Search for the Missing Universe

Chris Gondek writes "The Sydney Morning Herald has reported that one of the greatest discoveries of our time could be made under the Yorkshire moors. Deep in a Yorkshire mine, scientists are toiling to solve a cosmic puzzle that has baffled astronomers for 70 years: about 90 per cent of the universe is missing. Analyse the movements of stars and you can work out how much matter is making them swirl round in galactic islands and how much makes galaxies cluster together as they do - in other words, you can work out how much mass makes the universe look the way it does. But measurements suggest that the universe is not what it appears."

Comments

Bush Administration cites Missing Universe Theory

[Anonymous Coward]

The Bush administration today announced that they believe Iraq's WMD are being stored inside the missing 90% of the universe. "They're definitely there, in the missing 90%, because we can't see them." said White House Chief of Staff Ari Fleischer. "We'll continue to look for them, but if we don't find them, feel confident no one else will be able to, either."

For starters

[Faust7]

about 90 per cent of the universe is missing

I'd look in Windows.

Did you look in your shoes?

[.com b4 .storm]

Whenever I lose something, sometimes it turns up in my shoes.

</obligsimpsons>

Re:Did you look in your shoes?

[Greyfox]

I always look under the couch when something goes missing. I wouldn't be surprised if 90% of the mass of the universe is actually under my couch.

Hey, go ahead and laugh, but it's at least as good a guess as anyone else has managed to make. It just has much less funding.

Re:Did you look in your shoes?

[Anonymous Coward]

Hey, man: $45 will NOT buy you a decent steak dinner. Here's my recipe for the best steak you've ever had.

Go to a decent grocery store that sells USDA Prime beef. Find yourself some fillet steaks, also known as fillet mignon. You want two steaks as close to the same weight and thickness as possible. They should be between 6 and 8 ounces.

Heat your oven to 500. If your oven won't go to 500, set it for as high as it will go. Then sit down to watch The Simpsons or something, because getting a home oven to that temperature takes a while. Be patient here.

Dry your steaks thoroughly with paper towels. You want the surface to be completely dry, both on the top and bottom and on the sides. Why? Because liquid turns to steam, and we don't want steamed steaks. Your goal is perfect dryness here, so do a good job.

Once your oven is hot, put a heavy, all-metal, oven-safe skillet on top of the stove. Cast iron works, but I have a stainless-steel-clad, aluminum-core skillet with a riveted metal handle that I use for this. Turn the burner or element to high, and leave it there for at least five minutes. You're looking for something really incredibly hot here. Don't be afraid to let your pan get hot. It'll be fine.

Season your steaks liberally with salt. You want something with a coarse grain, because it makes a great texture when it cooks in. I like kosher salt for this (Morton's) but sea salt is good too. Fleur de sel is the best, but at $10 for a couple of ounces, it's a little pricey for most folks. But if you're blowing $25-$30 on raw meat, you might as well go all the way.

DO NOT PUT PEPPER ON YOUR STEAK. I don't care if you like it that way. Pepper burns at the temperatures we're planning on using. If you want pepper, crack a little over your steak once it's on the table.

Once your pan is hot enough to brand a steer--which is basically what we're planning to do here--plop in the steaks. No oil, no nothing. Just drop 'em into the dry, rocket-hot pan: szzzzzzz. There will be some smoke, so crack a couple of windows for ventilation.

Do not touch the steaks for two solid minutes. Seriously. Don't touch them. Don't move them, don't poke them, don't prod them. Don't talk to them. Don't ask them questions. Just let them sit there.

"But the meat will stick to that hot pan!" you cry. And you're absolutely right: it will. That's exactly what we want. What we're doing is called "searing." Searing is cooking in a dry pan over incredibly high heat. Searing isn't frying; frying involves lubricating the pan with fat or oil, and we don't want that. Instead, we just want dry, raw meat to hit blisteringly hot metal and to sit there for two minutes.

What's happening is called the Malliard reaction. (That's pronounced "my-yard.") It's complicated, but the short version is that proteins in the surface of the meat are denaturing and chemically changing into a brown, crusty substance that tastes really, really good. You don't get that with any cooking method other than searing.

After two minutes, turn the steaks over with tongs. Not with a fork, not with a spatula. Tongs. Grab the steaks gently around the middle and lift straight up. They'll lift right off of the pan, no sticking. If they do stick, just wait a few seconds. They'll let go by themselves because of the heat of the pan and that Malliard thing I talked about. Turn the steaks over and leave them for one minute.

During that minute, look at the seared surface of the meat. It should be brown and crusty, almost like it was battered and deep-fried, but darker than that. If there are tiny black specks here and there, that's okay. If there are big black specks, you left it on too long, but it's still edible. If the whole thing is solid black... well, the dog's in for a treat tonight.

After one minute, move the entire pan--use an oven mitt for god's sake, that pan is a branding iron by now--to the oven. We've seared the surfaces of the steak, and now we're going to cook the interior.

There

Re: Did you look in your shoes?

[Black Parrot]

> I guarantee you, if you follow these directions to the letter and use halfway decent ingredients and equipment, these will be the BEST steaks you've ever eaten. Period.

I'd rather just swing by Krusty's for a ribwich.

Re:Did you look in your shoes?

[SubtleNuance]

Better than USDA Prime: Find a local farmer who grows beef. You want farm-raised organic beef if you can get it. Not this factory-farm "USDA prime" BS.

In the winter ask him for a half side or something, pay him up front -- VISIT your beef through the year. LEARN to trust this man, build a relationship with your food. If this beef-farmer is worth his salt, he will also be aging the beef 2-3 weeks he eats himself... ask him to age YOUR beef as he would his own. Anyone who knows their ass from a hole in the ground knows 2 day-old dripping-blood supermarket beef == crap. Beef hanging in a cooler w/ a "little mold" (dont be alarmed) == WHAT YOU WANT.

This results in A) a better pc of meat for your table B) ecologically-sensative, ecologically-sustainable and responsible food-choices (if your going to eat meat at all) C) better profit for your local farmer (cut out the middleman) D) sustainable food-supply for yourself and your community because you havnt undermined local/small producers by ONLY buying food from FuckingWalmart and %Big-Agricorp%.

Perhaps it's not lost.

[bonsai_kitty]

There is allways the chance it is just compressed....with bz of course :)

Not 42?

[Joe Jordan]

So does that mean that the answer to the universe isn't really 42?

Re:Not 42?

[atomicdragon]

We know the answer is 42, we are just trying to fix the problem that we only have 4.2 now.

Re:Wrong credit

[benna]

http://www.telegraph.co.uk/connected/main.jhtml?xm l=/connected/2003/04/30/ecfwimp30.xml&sSheet=/conn ected/2003/04/30/ixconn.html

Re:Wrong credit

[Rhinobird]

Is you link mixed in with the 90% of the missing universe?

Re:Wrong credit

[Anonymous Coward]

Today, little beena we'd be learning a new word.

'preview'

preview
n 1: an advertisement consisting of short scenes from a motion
picture that will appear in the near future [syn: {prevue},
{trailer}]
2: a screening for a select audience in advance of release for
the general public
v : watch a movie or play before it is released to the general
public

Please write a 2000 page essay on this word, along with 687 sentences of 'preview' being used as a word and 582 sentences of 'preview' being abused as a word.

Professor Slash bin Dot.

Duh, which way to mars?

[fearless_froggie]

I find it slightly strange that we expect to know where to find the entire universe, when we haven't even made it to Mars yet.

froggie

Thought...

[Skyshadow]

Rather than 90% of the mass in the universe being AWOL, isn't it possible that we don't have an accurate understanding of how gravity functions on an extremely large scale? Could this, in turn, be related to how the expansion of the universe appears to be actually speeding up rather than, as we'd expect, slowing down?

I'd welcome any thoughts on this one... Anyhow, it's late and this is way out of my area of expertise, so forgive my spitballing.

Re:Thought...

[efuseekay]

Yes, modifications to Gravity is one of the way to explain away dark matter/dark energy problems. It is an active field of research, but it is a hard one.

The problem is that while there is no direct tests of gravity at very large scales, there are a lot of "consistency" checks of the various cosmological observations (say of the cosmic microwave background anisotropies) that you have to satisfy.

In other words, there is no proof that such theories of modified gravity do not exist. But to find one is really hard.

Re:Thought...

[efuseekay]

This argument is actually flawed.

The answer is a bit involved.

But basically, the weighing of the matter (as quoted in the article) does not depend on just mass, but a quantity called "mass-energy". It is true that a particle moving at very high speeds seemed to gain "mass". But depending on observers travelling at different velocities relative to this particle, each will see a different mass. However this particle, irregardless of its velocity, will have a consistent "mass-energy" to all observers. In other words, everybody in the unvierse can agree on the amount of "mass-energy" each particle have. So there is a consistent picture of weighing the amount of mass of the universe.

That is the beauty of Einstein's Special Relativity, which is to unify mass and energy into a (jargon warning) relativistically consistent picture of mass-energy.

Re:Thought...

[Zebede]

Perhaps instead of 90% of the universe missing, *we're* the ones made up of 'dark matter'.

Anybody ever stop to consider that the other 90% must have some sort of structure? There's probably dark matter stars, planets, gas clouds, etc. Perhaps some sort of dark matter inteligent life as well. Whereas we are trying to figure out where 90% of our universe is, the other side may be trying to figure out where their missing 10% is.

Most of us here belive in some sort of extraterrastrial life. I doubt many of us are naive enough to belive that life only exists on a small blue planet in the backwaters of a single galaxy. Considering dark matter occupies 90% of the mass in the universe, I think it would be naive to assume that life consisting of dark matter doesn't exist as well.

Oh well, it's just a random thought. We can't (yet) even prove the existance of dark matter, let alone manipulate and study it. Observing and contacting a civilization composed of dark matter would be all but impossible.

Wouldn't it be funny if *we* are actually the strange aliens composed of the 10% of mass missing from the 'real' universe?

Re:Thought...

[gilroy]

Blockquoth the poster:

Anybody ever stop to consider that the other 90% must have some sort of structure?

There is no logical necessity for that. Although you can conceive of matter that exists subject to a host of strong interactions but which does not interact with us -- that there are two "classes" of matter that exist separately -- there is no evidence for that. Occam's Razor says, don't invent whole universes for the heck of it. The simplest explanation consistent with the facts is taken to be true.

Indeed, many of the "hot" dark matter theories presume exactly no structure to the dark matter ... just streaming neutrinos flashing throughout the volume of the universe.

Historical Analogues

[Farley Mullet]

Back in the 19th century, astronomers had noticed that there was a minute procession in the perihelion of Mercury (in other words, the point in Mercury's orbit that is closest to the sun kept moving forward) that they couldn't account for using the Keplerian/Newtonian model of celestial dynamics. Astronomers thought that it must have reflected the influence of some massive, distant unknown planet; predictions were made about where this planet was and what its mass was, but astronomers couldn't find it. Then all of a sudden General Relativity came along, and our understanding of mechanics in gravitational fields was improved, and the procession was easily predicted (within an incredibly small margin, as I recall). So it seems just as likely that the "missing mass" is due to a theoretical deficit as it is due to an observational deficit.

Re:Historical Analogues

[krlynch]

While this is a useful cautionary tale, you have to be a bit careful in your interpretation of it. It is quite easy to show (and it is a typical undergraduate classical mechanics homework problem) that the perturbations of Mercury's orbit CAN NOT be explained within the Newtonian model by the addition of another point source (ie, a planet), because any such explanation would cause a larger than observed perturbation to the orbits of Venus, Earth, and Mars. And this was a well known issue BEFORE Einstein started working on his GR theory. In other words, physicists knew there was something wrong with the theory long before they had a theoretical solution, because the preminent gravitational model of the time was predicting the wrong thing when confronted with the available data.

The cautionary aspect of the tale, though, is well understood by the larger physics community, and dozens of modified and new models of gravity HAVE been proposed in the literature to explain the apparent "missing mass" of the universe without invoking unobserved particles; but they all run afoul of some observation or other. The current model has been arrived at by the consensus of a large number of physicists and astronomers around the globe over a long span of time ... it isn't a flash in the pan, and while it could be wrong, the data on many length and time scales just seems to get more compelling as we add to it, rather than less.

In this case, we understand GR, its cosmological implications, and the requisite post-Newtonian approximation schemes well enough that we have developed a model that match ALL known observations with the inclusion of dark matter and dark energy components. It isn't just one or two observations of rotation curves that have pushed us in the direction of dark matter, but literally dozens of observations, from widely different length and time scales, from cosmic background radiation to rotation curves, from earthbound laboratory measurements to interstellar radiotelescope observations. It is certainly POSSIBLE that there is a theoretical description available that doesn't require dark matter/energy, AND explains all of the data, but it looks more likely to the daily practitioner that the current theory is good at the length scales it is being applied to, and the dark matter/energy is the simpler solution.

I'd like to point out one other cautionary tale to those who want to blame the theory, and points out that well tested theories are not tossed out immediately when new or contradictory data comes along: in the early part of the 20th century, observations of beta decay led many physicists to conclude that the very fundamental conservation laws of energy and momentum (and the entire theoretical framework that so neatly explains them) would have to be tossed out the window, because the observed decay products (electrons and nuclei) didn't appear to follow those conservation laws. But some very smart people, including Pauli, said "Wait, the theory has worked so well up to now that we should look for a SIMPLER explanation; we propose a to-date unobserved particle with no charge and no mass produced in association with electrons in these decays." That was scoffed at by many, but a few years later just that very particle was observed: the electron neutrino. My point is just that, while you need to keep an open mind and be willing to challenge both experiment AND theory, you have to do so with the WHOLE picture in mind, and not just a tiny corner .... that is what science and the scientific process is all about.

So thats where my dryer sends my clothes

[1nsane0ne]

If 90% of the universe is missing, I'm betting that my dryer is the portal to the missing part. Let me explain. I put a load of clothes in the washer. Then I move them from the washer to my dryer. Then when the dryer gets done with them and I put them on my bed to be folded, stuff that was there when I put the clothes into the dryer is always missing. This has convinced me that my dryer is a portal of sorts to somewhere. On a side note if anyone wants to get in my dryer and try to open this portal somehow you're more then welcome assuming you get me my clothes back.A big plus would be that you'd get the credit for finding the rest of the universe.

Stephen Hawking's wishful thinking

[kindofblue]

In his book, A Brief History of Time, I think he said something to the effect that he believes that we'll figure out most of the big questions about the nature of the universe within 10 years or so. That was about 15 years ago. Does anybody remember reading this?

When I saw that, I remember thinking that's naive and contrary to the entire history of scientific research. Anyway, it reminds me that even some of the best minds say some of the stupidest things. Especially in physics.

I'm not a physicist but I'm pretty damn sure that Stephen Wolfram and Roger Penrose have had some pretty wacky theories when they venture away from straight physics, like into cellular biology, free will, philosophy, ...

Re:Stephen Hawking's wishful thinking

[Galvatron]

I think he said something to the effect that he believes that we'll figure out most of the big questions about the nature of the universe within 10 years or so. That was about 15 years ago.

I have a video clip (from circa 2001) where he's being asked about this very issue. His reply is "in 1980, I said I thought there was a 50-50 chance we would find a complete unified theory in the next 20 years. Well, we didn't make it. However, my estimate is still that we will find a complete unified theory in the next 20 years, but the 20 years starts now."

So, he admits he was wrong, that the promising theories did not pan out, but he's still optimistic. *shrug* If you think that a complete unified theory will never be found, that's fine, you're welcome to ignore his predictions. He's obviously biased, because he believes that there is a complete unified theory out there somewhere, waiting to be discovered, and he wants to know what it is.

Still, I wouldn't totally dismiss his beliefs out of hand just because it seems contrary to the history of science. If you think of the universe as being like a murder mystery, just because you've found many clues, which first caused you to to suspect one person, then proved his innocence and led you to suspect another, doesn't mean it's impossible to find out who the culprit really is. The analogy may not be perfect, but it is dangerous sometimes to conclude that future progress is either inevitable or impossible because of the past.

Just another WIMP-seeking experiment

[dragonsister]

The article is remarkably light in details, not even mentioning whether or not the experiment is looking for neutrinos or something else. There are a number of experiments involving big detection systems underground - most of them designed to pick out neutrinos - and there's an on-going discussion as to whether or not neutrinos have mass, because if they do, there's enough of them that they might well make up the missing mass of the universe.

To show that neutrinos have mass, it suffices to observe solar neutrinos and look for changes in neutrino flavour. Last I heard, although large regions in which the neutrino masses could have lain had been ruled out, the evidence was mounting in favour of flavour changes and neutrinos having mass.

However, with all I've heard about neutrino studies over the last few years in a Nuclear Physics department, this article doesn't give enough information to let me work out if I already know of the experiment or not (though I probably have attended seminars by associated researchers; these projects are not exactly three-person exercises capable of being missed!) They don't even give the experiment's *name* - NOMAD, CHORUS, SNO, etc (many listed on this page)

The article *might* be referring to the UK Dark Matter Collaboration who apparently look for neutralinos instead (neutralinos appear to crop up deep inside what we Nuclear Physicists call 'Particle Physics', which is full of leptons and mesons and other fun particles, fine, and some of the most brain-bending mathematics it has been my priviledge to not understand.)

Rachel

Re:Just another WIMP-seeking experiment

[zCyl]

and there's an on-going discussion as to whether or not neutrinos have mass, because if they do, there's enough of them that they might well make up the missing mass of the universe.

The discussion has pretty much moved toward conclusion, and the conclusion is that neutrinos DO have mass, and that the limits placed upon their mass, while greater than zero, do not yield enough total mass to account for the remainder of missing mass. These results might shift slightly with corrections of experimental error, but a drastic change is unlikely.

Black Listed

[OneArmedMan]

Its not that 90% of the Universe is missing, but because of all the Email spam problems we have, the Earth has been Black Listed. I contened that once we solve the spam problem, we will be able to reach the rest of the Universe. With that said, dont epect to be able to reach the rest of the Universe for quite some time.

Not True

[efuseekay]

Not true.

Gravity is only tested to solar system scales, and in an indirect way, galactic cluster lensing effects.

At very large scales, say of the Hubble radius, we have no tests of gravity. Cosmological models are almost always based on the belief that Gravity works at the very large scales, an extrapolation of many orders of magnitude. There is no proof that this is a valid extrapolation, and there are hints that they are not. (Like they lead to an extremely highly unlike situation. Check out This Talk )

Large scale modifications of gravity may affect the smaller scales, but these effects are naturally suppressed (you can cook up theories where they are not suppressed, but then it is not "large scale" modifications anymore). So to discover these effects are hard.

We have experimental constraints of course, but they are not very strong.

Re:Not True

[leonbrooks]

Gravity is only tested to solar system scales, and in an indirect way, galactic cluster lensing effects.

Agree. And we make an awful lot of assumptions about the continuity of physics even at galactic scales.

The bottom line is that we start by assuming that because a theory fits some observed properties of the universe -and- we have not yet thought of a better (or at least more appealing to us) theory, the one we have is true. "If the only tool you have is a hammer, every problem looks like a nail."

This is especially true of the really grand assumptions like "the universe has no centre and no edge" and "the en-bloc redshifting of distant objects is evidence of recession caused only by the stretching of space"; the problems these assumptions cause conventional science run deep, yet so well embedded in orthodox scientific dogma are they that the vast majority of scientists would rather reject the growing collection of conflicting data than the dogma. (see here for discussion of something even weirder).

Re:Not True

[efuseekay]

THe article you linked to is actually full of inaccuracies. Take the bit about quasars for example.


Very accurate positional measurements by radio telescopes (using very long baseline interferometry) revealed the astounding fact that some quasars appeared to be expanding at up to ten times the speed of light. This was in complete violation of the accepted laws of Einsteinian physics

This is an argument from incredulity. IN fact, the apparent superluminal expansion is explained neatly away by the fact that the jet of the quasars are pointed right at us. It is a nice little problem in relativity to show this is true.

Here is another one :
The orthodox view is that quasars are just abnormal (e.g. superluminous) galaxies and that they can only have a redshift caused by velocity. Arp drew attention to quasars interlinking with galaxies. But a large body of opinion now holds that galaxies can violate the redshift distance-relation. It is the most peculiar galaxies, those most like quasars, which offer the most compelling evidence for non-velocity redshift.

This is an argument from false authority. Most galaxies close to us obey the Hubble Law to a great accuracy (those further away has a distinct deviation from velocity-distance diagram, but they are exactly as predicted by general relativity with 75% dark energy). Peculiar velocity is a contribution to red-shift, that's true, but the contribution is very small. In fact, it is a known systematic that can often be removed. (THey lead to so-called fingers of god in redshift-luminosity diagrams, i.e. a small 'stretching' of otherwise homogenous distribution of galaxies.)

It is good to entertain heretical ideas, but they have to pass the same stringent tests as those which you called "scientific dogma". Science has no dogma, just tested ideas. Any of them can fall, but if you want to overturn it, you better come up with a better one, not just a different one.

I will end this with a fallacy of my own :), that's it, a personal attack : becareful of Arp's ideas, many (if not all) of them are plain wrong.

Re:The question bad then too?!

[inaeldi]

8 times 6 is 48

Dark data....

[mseeger]

Hi,

i'm currently investigating a similar matter: dark data. It seems to occupy around 90% of my hard disk.

Bye, Martin

The New Gravity

[mindpixel]

Dark Matter isn't the only explanation for Fritz Zwicky's 1993 observation.

MOND or Modified Newtonian Dynamics proposed by Moti Milgrom is I think better. If I were to bet on someone winning a future Nobel, Milgrom would be the person.

I'm driving the VLT as I type this...sentence was interrupted for a preset...I'm back now.

Anyway, I know a number of scientists that seriously consider the Newton's may not work at large scales. Nature recently rejected a paper from some rather prominent that seemed to confirm that gravity behaves differently at large scales. But, science is very reluctant to change its equations and publication will have to await more data.

Just remember - Dark matter may not exist. Be skeptical of those who treat it as fact.

MOND FAQ

Dark-Matter Heretic [This is a wonderful article]

Re:The New Gravity

[mph]

Dark Matter isn't the only explanation for Fritz Zwicky's 1993 observation.

Zwicky died in 1974, so explaning his 1993 observations will require truly remarkable new theories of time and causality. It will make explaining his 1933 observations look easy.

I'm at the Palomar 200-inch, by the way. But we're in fog for the third night straight, so I have plenty of time for posting to Slashdot.

Re:The New Gravity

[mindpixel]

That's what I get for driving and posting at the same time!! 1933 obviously.

Re:The New Gravity

[mph]

I'm actually the observer, not the operator. (This is fine example of our tendency to see the world through our own perspective; I assumed you were an observer.)

This is the last of my three nights and we haven't opened yet. Hasn't even been close. Tonight looked promising in the afternoon, but the fog has just completely stalled out here. Another two hours or so and it will officially be a completely useless run. Glad you're doing better... send some of that up here.

Re:The New Gravity

[mindpixel]

We were closed monday night...and closed early on another night this week...can't remember which...they all blur together...would be easier to figure out if people would just wear different clothes on different nights, but I 've given that one up as hopeless.

Re:Bush Administration cites Missing Universe Theo

[Anonymous Coward]

Furthermore, if Al Quaeda were to buy, steal, or receive plutonium as a gift from the missing 90% of the universe, then Al Quaeda would be dangerously close to having a nuclear weapon. This is unacceptable.

Clearly, 90% of the universe needs to be destroyed. Facing clear evidence of peril, we cannot wait for the final proof -- the smoking gun -- that could come in the form of a mushroom cloud.

Missing Socks

[mrbrown1602]

So THAT'S where all my missing socks are!!!

This was solved a long time ago...

[tlambert]

This was solved a long time ago...

...the missing mass is AOL disks.

-- Terry

Yes, there are tests...

[mindpixel]

Yes, there are tests for gravity at large scales. See for example: A Test of Newton's Law of Gravity in the Weak Acceleration Regime

From the abstract:

"A pilot experiment suitable to test Newton's law of gravity down to the regime of acceleration typical of galaxies has been carried out in Omega Centauri. Stars in the extreme periphery of this globular cluster are used as test particles immersed in such weak gravitational field. The stellar velocity dispersion is found to remain constant at large radii, rather than decrease monotonically, starting at acceleration a=10e-7 cm/s2. This is comparable to the acceleration at which the effect of dark matter becomes relevant in galaxies. Explanations for this result within Newtonian dynamics exist (e.g. cluster evaporation, tidal effects, presence of dark matter) but require fine tuning of the relevant parameters in order to make the dispersion profile flat. An interesting alternative is that this result, together with a similar one for Palomar 13 and the anomalous behavior of spacecrafts outside the solar system, suggests a breakdown of Newton's law in the weak acceleration regime."

Re:Yes, there are tests...

[efuseekay]

It is a test of Newtonian gravity. In fact it is not even a test of newtonian gravity, but just a test of the centripetal force = newtonian gravity law. You can imagine either to be wrong, or inaccurate.

They found that gravity "breakdown" at some small acceleration scale. The problem with "acceleration scales" breakdown is that 'acceleration', as defined in their paper, is not a (jargon!) covariant statement. In other words, they are saying acceleration with respect to the center of mass of the cluster. But of course a different observer, say somebody flying in a spaceship next to the cluster, will measure a different acceleration wrt to him. This means that the apparent breakdown is depends on coordinates you choose, but physics should not depend on coordinates. While there is no proof one cannot formulate some screwy theory which can fit this observations and be also coordinate invariant, nobody has done it yet. (It's called MOND, and somewhere along this /. article somebody has posted the links.)

But it is true that the so-called "small acceleration" breakdown at about 10^{-8} cm/s is an annoying thing that won't go away. The Pioneer 10 spacecraft has the same anomaly. The paper you cited is a increase in the "scale" to globular cluster scale, which is interesting, but you can imagine (as the paper itself noted) many things can explain it other than modification to gravity. (the paper suggested perhaps some objects are actually binaries, so their counting of mass may be wrong.)

The point of the paper is that while you can argue away the same "breakdown" in newtonian physics in galaxy scales by putting in dark matter, you cannot do the same with globular clusters, since DM is not known to cluster around such objects. This is interesting, but we'll wait and see :).

But anyway, these are consider tests at "small scales" :). The large scales I mean, bigger than Galaxy Cluster scales...

This much I know..

[ilyag]

..IANAP (i'm not a physicist), though.

There are two strage things happening in the universe on the large scale. The first one is the "dark matter". Basically, if we apply Newton's equations for gravity to various galaxies, we find out that they are spinning too fast. If the force holding them together is what we think it is, most of the stars in a galaxy should have been slingshoted away and left the galaxy. So there must be something making the attraction stronger than we think.

The second strangeness - the "dark energy" - concerns the expansion of the universe. Different pieces of matter in the universe attract to each other by gravity. This slows down the expansion of the universe. As far as we know, gravity is the only thing that can affect the universe on a large scale. So, the expansion of the universe should be slowing down. However, as WMAP showed, the rate of expansion of the universe is actually speeding up. So, there must be something that makes the universe speed up faster than we think.

In both cases, there are two possibilities. The first one is that the anomality is equally distributed through space. This would mean that our equations are a little bit off. For instance, we can account for the "dark energy" by adding an extra term to Einstein's equation for the expansion of the universe. If we change Newton's equation to make gravity stronger over large distances, we can eliminate dark matter.

Yet, there is a possibility that there can be more of the "strangeness" in one point in the universe than in another. For example, one galaxy may be held together tighter than another one of the same size. That would mean that there is another strange beast in the universe apart from the types of matter and energy we know. A whole new branch of physics will be needed to deal with the beast and ask questions like "Why is there more dark matter here than there is there?" and "Does dark matter interact with ordinary matter in any other way than gravity?". Dark matter will compress things on a smaller scale; dark energy will expand things on a larger scale. Obviosly, the statement that "Universe is 75% (or whatever) dark matter" will only be meaningful in this case. As far as I know, we need more precise observations to choose between the two possibilities.

I hope that someone who actually is a physicist, is not asleep, or can reach the "Reply" button will explain all the points I'm wrong on...

Re:This much I know..

[Keith Gabryelski]

Simply put... god is a hack -- He had a week to make the universe -- instead he watched kung fu movies for 6 of the days and pulled in an all nighter ...

when he was done he found galaxies weren't spinning perfectly with e = mc^2 ... (the bug is actually in the large_scale_effect() method -- but that is another story) ... so he put in a couple of frobs to get things moving at the rate he thought satisfied his artistic needs.

Checked it in... no one QA'd it... packaged and shipped it ... and we bought it en masse.

uhh... if you have a better explanation, bring it forward...

The answer to the riddle of the socks

[MousePotato]

If they ever find the missing 90%... I want back all my missing socks, several sets of keys, two wallets and my mind...

Earlier BBC article about this

[orbitalia]

There is a more detailed article about this at the BBC

Universe Lite

[Zakabog]

We couldn't afford the Pro version of the Universe which comes with 100% of the mass in a fully functional universe, so we settled with Universe Lite which is a toned down, cheaper, consumer market version. Most of the missing mass is in gas and small particles anyway so we didn't need it that badly.

Correction...

[clambake]

Clearly, 90% of the universe needs to be destroyed.

I think you meant "liberated".

Re:It's in energy

[TMB]

Nice try, but most of the mass-energy of the universe really is in mass. In the very early universe, most of it was in energy, but the density goes down faster with the expansion of the universe than the matter density does (R^-4 instead of R^-3)... the matter is (quick calculation) about 20,000x more important currently.

[TMB]

Re:That's twice.

[xaaronx]

I don't make jokes in base 13. Anyone who does should get help.
--Douglas Adams

Search for the Missing Universe - huh?

[kasperd]

Did they misplace it again? When are they going to learn it? Always put the Universe back once you are done using it!

Not just another WIMP-seeking experiment

[levell]

I'm feeling smug at the moment as I went to the official opening of the latest stage of this project last Monday and actually got to go down the mine!

There are a few experiments down there, the main three are Zeppelin I, Drift I and an NaI detector.

All three are looking for WIMPS - weakly interacting objects - heavy particles that provide extra gravitation to the universe but are hard to see. But there are differences between them. The NaI experiments main job is to rule out completely (or confirm) a possible discovery of WIMPs made at another such lab - Gran Sasso in Italy. The signal seen there is very strange and indiciates masses of particles we don't expect so I think most people expect it to have a problem with that experiment.

Drift I and Zeppelin I are both really R&D devices built to test technology to be used in bigger experiments (Drift II and Zeppelin II) that are being built now. Zeppelin is a conventional dark matter detector and can search for a bigger range of pssibe masses than Drift but Drift is the first WIMP "Telescope", if it sees anything it can tell which direction the WIMP came from which makes it easier to rule out background noise but will also tell us interesting things - is the dark matter in a disc like our visible galaxy or a sphere like some simulation predict it is.

The mine itself is very cool - deepest in Europe and they mine Potash and rock salt but the tunnels are rock salt so that you they feel soft to the touch, the tuneels are much bigger than I was expecting too! They drive vans around down there that have been lowered down the mine shaft nose first!

Is the basis of the mass question valid?

[slinted]

In following the "big questions" of astrophysics, it seems like it boils down to

1. Dark Matter - Look at spinning galaxies, our current theories of gravity say they spin too fast for so little mass...do some math, ok...we're short by 90% from what is visible.

2. Dark Energy - Look at far off galaxies, they are moving away from us...and they're accelerating, and since our current theories say that gravity, an attractive only force, is the only significant player on those scales.

So, if we lack an understanding of what forces act on large scale distances to such a degree that ...well, it isn't even orders of magnitude, its positive where we'd expect it to be negative...hell, we don't even *have* candidates for repulsive forces acting on something the size of a galaxy at that distance, then why do we think that our calculations of what a target galaxy's mass *should* be based solely on...yup, our imcomplete equations for gravity, would be correct? Seems to me like they're both wrong in the same direction...if there were a sustained repulsive force, say...the force or "geometry" behind einstien's cosmological constant, then we'd fill in both blanks: repulsions to make distant galaxies travel away from us faster, and a force which would explain the lack of mass in galaxies.

Re:Is the basis of the mass question valid?

[TMB]

So, if we lack an understanding of what forces act on large scale distances to such a degree that ...well, it isn't even orders of magnitude, its positive where we'd expect it to be negative...hell, we don't even *have* candidates for repulsive forces acting on something the size of a galaxy at that distance, then why do we think that our calculations of what a target galaxy's mass *should* be based solely on...yup, our imcomplete equations for gravity, would be correct? Seems to me like they're both wrong in the same direction...if there were a sustained repulsive force, say...the force or "geometry" behind einstien's cosmological constant, then we'd fill in both blanks: repulsions to make distant galaxies travel away from us faster, and a force which would explain the lack of mass in galaxies.

A few points:

1. They're wrong in opposite directions. Dark matter pulls things tighter, and dark energy repels.
2. We have a couple of candidates for repulsive sources of gravity, though they're unsatisfying. The vacuum ("cosmological constant") isn't all that ugly in and of itself - it's the size that's ugly. Quintessence is ugly, but it's a candidate.
3. There are theories that try to use the dark matter particles to power the cosmic acceleration, the so-called "Cardassian models" (no, I'm not kidding, that really is what they're called). Basically, you need something that has no pressure on "small scales" (small = tens of Mpc) so it predicts clustering and structure formation the same as the currently-favoured Cold Dark Matter models but negative pressure on very large scales so it can power acceleration. They usually try to do this by having the particles self-interact or decay on really long timescales.

So yes, people have thought about it, but no one's come up with a single theory to explain both that seems any less contrived than having two slightly-less-contrived independent explanations.

[TMB]

Topology of the Universe

[SaXisT4LiF]

I recall an earlier article about the universe being topologically equivolent to a torus. Could this topology account for some of the inconsistancies in these "mass of the universe" calculations?

Consider any two stars of mass m and M. With distance r between them:
The Gravitational force of attraction is G*M*m/r^2.

But you'd also have a gravitional force wrapped once around the torus of G*M*m/(r+L)^2.

Then you could wrap around again and again and again....

Of course, generally the distance would be too huge to make difference, but when you consider how many stars there are and the infinite number of loops around the torus you could make, it would add up eventually.

Any thoughts on this?

Re:Topology of the Universe

[QuantumFTL]

Hmm, interesting question. Let's look at it point by point...

I recall an earlier article [slashdot.org] about the universe being topologically equivolent to a torus.

Firstly, the experiment didn't prove anything by a long shot, it merely suggested that the universe may be topologically equivilent to a torus or cylander. But let's assume it is for a moment.

Consider any two stars of mass m and M. With distance r between them: The Gravitational force of attraction is G*M*m/r^2.

Nice to see someone remembers their introductory physics :) Unfortunately that's a classical approximation to gravity's actual effect, and we don't have any proof that it works like that on the kinds of scales we are talking about (see another post in this thread about Modified Newtonian Dynamics). But even assuming this is true, there's still a few problems.

Then you could wrap around again and again and again.... Of course, generally the distance would be too huge to make difference, but when you consider how many stars there are and the infinite number of loops around the torus you could make, it would add up eventually.

Well, kinda. There's two flaws with this. Lets look at the first one, mainly the inverse r^2 dependence and wrapping. Basically the magnitude of the gravitational effect from any given object A with mas m on an object B with mas M will be:

Sum n=1->infinity of G*m*M*(-1^(n+1))/(r+n*W)^2
where W is the width of the universe. The oscillating negative 1 term reflects the fact that the object Ahas "mirror images" on BOTH sides of object B (think about pacman, if you go far enough to the left, you'll eventually reach something to your right). This series converges VERY quickly (it's 1/(n^2) not 1/n so it converges, plus it's oscillating so additional terms pretty much cancel out). Because the width of the universe W is very large, and the series oscilates, the first term (classical term for an open universe with no wraparound) completely dominates. This would be true if the only two things in the universe was a large black hole the mass of the universe, and your object B... essentially closed or open makes almost no difference on the amount of attraction you feel unless you are at a distance from the object on the order of magnitude of W. (yes I know general relativity affects things like black holes but the length scales here pretty much nullify any need to take that into account)

So already this doesn't really make much of a difference, but there's still another reason! The universe is roughly isotropic as far as we can tell from long distances away... That is, the amount of mass to one side of you in the universe is pretty much the same as the other side. This means that mass that's far away from you has little effect, because all the force vectors from all the other galaxies pretty much add up to zero (they cancel each other out). So even if this wraparound effect really did add up to a lot, it's coming from EVERYWHERE and would cancel itself out!

But wait I'm not done yet, there's yet another reason! Even assuming that the visible mass of the universe created a net force on stars in some direction because of this wraparound effect, it makes no difference to intragalactic dynamics! The length scale here is the width of the universe, so this force would not vary significantly along the width of a galaxy, and would pretty much be a uniform acceleration. This uniform acceleration does not affect the relative motions of the stars WITHIN the galaxy (intragalactic dynamics). So even if everything you speculated was completely true, it'd still never make a difference. We're looking for a source of gravity pulling things TOWARDS the center of the galaxy, not away from it or in some arbitrary direction. As far as we can tell, the only force that can do this is gravity from some hidden source within the galaxy (unless you make modifications to the fundamental theory of gravity on these

Supermassive Black Holes

[Peverbian]

I can't believe no one brought this up yet. Recently some astronomers have been using hubble to look at the middle of galaxies and have discovered Supermassive Black Holes there. In fact, they've found a bunch of 'em, and there's a relationship between the size of the galaxy and the size of the singularity, and every galaxy seems to have one, even our own! And IIRC they figured this would account for the missing stuff.
-Peverbian

Re:Supermassive Black Holes

[QuantumFTL]

can't believe no one brought this up yet. Recently some astronomers have been using hubble to look at the middle of galaxies and have discovered Supermassive Black Holes [thehubbletelescope.com] there. In fact, they've found a bunch of 'em, and there's a relationship between the size of the galaxy and the size of the singularity, and every galaxy seems to have one, even our own! And IIRC they figured this would account for the missing stuff.

Well, as far as I understand, that's some missing mass, but not nearly enough. More importantly, it's not the right distribution to explain the velocity curves. I did some googling (you can do some more if you like) and found this page. I'm sure theres better ones out there but it appears to be pretty accurate. This is not simply a problem of having enough mass in the galaxy, but having enough mass in the right places... The velocity curves of stars in different galaxies of the same mass provided that the mass is distributed differently. The curves we get are rather consistant with a spherical halo of dark matter (yes there's other theories but this is simple to imagine) which acts much different than a point mass at the center of the galaxy. This can be seen by the fact that anything inside a spherical shell of matter feels no net gravitational pull. for instance, if the earth was a perfect hollow sphere, on top of it you'd feel plenty of force, but go inside of it, and the forces from all directions cancel out. Same with a spherical halo of dark matter, stars only "feel" a force from the dark matter in the part of the halo that has a radius smaller than their orbital radius, the rest cancels itself out. This makes a significant difference in the measured velocity curves, and these curves do not point to dark matter simply being a point source in the center of the galaxy.

So I don't really think that discovery is that relevant to this discussion. Cool? Yes. But doesn't come close to explaining the mystery that is dark matter. (Yes, I'm aware of various modifications to gravity theory that could also explain this as well)

Cheers,
Justin

Disclaimer: I am not a physicist yet (still one more year to go before my degree). I do however have published research in astrophysics, as I do research with two respected astrophysicists here at Cornell University. If I've made a mistake anywhere in my reasoning here, someone please correct me :)

Poor CIA...

[Black Parrot]

> I thought Iraq kept their WMD in heaven?

Now each CIA operative is being required to frisk 72 virgins in search of the missing WMD.

Socks!

[printman]

Actually, we already know what the 90% of the "missing" Universe is - socks!

One Quibble

[Greyfox]

I don't like filet for... well... anything. It's too soft. That's good if you don't like your meat to have any texture at all, but I do. Go with a nice ribeye or New York Strip and otherwise keep the recipe the same. (That's 500 Fairenheit, by the way.)

Most people are afraid to get their oven and cooking utensels hella hot, and that's a shame because that's the only way to really cook your food well. For the longest time, I shared my mom's fear of taking the oven over 375 (Fairenheit) and my cooking suffered for it. Now I'll crank it up as high as it'll go and am always rewarded.

By the way, you absolutely do not want to use a teflon or other non-stick coated surface for this. I have a cast iron pan I got at K-Mart for $5 and its entire purpose in life is to cook meat like this. And also don't ignore the suggestion to use prime meat. The difference between the USDA choice and prime ratings is easily noticable even if you don't eat a lot of beef. You might use a couple of choice steaks to get used to the idea of using a pan that's freaky-hot. They'll still be tasty. But once you move up the scale to prime, you'll see a huge difference and everyone you entertain will always talk about how you make the best steaks in the world.

In other news..

[Frank of Earth]

... France surrenders

You really have no clue...

[DesertFalcon]

how unbearably sexy it is to hear a girl discussing mind-bending physics. Or anything that's way over my head, for that matter.

This recipe is legit.

[positive]

It sounds very similar to Alton Brown's Pan Seared Rib Eye recipe. Regardless, the steaks are delicious, and using pepper (as Alton's recipe calls for) doesn't seem to cause any problems. I really need to get myself a cast iron skillet.

Recursive Universe

[Mittermeyer]

Personally I think the universe is recursive, i.e. the higher dimensions curve back into what we consider to be 4-D mass and exerts effects far beyond the relatively simple Newtonian gravity.

It's a side effect of the zero dimension, i.e. no length, width, depth or time, everything is connected.

You heard it here first.

Dark side of Particle Physics

[Roger W Moore]

Being a physicist and Yorkshireman I can't help commenting on this...The mine in question is the Boulby Potash mine and there have been Dark matter experiments going on there for quite a few years.

Although these experiments are performed deep underground, like neutrino, experiments their physics is somewhat different. Dark matter experiments are aimed at finding new fundamental particles as yet unknown to physics. Neutrino experiments, on the otherhand, study the properities of neutrinos and it is these experiments (SNO, SuperKamiokande) which have produced the exciting discovery of neutrino oscillations.

The reason dark matter is such an interesting field at the moment is because of the WMAP result. This indicates that only ~5% of the universe is what we call "baryonic matter" i.e. the stuff that we are made of. A further ~20% is made up of non-baryonic matter. This includes things like neutrinos, but just neutrinos is nowhere near enough. So, if we believe the WMAP result, there is a sizeable amount of matter which we cannot account for given our current understanding of physics.

However, dark matter experiments are not the only ones out there looking for this missing mass. I'm working on a collider experiment called D0 on the Tevatron collider at Fermilab near Chicago. This is currently the highest energy collider in the world (until the LHC at CERN, Geneva starts in ~2006). As such it is an excellent place to look for new physics and one such example is something called SuperSymmetry. You can essentially think of this as a symmetery between force and matter (in technical terms its a symmetry between fermions and bosons) and it doubles the number of fundamental particles.

So how does this explain the dark matter? Well, a lot of supersymmetrical models have the lightest supersymmetric particle being stable i.e. it cannot decay. Now being neutral, stable and weakly interacting, this would be an ideal candidate for dark matter and might make up the missing mass of the universe. So instead of looking for these particles scattering off nuclei (as dark matter experiments do) we can actually look to see if we can make them in high energy interactions.

Some interesting web sites you might like to read for more information are

• UK Dark Matter Collaboration
• D0 Public Information Page
• The Particle Adventure: Basic explanation of particle physics

I'd particularly recommend the last site if you want to know how much we still have to understand! (click on "Unsolved Mysteries")

Crighton who?

[thepupil]

Okay, check this out. Thomas Young proved around 1801 that light was a wave using a double slit experiment in which light created an interference pattern. However he was flooding photons into it. In 1989 this experiment was done again with a twist. Only one photon at a time was sent into the detection area, but the same pattern emerges. So what is causing the interference? And couldn't this interference also explain why we "think" 90% of the universe is missing? Couldn't it simply be just a macro scale effect. I leave you with references other than Michael Crighton: http://www.fnal.gov/pub/inquiring/questions/light_ dual.html http://physicsweb.org/article/world/15/9/1 I might have only a passing interest in science, but I do try to discern between legitimate sources and science fiction. As Dirac is said to state that each photon is interfering with itself it has also been postulated by multiverse theorists (such as David Deutsch) that the interference is coming from photons in parallel universes. Since we really don't have a complete understanding of quantum mechanics couldn't it be possible that the so called "missing" 90% is just the effect that parallel universes are exerting on this universe?