesting stance - I don't see any tigers, therefore my eyes are not sensitive enough to see tigers.

An important fact regarding CDMS is that Dark Matter direct detection experiments are only just beginning to probe the sensitivities required to observe Dark Matter, according to the theorists. The most popular WIMP candidate, the neutralino, is predicted to exist anywhere from an order of magnitude above CDMS's current sensitivity, down to several orders of magnitude below. The WIMP is well-motivated, and sure - it might not exist - but that will tell us at least as much about the universe than if we were to find it.

Re:Not completely zero

[kyoko21]

Good point. The exact thing that we maybe looking for could be just a flawed theory all together.... :-/

Well, if it is...

[Pi_0's don't shower]

I hate to say it, but CDMS II (this experiment) was SUPPOSED to not find WIMPs in this range. There was an experiment called DAMA which had found a modulation in their noise consistent with their being WIMP dark matter, and they claimed detection. The whole purpose of this press release is to say that DAMA's claimed detection is now *ruled out*.

As for the description of gravity being incorrect, I hate to tell you this, but general relativity solves *so* many problems that cannot be solved otherwise that it's preposterous at this point to consider anything else. Gravitational lensing, bending of light by masses, binary pulsar decay, Mercury's perihelion precession... etc. etc... NO other theory of gravity explains any of this, unless it starts with General Relativity and expands on it.

As for your proof that there is no dark matter because it's there in small quantities in three (out of ~250,000) galaxies, give me a break. Normal matter clumps and interacts with itself, so it's quite reasonable to expect we will get some cases where we have more normal matter than dark matter.

On average, though, Dark Matter is well known (see my comment history for examples) to exist in about 6-7 times the abundance of normal matter.

Sorry if this is a rant, but talk about throwing the baby out with the bath water...

Re:Well, if it is...

[websensei]

general relativity solves *so* many problems that cannot be solved otherwise that it's preposterous at this point to consider anything else

while I agree that the case for GR is pretty compelling, this same line of thought is why it took so long for ptolemy's ridiculous (in hindsight) orbits to be debunked. "but they solve so many problems that cannot be solved otherwise that it's preposterous to consider anything else"... ditto for many other "givens" (sun circles the earth, etc) in history. my point is that a scientific mind is always prepared to be repeatedly shown completely wrong - and in fact delights in this process, as it moves understanding closer to fullness. /$0.02

Re:Well, if it is...

[trentblase]

Gravitational lensing, bending of light by masses

Not that I disagree with you, but aren't those the same thing? Well, I guess you have no problem repeating yourself:

etc. etc...

Re:Well, if it is...

[EvilTwinSkippy]

A if more scientists were of the scientific mind. More often it seems they go in expecting to see a specific outcome.

What do you exect from a field dominated by researchers.

Re:Well, if it is...

[blincoln]

As for the description of gravity being incorrect, I hate to tell you this, but general relativity solves *so* many problems that cannot be solved otherwise that it's preposterous at this point to consider anything else.

Newton's physics accurately describe a lot of things - and are still very useful - but they are *not* a correct description of the way the universe really works.

General Relativity is the same way. It accurately describes many things, but eventually it will be superceded by a more complete theory.

Re:Well, if it is...

[Anonymous Coward]

Still, Simon's point is valid:

There are either WIMPs, or relativity is wrong. It doesn't have to be completely wrong; it just doesn't account for this 'missing' matter/gravitation effect.

Notice the substitutions:

As for the description of motion being incorrect, I hate to tell you this, but newtonian physics solves *so* many problems that cannot be solved otherwise that it's preposterous at this point to consider anything else. Newtons laws of motion, equal and opposite reaction... etc. etc... NO other theory of motion explains any of this, unless it starts with newtonian physics and expands on it.

Newton was almost right, but some things were not explained, and Einstein's theories fixed the errors that people were observing in actual data.

Now, we are in a situation where observed data does not match theory again. Maybe the observed data is wrong, or maybe the theory is wrong. Is that so hard to accept?

Re:Well, if it is...

[shadowbearer]

I think it would probably be more accurate to say that GR will eventually be incorporated into a more complete theory, not superseded. GR has been tested to nine nines - Newtons theories were tested and found wanting, and GR has not been, indeed every more sophisticated test we can device confirms it to a deeper level.

IMO whatever is going is probably independent of GR and possibly related more to our poor understanding of how the universe is shaped and how that affects observations over large distances and deep time.

Ob: IANAPP

SB

Re:Well, if it is...

[Stalyn]

I hate to say it, but CDMS II (this experiment) was SUPPOSED to not find WIMPs in this range. There was an experiment called DAMA which had found a modulation in their noise consistent with their being WIMP dark matter, and they claimed detection. The whole purpose of this press release is to say that DAMA's claimed detection is now *ruled out*.

Maybe I'm confused but in the article they use words like incompatible and inconsistent with DAMA. The also say this is the new limit on WIMP-nucleon scalar cross section. So apparently unless I'm wrong.. which I probably am CDMS II went further then DAMA and didn't find anything. Anyway check out fig. 5, and if I am wrong an explanation of it would be nice.

Re:Well, if it is...

[Stalyn]

i'm an idiot i confused now with not... stay off the drugs man

Re:Well, if it is...

[ion_]

As for the description of gravity being incorrect, I hate to tell you this, but general relativity solves *so* many problems that cannot be solved otherwise that it's preposterous at this point to consider anything else. Gravitational lensing, bending of light by masses, binary pulsar decay, Mercury's perihelion precession... etc. etc... NO other theory of gravity explains any of this, unless it starts with General Relativity and expands on it.

The theory of relativity works very well in large scale, but it doesn't work in small scale, i.e. the subatomic particle scale. It and the quantum field theory simply refuse to work together. That's why a general theory of everything is needed.

One very promising theory is called the string theory. I recommend exploring the website, it's very interesting reading.

No events != 0 sensitivity

[Shurhaian]

Wow, what a suprise, hyperbole in the Slashdot summary.

The fact that the detector hasn't found the thing it was designed to detect doesn't mean that it has a zero sensitivity or that the hypothesis is bogus(you can't readily prove a negative except by proving a contradictory positive), just that, in the finite time it's been running, it hasn't been sensitive ENOUGH to detect anything. 20 x 0.00000000000000000(you get the picture)001 is still an improvement, and may be enough to make progress.

Re:No events != 0 sensitivity

[Muttley]

Still, the original post has merit. They haven't detected a WIMP particle within the sensitivity of the original experimental device, and now they want to make it bigger. What if they still don't register WIMP events? Why didn't they make detector big enough in the first place? One could easily say 'they couldn't know how big it needed to be until they built it', but you can't endlessly get grants for 'bigger', you also need 'smarter'. They should also be looking at different experimental methods. An example of great experimental physics is the Neutrino Detection Facility at Kamiokande(Nobel Prize 2002)

Re:No events != 0 sensitivity

[Shurhaian]

This is certainly true. Obviously, common sense needs to be applied. The only point I was initially trying to make is that the "20 times zero is what?" comment in the post was at best an exaggeration.

There definitely comes a point where these people should be told to fund it themselves if they're so keen on it, but a lack of results does not in and of itself guarantee that the notion is unsound. A whole bunch of conflicting results is another matter, but a lack of evidence isn't statistically significant(sample size is zero).

Actually, I take that back. The sample size of this technique is insufficiently large to reject the hypothesis on a result of zero. Given that it's made to detect inherently rare events, a size of 0 would be within its data scatter. There's probably a point at which they can state that if they're not detecting WIMP interactions, then WIMP - at least alone - can't account for all of dark matter(or the proportion they thought it did according to the hypothesis). They might be some of it, but other things will then need to be looked at.

In short: It's possible for a limit value(in this case, zero events) to not be statistically significant. Consider it as a truncated normal curve, with 0 within a few standard deviations. You have two basic ways to avoid the insignificant limit problem: increase the mean value, or decrease the standard deviation. The former is possible by making a more sensitive detector(which could simply be bigger), the latter by making it more precise(which would probably mean, among other things, covering a MUCH larger area and likely multiple sites, and is in general harder to accomplish if you aren't even quite sure what you're looking for outside of unproven math).

So, while WIMPs wouldn't be disproven by a lack of results, it could eventually be stated that, since a count of zero is no longer within the variance of the hypothesis and the instruments used to test it, a persistant zero count would mean that the WIMP count is significantly lower than the prediction of the hypothesis, so the hypothesis would need to be revised.

Have you seen my matter?

[corporate_ai]

I was flying from Cleveland to New York recently and put a large quantity of dark matter in my suitcase. When I got my suitcase from the baggage area, the locks had been busted open and my dark matter was gone! So either it violated a new FAA security rule or one of those baggage guys ran off with it. Either way, I guess these guys won't be able to help me find it.

Soudan Mine

[swb]

The observatory is at one of the lowest levels of the Soudan Mine in Northern Minnesota. It's open for tours, including a mine tram ride to an ore extraction site, and a quick glimpse of part of the CDMS labs at the bottom of the mine. I wish they offered more extensive tours of the labs, and maybe they do, but not on the weekend I was there.

If you're in the Ely area, it's definitely worth a quick side trip to see the mine.

Re:Soudan Mine

[shadowbearer]

I've been there also, and it's a fascinating place. It was a lot of fun to be able to talk to a couple of the scientists there - briefly :(

This page has some more info and a contact number. It's well worth a visit if you are in the area.

If you have time, don't forget the fishing pole, either - there is some fantastic fishing, canoeing and hiking in the area. Just go before the bug season starts, or you'll come back short a few pounds of flesh :)

SB

Another Hare-Brained Idea

[Undefined Parameter]

So... between reading this blurb (haven't gotten to the actual paper yet, and I'm not sure I'll understand it when I do) and the article about the shape of the universe, I'm starting to form a hare-brained idea of my own.

What if the entire damn universe consists of matter and energy trapped within an unimaginably large black hole? I mean, it's probably just wishful thinking, but it might make sense... the shape of the universe, if roughly true in the article about it, would make sense if the universe as we see it formed the portion of the black hole not lumped(?) at the relative "bottom." All the energy is going back to the source (the main part of the black hole), all the mass returns to that source, etc. The stuff "below us" seems to be accelerating away, and the stuff "above" us is blue-shifted because it's coming toward us from the edge of the universe, so to speak. All this "extra" gravity stuff would just be the gravitational effects of the main mass of the black hole drawing everything back in; whenever everything went back to being lumped together, there would be an explosion, again (so much energy & mass, with no place to go!), and another black hole universe gets started, again. Given the way water, when caught by gravity, goes down a drain (in that spiraling motion), it may explain the proportions of red-shifting galaxies to blue-shifting ones.

Anyhow, like I said, it's another hare-brained idea... and I'm probably not the first to come up with it.

(One last thing--I'm a history major, not an astrophysics major, which is why I say it's a hare-brained idea. I have relatively little knowledge and understanding of astrophysics and the universe, when compared to those who've been and studied the field for so long (the guys who write papers like these, or papers discrediting the theories made by the guys who write papers like this one.)

~UP

Re:Another Hare-Brained Idea

[lars-o-matic]

The basic idea is not hare-brained at all. In "classical" General Relativity, it is equivalent to asking whether the universe is closed (i.e. there's enough matter / energy in it to halt & reverse the expansion, eventually, into a Big Crunch) or open (will expand forever into the Big Cold).

Your speculation about stuff above/below us is considerably less established in the literature. :-)

Claims & disclaimers: I studied physics years ago, but never at the level of the article.

Re:Another Hare-Brained Idea

[Roger W Moore]

What if the entire damn universe consists of matter and energy trapped within an unimaginably large black hole?

Then is a pretty damn strange black hole since all the evidence so far indicates that the Universe's expansion is accelerating not slowing down and Black Holes should not rapidly expand without lots of mass being added to them, which, as far as we know is not happening to the Universe.

Re:Another Hare-Brained Idea

[Patrik_AKA_RedX]

Scientific American wrote about a simulare idea like this.

Re:Another Hare-Brained Idea

[shaitand]

"which, as far as we know is not happening to the Universe."

While that statement is true, you neglect to mention that we really wouldn't have the slightest clue if it were.

We can't even claim with a straight face we have more than almost zero fact based imaginings we are even aware of the size of the Universe.

We can't even see all that we ARE aware of at present.

And the last thing we can do is claim that there isn't mass being introduced somewhere.

Re:Another Hare-Brained Idea

[Undefined Parameter]

Then is a pretty damn strange black hole since all the evidence so far indicates that the Universe's expansion is accelerating not slowing down[....]

That still fits in my scenario--who says that the Universe isn't accelerating back toward the main part of the black hole?

~UP

Re:Another Hare-Brained Idea

[Roger W Moore]

We can't even claim with a straight face we have more than almost zero fact based imaginings we are even aware of the size of the Universe.

Actually the amazing this is that we CAN claim to be aware of the size of the universe! Since everything is accelerating away from us as the Universe apparently expands we can extrapolate this expansion back in time until all the matter in the observable Universe was at a point i.e. the Big Bang. Since we now have a time when the Universe began we now have a maximum size limit for the Universe ~ speed of light x age.

And the last thing we can do is claim that there isn't mass being introduced somewhere.

Well that is not quite true. We can observe a tremendous amount of the Universe and we see no evidence for mass being created since creating mass from nothing would violate probably the most fundamental law of physics, namely conservation of energy. This conservation law is caused by invariance of all the physical laws (that we know of) under spatial translations. So in order to create matter/energy you would need to introduce a new physical law that does not hold the same for all spatial coordinates.

So while we cannot categorically rule out mass being created somewhere in the Universe it requires lots of new physics for which there is absoulely no evidence. Thus it is far more likely, given our current understanding, that mass is NOT being created and added to the Universe.

Re:Another Hare-Brained Idea

[shaitand]

"Actually the amazing this is that we CAN claim to be aware of the size of the universe! Since everything is accelerating away from us as the Universe apparently expands we can extrapolate this expansion back in time until all the matter in the observable Universe was at a point i.e. the Big Bang. Since we now have a time when the Universe began we now have a maximum size limit for the Universe ~ speed of light x age."

I said based on almost no facts, you haven't said anything here which challenges that. The big bang is a theory, that makes any facts determined based on when it happened a theory also. Your basing the starting point on pure theory. There are no facts in anything you've just said. And you certainly can't presume to impose proofs which rely on another contradictory theory on his theory.

"until all the matter in the observable Universe was at a point"

For a second let's pretend to give you the big bang. Now, you say we determine this from knowing when all matter we can presently observe was at a single point based on the rate of theoretical expansion that may or may not be happening. No matter how far we've looked, and been able to look, we've found more universe. So wouldn't it be fairly reasonable to believe it might just be a tad arrogant to believe that how far we can presently see is as far as can be seen?

And if so, what about the time it takes for the rest of the matter we CANNOT see yet to get back to this single point of yours? Ok, so now we've discovered that both the method by which you propose to gauge the size of the Universe and the Age are full of holes. And as you propose them are Paradoxically reliant upon one another. How can you determine the size of the universe by determining how long it would take for all of it to be retracted back to a single point, when you don't know the size and thus how far it stretches to begin with? Further how do you know the Universe expands at a constant rate (if it expands)?

If it accelerates, what makes you believe it accelerates at a constant rate. Unfortunately physics in the present day is full of these kinds of holes at almost every turn and is pretty shakey at best.

"Well that is not quite true. We can observe a tremendous amount of the Universe and we see no evidence for mass being created since creating mass from nothing would violate probably the most fundamental law of physics, namely conservation of energy. This conservation law is caused by invariance of all the physical laws (that we know of) under spatial translations. So in order to create matter/energy you would need to introduce a new physical law that does not hold the same for all spatial coordinates."

Yes, we have observed a tremendous amount of the Universe, relative to our perception of it. A field mouse on a hill might believe he's observed the entire world, or most of it, but that hardly makes it true. We have no way of knowing in fact the size of the Universe, and therefore have no way of knowing if that portion we know about constitutes a billionth of a percent of it, 50%, or even no percent in an infinite universe.

Further, nobody has proposed creating mass from nothing here, someone has however proposed that mass from another location is moved to this location. That in itself violates none of the fundemental laws of physics that I'm aware of.

"So while we cannot categorically rule out mass being created somewhere in the Universe it requires lots of new physics for which there is absoulely no evidence. Thus it is far more likely, given our current understanding, that mass is NOT being created and added to the Universe."

Odd, I was under the impression that about the only thing in physics we could be absolutely sure of was that mass was at one point created. After all it had to come from somewhere right?

Re:Another Hare-Brained Idea

[Roger W Moore]

I said based on almost no facts, you haven't said anything here which challenges that. The big bang is a theory, that makes any facts determined based on when it happened a theory also. Your basing the starting point on pure theory. There are no facts in anything you've just said. And you certainly can't presume to impose proofs which rely on another contradictory theory on his theory.

Actually the Big Bang theory is based on lots of facts, for example the cosmic microwave background. Saying that because it is a theory means that its not true is an illogical argument. All physical laws are "theory" - we just tend to believe that the "theories" with experimental data to back them up (like the Big Bang). However they remain theories since we cannot test them under all possible circumstances. The Big Bang is by far the best theory that we have to explain all the data so far. Could there be a better one - possibly - but that is not guarenteed and so until and unless someone comes up with it the Big Bang is what we believe.

For a second let's pretend to give you the big bang. Now, you say we determine this from knowing when all matter we can presently observe was at a single point based on the rate of theoretical expansion that may or may not be happening. No matter how far we've looked, and been able to look, we've found more universe. So wouldn't it be fairly reasonable to believe it might just be a tad arrogant to believe that how far we can presently see is as far as can be seen?

No because we actually believe that we have seen the "edge" of the Universe - it's the cosmic mictowave background. To my knowledge there is no other theory out there which can explain this and the prediction and subsequent observation of fluctuations (which using Big Bang models give dark matter consistent with galactic rotation speeds) adds lots of weight to the Big Bang's believability.

Further, nobody has proposed creating mass from nothing here, someone has however proposed that mass from another location is moved to this location. That in itself violates none of the fundemental laws of physics that I'm aware of.

It does when you are talking about the universe. Where is this other location? By definition it has to be outside the Universe and, currently, that is a physical impossibility.

Odd, I was under the impression that about the only thing in physics we could be absolutely sure of was that mass was at one point created. After all it had to come from somewhere right?

I'm using energy and mass interchangeably here. You can convert one into the other but that's all. There is no know way to create new energy/mass.

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[account_deleted]

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Mod parent -1 Offtopic

[Anonymous Coward]

This is more offtopic that than CowboyNeals ass.

Unusual science

[Control Group]

I freely admit to not being a physicist, cosmologist, or astronomer. However: when Einstein formulated general relativity, he discovered that his model demanded either an expanding or a contracting universe. Since he "knew" the universe to be static, he introduced the cosmological constant to "fix" the model. Later, of course, when Hubble (I think?) demonstrated the universe to be expanding, the cosmological constant was dropped, and Einstein referred to it as his greatest mistake.

This research, though, seems to be taking the same route: rather than questioning the model, they continue a so-far fruitless search for the "missing matter." If the model demands something the existence of which we are completely unable to verify, shouldn't we be questioning the model? Doesn't the very fact that there's all this "missing" matter indicate that perhaps our understanding is flawed?

Or am I just displaying rampant ignorance of the current state of physics and cosmology by asking this?

Re:Unusual science

[rblum]

You might want to read up on VSL theories. They do make sense of the cosmological constant, and they solve several other problems. Homogeneity amongst them, which, AFAIK, is a rather big deal to cosmologists :)

It's not proven or anything, and it competes with inflation theory. But it looks like it might be experimentally verifiable, as opposed to inflation.

Re:Unusual science

[jpflip]

It's true we should consider the possibility that our model of gravity is wrong, and some physicists are working on just this idea. The thing to remember is that there isn't just one observation that general relativity and dark matter are meant to explain - there are an enormous number of different kinds of measurements, ranging from star orbits to gravitational lensing to the abundances of light elements in the universe. It's actually very difficult to tweak (or even completely rewrite) our gravitational theory in such a way that it does away with dark matter and yet makes all the observations work so precisely. It might be true that our model of gravity is wrong, but dark matter is actually the SIMPLEST explanation we know of for the amazing stuff we see in the universe, not some kind of weird idea that's getting ruled out.

Re:Unusual science

[stand]

This research, though, seems to be taking the same route: rather than questioning the model, they continue a so-far fruitless search for the "missing matter." If the model demands something the existence of which we are completely unable to verify, shouldn't we be questioning the model? Doesn't the very fact that there's all this "missing" matter indicate that perhaps our understanding is flawed?

We know the missing matter is there because we can verify it. One example of how we know is that we can measure the rotational velocity distribution of a spiral galaxy as a function of radius from the center. We can also measure the luminosity distribution. Given the latter, and the fact that we have a pretty good understanding about how stellar luminosity relates to stellar mass, we expect the velocity distribution to vary in a predictable way according to gravitational laws. This comparison indicates that there is a lot of mass in galaxies that doesn't produce any luminosity.

This is a case where independent measurements don't produce consistent results, not of a theoretical model failing to match up with measurements.

Re:Unusual science

[SEE]

You know, when our probes hit the sphere surrounding the solar system and reveal the entire cosmos beyond 250 AU is just an animated image on the shell of the Universe, you're going to feel awfully silly for believing in dark matter.

Of course, since Shiva will then destroy the world, you won't be feeling silly very long, which is a blessing.

Re:Unusual science

[jkantola]

... Einstein referred to it as his greatest mistake.

Einstein was a silly old joker and people are generally missing his point by quoting primarily these 'god does not throw dice'-oneliner's he'd probably forgotten before the end of the sentence. But I digress.

If the model demands something the existence of which we are completely unable to verify, shouldn't we be questioning the model?

That depends on the model :) Compare with the search for the Higgs boson for example -- the previous round of particle accelerators was able to conclude that the Higgs boson cannot be found with those equipment. So now they are building bigger ones, even as they cannot be certain that the new (amazingly expensive) accelerators WILL find the Higgs'. So why continue the search, why not scrap the model instead because so far there's no proof of it being the correct one? Because the Higgs model is so elegant, it makes so much more sense than many/most of the competitors that it remains worth pursuing, especially as the other models wouldn't be any easier/cheaper to verify/falsify.

Doesn't the very fact that there's all this "missing" matter indicate that perhaps our understanding is flawed?

Of course it does, but what are you driving at?

Our understanding is flawed, in the sense that we don't know which of the many candidates, or a combination of them, is the correct one for accounting to the 'missing' matter, which we know to exist by studying the motions of galaxies and assuming that the galaxies are governed by the same physics as a yo-yo.

But hey, at least we have candidates; and at least our models and theories are so darn accurate and applicable that we can even know about the 'missing' mass.

And anyways, you basically don't scrap a model for a lack of a better one. In fact, the only way a better model or theory can come into existence is by interpreting the best current model as a 'true' model for reality, and then checking for problems.

Re:Unusual science

[Anonymous Coward]

Compare with the search for the Higgs boson for example -- the previous round of particle accelerators was able to conclude that the Higgs boson cannot be found with those equipment.

Actually I'm fairly sure the calculations involving the Higgs boson suggest a range, if not a specific mass and it was known they would not be able to find it with current accelerators. One of the books I read about it had the author going off about the SSC (cancelled superconductor project) because it was likely going to be enough to detect it even if it hit the maximum bounds.

As long as you have an upper limit, building more and more sensitive machines to detect things is fairly reasonable

Re:Unusual science

[sharekk]

If the model demands something the existence of which we are completely unable to verify, shouldn't we be questioning the model? Doesn't the very fact that there's all this "missing" matter indicate that perhaps our understanding is flawed?

I used to say the same thing (mainly in relation to the undiscovered Higgs boson) but it is not unprecidented in physics. If you read up on the discovery of the neutrino it was also hypothesized and then shown to exist a ways later. There was an experiment where two particles were 'shown' breaking the laws of momentum. Fermi decided that it'd be much nicer to assume there was some invisible/undetectable particle moving in a third direction (thus keeping momeutum conserved) than to scrap the conservation law. He was proven right when the neutrino was discovered, as soon as equipment had improved enough to detect it.

Of course I'm sure there are lots of examples where things didn't pan out but it's not unreasonable to try to keep your nice equations intact.

Re:Unusual science

[Anonymous Coward]

If the model demands something the existence of which we are completely unable to verify, shouldn't we be questioning the model?

Sure. That's why we do experiments - to test the model. If we were going to just believe what the theorists came up with, we wouldn't need to do experiments at all. So we have this model which says that there's so much dark matter in the universe, we have a list of things that we think it might be, so we go and try to build detectors sensitive enough to see it.

If the theory says "you need to see 10 interactions per year in detector X for a particular kind of particle to be the solution to dark matter, and we see 0, then you need to go look for a new theory.

If the theory says that your detector ought to have 10 interactions per year, but it's only sensitive enough to notice 1000 interactions per year, or 1,000,000 or something, then you need to get better at building detectors.

That's the way physics works. We know that there isn't any unknown stuff within the sensitivity range of current detectors, or we'd have seen it, which we haven't. Any theory which required such stuff to exist has already been ruled out.

Too much herb...

[Saeed al-Sahaf]

Sorry, all this just sounds like wayyyyy to much Star Trek. Or too much herb...

Re:Too much herb...

[Hatta]

No such thing bro.

The answer lies on the other side of the aether

[eljasbo]

I am not a physicist, but I think the dark matter is a totally false idea fabricated to explain things we cannot explain with our current perception and knowledge of physics. It is similar to the aether idea that was fabricated to explain Maxwell's equations on a cosmological scale so they did not collide with Newton's theories. The more we figured out about the properties of the aether, the more magnificent it needed to be. Einstein realized that Newton's common sense laws were actually different than we perceived and rewrote physics by determining that the existance of the aether was incorrect, and what we observed was caused by relativity. I think the same holds true with dark matter. What we are observing is the effect of gravity traversing dimensions other than the four we normally encounter. The other eletromagnetic forces do not cross into these dimensions, but gravity does. This would also explain why gravity seems so much less powerful than the electromagnetic forces, it is spread out through multiple dimensions. We know there is a force somewhere and lots of it, but can see no evidence of it because it is beyond our perception. We only see the effect of gravity particles (gravitons) that are traversing into our dimension from the others. Perhaps there really is the aether all around us, and it is more spectacular than ever imagined. This aether would be multidimensional and be everywhere. We cannot see or cross the dimensions we are in into another one. But they are there on the other side of the aether. The gravitons pass right through it and that is what we observe.

Re:The answer lies on the other side of the aether

[Unnngh!]

1. modded funny? I don't think eljasbo was joking...

2. While I think your concept of dimensions sounds a bit flawed, I agree with your reasoning on dark matter. It is a convenient "hidden variable" to explain our lack of comprehension of so much else. While GR blew Newton's universal theory of gravity out of the water, and provides more accurate predictions, I would imagine a more complete theory of gravity will some day come along and do the same to GR.

Re:The answer lies on the other side of the aether

[citdude]

I feel like a broken record here. Here are the facts: we can see how much stellar matter is in a galaxy from its luminosity. We can see how much dust mass there is. Add those together to get the visible matter. Now, look at a rotation curve of the galaxy (this involves measuring redshift as a function of distance from the center of a spiral galaxy with its side facing you). In case you don't own a 10-meter telescope in orbit, it looks like a plot of f(x)=constant*x. The most logical explanation is that there must be some mass farther out beyond the visible edge of the galaxy to cause the outside to rotate as fast as it does.

Now, about this additional dimensions. You don't know what you are talking about. Adding gravitational dimensions is tricky because gravity very certainly follows the same 1/r^2 law that electric forces due (magnetic forces follow the 1/r^2 law relativisticly, making it seem like its 1/r^5th? I don't recall the exact exponent.). The reason gravity is so weak is because the gravitational constant G is much smaller that the electric constant k. End of story. It follows no 1/r^5 law. It is not affected by additional dimensions. The other dimensions that physicists speak of is IIRC in relation to the strong and weak (nuclear) forces that follows a 1/r^5 law and that bind nuclei together.

I also don't understand how you reintroduced the "ether" and your definition of dimension is obviously not the same as that used by physicists since you speak of crossing into dimensions like something from Sliders rather than just another eigen-direction.

Re:The answer lies on the other side of the aether

[pavon]

Now, about this additional dimensions. You don't know what you are talking about.

He was making a reference to string theory. One of the ideas thrown around by string theorists is that while the particles for the electromagnetic, and strong and weak nuclear forces can only move in our 4 relativistic dimensions, gravitons can move in many more of the 11 dimensions. This would explain why it is so much weaker than the rest of the forces, since it expands in so many more dimensions.

But if gravity is weak because gravitons are "leaking" out into other dimensions, then it makes you wonder why it wouldn't also leak in as well, which is the point he is getting at.

The reason gravity is so weak is because the gravitational constant G is much smaller that the electric constant k. End of story.

Constants are simply numbers that we have determined experimentally, and thoughout the history of science we have often developed new theories that explain why the constants are what the specific values they are. What we know about subatom particles today is most assuredly not the end of the story, and there is no reason to think that we won't someday discover explainations for why the different particles have different constants.

Re:The answer lies on the other side of the aether

[Phragmen-Lindelof]

"But if gravity is weak because gravitons are "leaking" out into other dimensions, then it makes you wonder why it wouldn't also leak in as well, which is the point he is getting at."
One idea is that the inverse square law is incorrect at great distances; look at the research of Georgi Dvali, for example. I think of this as being like a Brownian bridge (= a Brownian motion which starts and ends at specified locations) but I could be wrong.
You can call this string theory or M-theory if you like. The claims of the grandparent post are no more or less believable than mine (or any one else's claims) unless they provide (links to good) evidence.

Re:The answer lies on the other side of the aether

[citdude]

You clearly have no understanding of fundamental physics. Like I said the rotation curve is f(x)=x. This means that there MUST be some amount of mass outside of the visible galaxy or our understanding of everything (circluar motion and force) is fundamentally flawed to the point where nothing on Earth should make any sense.

Maybe it's just me, but I do not understand how dimensions can explain how matter can produce gravitational effects as if it were in ten places at once, in addition to where we see it. For every gram we see inside the galaxy we are measuring that ten times that amount must effectively be outside the galaxy by hundreds of light years. Explain that. And don't forget that the dimensions hypothesized by String Theory are all to small for us to detect at less than a micron wide (as opposed to nearly-infinite like the 3 spatial dimensions with which we are accustomed).

As far as how we can theoretically derive constants, I have no idea what you are referring to.

Scott

Re:The answer lies on the other side of the aether

[Phragmen-Lindelof]

"You clearly have no understanding of fundamental physics." Thanks for letting me know. My Ph.D. is in math (not physics) and I have not conducted research on cosmology so I do not claim to be an expert. I presume your Ph.D. is in physics or astronomy? I also assume you know differential geometry (and, perhaps, algebraic topology or some related areas of math) well enough to understand string theory?

"matter can produce gravitational effects as if it were in ten places at once" I do not understand this comment. Is this a comment about quantum mechanics or about Dvali's research or what? "... the dimensions hypothesized by String Theory are all to small for us to detect at less than a micron wide ..." This statement is misleading. Most, but not all, versions of string theory do assume this. (Once again, look at Dvali's recent publications.)

"As far as how we can theoretically derive constants, I have no idea what you are referring to." I did not refer to "theoretically derive(d) constants" and have no idea what YOU "are referring to."

It is difficult to take you seriously. Please give us a little background information about yourself. How many preprints do you have at arxiv.org? (I have none since my research is in applied math but not in "physics"; I do have about 30 papers including articles in Crelles Journal, Archive for Rational Mechanics and Analysis, TAMS, PAMS, PJM, etc.)

Re:The answer lies on the other side of the aether

[Anonymous Coward]

You clearly have no understanding of fundamental physics. Like I said the rotation curve is f(x)=x. This means that there MUST be some amount of mass outside of the visible galaxy or our understanding of everything (circluar motion and force) is fundamentally flawed to the point where nothing on Earth should make any sense.

Well, not quite. The choices are:

1. There's more mass out there. That's dark matter.

2. Gravity is not quite an inverse square law.

3. Something deeply funky is going on.

Number 2 is quite strongly disfavoured, hence the popularity of dark matter theories.

hehe

[imsabbel]

Considering the alternatives are MACHOS, i sense people who like creating funny acrynoms...

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[account_deleted]

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Missing Matter... Still Missing

[carlos_benj]

I didn't take it. I promise.

Does it matter if the matter is missing if the missing matter never mattered before?

mutter.... mutter....

1000x More Massive

[Anonymous Coward]

I'm confused ... I thought a proton had zero mass. How can this be 1000x more massive than zero?

Re:1000x More Massive

[citdude]

You are mistaken. Protons do not have zero mass. They weigh about 1.660538 × 10^-24 grams. Neutrons weigh slightly more (0.2% more) and electrons weigh much less (0.05% of a proton or neutron).

No, the answer is 1

[Anonymous Coward]

For suitably large values of zero.

Crawford math

[MoxCamel]

What's 20 times 0? And don't tell me zero!

I'd just like to be the first to say that it's an honor, Mister President, to count you amongst the Slashdot readership.

Wow

[Marvin_OScribbley]

I find this quote interesting...

[Dark matter] is thought to come from a variety of heavy particles that rarely interact with regular matter and can pass through conventional objects unseen.

That sounds like another phenomena of a less scientific nature... ghosts! In some belief systems spirits or souls are more massive or dense then normal matter as well.

If this were true, I would suggest the reason that this experiment didn't find any "dark matter" is because there wasn't any in the vicinity, because the organization and distribution of this dark matter is neither even nor random.

Astronomers believe this arises from the gravitational effect of 'halos' of dark matter around spiral galaxies. (source)

Together, these two results suggest, to me anyway, that dark matter could really be more advanced civilizations or intelligences that we know nothing about.

Re:Wow

[Anonymous Coward]

That sounds like another phenomena of a less scientific nature... ghosts! In some belief systems spirits or souls are more massive or dense then normal matter as well.

I guess. The difference is that scientists are examining something in the universe, and testing possible explanations for a fit. Any number of them, or even a regular Joe with access to the equipment and data can see it for himself.

None have yet produced any repeatable, measurable observations of ghosts.

Re:Wow

[Anonymous Coward]

None have yet produced any repeatable, measurable observations of ghosts.

Or any WIMPs, either. And we at least have anecdotal evidence of ghost observations. ;-)

Multi Dimensions?

[novakane007]

What are the implications if we can't detect the 'dark matter'? What if our understanding of energy and gravity are wrong? String theory promotes the idea of multiple dimensions. If that's the case than how would we be able to detect those dimensions? We can show their existence with mathematics, but it's quite possible that's it's beyond our current understanding to 'see/feel' it.

Re:Multi Dimensions?

[Chris Ashton 84]

One of the possible outcomes of string theory is multiple universes, each separated by a fairly small distance (of course this distance is in a higher dimension so we can't notice them). If these alternate universes do exist, it is thought that the gravity from particles in our universe affects the other nearby universes. Imagine our universe as a flat sheet and another universe is a parallel flat sheet close to ours. In this model, gravity would still be three dimensional - ie, it would be able to bridge the gap between universes and affect the other universe. Perhaps this is what we're noticing - the gravity of massive particles in another universe?

BTW, I am not a physist but I have read up on this stuff. The theory of gravity carrying over to other universes actually does make sense - it explains why gravity is so much weaker than the other forces, because much of gravity's effect isn't on this universe. There's experiments going on now to test and see whether this is actually the case but I don't know the outcome. Anyway, this is just my thought on perhaps why we can't detect the dark matter - because it's not physically in our universe.

Re:Multi Dimensions?

[Oligonicella]

"In this model, gravity would still be three dimensional"

Why, because it's convienent to leave it so?

"The theory of gravity carrying over to other universes ... There's experiments going on now to test and see whether this is actually the case..."

They're going to test to see if our gravity is leaking into another universe? A I>hypothetical" universe?

Re:Multi Dimensions?

[Chris Ashton 84]

If I remember correctly, if the theory holds then gravitational attraction from objects in our own universe would be very slightly reduced... reduced by an ammount much smaller than previous experiments could detect. The experiment was to check extremely precisely the gravitational attraction of an object, and see if it was actually reduced. Note that I read this a few years ago and haven't heard about any outcome so perhaps nothing has come of it.

Dark Matter?

[nr]

Is this Dark Matter the same thing as or related to anti-matter or something whole different?

Re:Dark Matter?

[painandgreed]

Is this Dark Matter the same thing as or related to anti-matter or something whole different?

Something compeltly different. Matter is dark because we cannot see it normally with telescopes. However, some dark matter might be anti-matter.

The basis for dark matter is that the galaxies are spinning and by how fast they are spinning and realative movements, we can figure out how much mass they contain. Yet, with telescopes we can only detect aobut 10% of the mass needed for make galaxies as massive as they are. Through various methods we can figure out how much normal matter (including anti-matter) might be around that we can't see because it's behind other matter, really dark, or otherwise undetecatble. This dark normal matter is only about another 10% of the mass needed. Thus we are needed much more mass to make up the difference.

Various explanations consist of superblack holes, exotic matter such as WIMPS, etc. one such solutions is MOND which says that our equations governing gavity need to be revised to match what we are seeing experimentally with the telescopes and other data. This theory has just as many problems as they others. Various phsysists have their pet theories but most seem to beleive there is mass or energy out there we cannot directly detect yet.

Re:Dark Matter?

[citdude]

Totally unrelated. Anti-matter is something we know about and something we can detect. Dark matter is something that we think exists. I suggest reading both of the above links if you are interested.

But wait a minute

[Billly Gates]

Only according to some sources 1/4th of the matter in the universe is dark matter. How can it not be undectable then if its this massive particle 1000x more dense then a proton?

I personally think its a lack of understand of space/time that creates the illusion of dark matter. The string theory could also prove that bends in the time/space contium alot like threades of lint in carpet exist. When light passes through them they amplify when they reach the bend.

There is alot of stuff in the 4th, 5th, and other dimensions that we do not know about.

Re:But wait a minute

[citdude]

Here is how it works. WIMPs are heavy. WIMPs are also neutral (like neutrinos) which means they will not react electromagnetically with anything so the only way to detect them is if they get close enough to a nucleus to react via the strong or weak nuclear forces. Now, if the atom were the size of a football stadium, the nucleus would be the size of a marble. Now hit that with a piece of wimpy lead shot from just the next galaxy over. You would need lots of luck too.

Read the first paragraph of this post for comments about additional dimensions.

Re:But wait a minute

[jpflip]

A particle is only detectable if it interacts with your detector - it doesn't matter very much if it's heavy or light. Matter is almost entirely empty space (think about the space inside an atom between nucleus and electron), and so a particle should just pass through atomic matter unless it "reaches out and grabs" the electrons or nucleus. Protons, electrons, and most ordinary particles do just this - they interact strongly with matter, either via electric charge or the strong nuclear force. Dark matter particles are expected to be like neutrinos, only heavier - they interact so weakly that billions can pass through your body every second and never interact.

yes, yes, yes

[rozz]

oh finally ... it's been such a long time since i had this feeling that something's missing from my life .. poor me, i always thought that would be some million $ from my bank account .. or lately, some /. karma

btw, when they find this wimps i plan to sue them and get some compensation for the years of stress they made me endure!

"Dark matter" sounds like

[mfago]

the search for "ether."

Lemme know when someone figures out what is really going on.

Fortunately, we have large quantities of ...

[burgburgburg]

protomatter.

Despite it being described as an unstable substance which every ethical scientist in the galaxy has denounced as dangerously unpredictable, I've found that it is the only way to solve certain problems.

Re:Fortunately, we have large quantities of ...

[My_Dirty_Facist_Ass]

Hehe; I hear Klingons are dangerously unpredictable too.

[kirk] I......HAVE HAD......ENOUGH OF........YOU!!!!!!! [/kirk]

Enron? Worldcom? Tyco?

[tacokill]

Do you work for Enron? If not, want a job?

We have an excellent "culture" for a person possessing your skillsets.

They're having trouble finding it

[CowboyShit]

cause they're using Windows!!!

Why is this important you may ask?

[kulakovich]

Think about an ion engine that is shedding WIMPs at nigh-luminal speeds.

kulakovich

Working detector?

[Anonymous Coward]

CDMS detectors detect heat (vibrational energy) which is deposited in their superconductors when any kind of particle flies in and hits them. The localized heat causes the hit region to go non-superconducting, and as a result they can measure a reduced current as would be expected from a normal conductor.

All sorts of particles are constantly flying in and creating signals in their detectors. This is how they know that it is working. The trick is to veto the known signals by surrounding their superconductors with other detectors which can detect ordinary matter, but not dark matter. Therefore if the other detectors tell you that some ordinary matter entered the superconductor, then you would reject that signal.

In the context of a dark matter flux (flow) measurement, greater sensitivity means a greater ability to detect low fluxes. So far they've measured 0 dark matter particles in a few years of running. This means that the flux is less than 1 particle per detector area per few years (also per detector efficiency).

Suppose the numerical value of their measurement is that the flux is less than 100/m^2/year (just to use round numbers). Then, if the true flux given to us by nature is 1/m^2/year, then they would have to run for another ~100 years in order to detect 1 dark matter event. On the other hand, if they make their detector 100 times larger, then they can detect the 1 dark matter event with only 1 more year of running. This is what they mean by increased sensitivity by building a larger detector. Meanwhile, in the time taken to see the 1 dark matter event, they probably reject several trillion false events which are caused by ordinary matter particles.

A. Physicist

Maybe the current theory is wrong.

[Jagasian]

Maybe there is no dark matter. Science only describe predicted observations. Reality doesn't necessarily obey the laws of science. Belief in such is similar to belief in a deity. Maybe the universe is governed by the laws of science, but then again, maybe it is governed by such-n-such a deity.

So if a theory isn't cutting it, then create a new model of whatever observation that you are trying to describe. It seems silly to try to fit nature to the theory, and not the theory to nature.

Re:Maybe the current theory is wrong.

[dustmite]

Could you tell us specifically which scientists believe any of the particular current hypotheses that attempt to explain dark matter? AFAIK scientists make hypotheses. They don't make up something and then say "I believe this", the make up something and say "maybe this is an explanation, maybe not, let's try come up with some tests to determine if it is". Can you please point out the "scientists" which have gone straight from hypothesis to true belief without the necessary step of some sort of experimental proof, or did you just make it up, or are you just confused about what "science" is because your understanding of it is derived from mainstream media articles?

These same guys are also looking for:

[Geekenstein]

The Northwest Passage
Cold Fusion
Perpetual Motion

and.....

*drumroll*

Dubya's Economic Policy

Just because you can't find something, doesn't mean you aren't looking hard enough, it just might not be there! :)

A Chem Lesson For All

[Anonymous Coward]

a proton, one of the particles found in an atom's nucleus

And here I thought that slashdot was above the USA Today, written at the 3rd grade reading level.

I over estimated you slashdot.

Try the dryer

[ad0gg]

Missing matter is in same place as my socks

Missing Matter...

[edxwelch]

Have they tried looking behind the cushions of the sofa?

It's hidden in the cave with Osama?

[Anonymous Coward]

He's got all our dark matter!

The bastard!

Basic assumptions may be wrong

[arminw]

The theory of dark matter is based on the assumption that the basic properties of the Universe have never changed over time. If the intrinsic properties of space itself HAVE changed significantly, then there is no need to postulate such a thing as dark matter. Scientists are very reluctant to accept new data that shakes their preconceived pet ideas to their foundations. It took over 200 years after Roemer first measured a finite light speed, for the majority of scientists to accept the fact that light did not get instantaneously from point A to point B, as was the belief for centuries. In the same way, the majority of scientists today refuse to even consider the idea that some very fundamental "constants" may have changed dramatically since the beginning of time. For example, the cause for the "Red Shift" of distant star light is traditionally attributed to the Doppler effect, and in light of that INTERPRETATION of the cause for an observed fact, (the shifted light) all sorts of cosmological observations are very difficult to explain. Humans (including scientists) like to assume that certain things stay the same for all time, but that is a fervently desired wish based on faith, not observed fact. It seems that in the physical universe, there is nothing as constant as change! AAW

Re:Basic assumptions may be wrong

[Anonymous Coward]

Dark matter is needed to make up the extra mass required by "early expansion" BigBang theories. If the expansion guess is wrong, then no extra matter is needed. Kinda ... w-i-m-p-s out ... hehe

Re:Basic assumptions may be wrong

[Mant]

Scientist assume things stay the same, unless they have some evidence to the contrary. This is just Occam's Razor (Entities should not be multiplied beyond necessity).

If you don't have evidence the constants change, and they are called constants becuase they have always been observed to be the same, don't start assuming they have been without evidence. It isn't about faith, you assume it has not changed based on the observed facts that nobody has seen it change. If there is evidence of change, you rethink your assumptions.

Sometimes new ideas do take a while to displace old ones, as there is indeed resitance to paradigm shifts in science. Sometimes for the all too human reason of disliking change and what you thought you knew being swept away. It's better than jumping on any new theory or assuming things never observed to change have done becuase it is convenient to current thinking.

If the basic assumptions are wrong, they will eventually be disproved under the weight of evidence, but they should only be thrown out at that point.

Re:Basic assumptions may be wrong

[skuban]

You point out the huge assumption whenever historical facts are attempted to be gleened from current data which is called Uniformitarianism. (Uniformitarianism, is the belief in the Uniformity Principal which states: that everything observed today is uniform with the past and therefore experiments done in the present can give answer to the past.)

I believe that another fundamental assumption has been overlooked with regards to Dark Matter and that is: the Big Bang.

"Now, wait a minute!" says the crowd "we know the Big Bang occurred." That's right - of course we know the Big Bang occurred because A) we looked and discovered Universe was expanding and B) we used Uniformitarianism to roll back the clock so to speak. Unfortunately, recent observations (with newer, more accurate instruments) have replaced the old ones and they don't fit the model quite as well. The universe is expanding but differently than originally thought and - well - it seems to make it all work we would need about 70% more mass than we can currently observe. The answer? Dark Matter.

That's right, Dark Matter. We can't see or observe it, but it must be there because our (theoretical) model says so and we're quite sure that a model created by scientists couldn't be flawed or even slightly askew.

Now this is that part that amuses me. If we are honest for a moment the theory of the Big Bang exists to remove the necessity of a supreme being. All religious issues aside, something had to get this crazy top spinning (Don't forget the Law of Conservation of Matter and Energy) so either A) a God/Higher Power/Supreme Being/Q (for the Star Trek fans out there) at least got the ball rolling or B) It got rolling by itself. Enter the Big Bang: there was nothing, then there was something, and then it exploded (because the something was RREEAALLYY dense).

If you don't see the humor yet, I'll lay it out here. Scientists are currently spending time and quality research brains, not to mention Millions of dollars trying to find something that can't be seen or observed so that they can rest assurred that something that they can't see or observe doesn't exist. :D

Re:Basic assumptions may be wrong

[lyphorm]

Nice essay. Too bad it's wrong. The theoretical model is continuously being revised to try and match it with what is observed. The term Dark Matter (and Dark Energy too) is just there to describe the discrepancies between the model and the observations. Some scientists are sure Dark Matter is real matter, but currently only detectable by its effects on other observable matter. Other scientists believe it is the physical model that is flawed and Dark Matter isn't matter at all. Both camps (and others) are trying to find evidence to support their case.

Of course the not-so-constant constant idea has come up, but so far there is no convincing evidence to support it.

The humorous part is how you made a bunch of assumptions about how science works, while chastising the scientists for making assumptions...

Re:Basic assumptions may be wrong

[stevelinton]

You're confusing dark matter with dark energy.

The evidence for dark matter is its gravitational effect on relatively small things like galaxies, which can be examined quite accurately by looking at the mov ements of stars, the distribution of dust and gas and so on. They all confirm that there is a lot of stuff in galaxies (and not in the space between) that we can't see, and give us a pretty good idea about how it is distributed within the galaxies and so on. It seems pretty clear that this really is matter, subject to gravity in the normal way, and fairly unaffected by things like magnetic fields. The only real question is WHAT KIND OF MATTER it is. People have suggested everything from "failed stars" not quite big enough to ignite to various kinds of new, heavy, stable and not very interactive particles.

Dark energy is much more mysterious, and can be viewed as just a name for certain basic properties of the Universe changing with time, or not working quite the way we thought. It is essentially just a name for whatever it is that explains why the expansion of the universe seems to be speeding up, rather than slowing down as expected.

Re:Darl Matter

[Anonymous Coward]

Since Herr Blepp (one of SCO Germany's managers) claimed that SCO's missing code is in his suitcase perhaps the dark matter is in there too?

BBC Got it Wrong

[Roger W Moore]

Just in case you got as far as the BBC article they got the dark matter percentage way off. It's actually about 23% that is dark matter. The 70% number is for dark energy which is a completely different beast which nobody yet really understands (at least to my knowledge) since it is actually gravitationally repulsive and is what is thought to be causing the Universe's expansion to accelerate.

The numbers come from NASA's Wilkinson Microwave Anisotropy Probe (WMAP) which measured fluctuations in the Cosmic Microwave background (afterglow of the Big Bang). There's a good review of their results in hep-ph/0308251 accessible from the LANL preprint server though it might be a bit technical for most.

Re:BBC Got it Wrong

[fizbane]

The BBC Article says that: "This form of matter comprises more than 70% of the Universe's mass, far more than the stars and galaxies we can see." This is technically correct. The WMAP results are that 73% of the energy density of the universe is "dark energy." The remaining energy density is matter. From galactic rotation curves, gravitational lensing, etc. we suspect that dark matter accounts for around 80% of the matter (mass) in the universe.

Re:BBC Got it Wrong

[Roger W Moore]

Actually even with that interpretation the result is still not 70%. WMAP shows that 4% of the Universe is baryonic matter and 23% non-baryonic matter. Thus ~83% of the matter should be dark matter, not ~70%. So with either interpretation the BBC result is still wrong.

Found it!

[jelle]

I found the missing matter.

It was in the black hole. Ask beavis and butt-head for details.

There is one problem though: It doesn't matter.

Maybe it's broken?

El Barto

[Anonymous Coward]

I didn't take it.
No one saw me take it.
You can't prove anything.

Thier detector may not have found anything...

[ifwm]

but my bullshit detector has been pinged since this dark matter nonsense started. I have yet to see a single piece of credible evidence that shows the dark matter hypothesis is anything more than a hastily concocted attempt to explain why some physicists theories don't jive with experimental results. Just admit that you don't know why, rather than attempting to pass off a clearly inferior piece of intellectual flotsam as the next great thing. Show me some evidence, ANY evidence, and then you'll get my money.

The missing matter was used...

[Arpie]

...to pack the new multidimensional version of the Hitchiker's Guide to the Galaxy. Douglas Adams clearly explains this in one of the books ("Mostly Harmless", I think).

Since this comes from a guy who know the answer to the question of "Life the Universe and Everything", (spoiler) I don't see why anyone is wasting time with that.

Note: Googling brought up The Ultra-Complete Index to the Hitch Hiker's Guide to the Galaxy, pretty cool.

There's an even better explanation!

[Anonymous Coward]

Well duh! Everyone Scientologist should know their cosmology, it's very simple.

As any Scientologist should know, this "missing" matter is really part of the Eternal Battery[1] used to power the electronic trap holding Xenu, the evil galactic overlord. It's somewhere here on Teege^W uhh, or however you spell that funky alternate name for Earth. Note that it's completely unlike R'yleh because Xenu is never supposed to escape from the trap, unlike Cthulu who is merely slumbering. Besides, Cthulu is just nonsense made up by someone insane...

[1] This doesn't violate the 2nd Law of Thermodynamics. Why? Because L. Ron Hubbard said so. Wouldn't you rather believe an (Ig) Nobel Prize Winner or some actual scientists?

Posted anon because Scientology is even more litigious than SCO!

It's gravity.

[rikkus-x]

It's gravity.

Rik

Our laws of physics are wrong

[Anonymous Coward]

I have considered 'Dark Matter' for many years.
Always a good conversation topic, for any occasion:)

Me and my fellow geeks came to a startling conclusiuon last time around....

The laws of physics are not uniform within the universe. In fact - why should they be? Once you remove this assumption everything makes sense. Our local frame of reference, and every observation possible from within it does not accord with the laws of physics at play on a grander scale elsewhere in the universe.

For years we have had this paradox. Either.. the observations are wrong, or our local laws of physics are wrong.

Given the observations I favour the latter.

Prisoner 9

Two atoms were sitting in a bar...

[Linker3000]

"Oh no", says the first
"What's up?", Says number two
"I've lost an electron", says #1
"Are you sure?", Asks 2
"Yep, I'm positive" Says 1

The case for dark matter (abridged)

[jpflip]

The thing that makes the dark matter explanation compelling is that it makes so many different observations work. We don't have to fine tune things so much - it all fits together. Here are some examples.

1. Galaxy rotation curves - you can watch the orbits of stars in a galaxy to determine the distribution of matter in the galaxy. This shows that there is a lot more matter than can be accounted for by the stars and that it is distributed differently.

2. Gravitational lensing - you can see how light is bent by distant galaxies to map out their matter distributions. Again, there's a lot more matter than the stars can account for, distributed differently.

3. The cosmic microwave background - this one is complicated, but the idea is that you look at the "afterglow" of the big bang, released when the universe was as dense and hot as the surface of a star. We understand the physics of matter at these temperatures very well, and by studying the signatures of vibrations in this hot plasma, we can measure the properties of the early universe. We can see from this that the universe contains a lot of matter, and that the large majority of this matter is not composed of ordinary atoms (hard to explain, but fairly rock solid).

4. Light elements - Most of the universe's helium, deuterium, lithium and beryllium were created in the early universe, not in stars (the conditions aren't right). Again, the physics is very well-understood, nothing fancy. By studying the relative ratios of these elements, we can figure out the properties of the plasma in which they were formed (a bit hotter and you get less deuterium, the temperature falls too quick and you get less helium, stuff like that). Again, the universe has a lot of matter, and most of it isn't made of atoms.

5. Structure formation - if you work things out on supercomputers, you find that (if the universe containst only ordinary matter) the universe hasn't been around long enough to form the galaxies and galaxy superclusters that we see. Adding dark matter to the mix makes galaxies form faster - just enough faster!

And the beautiful thing is that all of these different arguments give essentially the same answer for the amount of dark matter and its basic behavior. You can tweak your theories to explain some of these observations, but no one has been able to explain them all - except with dark matter, the SIMPLEST explanation!!

Before you say something is "clearly inferior intellectual flotsam", learn what you're talking about...

Re:The case for dark matter (abridged)

[ifwm]

You assume I haven't "learned what i'm talking about." I know enough about it to know that it is not the panacea that you (and others) pretend it to be. Many people seem to have latched onto a theory because it helps them save face, and hang on to previous theories that are near and dear to them. There are many other exlanations that are currently just as plausible, especially when you consider the dearth of real evidence.

By the way, why do people always play the "you don't know what you're talking about" card? Do you honestly think you're the only one who has ever read a physics paper? Or are you so arrogant that you think you're the only one who can really understand one?

Re:The case for dark matter (abridged)

[jpflip]

I apologize, the last statement was arrogant and wasn't needed. I was reacting to the "if I don't understand it then those fancy scientists must be wrong" card that I hear played far too often, which often comes from a different sort of arrogance. My end point was that I don't know of other explanations that are just as plausible, and that there actually is a great deal of evidence. The exact identity of dark matter is, of course, still a mystery, and it's even possible that this whole concept will be replaced by something much more interesting.

Re:The case for dark matter (abridged)

[deglr6328]

"By the way, why do people always play the "you don't know what you're talking about" card? Do you honestly think you're the only one who has ever read a physics paper? Or are you so arrogant that you think you're the only one who can really understand one?"

Arrogance is willfull ignorance in the face of overwhelming evidence. Arrogance is a statement like yours, which after a perfectly reasoned and lucid point by point explanation by jpflip, you merely wave off as all so much 'saving face' by scientists, as you rediculously purport. Let me ask, have you considered that people always "play the you don't know what you're talking about card" with you because, perhaps you are a pompous know it all who realy dosen't know what he's talking about!!?

Re:The case for dark matter (abridged)

[newhoggy]

What do the models say about WIMPs interacting with WIMPs? Are there suppose WIMP 'planets' and WIMP stars too? Or do they interact so weakly among themselves that they just smear out in clouds that don't collapse?

Re:The case for dark matter (abridged)

[Grayswan]

...no one has been able to explain them all dark matter, the SIMPLEST explanation!!

So, dark matter is just like God. It explains everything and has never been experimentally observed. Ya just gotta believe. Physics is the new religion and physicists the new priesthood. I think someone predicted this a while back.

Re:The case for dark matter (abridged)

[Celandine]

Don't forget the velocity dispersions of clusters of galaxies, which should come in somewhere between 1 and 2. Rotation curves of galaxies tend to give lower values for the amount of dark matter needed, but you're right that the other measurements are in reasonable agreement.

Re:The case for dark matter (abridged)

[Anonymous Coward]

Dark matter is a naturalistic place-holder until addition observations can be made. God is an anthropomorphic supernatural extension of human fancy. The explanation of "God" is not intended to be a place-holder until further explanatory observations can be made.

Re:The case for dark matter (abridged)

[jpflip]

The usual assumption is that WIMPs interact very weakly among themselves, as well as with ordinary matter. We expect them to remain as "smeared out" clouds, not as planet-scale objects. If WIMPs collapsed and clumped the way ordinary matter does they actually wouldn't be able to explain our observations - galaxy rotation curves ("watching star and galaxy orbits") indicate that the dark matter cloud is much bigger and smoother than the visible galaxy. That being said, many models yield WIMPs which interact weakly with each other and ordinary matter (hence the hope of detecting them at all). We also expect (though the reason for this is more theoretical) that the universe may contain approximately equal amounts of WIMPs and anti-WIMPs. They wouldn't annihilate much because of their weak interactions, but in places where WIMP density is unusually high (the galactic center, WIMPs captured in the sun's core, etc.) you might see a gamma ray signal from WIMP annihilation. Gamma ray astronomers are looking for this sort of indirect evidence, and some even claim to see a signal.

I found it

[Keruo]

It's in my fridge.
And if anyone wants it, feel free to collect.
But do take some jar to contain it with. I think it's moving.

I cannot vote, but this is 1st quality.

[Anonymous Coward]

Very good. And no need of swearing to make fun. Really 1st grade. Congrats.

Re:I cannot vote, but this is 1st quality.

[Anonymous Coward]

They put a spin on it by showing the top and bottom of the wimp. It was charming.

That may be because...

[Anonymous Coward]

Perhaps they're using the wrong math...
Using standard calculus, the scientist who created Autodynamics simplified Einstein's equations, and found out that some of them had errors, which accounts for the "extra energy" that led to the theory of Neutrinos. Detection rates for Neutrinos falls within expected error rates for machines.
Perhaps this Dark Matter remains elusive due to incorrect mathematics?

www.autodynamics.org
Interesting info...

The Real Dark Matter

[ivan1011001]

Packaging peanuts :D

Got me a whole box of missing matter just a while ago from ThinkGeek.
Alas, no Hitchhikers Guide Mk2 though :(

Well

[Lord Kano]

The most powerful search yet for the Universe's missing matter has come up empty handed,

No kidding? I guess that's why it's referred to as MISSING matter!

Maby Suntola is right with his DU theory

[Anonymous Coward]

* in DU there is no dark matter (if I understood right)
* DU is simpler than General Relativity
* DU predictions are close to GR, but differs slightly - those exceptions should be verified
* DU theory predicted also that the speed of light is getting slower - phenomenon found by Australian scientists lately

Check:
http://www.sci.fi/~suntola/DU,%20Main/DU %20Main.ht m

Other dimensions would resemble this one

[jgardn]

IF that were true, then were matter "clumped" together in this universe would be where matter clumped together in other universes. In fact, the universes would have to collapse into a single, common distribution in general.

Re:Noseeums

[slickwillie]

I was hoping WIMPs would explain the rash I get when I go to the beach.

I think I found it

[Orion Blastar]

and it also explains how most fat people gain their weight. They found the missing matter and absorbed it. ;)

Big Macs and Fries are made out of dark matter apparently. :) Hard to digest and it sticks with you for a long time as fat. :)

Re:I think I found it

[Anonymous Coward]

Big Macs and Fries are made out of dark matter apparently. :) Hard to digest and it sticks with you for a long time as fat. :)
Actually quite the contrary--the dark matter is the part that doesn't stick, which is ejected from the body in a more pure ("dark") form within 24 hrs after ingestion.

It's not quite Zero

[serutan]

It's just mostly zero.

Re:It's not quite Zero

[Warped-Reality]

Which is a lot different from all zero, because it's still somewhat non-zero.

Re:Noseeums

[linzeal]

I'm more worried about catching something else from my shower curtain. I wish someone would make an anti-bacterial shower curtain, but until than I will use this stuff I guess. Damn showering with 3 people plus who they sleep with and who they sleep with, arghhhh. No more showering.

I know where it is.

[Anonymous Coward]

It's in the middle. DUH!

It's like looking for the nucleus of an atom in the vacinity of the 4th orbital. ... a sphere whose surface is it's centre, and whose volume != 0. A particle whose mass is 1/infitiy i.e. non-zero mass = infinite trace... probability of mass/energy = proximity of traces, trace orbits nucleus of universe, dark matter at nucleus, invisible throughout the sky beyond visible light.

As above, so below.

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Push it further...

[Mikeface]

An important fact regarding CDMS is that Dark Matter direct detection experiments are only just beginning to probe the sensitivities required to observe Dark Matter, according to the theorists. The most popular WIMP candidate, the neutralino, is predicted to exist anywhere from an order of magnitude above CDMS's current sensitivity, down to several orders of magnitude below. The WIMP is well-motivated, and sure - it might not exist - but that will tell us at least as much about the universe than if we were to find it.

There really is a huge amount of research that supports dark matter in some form or another. Read up before you criticize CDMS as being a white elephant experiment!

Applications

[Lord_Dweomer]

So lets say they figure out where all this dark matter is. Lets say the detector gives them the results they need, etc.

Can someone please explain how this will affect future technology? Would this lead to anti-gravity? Teleportation? What sorts of sci-fi things could we make if we discovered this?

Whoa

[TrevorB]

It's all Dyson Spheres, man....

OK, maybe this theory is a bit out there, but has anyone truly worked out if the missing matter is truly evenly distributed? Is this even possible, even with very accurate measurements?

Tone down your attitude, Mikeface

[Anonymous Coward]

... or face destruction at the ping-pong table!

This is simply dangerous work...

[finelinebob]

All studies looking for "missing matter" should cease immediately!

It is my theory that this missing matter -- things like that sock that disappears from the dryer, people's cigarette lighters, and the shoe that matches the other shoe lying on the side of the road -- all exists in a common extra-dimensional space. Given that something like 99% of the universe is Hydrogen, the same should hold true of missing matter.

Now imagine, if you will, what would happen if someone FOUND their sock or their lighter. Static cling? Flicking your Bic? Can you imagine what would happen if someone did that around all that Hydrogen?

Can you say "Big Bang"? Sure you can! It's the end of the universe as we know it!!

Just say NO! to dangerous scientific research!

...while I'm at it, death to Tully-Fisher! Up with Wilson-Bappu!! WooHooo!!!

Healthy

[Anonymous Coward]

The wimp is fucking FAT!

But...

[zmooc]

If dark matter does interact with conventional matter through gravity and passes through conventional matter, then shouldn't all stellar objects be completely full of it?

Dark matter may not exist

[Phragmen-Lindelof]

The assumption that "dark matter" exists is a common one based on (some of) the observations of the universe. Dark matter does not explain the increased rate of expansion of the universe at great distances. This requires another assumption - "dark energy" (or a positive "cosmological constant").
There are versions of M-theory which do not require one or both of these. There is also a theory, as yet unpublished (since it upsets physics journal editors), which eliminates the "clock hypothesis" and accounts for inflation and accelerated expansion. (One has to be careful to take each new (and old) theory in physics with a big grain of salt.)

Just as the biological community "sold" the human genome project as THE ANSWER (one gene = one protein) and is trying to sell the protein folding problem as the NEW ANSWER (and it is an important problem), the (majority of) the (astro)physics community is trying to sell "dark" (matter or energy). "Dark" may well exist. I believe that it is important to allow a variety of views in the physics community to be heard (i.e. published) and let scientists design experiments to test various hypotheses. The "popular" theory may (or may not) correspond to observations.

Poster stole my quote!

[st0rmshadow]

The insensitive clod!

Socks

[shadowbearer]

The should be concentrating on where that missing sock always goes when you do laundry at a laundromat. Find that, they'll probably find the missing matter. At least the research should be cheaper :)

SB

Big difference

[Anonymous Coward]

The Top quarks don't exist if you don't create them.

The WIMPs are hypothetically everywhere, we're soaked in them.

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TOO MUCH!!

[TheUnFounded]

I think I'm getting a nosebleed. Good thing I went with EE instead of Physics...

It seems to be a trend.

[/dev/trash]

The last President tried to redefine the word 'is'.

Mod this one up!

[forgetful]

Not since 1905 has so much insight occurred in one paper. The ultraviolet sock catastrophy explained!

Scientific Faith

[beldraen]

Despite what most people of science seem to state, science does operate on faith. Two assumptions are taken on faith:

First, that the universe is the same everywhere; thus, the physics on earth is representative of the universe. On a side note, this implies that though a deity may have started the ball rolling, no deity currently plays a large, active roll in the day to day events of the universe.

Second, that there were things in the past that seemed impossible to understand, but have since been determined as predictable; thus, things that seem to be unpredictable/unknowable at this time are still probably determinable even though we don't have the slightest clue how to do it, yet.

Scientific faith does not rule out God, only that He doesn't regularly play in our sandbox; therefore, science attempts no inclusion of a deity because deities are not predictable in the sense of an equation.

The second part is that one can only try to fit nature to theory. Nature doesn't come with a manual. So, one observes something, then one postulates a hypothesis, then one tests the hypothesis. Hypothesis that are readily repeatable and fit with observation become "law;" meaning, it's still a theory, but people do not despute it because no one has yet shown remarkable evidence to suggest that the theory has limits or is out right wrong.

The Standard Model is a theory and it has predictions that there are certain types of events that are not normally noticed. These predictions are being tested. It's no different than when Newton's laws were gospel and people began testing things and realized that Mercury's orbit just doesn't quite jive. They will either find something or not. If they do not, it will suggest the bounds where Standard Model can predict things. At some point, people will have to say that the Standard Model has reached its limit and turn to an alternate hypothesis and start the process anew.

Re:Scientific Faith

[Anonymous Coward]

'Faith' in the religious, at least modern Christian sense, is very different, philosophically, to the kind of belief without justification that scientists often engage in (in common with every one else).

scientists build models, then test them. that's all they do. they do it because it's fun, and because it turns out to be useful (both for future models, and economically and socially).

philosophers of science go one step further, they argue that because the remit of science includes all we observe, then there is no reason to not make an equivalence between the best model and 'reality'. Because if there was a difference, then by definition we would forever be unaware of it - if we assume all knowledge is a result of experience - and it is this that religion argues with. it is here that religious idea of faith enters, that we can know things beyond experience, that we have a knowledge derived from God. this 'faith' is uniquely religious, and is what sets it apart from science.

Re:Scientific Faith

[dustmite]

In other words, "faith" in the Christian sense is believing something without any evidence.

Re:Why No dark matter found

[Propaganda13]

I thought we already figured this out

Zero approximation is pretty approximtate

[BrianMarshall]

If 1 / (zero_approximation) is 15, doesn't that mean that zero_approximation is (1/15)?

Or did the thing wrap or something?

1/15 is only approximately zero when you are talking about things like sticks of gum; when you are talking about the capitalization of Microsoft...

A=B if A=0 then B=0

[aimew]

What else is there to say?

If the theory doesn't test out against the Universe, just change the definition of the Universe until it does! Ahh, but doesn't that mean that = 0 ?!?

Just keep banging those rocks together guys!

Not Faith

[peachpuff]

"First, that the universe is the same everywhere; thus, the physics on earth is representative of the universe."

For people who believe that, they sure spend a lot on telescopes.

"Second, that there were things in the past that seemed impossible to understand, but have since been determined as predictable; thus, things that seem to be unpredictable/unknowable at this time are still probably determinable even though we don't have the slightest clue how to do it, yet."

Thinking that something is probably true, based on similar experience in the past, is not faith. Faith is when you believe that something is definitely true, especially something that your past experience does not support. Believing that good people go to heaven is faith. Believing that you will probably receive another morning paper tomorrow is not faith.

The second half of your post seems to contradict the first half. If it's all based on faith, why are they in the process of (repeatedly) talking themselves into changing their minds?

Comment removed

[account_deleted]

Comment removed based on user account deletion

Gumshoe.

[rice_burners_suck]

The most powerful search yet for the Universe's missing matter has come up empty handed...

Then Broderbund needs to make a new game: "Where in the Universe is Carmen Sandiego?" Good morning crime stopper. Your current rank is gumshoe. ... 60% of the universe's matter was discovered missing yesterday, along with the St. Louis Gateway Arch and Riverfront, and the campus of Microsoft. Authorities have tracked Carmen to the Horsehead Nebula, but lost her trail there. Fortunately, we have some leads. ... These cases need solving. Good luck Gumshoe.

Ah, the good ol' days of the late 80's, when I used to play my kids' videogames. Oooooooh well.

Re:Gumshoe.

[JRootabega]

Son of a!

Why is the joke you want to make always on the last page?

There is no spoon

[Anonymous Coward]

The reason we can't find any dark matter is because there isn't any. The only reason we're looking for any in the first place is becuase we're ignoring the fact that nearly all matter in the universe exists as plasma. Treating the universe in terms of neutral clouds of gas and only considering gravitational effects on galactic+ scales is irrational at best.

Face it, using dark matter to prop up the Big Bang is the same as Aristotle adding epicycles to the planetary orbits in order to maintain the assumption that they revolve around the earth in perfect circles. It might roughly fit, but it is arbitrary and has no previous justification. There is no theoretical prediction of dark matter, we just invented it to fill a gap and then reverse-engineered it into theoretical existence.

This also happened in 1990 - the COBE results returned 0.000000 variations in the CMB. The lumps we finally managed to bludgeon out of the data over the last decade were 10000 times smaller than originally predicted, but that's okay because we can always just throw some bigger numbers at it and fill the gaping hole with dark matter.

Another Dark Matter Project...I Think?

[Iron_Ranger]

There is an old iron ore mine shaft about an hour away from my house and from what I understand, they too are trying to find dark matter. The University of Minnesota I think is the major funder to the MINOS project. I'm no physics major so I'll let you figure out whats happening. I found a link describing what they are doing.

There's NO MISSING MATTER it is aSimple as that!

[Chris Coles]

The problem with the debate about missing matter is that the underlying theory, Big Bang, is fatally flawed and thus all the derived associated theories are built upon incredible foundations. Like a house built on soft mud, no matter what you try, it keeps falling down. You may have noticed that Steven Hawking recently abandoned his Theory of Everything. UK Sunday Times Colour Magazine "Hawking's Big Bang". We believe he did that because he has read a new book, The Universe is a Cloud by me, Chris Coles. Further, we have produced a e-book of a second edition http://www.lrsp.com/ebooks.html that goes even further into where the present theories are wrong. One of the consequences of this book is that you should by now have noticed that the singularity has dissappeared. Take for example the big bit in Scientific American about time this month. In essence, they have made some really silly mistakes that, because they are so silly, really stupid mistakes, they are not even prepared to debate them. The first BIG mistake was that when a stars mass, (any star's mass), grew to the point that light was prevented from escaping because of the strength of gravity, (what is described as an Event Horizon - the point beyond which light does not transmit), they always proposed that from that moment all the additional mass that was sucked into the star was also, from that point onwards, always inside that event horizon. But think about that. The event horizon is simply a mathematical point; mass sufficient to prevent light escaping. Thus that mass is always the point where light cannot escape. Adding mass is like trying to pour more coffee into a cup once the cup is full. For once the cup is full, all the additional coffee must be outside of the cup. It is mathematically impossible for the coffee to be added to the cup; same with an event horizon. The event horizon is simply a notional point where gravity is so high, light cannot escape. Beyond that point, all mass must be OUTSIDE of the event horizon and that leads us into a completely new view of the universe. Read it and find out why Steven Hawking has abandoned his theories. http://www.lrsp.com/ebooks.html

++Informative!!!

[Anonymous Coward]

Thanks for a fascinating read!!!

Alternate Explanations

[nimblebrain]

There is a thery that there is little or no dark matter, and the difference is accounted for by the assumption that the inverse square law for gravity fails at large distances

I've read one paper that posits that very thing - this particular one is from amongst the push-gravity theorists, and basically states that the graviton "shadows", like light, can slowly fall off at faster than inverse-square due to interference with matter.

There are other possibilities, of course, including intergalactic space containing much more in the way of hydrogen molecules (from which it's difficult to get an absorption, never mind an emission, spectrum at such low temperatures, unlike hydrogen ions... well, protons :) than we would have suspected, or there's always the field of plasma cosmology, that puts a at least as much emphasis on currents as on gravity, and also provides for a non-black-hole-dependent theory for why galactic jets form.

Do The Math

[SEWilco]

What's 20 times 0? And don't tell me zero!

20 times 0 is nonzero for some values of zero.

That's what the angels are for!

[Anonymous Coward]

They go around nailing the forces to the fundamental structure of the universe so they can't move.

One unique test of dark matter is that it is dynamical; it can move.

D'oh? (-:

Or to put it another way, name one thing in the universe which can't move and isn't dynamic?

If the rock comes down wet...

[Anonymous Coward]

...then there was a cloud. Too hard!

Next! (-:

Your long list of tests...

[Anonymous Coward]

...might be better passed with a completely different theory. Find the cartoon of Calvin's dad explaining the sun to him one day and read it.

You forgot to attribute that

[Anonymous Coward]

-- Rusty and the Ventrilomatic

False premises kll all five points

[Anonymous Coward]

1. You can't "watch the orbits of stars", we haven't been here long enough, let alone had useful telescopes for long enough, to plot a significant amount of a star's orbit. All that we know about them is interpolation and extrapolation;
   
2. There's a lot more bending than the observed stars and the current theories of cosmology can account for between them. As a sibling post has implied, if the theory was broken, that would also account for it - and historically, the odds are well in favour of the theory being broken;
   
3. There's still a lot of argument about the CMB, even Setterfield's theory predicts it much better than orthodox cosmology;
   
4. Again, the progress of these ratios cannot be measured, there was nobody there with a spectrometer at the time, and are based entirely on theories of cosmology which all assume many things, such as approximately static conditions at a large scale;
   
5. Ah, the invokation of the mystical supercomputer. Well that makes it all right then. Again, the supercomputer's results are the expression of theories which have been falsified repeatedly. Of course they're going to match the theory that they were designed under!

I know where where the missing matter is

[Anonymous Coward]

> I'd just like to be the first to say that it's an
> honor, Mister President, to count you amongst the
> Slashdot readership.

That's for noticing. That's why I want to go to Mars. Obviously Saddam and Osama hid the missing matter with the WMD on Mars. We need to invade Mars and free all Martians.

In Other News

[theora55]

In other news, Generalissimo Francisco Franco is still dead.

Re:There's NO MISSING MATTER it is aSimple as that

[Phragmen-Lindelof]

There may be reasons to question "the big bang" (e.g. using branes). However, your analogy of a `full coffee cup' is idiotic. There is a (spectulative) theory that a new form of matter (kind of like a Bose condensate) does exist at extremely high density but nothing in that theory prevents more matter from being added to the extremely dense object. Not to be unkind and realizing that a single /. post is not enough evidence with which to work but ... you sound like a kook.

Obligatory HHGTTG Reference

[n1ywb]

The missing matter is in all of the packing materials for all of the computers and instruments and equipment they've purchased to find the missing matter.

Well, we all know...

[Pig Hogger]

Well, we all know that the "missing matter" is the styrofoam beans the Universe was packed with...

Re:There's NO MISSING MATTER it is aSimple as that

[Anonymous Coward]

Sorry. You're an idiot, and your opinions have no value.

Re:There's NO MISSING MATTER it is aSimple as that

[Chris Coles]

Nothing like a closed mind to come up with a word like Kook!!

It is a matter of fact that 2 x 2 = 4, so, go on, add another digit to the calculation. Try it? 2 x 3 = 4? Well, that is what you are saying, that you can add mass to the calculation. At a specific mass, (depending on the density and diameter of the object, yes), the gravity is sufficient to prevent light from escaping. That is called the event horizon. But it is simply the point where the mathematics calculate that the gravity from the existing mass has reached a sufficient level that the point has been reached where light cannot escape. So, at that level of mass, gravity prevents light from escaping. So, ALWAYS, from that moment onwards, at that level of mass, light cannot escape.

Adding more mass does not, indeed, cannot, change that relationship. So from that point onwards, any additional mass is more than required to create an event horizon and thus is not in the original calculation, but outside of it. (You still have a star shining away inside the event horizon, but no light escapes).Thus any additional mass added is more than is needed to create the event, and light not escaping.

That extra mass is outside of the event horizon. If that is so, then all the energy from the extra mass must, because the gravitational force is so high, be sucked into the original star under the event horizon leaving behind inert mass with no energy.

Thus what happens is that outside of the event horizon you get a layer of super dense, inert, (SDI), mass. As that mass grows in depth, you reach the point where the SDI mass is deep enough as a layer to have balanced gravity effects within that SDI mass such that, from that point onwards, instead of all the energy of the extra mass going into the original star, it starts to collect in a ring inside the SDI mass. In time the size becomes such that it acts as though a sandwich between the teeth and energy squirts back out into space as a jet from both ends. A quasar at the larger end and a planetary nebula at the other. Thus it is impossible to create a singularity as the object ejects energy back into space in all senarios.

If you look at the book you will find I have also explained how the Whirlpool Galaxy is the way it is because of tidal forces causing the outer ring of SDI mass to split into two causing a two arm galaxy.

Again, the USGS gave permission from The Department of the Interior for a web page from their site as an annex for the book because I show why we have an inner and an outer core on Earth. (Caused by balanced gravity effects never before proposed).

And please notice, I have not profaned or called you names either.

Read the e-book. See for your self.

Chris Coles.

Re:There's NO MISSING MATTER it is aSimple as that

[Chris Coles]

Nothing like a closed mind to describe an alternative argument as from an idiot!!

It is a matter of fact that 2 x 2 = 4, so, go on, add another digit to the calculation. Try it? 2 x 3 = 4? Well, that is what you are saying, that you can add mass to the calculation. At a specific mass, (depending on the density and diameter of the object, yes), the gravity is sufficient to prevent light from escaping. That is called the event horizon. But it is simply the point where the mathematics calculate that the gravity from the existing mass has reached a sufficient level that the point has been reached where light cannot escape. So, at that level of mass, gravity prevents light from escaping. So, ALWAYS, from that moment onwards, at that level of mass, light cannot escape.

Adding more mass does not, indeed, cannot, change that relationship. So from that point onwards, any additional mass is more than required to create an event horizon and thus is not in the original calculation, but outside of it. (You still have a star shining away inside the event horizon, but no light escapes).Thus any additional mass added is more than is needed to create the event, and light not escaping.

That extra mass is outside of the event horizon. If that is so, then all the energy from the extra mass must, because the gravitational force is so high, be sucked into the original star under the event horizon leaving behind inert mass with no energy.

Thus what happens is that outside of the event horizon you get a layer of super dense, inert, (SDI), mass. As that mass grows in depth, you reach the point where the SDI mass is deep enough as a layer to have balanced gravity effects within that SDI mass such that, from that point onwards, instead of all the energy of the extra mass going into the original star, it starts to collect in a ring inside the SDI mass. In time the size becomes such that it acts as though a sandwich between the teeth and energy squirts back out into space as a jet from both ends. A quasar at the larger end and a planetary nebula at the other. Thus it is impossible to create a singularity as the object ejects energy back into space in all senarios.

If you look at the book you will find I have also explained how the Whirlpool Galaxy is the way it is because of tidal forces causing the outer ring of SDI mass to split into two causing a two arm galaxy.

Again, the USGS gave permission from The Department of the Interior for a web page from their site as an annex for the book because I show why we have an inner and an outer core on Earth. (Caused by balanced gravity effects never before proposed).

And please notice, I have not profaned or called you names either.

Read the e-book. See for your self.

Chris Coles.

Re:There's NO MISSING MATTER it is aSimple as that

[Phragmen-Lindelof]

Let me take your points one at a time.

In your second paragraph, I believe that you are saying that, in the classical theory, the event horizon is just a mathematical construct and is not "real." I would agree with this statement. If the object gains more mass, the event horizon get larger. However, according to the classical theory, an observer going through the event horizon would not notice anything special at that moment. (In the alternative ("new form of matter") theory I mentioned, the observer would crash into a real (extremely dense) object (and die).)

Your comment "So, ALWAYS, from that moment onwards, at that level of mass, light cannot escape" ignores the `evaporation' of matter from black holes (caused by the creation (and `partial capture' by the black hole) of virtural particles). If the mass were to remain constant, then the event horizon should not change size.

Your third paragraph is very difficult to understand. Adding more mass (in either of the two theories mentioned above and ignoring the question of the `reality' of the event horizon) increases the size of the event horizon. I believe there are observations which are consistent with mass being added to very dense objects (black holes, neutron stars, etc.) Your "star shining away inside the event horizon" comment is very strange; stars shine because matter is changed into energy (e.g. some small proportion of the mass of hydrogen atoms is converted into energy when helium is created) and "a star shining" requires a source of energy (so what do you propose?).

Your fourth paragraph is better (i.e. more humorous). I like "leaving behind inert mass with no energy"; if it is left behind, then it (magically?) is not subject to the gravitational attraction of the black hole and has no energy (although mass=energy)?

Your fifth paragraph seems to be the result of reading too many bad science friction novels. I like (and read) SciFi too. I just do not confuse it with the real world. By the way, your "SDI" may help (former) President "Ray-Gun" finally obtain SDI.

In your sixth paragraph, you mention "the book". Is this the Bible (or the Koran or what)? Buying (or even reading) your book is about the last thing I plan to do.

Moving on. "Again, the USGS gave permission from The Department of the Interior for a web page from their site as an annex for the book because I show why we have an inner and an outer core on Earth. (Caused by balanced gravity effects never before proposed)." Do you think gravity works the same way that electromagnetism does? What are "balanced gravity effects" (which are "never before proposed")? Is this like the tunnel through the earth (with no effective gravitational force at the center)?

"And please notice, I have not profaned or called you names either." I said "you sound like a kook." I do not know you and can only judge you on the basis of your statements. On the basis of your statements, you do sound like a KooK. This does not mean you are a kook and I am not calling you one; I do not have enough information. (For example, you could be trolling rather than just crazy.)

Enough of this fun. I will let another reader of /. `dance' with you. Enjoy your life; say "hi" to the aliens for me.

Re:There's NO MISSING MATTER it is aSimple as that

[Chris Coles]

For the event horizon to grow larger, the mass within it must have less density. The mass is no more, no less than that that which produces a gravitational "pull" sufficient to prevent photons form breaking free from the surface. That is it, there is nothing more than that to an event horizon. Nothing. If you have a mass, say, ten times more than the mass needed to prevent the photons from escaping, then, from the moment that the mass reached `one', there were no photons escaping. At `two' there is mass `one' plus another `one' The first mass stopped photons from escaping, so from that moment, the event horizon was in place. No matter what you do to the extra mass, `one' remains the level of mass required to stop the photons escaping from the surface. The "Event" was reaching `one'. At `two', there is the event - still there at `one'. The event horizon cannot grow larger than that needed to create the effect, (preventing photons from escaping), in the first place. It would be churlish for me to add anything further as you have already asked me to stop and after this I will. But you will find that I have given a completely new explanation for gravity. I also have the support of NMSU/PSL, and my proposals for a Visual Gravity Observatory are being looked at by NSF, NOAA, Dept of Transport VOLPE center and USGS as I believe I have defined exactly what gravity is, how to observe it in real time and a path to the control of gravity. I will be pleased to sit down and debate this with you anytime. But, sadly, no one that knows me well thinks that I am mad so you may be greatly disappointed; and, I do not know any aliens. Chris Coles cfc@lrsp.com

RUMSFELD'S COSMOLOGICAL PRINCIPAL

[Anonymous Coward]

The absence of evidence is not evidence of absence.

Re:There's NO MISSING MATTER it is aSimple as that

[Anonymous Coward]

OK, not an idiot.

A drugged-up, cracked-out, gibberish-babbling, mindless idiot.

That better?

(Your entire post was gibberish. Hope you had fun doing those drugs!)

"the cosmological constant."

[vickey7777]

Hey, how about you guru's out there explain to me how "the cosmological constant" proposed by Einstein fits into this flat, expanding, accelerating, universe theory. Seriously I am having trouble fitting it in and need some "smart" person to elaborate.

Science ..

[dustmite]

Physicists don't "believe in" dark matter, some of them merely hypothesize dark matter as a possible explanation for apparent gaps in our current models, and then set about trying to test their models to see if they might be true or untrue. Actually the term is a little misleading because "dark matter" is actually a generic "variable" term for the known existence of some or other gap in our current models, and different scientists propose different explanations for this known gap, one of which is this "invisible" mass. This isn't a case of "current theory" which "scientists believe", that is utter claptrap and a total misunderstanding of what science is and how it works. There are actually several differing hypotheses from different scientists, not one "current theory".

I get tired of people who think scientists just go on faith and simply "believe" this or that idea. I blame it partly on poor science reporting in mainstream media, where they always try spice things up by pitting hypotheses from different scientists against one another in a pseudo "battle" - "scientist A believes X, scientist B believes Y - watch them battle it out". Mainstream media love to report that scientists "believe" this or "believed" that. Scientists hypothesise.

There will always be scientists who become extremely convinced that their own hypotheses must be correct, for whatever reasons, but that is no longer strictly "science" (whether a scientist happens to be right or wrong), and these cases are failings of individual human scientists not failings of science itself.

Holographic principle, Origami world

[acgetchell]

That's not what the holographic principle says.

The holographic principle, more generally known as the covariant energy bound (Raphael Bousso, "The holographic principle", Rev.Mod.Phys, 74, 2002), was formulated by t'Hooft and Susskind as the "spherical energy bound." The name comes from the postulate that all physics in a region of space is described by data that fits on its boundary surface, at one bit per Planck area.

There turned out to be problems with this definition; for example, it does not hold for black holes, which ruins the idea as a general cosmological principle. Further refinements giving rise to the covariant energy bound. Even now, it has only been considered for cosmologies that are thought to be "realistic" (in particular anti-DeSitter Conformal Field Theory).

An interesting idea was put forward by my Cosmology professor (Nemanja Kaloper, "Origami World", hep-th/0403208). The basic idea is to solve the gauge hierarchy problem (e.g., why is gravity so weak) by using 6-dimensional anti-DeSitter spaces to generate 4-dimensional gravitons. Unlike versions of string theory, the extra dimensions are not compactified. The intersections of various branes in 3D gives GR gravity, but the 4D bulk propagation produces the very weak gravitational constants. As an added bonus, particular foldings consisting of galaxies "millimeters" away in the bulk create dark matter.

That is, dark matter is the result of the 4-d "shadow" onto 3-space. Or, the Milky way galaxy could generate it's own dark matter simply by being folded in the 4-D bulk.

Re:Holographic principle, Origami world

[EvilTwinSkippy]

Of course you run a slippery slope by blaming things on extra dimensions. You end up with turtles standing on top of the backs of other turtles, with no idea what the bottom turtle is standing on. Assuming there IS a bottom turtle. At least that's my complaint with String theory.

This anti-DeSitter space theorum is intreguing. But, like most cosmology theories, the question is whether you can test it. I agree with you, GR is a bit overhyped, and it's study is often done at the neglect of alternate theories.

As far as Black hole pooh-poohing Holographic theory, we really don't have much more proof the black holes exist than we do of the Sasquatch. A series of highly-doctored fuzzy photographs. Indeed, at least from the Yeti we have a few eyewitnesses and some tracks.

Yes, we have seen evidence of super-dense areas of mass space. Yes, they produce massive bursts of x-ray energy in accordance from some theories, and they can be seen sucking matter from nearby stars. But (and I know I sound like a spook for saying this) that's the extent of our experience with a black hole.

Re:Basic assumptions may be wrong (about God)

[arminw]

You have hit the nail on the head! Many people (including scientsts) do not wish to entertain the thought that there may be a God after all. The first sentence of the Bible reads: "In the beginning God created heaven and Earth" In scientific terms it could be: God created time-space-matter-energy. All scientific disciplines that ask questions of origins or beginnings ultimately come to a dead end beyond which God stands there as a better alternative than any other explanation. The problem is not with science, but when anyone dares to accept the idea of the existence of God, a number of disturbing questions arise, among which are: If there really is a God, then perhaps I am accountable for my life. What if there really is a heaven and a hell? What if the reality that science can explore is only like the tip of the iceberg of all that exists? Another quote from the Bible: "And as it is appointed unto men once to die, but after this the judgment:" (Hebrews 9:27) No one argues with the first half of this verse, namely that we are all subject to death, but many are not willing to accept the second half about a judgment. It may be this innate, unarticulated fear of the final judgment that drives the frantic search for dark matter as an ultimately futile attempt to explain away God and everyone's requirement for a final appearance before Him. AAW