Slashdot Mirror
Dark Matter Discovered
sebFlyte writes "Wired is reporting that scientists have come up to a solution as to where all the matter in the universe actually is. Experiments being done with Chandra, NASA's X-ray telescope have shown up a likely candidate for the solution of the dark matter problem. There are massive quantities of Baryons in a super-heated gas cloud several hundred million light years away."
There are massive quantities of Baryons in a super-heated gas gloud several hundred million light years away."
Which, IMHO, is a damn fine place for them to be, rather than here.
The absorption pattern, as detected by Chandra, is consistent with interference caused by carbon, neon, nitrogen and oxygen ions -- in other words, baryons.
It's really a neon sign on Frogstar World B announcing the construction of a restaurant to be constructed on this location in several billion years and reservations are welcome.
"Assuming that what we see is a standard portion of the universe, we extrapolated the data and derived the volume density (of baryons in all the clouds) -- and it's consistent with 50 percent," said astronomer Fabrizio Nicastro, of the Harvard-Smithsonian Center for Astrophysics and lead author of the study.
Later a two-headed, three-armed man entered and ate a piece of fairycake and destroyed their model.
Whereas baryons account for 4 percent of the total matter and energy in the universe, dark matter is thought to make up 23 percent. The remaining 73 percent of the so-called matter-energy budget consists of what scientists call "dark energy." This energy acts like an anti-gravitational force that, in theory, is causing the universe to expand rather than contract.
And here I thought it all existed somewhere along Lucas Valley Road and explained the Jar Jar character and Episodes I-III...
A feeling of having made the same mistake before: Deja Foobar
And would this "superheated gas pocket" perchance reside in Nibbler's lower intestinal tract? ;D
In case anyone's wondering what a baryon is...
http://en.wikipedia.org/wiki/Baryon
I don't see anything??
Here's a picture.
They found some of the ordinary matter that has gone unaccounted for, not dark matter. Read the article.
CDE open sourced! https://sourceforge.net/projects/cdesktopenv/
"There are massive quantities of Baryons in a super-heated gas gloud"
Google wants to know if you mean "gas cloud".
Wired is reporting that scientists have come up to a solution as to where all the matter in the universe actually is.
WIRED also said that "Push is the next Big Thing."
In physics we don't call it dark matter. We call it "make the theory fit the data" matter.
The summary is not correct (big surprise there) in that this is a confirmation of a long-suspected theory as to where the missing ordinary (baryonic) matter in the universe is. This does not solve the dark matter problem at all.
9
Read more at the press release from the Chandra team at Marshall: http://www.spaceref.com/news/viewpr.html?pid=1604
Dark matter is yet another topic altogether, as is the even more elusive dark energy.
They are extremely interesting for anyone fascinated with physics.
Creative Demolition
This should be "Missing Matter Discovered" not "Dark Matter Discovered"
They HAVE NOT found dark matter, they've found the 'missing matter' as the article says. They have found a clue as to the dark matter, as a result of the discovery.
Although discovering the dark matter would be much cooler, (yeah I was excited when I read the title).
[rant] Why is it the only 3 times I've 'emailed the on duty editor' before publishing, I've been ignored and the mistakes gone through?? [/rant]
Windows in 6 Bytes (IA-32) : 90 90 90 90 CD 19
I mean really now, Baryons, oh come on nasa. Try something new and exciting like, antiquantafusitrons.
"Baryons, along with mesons, belong to the family of particles known as hadrons, meaning they are composed of quarks. Baryons are fermions composed of three quarks, while mesons are bosons composed of a quark and an antiquark."
Wikipedia cleared that one up nicely!
-=test-sig_0.1.5(NoWhitespaceVersion)=-
It was only a (dark) matter of (space) time.
Sincerely,
Pan Tarhei Hosé, PhD.
"Homo sum et cogito ergo odi profanum vulgus et libido."
Is how do these extremely difficult scientific questions get answered so quickly lately.
It was just a couple days ago that slashdot reported that dark matter was being postulated as the reason for the extra mass of galaxies:
Simulating the Universe with a zBox.
Now, in less than a week, we have proof for the existence of dark matter? Amazing!
How can scientists go from hypothesis to proof in such a short time? Are we really progressing by such leaps and bounds? Or, is this an example of media jumping to conclusions about initial research.
Hey! Stop copying my sig!!! Stop copying my sig!!! Stop copying my sig!!! Stop copying my sig!!!
Its the hunters running away from the stench of Bloodnut the flatulent...
In other words, if regular stuff is about 5% of the energy density of the universe, with dark matter at about 20%, and dark energy at about 75% -- the stuff in this story comes into that 5%, ie, regular stuff and not dark matter.
Here's what I do: Bitty Browser & Andromeda
I have it on good authority that all the dark matter is in Iraq, and that's why we had to invade.
Tachyons are in fact hypothesized faster-than-light-particles, appearing for instance in certain string theory scenarios.
:-)
But baryons are by no means the counterpart to tachyons. All known elementary particles in the universe are either fermions (particles with spin in integer multiples of 1/2) or bosons (particles with integer spin). Bosons include the photon, the gluon and many others. The fermions are further subdivided into leptons and quarks. Leptons include the electron and the electron neutrino among others. Baryons are particles made up of three quarks, and are fermions and include among others, the proton and neutron, which are the most commonly found baryons in nature, since all heavier baryons normally decay.
Two quarks (fermions) can combine to form mesons, which are in fact bosonic in nature (since two quarks with spin half combine to form a particle with integer spin).
Hope that confused the issue a little
A bit more on-topic: Finding baryons in this amount is a big deal, since baryon has previously been suspected to primarily exist in galaxies, and only in small amounts outside galaxies. While it by no means doesn't solve all problems of cosmology, it is a big help.
So they say they've found the missing matter, but nowhere in the article do they actually tell us where all the missing socks went. Sure sounds like a scam to me!
> > In case anyone's wondering what a baryon is...
> > http://en.wikipedia.org/wiki/Baryon
> In case anyone's wondering what slashdot is...
> http://www.slashdot.org/
In case anyone's wondering why the hell am I wasting my time so pointlessly.... I have no life.
They reversed the anti-proton to tachyon ratio in the main deflector array after flooding it with a plasma burst diverted from the warp core and then polarising it by reinforcing the nucleon field.
Drill baby drill - on Mars
Wasn't Google looking to buy up all the Dark Matter, not too long ago? Sware I read it here...
"Who are in control, they are not in control of anything - they don't even control themselves!" - Glen Beck
I thought one of the sure indicators that showed the presence of unseen matter was that most galaxies behaved as though they were more massive. That the rotational energy of many/most/some galaxies should be ripping it apart, yet clearly there was some extra amount undetected mass in a galaxy that held it together.
These clouds are great for a macro-framework missing mass solution but unless they are found to exist in a somewhat smooth (or central) distribution in a galaxy how would massive clouds several hundred million light years away provide a solution for cases like this?
Huntred
Assuming that what we see is a standard portion of the universe
An astrophysicist, a physicist, and a mathematician are attending a conference in Scotland. During a break, they take a walk through some of the countryside, and come upon a black sheep.
"Aha," exclaims the astrophysicist. "I had no idea that all sheep in Scotland are black."
The physicist looks at her colleague in disbelief. "All sheep in Scotland are black? Are you nuts? We've only seen one sheep!"
The mathematician interrupts. "And only one side of that sheep."
Which is what they're constantly doing. I heard the theories in my astronomy class. There's plenty of them, such as brown dwarves just drifting around out there. How do you explain them? Well some star has a vector or some light appears bent (lens effect) and it's figured there's some large enough object out there not emitting light which is doing it. And who's to say it isn't large amounts effectively of bits the size of pea gravel drifting around?
In other words, if regular stuff is about 5% of the energy density of the universe, with dark matter at about 20%, and dark energy at about 75% -- the stuff in this story comes into that 5%, ie, regular stuff and not dark matter.
Dark matter is, as I understood, matter which isn't emitting some radiation, i.e. visible light or gamma rays. It's predicted, because without something being somewhere a number would be +0.0000150 instead of +0.0000146 and we can pretty much drop the old Intel Pentium jokes.
A feeling of having made the same mistake before: Deja Foobar
I can see the project now: "Gloud: The GNU open source cloud."
Mythos : Logos
Not exactly... They think the regular stuff they CAN see is being held together by stuff they can't... Like when you glue your hand to a phonebook, you can't see the glue, but you know there has to ba a reason the phonebook isn't falling to gather all the "normal matter" in the Earth.
Watch for Penguins, they eat Apples and throw rocks at Windows.
+/- 3 orders of magnitude is considered precise.
"Reality is that which, when you stop believing in it, it doesn't go away." - Philip K. Dick
Turns out it was behind the sofa cushions all along.
"Win treats sysadmins better than users. Mac treats users better than sysadmins. Linux treats everyone like sysadmins."
Obviously that's where the bulk of all the Univere's matter is. Each pound of the stuff weighs 10,000 pounds.
First, I had to look up "tachyon". You are right, tachyons are apparently particles that travel faster than the speed of light. I've only heard the term from Star Trek, and for the time being that's where these particles are from - the realm of (science) fiction. I've certainly never had them mentioned in class!
Baryons are not the counterpart to tachyons. Baryons are simply particles that are made up of quarks. The two best known examples are neutrons and protons, which make up virtually all of the stuff you own. Yes, baryonic matter is pretty much everything we interact with.
Two examples of particles that are very common and all around us are electrons and neutrinos. You're familiar with electrons (which are not baryons!), and the nuclear reactions in the Sun are constantly producing a mind-boggling number of neutrinos. Generated in the centre, they travel at nearly the speed of light which means that the ones passing through your body right now are about 8 minutes old. By comparison, the light from the Sun (photons, also not baryons) bounces off all the photons there, so by the time it actually reaches you it's about a million years old.
Finally, and most importantly, dark matter has not been discovered. You are also right in that the reporter is very much out of his depth. The article states that there is evidence for baryons to be found in places where we have not seen them before. What's one theory as to how they got there? Dark matter.
Just to add my two cents (I do cosmology research) to the chorus of complaints about this post, this research is NOT about discovering a new form of dark matter. This is about solving the "missing baryon" problem, which is a whole different kettle of fish. It's well known how many baryons (normal stuff) there should be according to big bang theory. However, if you look out at the universe and count observed gas and stars, you just don't see as much as you should. So people have assumed there are some hidden regions, where the gas is too cool to emit significant radiation for example, that contain enough baryons to make up the missing baryon budget.
Also, this seems pretty provisional stuff. I doubt this is the final word on the missing baryon problem. It certainly has nothing to say about the nature of dark matter or dark energy. But I guess some gushing "dark matter discovered" hype is just too tempting.
The world is everything that is the case
Not correct, there are two classes of elementry particles (that we know about) Bosons and Fermions.
Bosons are things like :
- Photons
- Gluons
- W and Z Bosons
- Higgs Bosons
Bosons don't have anti-particles, and are less likely to form stable structures.Fermions are things like :
- Quarks
- Electrons
- Neutrons
- Protons
Fermions do have anti-particles, and form the everyday matter that you interact with.IANAP, but two photons cannot cancel each other out, however two beams can (assuming they are co-axial and anti-phased).
As for the flashlight, general light is not regular so you certainly can't make one using interference.
Windows in 6 Bytes (IA-32) : 90 90 90 90 CD 19
At least there were, several hundred million years ago.
slashdot broke my sig
There is a problem of assumptions here. The reason all these simulations say that there is missing matter is that they share one faulty assumption -- the Big Bang. If you stop to consider for a second that maybe the Big Bang theory is just a theory, those simulations don't say anything except what MIGHT happen if the Big Bang theory were true. Since they show that lots of additional matter must exist, then either the theory is flawed or there must be more matter somewhere.
As more experiments and opbservations come in, we consistently see that any additional matter we find is not nearly enough to satisfy the simulations of the Big Bang. They've been trying to find this missing matter to "save the theory" for a long time now, and this is another pebble, but they haven't found it yet. I personally am convinced that the Big Bang is a defunct theory. You don't have to be convinced yet, but I am.
If you want something to chew on, read "The Big Bang Never Happened" by Eric J. Lerner. It has details and citations aplenty.
To those of you for whom this idea is new, remember this post. In ten years when everyone "knows" that the Big Bang is a dead theory, you can say that you knew that way back in 2005.
--Sandy
"Dark" matter is regular stuff. Forget all the hyperbole about "exotic" new forms of unpredictable Star Trek technobabble with physics-defying properties. It's called "dark" matter because it's not "bright" matter, like stars, conveniently radiating bazillions of units of energy for us to easily spot them.
It seems perfectly reasonable that there exists matter that's not formed into glowing plasma balls and is thus harder to spot.
But that presentation is kind of prosaic, and wouldn't sell lots of issues of the World Weekly News.
I've got a friend over at NASA who gave me a preview of some of the pictures.
Pretty fascinating if you ask me.
http://www.masturbateforpeace.com/
The tactic of citing the lack of peer review is rather amsuing considering most of the Astronomical community is enthralled with the conventional gravitation dominated Universe and refuse to recognize alternatives or dismiss them without explanation. On to the Dark Matter issue (taken from http://www.bigbangneverhappened.org/):
,Astrophys. J., vol. 529, p.911; B.R. Oppenheimer et al Science, 292, p. 698]. While these observations have been sharply criticized, they have been confirmed by new observations [R. A. Mendez ,arXiv:astrop-ph/0207569].
The existence of "dark matter"
Dark matter, or "non-baryonic" matter is a hypothetical form of matter different from any observed on Earth but which is nonetheless required by the Big Bang. Current versions of the (ever-changing) theory require that total gravitating matter density be equal to 0.3 of the critical density but that of ordinary, baryon matter be only 0.05 of the critical density. This means that 0.25 of the critical density has to be in the form of some undiscovered, non-baryonic matter, generally described as Wimps, weakly interacting massive particles.
This "cold dark matter" or CDM, was hypothesized as essential for the Big Bang theory back in 1980--23 years ago. Since then physicists have searched diligently with dozens of experiments for any evidence of the existence of these dark matter particle here on Earth. Oddly enough every one of the experiments has had negative results. In fields of research other than cosmology this would have long ago led to the conclusion that CDM does not exist. But Big Bang cosmology does not taken "NO" for an answer. So the failure to find the CDM after so many experiments does not in any way shake the faith of Big Bangers in such CDM. This is evidence that what we are dealing with here is a religious faith, not a scientific theory that can be refuted by experiment or observation.
The idea that neutrinos might form a bath of Hot Dark Matter has also been undermined by experiments that indicate that while neutrons do probably have some mass, it is of the order of 0.1 eV (energy equivalent), which means that total neutrino mass in the universe is likely to be around one tenth of the mass of ordinary matter.
Wright argues that the existence of dark matter if proved by the difference between the total gravitating mass inferred for galaxies and cluster of galaxies and the mass in observable stars. But this is an absurd non-sequitor. Observations have demonstrated that stars constitute only a small fraction of the total mass of ordinary matter that can be observed. In clusters of galaxies we can observe by X-ray emissions huge clouds of hot plasma, which have masses far greater than that of bright stars.
There is extensive observational evidence for ordinary matter in two other forms that are relatively dim, One is white dwarfs in the halos of spiral galaxies. Recent observations of high proper motion stars have shown that halo white dwarfs constitute a mass of about 1011 solar masses, comparable to about half the total estimated mass of the Galaxy [R.A. Mendez and D. Minnitti
Observations of ultraviolet and soft x-ray absorption has revealed the existence of "warm plasma' with a temperature of only about 0.2keV, which amounts to a mass comparable to that of the entire Local group of galaxies.(Nature 421, 719). If we adds up the warm plasma, which is sufficiently dim to be observable only as it absorbs radiation from more dint objects, the hot plasma, and the white dwarfs, we have enough matter to equal that which is inferred by the gravitational mass of cluster of galaxies. So there is no need for non-baryonic matter and there is no room for it either.
Conclusion: the evidence against the existence of non-baryonic"dark" matter is stronger than ever. Ordinary matter is only the only type of matter that exists.
For further evidence (taken from http://www.skepticalinvestigations.org/controversi es/bigbang.htm):
You can detect hydrogen in X-ray telescopes. You're correct, there are no transitions and therefore no lines. However, X-rays ionise hydrogen and are absorbed, reducing the flux at low X-ray energies (below ~500 eV). It makes spectra kind of curve off towards zero at low energies.
Our view of distant galaxies is affected by this, you always have to take account of a) the ~known amount of hydrogen in our galaxy and b) any other hydrogen between us and the source - this will give a redshifted absorption since it's at cosmological differences. It's pretty tricky with the quality of data you get with current telescopes to work out the redshift of any hydrogen that's out there (i.e. to figure out if it's associated with the source or an absorber on the line of sight like the one they discovered), because it's a smooth curve and not a line. That's probably why there are no numbers given. I'll have to read the paper though...
Slashdot - Mutual Assured Discussion
Dark matter might yet prove to be baryonic, but since about 70% of the universe is the even weirder dark energy, why is it so impossible to believe that 25% could be a new type of matter that interacts gravitationally, but not in other expected ways?
Here's what I do: Bitty Browser & Andromeda
Confusion sometimes arises because there are expected to be several different kinds of dark matter, and several different dark matter problems. The current best picture of the makeup of the universe is that it's about 4% baryons (i.e. atoms), 23% non-baryonic dark matter (exotic particles), and 73% dark energy. This comes from the WMAP satellite's measurements of the cosmic microwave background radiation, combined with (and checked by) independent results from galaxy surveys, supernova distributions, big bang nucleosynthesis, etc.
But most of the 4% baryonic matter is not stars, or easily visible gas and dust. It's made of normal stuff, but also dark - baryonic dark matter. That's what's under discussion here.
Even if this points the way to all of the baryonic dark matter, the 23% non-baryonic dark matter and the 73% dark energy still need accounting for. So you don't have to find _all_ the kinds of dark matter to have discovered some of the dark matter, and there's nothing wrong with the headline.
(Missing mass and dark matter, by the way, are pretty much synonyms.)
That paper you linked did not sway me, in part because it was clearly written without an open mind. It uses phrases like "the only way to do X if you rule out Y is to theorize something clearly unreasonable" to make its points. If observations disprove one theory, it does not prove the only known alternative. It simply means that you should question some more of your assumptions to figure out what you missed.
Clearly not all matter is in stars, so if that is your definition, then some dark matter must exist. My BS subject refered to the theories that dark matter must be something undiscovered, because we can't seem to find enough to fit the Big Bang theory's predictions. I remain convinced that the percentage of dark matter necessary to make Omega equal to 1 does not fit with observation.
I don't pretend to know what the correct theory is, but I am convinced that the Big Bang is not accurate, and that there are forces/processes at work in the cosmos that are being thrown out prematurely because they contradict the Big Bang, thus preventing the most accurate theory from surfacing. Ned Wright's defenses and criticisms are not the open-minded evaluation that I was looking for.
--Sandy
At the bottom of the Wired story, there is a Google ad, "Buy Dark Matter on eBay".
I just wonder if they throw in free shipping.
Pete Carr Owner Chatmag.com
Hi --
Distinguishing between baryonic matter -- stuff that bears any resemblance to everything around you, whether it is visible or not -- and other "dark" matter that does not fall into that category, is actually pretty commonplace in astrophysics. This seems like semantics, but turns out to be an important distinction.
The point is that the fraction of baryonic matter in the universe is, we think, reasonably well constrained (by both observations of light element abundances in conjunction with Big Bang nucleosynthesis models, and by measurements of fluctuations in the cosmic microwave background) to be only about 5% of the total mass/energy density. Yet there's an additional matter component (accounting for about 25% of the total density) that we know little about -- this is what most astronomers mean when they say "dark matter" these days.
This article says nothing at all about that 25%. It does, however, provide some clues towards a more complete accounting of the 5% that is "normal" (i.e. baryonic) matter. This is a very significant result, but the slashdot writeup and most of the comments to this article are completely distorting it.
The puzzle regarding the "normal" 5% was this: in the local universe (redshifts less than 2), only 10% or so of it is luminous matter, stars and galaxies and the like. More (40% or so) has been accounted for by studies of cool clouds of gas residing between stars, but this still left 50% in an unknown reservoir of baryons. Theory/simulation had suggested that one such reservoir might be the "warm/hot intergalactic medium" -- gas that is heated to millions of K.
The problem is that detecting low-density gas at that temperature is quite difficult, partly since most bound electrons have been lost. Only the more massive elements retain any electrons, and so can be visible in absorption in the FUV or X-rays.
What the paper discussed here (published today in Nature) does is to describe a plausible-looking detection of such filaments of "warm-hot" gas, through X-ray absorption. They use this detection to extrapolate a matter density of this WHIM component, and find that it could account for 30-50% of the baryonic mass, and so constitute the "missing" baryonic matter.
Note that this says nothing at all new about the 25% of truly "dark" non-baryonic matter.
One fairly large quibble is that the 30-50% number represents an extrapolation from just two absorbers, over a comparatively short distance, to infer the WHIM density in the whole universe. That's sort of a big jump, in case that part wasn't obvious. But you can't do this sort of analysis for very many sightlines -- you need a really bright emitting object on the other side of the WHIM clouds if you're going to see them, and such objects are few and far between -- so for right now that's what you get.
If you happen to be somewhere that has a subscription to Nature (most universities do), you can check out the two articles related to this in today's edition:
There's a "news and views" article by Mike Shull that's a nice summary of the issues involved. And there's the full research article by Nicastro et al.
Hope that clears at least a few things up. If I have time later tonight, I'll try to come back and respond to some of your other points.
cheers.
That's because intergalactic baryons not only fill a gap in scientists' understanding of the universe, but they may also lead to a better understanding of "dark matter," a mysterious and unseen form of matter that has so far only been detected by the gravitational pull it exerts on other bodies in the universe. "If we are right, each single one of these filaments is connected to a cloud of dark matter," said Nicastro. "If there wasn't dark matter there, or something with strong gravity that pulled on the matter in these filaments, we wouldn't have galaxies or filaments." Rather, the baryons would be pulled into galaxies and the galaxies into each other.
Basically speaking it could be that the reason this big cloud of baryons hasn't collapsed into stars is because of dark matter.
"Physics is to math as sex is to masturbation." -R. Feynman
2. Several ways --- rotation, motion of a number of satellite galaxies, mass/light ratio, Tully-Fisher relation, and, if it's a spiral, simply by the size if we know the distance (this is pretty rough, but a decent indicator)
3. Within a galaxy, I don't think so. But intra-galactic dark matter is just one type. There is also non-luminous matter in between galaxies in clusters to account for their motion. Hot X-ray gas is one candidate, but I thought I remembered that there didn't seem to be enough of that stuff to account for cluster dynamics. Maybe this new stuff will help out, though the mass deficit was much more than this 2% if I recall correctly, and is probably non-baryonic.
3. Yes, they should. That's the problem. Outer stars and globular clusters are orbiting way to fast if all the mass in the galaxy is traced by luminous matter. A good model to account for the rotational behavior is a spherical halo (not just a disk) of non-luminous matter. This is the intra-galactic dark matter, and not relevant to the article.
First, this result only applies to BARYONIC dark matter, which is only a fraction of all the dark matter out there. Second, we already knew that a lot of it at the epochs in question was in the form of hot intercluster gas.
The current work is an improvement over previous studies, and is good work. But the headline rather sucks. I thought we'd detected axions or something, even though I'd already read about this result.
I teach techniques to estimate cluster masses based on X-ray emission, and have used the Chandra X-ray Observatory myself. A headline about such work shouldn't trick me.
Professor of Astronomy, Author of Spider Star & Star Dragon (Tor)
If you just think astrophysics is math, you'd flunk the heck out of my astronomy exams no matter your mathematical sophistication. Probably every level of astronomy, from non-major to graduate level. At least the way I teach it.
Math is a very useful tool in astrophysics, but there's a reason that math is a separate department from any physical science.
Professor of Astronomy, Author of Spider Star & Star Dragon (Tor)
Actually, it is well established that the dark matter is NOT baryonic.
The story is a bit about dark matter, because there is a dark matter presence implied by the newly discovered gas clouds. But that's no surprise - the observed structure of ordinary galaxies already implies that they as well are permeated with dark matter.
Cosmologists, primarily based on data from the Wilkinson Microwave Anisotropy Probe, are now willing to put pretty hard numbers on the ratios of baryonic and non-baryonic matter (about 1:7 or so). ALL of the non-baryonic matter is dark. A good fraction of the baryonic matter is dark, in the sense that it doesn't emit much light (e.g., very cool stars, non-accreting black holes, planets, etc.).
There sure is dark matter out there that we don't understand well at all, and probably more than one kind. Neutrinos are one form, since recent experiments indicate they do have some mass. Neutrinos are pretty exotic compared to normal baryonic matter. There may well be weirder stuff.
Agree with you though, that Star Trek overdoes it.
Professor of Astronomy, Author of Spider Star & Star Dragon (Tor)
Because none of it exists within our own solar system. Else it would have played merry games with our orbital calculations, and we would know where to look for it -- up close and personal.
Seriously: We can model the solar system quite well using only the derived* masses of planets to within a few percentage points per thousand years... Yet supposedly the universe has some random form of gravitational energy which accounts for over 80% of the 'mass'. Get real.
Non-baryonic matter is the luminiferous aether of today.
If I'm wrong, great. But the whole theory stinks of hand-waving. Just becuase you don't have a clue doesn't mean you invent some wild theory -- not when there are dozesn of equally (or more) likely, simple explinations.
Every few years somebody finds another few percent of the 'missing' matter. I'm just waiting.... For some good evidence to satisfy my cynacal nature, or for them to get up to about 90% so that I can openly mock the concept.
For now I do admit that, in general, I don't know more about physicsthan the average masters holder therein; I do, however, know a LOT about gravity -- enough to make me question everything about non-baryonic matter anyway.
*It would be incredibly unlikely that we could 'accidentally' account for any matter/mass from the observational methods by which we derived the present, assumed masses for the planets.
OK, lets be honest: I haven't read the article. Still, with the mention of 'dark matter,' I thought I'd ask the opinion of my fellow /.'rs.
From what I understand, the theory of 'dark matter' is the way we explain the existence of forces that seem to have no originating matter. We see the effects, but don't see the matter that is causing it. So we say that there is 'dark matter.'
Fast forward a few decades. We have this new thing called string theory. One part of string theory is that our force of gravity is not, as it seems, a force inferior to our other forces, but that gravity 'strings' do not have endpoints on our own plane, but in stead loop back upon themselves. This allows for the idea of gravity 'leaking' from our plane into parallel dimensions.
Here is my idea: if gravity can leak from our plane to parallel dimensions, isn't it plausable that forces might leak from parallel dimensions into our plane? Wouldn't that explain the apparently massless forces that we observe?
Yeah, at least part of them. You can go to my website above, hit "Astronomy Work" link on the left, and be taken to http:physics.uwyo.edu/~mbrother where you'll find links to three recent courses I've taught. The intro astronomy course (1050) is currently in session and so the slides for that one are incomplete. These are slides, meant to accompany lecture, so they aren't enough on their own, but you might enjoy looking anyway.
Professor of Astronomy, Author of Spider Star & Star Dragon (Tor)
Most of science is speculation, and therefore, shouldn't be taken seriously.
You're obviously not a scientist then.
"Speculation" is what drives science (ie. I observe something then I speculate as to what a possible explanation could be). But it doesn't stop there. That's where experimentation comes in, to throw out my hypothesis, or not. Science is actually the whole process, not just the initial attempt at explaining an observation.
Speculation would be "Diet Coke is fattening, because most fat people drink diet coke".
This is not science. You have to PROVE your statment. And not only that, but you have to publish HOW you derived the proof, so that everyone can see it and has a chance to spot errors in your technique. AND everyone has to be able to obtain the same results as you got. Then it becomes science. That's about as far away from speculation as you can possibly get.
Now if you want to know about doppler shift and how interstellar/intergalactic distances are measured and all the "theory" and "speculation" behind it, you can pick up any physics textbook.
If you flip a light switch and the light fails to come on there are only two possibilities: There is an interruption in the circuit (ie the lightbulb burned out, most commonly) or there is no power to the circuit. There is no speculation as to the results (ie maybe I was bad and God didn't want the light to come on as punishment).
Seven puppies were harmed during the making of this post.
We understand nothing of gravitational dynamics on the galactic scale. For example, there was a paper in Nature on an ultra compact dwarf galaxy that predicted a dm/m ratio of 100/1, and when they did the measurement, instead of finding 100 dark matter masses for ever normal mass, they found ZERO!
ZERO is what MOND [MOdified Newtonian Dynamics] predicts because if the compact nature of the galaxy in question, it is still in the Newtonian regime.
It's time to reconsider Newton on large scales.
Wayne Hu at the university of Chicago has a great set of webpages that explain these results. If you don't have much of a background, start with the lowest level and work up. To get to the hard numbers (two significant figures), check out the "experiments and data" link. They're based on the relative amplitudes of the acoustic peaks in the microwave background.
The page can be found here.
Professor of Astronomy, Author of Spider Star & Star Dragon (Tor)