Is dark matter real?

tullio
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RE: here's another article

Message 38291 in response to message 38290

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here's another article on searching for dark matter


The article is about the Large Hadron Collider at CERN. I always thought that the LHC would look first for the Higgs boson, which is part of the Standard Model of elementary particles, but it is always true that new particle accelerators discover not only new particles but also new problems. This was pointed out by Emilio Segre' in an article in the "Endeavour" magazine (l972?) and new problems require new and more powerful accelerators and so on. Physics is a recursive function, it calls itself. There was a book by two Italian physicists, Angelo Baracca and Silvio Bergia, "La spirale delle alte energie", where "spirale" refers not only to the particles' trajectories in a cyclotron but also to the spiral of rising costs and time to build a new machine. I have read on the NYTimes today that the LHC will be delayed until 2008 for full energy operation. It is also true that particle accelerators are currently used in cancer therapy and other useful applications.
Tullio

Stan Pleban
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Here is another interesting

Here is another interesting theory that dispenses with dark matter entirely.

I believe it also responds to the "Pioneer" anomaly.....

just another shot in the "dark"!!!as far as theories go.....

hockeyguy
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RE: Here is another

Message 38293 in response to message 38292

Quote:

Here is another interesting theory that dispenses with dark matter entirely.

I believe it also responds to the "Pioneer" anomaly.....

just another shot in the "dark"!!!as far as theories go.....

OMG great job stan. so basically this artical says there is a density of gravity or gravitons and the density of gravity is higher near galaxies than further from them! That makes so much more sense than dark matter! It will be great if this theory predicts cosmic background radiation. And if it does, will people buy into this idea? will it be taught in high school physics? well, maybe not highschool, but you get the point.

If i didnt interpret the article right, please correct me.

Stan Pleban
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Hockeyguy....there was a

Hockeyguy....there was a blurp about this MOND in a recent Discover Magazine.

Unfortunately, they will not give you the whole article without a subscription.

But, what you should find interesting is this article on the Math behind this theory.

Be careful to follow the new constant " a "subscript 0"". You need to follow that discussion for the basics.

Also follow down the discussion on Tensor Vector Scalar gravity which is a proposed relativistic theory of MOND which purports to explain gravitational lensing, a cosmic optical illusion.

Remember, what makes all this so interesting is that we are in the "hunt" for the "real" answer.

Being a Math Major from many many years ago, I still get a kick out of messing about such ideas.

Mike Hewson
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RE: Hockeyguy....there was

Message 38295 in response to message 38294

Quote:

Hockeyguy....there was a blurp about this MOND in a recent Discover Magazine.

Unfortunately, they will not give you the whole article without a subscription.

But, what you should find interesting is this article on the Math behind this theory.

Be careful to follow the new constant " a "subscript 0"". You need to follow that discussion for the basics.

Also follow down the discussion on Tensor Vector Scalar gravity which is a proposed relativistic theory of MOND which purports to explain gravitational lensing, a cosmic optical illusion.

Remember, what makes all this so interesting is that we are in the "hunt" for the "real" answer.

Being a Math Major from many many years ago, I still get a kick out of messing about such ideas.


It's a favourite area of my interest, this non-Keplerian velocity curve for galaxies - fairly straightforward to measure, but much harder to explain. I think to alter Newtownian or Einsteinian gravity is very hard for some to cope with, as many are weaned on these theories, and may not be weaned off them!
While change is not for it's own sake, to create an entire class of matter ( dark ) without any other observation or justification is to make the same error as:

Quote:
One reason why some astronomers find MOND difficult to accept is that it is an effective theory, not a physical theory


Dark matter is just as effective! The point about distance scale changing the expected force of gravity is a good one. It is not so foreign an idea really. Quantum effects as applied to other forces leads to much the same results - an altering of the underlying interaction strength as one penetrates further into a cloud of virtual particles that surrounds some central force charge.
Then again we don't have a quantum theory of gravity, so here is an opportunity to brew one up - incorporating effects at high and low acceleration scales. Newton started with apples and moons, others generalised quite sucessfully, but perhaps it is time to revise.
Cheers, Mike.

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

Nereid
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RE: Is sounds to me like we

Quote:
Is sounds to me like we simply added dark matter to make our equations work, kind of like Einstein's cosmological constant, or his "biggest blunder". What I am asking is is it possible that dark matter is not real,

Yes, it is possible ... just as it is possible that any 'real' thing, in any part of modern science, isn't 'real'; that's the nature of science*

Quote:
and there are flaws in our equations or in our way of thinking?

In a nutshell, there are three ways there could be 'flaws' - internal inconsistency (unlikely), inconsistency with some other part of physics that is well-established (this is certain - QM and GR are mutually incompatible, if only in the Planck regime), or inconsistency with good, relevant experimental or observational results (and what's your verdict on this?).

Of course, if a better theory comes along tomorrow, then we will be able to see the 'flaws' of today's theories clearly; but until such an alternative is 'put on the table', ...

Quote:
Is there any actual evidence that dark matter is real, besides the fact that there are anomalies in our understanding of physics?

If you apply the same question to neutrinos ("Is there any actual evidence that neutrinos are real, besides the fact that there are anomalies in our understanding of physics?"), especially between 1931 and 1957, how would you have answered?

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Why havent we found dark matter on or near earth?

Because there's very little of it? Because we don't know what signatures it should leave (so we don't know how to look for it)? ...

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Can string theory offer any alternate explanations to the anomalies?

String theory offers an embarrassment of riches - too many answers that might be real for even a million physicists each completing a million projects a year, for a million years, to be able to address.

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And if it is real would it help explain the Pioneer anomaly?

No - whatever DM is, it cannot account for the Pioneer anomaly (or, if you prefer, if it did, then it couldn't be dark 'matter').

*Do we live *in* a 4D universe, or *on* the surface of (some other D) universe? In some versions of theories being examined today, both are 'real', in the sense that there is no experiment, or observation, that you could do - even in principle - that would enable you to tell the two apart. Lends a whole new dimension of meaning to the word 'real', n'est pas?

Nereid
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MOND - the unanswered

MOND - the unanswered questions ...

As MOND itself does not include relativity, and as there are hundreds of good observations that relativity 'works' on the same scale (in the same domain) as MOND (crudely, galaxies) - gravitational lensing, both weak and strong - MOND by itself cannot be 'right', or 'real'.

If by 'MOND' you mean 'any theory which reduces to MOND in the appropriate limit, and which includes all the relevant parts of GR' (so TeVeS, for example, is 'really MOND'), then we have a completely different kettle of toast.

But let's not forget that even the most ardent of MONDians are honest enough to admit that there is one class of astronomical object where their idea fails - rich clusters. True, the 'mass deficit' (or whatever they call their equivalent of DM) is 'only' a factor of 2 (giving them the fairest of fair winds in interpreting the data), but since one great hope of MOND was to do away with all significant instances of 'dark mass', its failure to account for such spectacularly obvious things as rich clusters is a bit of worry, I should think.

Stan Pleban
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RE: *Do we live *in* a 4D

Message 38298 in response to message 38296

Quote:
*Do we live *in* a 4D universe, or *on* the surface of (some other D) universe? In some versions of theories being examined today, both are 'real', in the sense that there is no experiment, or observation, that you could do - even in principle - that would enable you to tell the two apart. Lends a whole new dimension of meaning to the word 'real', n'est pas?

Nereid...I agree with your utility/discussion/usage of the the word 'real'....

better than the way in which I used 'real'.....

Good thoughts on your part and appreciated .....Stan

Chipper Q
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Nereid said: RE: Of

Nereid said:

Quote:
Of course, if a better theory comes along tomorrow, then we will be able to see the 'flaws' of today's theories clearly; but until such an alternative is 'put on the table', ...


I happened to run across 'Modulated Quantum Neutron Fusion', and therein is a 'Comprehensive Unification Theory', and also several additional papers on the subject. I wouldn't say it's a new theory, or a better theory, but it looks like a possible way to apply relativity to quantum mechanics, so as nearly as I can tell, it's basically the same theories.

The gent (W.T. Gray) applied the familiar equations, laws, and principles of physics, and he developed a 'proton:electron:proton nuclear model' that can be used to 'explain and derive specific values for 60 unexplained phenomena to within 1% of their empirical values,' including things like magneton, structure, spin, and binding energy of various isotopes.

If Gray's method worked for just regular hydrogen, it might not be impressive, but if it works for deuterium, tritium, He-3 and -4, and various other isotopes of other elements, then it's hard to see how it could be wrong. I look forward to hearing what everyone here thinks about it.

Mike Hewson
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RE: I happened to run

Message 38300 in response to message 38299

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I happened to run across 'Modulated Quantum Neutron Fusion', and therein is a 'Comprehensive Unification Theory', ........... how it could be wrong. I look forward to hearing what everyone here thinks about it.


Crap on a stick, alas. He tried to get funding from the DoE, and they politely and rightly punted him over the fence. His 'papers' are reams of piffle/waffle .... please don't anyone give this guy any money :-)
Cheers, Mike

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

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