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Scientists say dark matter doesn't exist

Fnord said:
I am saying from an engineering standpoint that without a practical application, the Dark Matter hypothesis is irrelevant, no matter how truthful and valid it may be.
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I'll bet there were people just like you a 100 years ago (or 2-300 years ago) saying exactly the same thing about electricity and radio waves.
 
Skepticism isn't the problem here. Skepticism is just fine. Questioning theories is just fine. Saying that you see something wrong with a scientific theory is just fine.

However, if you argue out of pure ignorance without doing even the most cursory study on the issue, then you come off as foolish.

I just want to add that indirect observation is heavily used in science. It's how we originally found a black hole; not by looking "for a black hole" (that would be silly), but instead looking for the effects of gravity lensing on light sources.

The individual that found a black hole had to spend days and days and days poring over images of stars, looking for a minute difference in light levels to find the theoretical gravity lensing. Until that point, it was all theory -- calculations demonstrated that a black hole could theoretically exist, but it wasn't directly observed.

As far as I understand it, we can observe black holes today through X-Ray imaging. But that's about it. And even that is technically indirect, as the x-rays are emitted by the accretion disk around a black hole that generates friction.
 
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Fnord said:
It can be detected by its gravitic effects on light and matter. So why not just call it 'matter'? Is it necessary to posit the property of invisibility? Why not just say "We can't see it, but we know it's there by using the same principle we use to find extrasolar planets"?
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Your big problem seems to be in what it's called. So why not call it "the matter in the universe that appears to have the same gravitational effect as normal matter but can not be detected in the same way that we have detected normal matter in the past". That would certainly speed up communication.

I don't know much about electrical engineering, but I'll bet that just like virtually every other profession it uses terms that were made up so you didn't have to use a paragraph of words every time you wanted an assistant to hand you a voltmeter- and probably some of those terms were created by putting together 2 words already in use. Do you really think a 'monkey wrench' is actually made from monkey's? Or that a grease monkey is a monkey made out of grease?

When scientists talk about the possibility of wormholes, do you really think they're talking about holes that worms dig?
 
Fnord said:
Does the difficulty in relating neutrinos to "Dark Matter" have to do with (1) the difficulty in detecting neutrinos
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No.

(2) their infinitesimally small rest mass
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Yes.

(3) the possibility of a so-called "Sterile" neutrino?
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I believe that remains a potential DM candidate, but making it work isn't easy. See http://www.citebase.org/abstract?id=oai:arXiv.org:astro-ph/0605271 for example.

Bad Astronomer said:
Scientists made a list of potential candidates. Rogue planets, white dwarfs, black holes, cold gas, neutrinos ... all of these have been crossed off the list for various reasons. What's left now are weird things like WIMPs and axions. We are very close to being able to detect WIMPs, BTW.
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It's going a little too far to say that all these have been "crossed off". In their simplest form, maybe, but there are lots of viable ideas based on the items in that list.

As for MOND (or any other theory of modified gravity), the bullet cluster observations were the last nail in their coffin, IMO.
 
Right now, I'd say that my money's on some breed of neutrino - or all of them - as the primary candidate(s) for the composition of "Dark Matter," and that the "Dark Energy" they're responsible for is a mixture of the weak force and gravity.

But, there'd have to be a multi-tera dumpload of those little beasties!
 
Fnord said:
Right now, I'd say that my money's on some breed of neutrino - or all of them - as the primary candidate(s) for the composition of "Dark Matter," and that the "Dark Energy" they're responsible for is a mixture of the weak force and gravity.

But, there'd have to be a multi-tera dumpload of those little beasties!
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Firstly, there is currently no evidence that Dark Matter and Dark Energy are related. It is just an unfortunate set of corresponding names. There are some theories which depend on their interaction, but no evidence of that interaction has been yet found. They are both called "Dark" because we can't see then with photons, which really doesn't even make sense for "Dark Energy", as we can't see ANY energy with a photon, just matter. "Dark Matter" at least makes some sense in the "It's matter, but we can't see it with photons" way.

Secondly, neutrino's were on 'the list' of things that could account for dark matter. For some time it was a front running theory. Neutrinos have a lot of the properties that dark mater needs. They're produced in great numbers, they hardly interact with normal matter, and they probably have a (small, very small) rest mass. But when we added up all the possible neutrinos that have been generated since the big bang, we ended up about two orders of magnitude too small. There just weren't nearly enough of them. And that's the same basic story for every 'non-exotic' source of mass that we've thought up. so now we're stuck looking for something exotic.
 
GodMark2 said:
Firstly, there is currently no evidence that Dark Matter and Dark Energy are related. It is just an unfortunate set of corresponding names. There are some theories which depend on their interaction, but no evidence of that interaction has been yet found. They are both called "Dark" because we can't see then with photons, which really doesn't even make sense for "Dark Energy", as we can't see ANY energy with a photon, just matter. "Dark Matter" at least makes some sense in the "It's matter, but we can't see it with photons" way.
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Now we're getting somewhere (well, on the right road at least, just not so sure we aren't traveling backwards). Since Dark Energy and Dark Matter surely infer Light Matter (or wouldn't it be Lit Matter) and Light Energy, I'd be willing to accept Dark Gravity and Light Gravity into the discussion.... but if anyone says Dark Light or Light Light I'm outa here!
 
Lonewulf said:
....
After you've researched dark matter as well as you can, then come back and tell us that the evidence is "nothing". And if you wish to continue to dismiss Dark Matter as non-existant, then please give a theoretical model that could account for the discrepancies that led to the theory of dark matter.

Thank you.
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This is a common repeating pattern with science. A disbeliever knows little or at least not enough about a particular scientific theory, be it evolution, the 4.5 billion year old Earth, the Big Bang, or in this case dark matter. The disbeliever, clearly not convinced of the theory proclaims, "it hasn't been proved"* (*or substitute a word which is acceptable to you if you are a science conversational purist: tested, confirmed, or??). But the person who remains unconvinced has little or no knowledge of the science which the scientists use to confirm the theory or hypothesis.

Don't understand the method by which rocks are dated, proclaim the science doesn't prove the Earth is billions of years old. Don't understand the method by which dark matter is detected, proclaim the science doesn't support the existence of dark matter.

Dark matter is detectable, it isn't just a mathematical fudge factor that makes gravity calculations work. If it were simply a fudge factor, then it should be consistent throughout the Universe and it isn't. It isn't evenly distributed.

Dark matter can be 'seen' with instruments. We cannot 'see' light waves that are outside the visible spectrum, but we know they exist because we can see them with instruments. Dark matter doesn't interact with light. But its mass has gravity and the gravity is detectable with instruments.

Maybe this is posted, I haven't gotten to the end of the thread:

VISUAL "MIRAGES" PROBE DISTRIBUTION OF DARK MATTER

The Sloan Digital Sky Survey set out to find gravitational lenses. That is, gravity which bends the light behind it the same way a lighthouse lens bends the light it is sending out into the night. When stars pass behind an invisible patch of dark matter, the gravity bends the light making it temporarily brighten. And that is detectable.
 
Schneibster said:
Take a look at the picture I linked in my post. It's currently my screen wallpaper. The dark parts are dark matter; they've mapped it by checking the distortion of galaxies behind it. The darkest parts are where the light from the galaxies behind it is the most distorted. What you're looking at is a gigantic tube-like structure, millions of light years across and hundreds of millions of light years long, with the open end pointing approximately at us. In the middle of it is a supercluster of galaxies.

That do it for you?
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Ahh yes, someone has posted it, I see, and a few others have described it as well.

Here is a pretty good illustration of gravitational lensing on YouTube.

http://www.youtube.com/watch?v=yamVbK-J69M

And here is a really quick illustration of the phenomenon morphing into the actual image:

http://www.youtube.com/watch?v=BkBNf_nFuhM
 
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GodMark2 hit the nail on the head: we don't want complicated physics!! We'd be perfectly happy with a Newtonian clockwork universe. We're not in the game of making complicated things just for the fun of it (and certainly not the profit of it). We've already tried all the easy answers to dark matter, and they all come up short. This forces us to more and more exotic answers, because the mundane ones aren't cutting it! We are forced by observations to make the conclusions we're making.

Oh, and another reason neutrinos are out for dark matter is that they are too "hot": since they are relativistic (fast), if they made up the dominant matter in the universe, we wouldn't have any structures smaller than galaxies! This leads us to conclude that dark matter is "cold" and massive.

Also, when we say that dark matter is weakly interacting, we don't mean "some new but very weak force". We mean THE weak force, aka the Weak Interaction.

Also also also, dark matter is a separate animal from dark energy, except for the name. If you would like to open a separate thread for dark energy, I would be more than willing to discuss it there.
 
Schneibster said:
The dark areas are areas where we can see the light has been bent...
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It might be of no matter <groan>, but don't the frosted areas in the pictures map the dark matter (just judging from the stars' apparent brightness)? :confused:
 
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"Long ago, the Earth was thought to be flat..."

Well, when long ago? The Earth has been known to be spherical for quite a long time...
 
blobru said:
It might be of no matter <groan>, but don't the frosted areas in the pictures map the dark matter (just judging from the stars' apparent brightness)? :confused:
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I don't think so, though I could be wrong. The stars' brightness is not what's affected; they are in the foreground, much closer than the galaxies since they are in our own galaxy. I'll try to find out in order to be sure.
 
GodMark2 said:
Firstly, there is currently no evidence that Dark Matter and Dark Energy are related. It is just an unfortunate set of corresponding names...

Secondly, neutrino's were on 'the list' of things that could account for dark matter. For some time it was a front running theory. Neutrinos have a lot of the properties that dark mater needs...
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I'm not saying with any certainty that neutrinos are "Dark Matter" (God knows I'm not qualified to say that). I'm just saying that if some bookie were taking bets, my money would be on neutrinos, or some variant thereof.

Right now this is one of those "We won't know until we know, and even then we can't be certain" topics. But, hey...

... at least I've come over to the "Dark (matter) Side!"

:jedi:
 
"The currently fashionable concordance model of cosmology (also known to the cognoscenti as 'Lambda-Cold Dark Matter,' or 'LambdaCDM') has 18 parameters, 17 of which are independent. Thirteen of these parameters are well fitted to the observational data; the other four remain floating. This situation is very far from healthy. Any theory with more free parameters [hypotheses] than relevant [astronomical] observations has little to recommend it. Cosmology has always had such a negative significance, in the sense that it has always had fewer [astronomical] observations than free parameters [hypotheses] (as is illustrated on page TK), though cosmologists are strangely reluctant to admit it. While it is true that we presently have no alternative to the Big Bang in sight, that is no reason to accept it. Thus it was that witchcraft took hold."

"The three successful predictions of the concordance model (the apparent flatness of space, the abundances of the light elements and the maximum ages of the oldest star clusters) are overwhelmed by at least half a dozen unpredicted surprises, including dark matter and dark energy. Worse still, there is no sign of a systematic improvement in the net significance of cosmological theories over time."
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Michael Disney, September-October 2007 issue, Volume 95, American Scientist
 
One would think that after the thousands and thousands of years of science, this would have been figured out by now.

Paul

:) :) :)

Oh, Please :boggled:
 
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