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Cosmic string
New Member
USA
37 Posts |
 Posted - 07/28/2002 : 22:10:26
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MoND is an attempt to rectify the rotational velocities of galaxies and clusters with the lack of substantial, observed dark matter. Its premise is that, at very small accelerations (such as gravitationally induced acceleration over galactic and intergalactic distances), acceleration (indicated by rotational velocities) does not approach zero, but instead a minimum acceleration, called a[0]. What do you think of MoND?
1) Probably is the cause of the perceived dark matter
2) Probably contributes to the observed rotational velocities in addition to dark matter
3) Unsure; need more evidence to decide
4) Might contribute to the observations, but unlikely
5) Way wrong
“The truths of religion are never so well understood as by those who have lost the power of reasoning.” --Voltaire
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Cosmic string
New Member
USA
37 Posts |
 Posted - 07/28/2002 : 22:32:09 [Permalink]
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3)Unsure; need more evidence
There is currently both supportive and potentially contradictory evidence now, thought the full results and implications of MoND have not been worked out. The supportive evidence:
1. Rotation curves of spiral galaxies that have been studied and compared with MoND are extremely consistent with those predicted by MoND
2. Relative velocities of galaxies in clusters are consistent with MoND
3. MoND provides a mechanism for the Tully-Fisher relation
Suggestive implications:
1. a[0] is intimately related to basic physical constants,including the Hubble constant, the speed of light, the deceleration parameter, and the cosmological constant. It is equal to the acceleration needed to accelerate an object to the speed of light in the time span of the age of the universe
Difficulties with MoND:
1. It has not been successfully mated with general relativity, and as a result -
a) cannot account for observed gravitational lensing
b) is not (yet?) able to work with the observed Hubble flow
2. The observed temperatures of interstellar gas are inconsistent with MoND unless there is sufficient dim matter
3. It can't account for phenomena such as the Great Attractor, which seems to require at least some dark matter
I consider MoND to be worth further testing and believe that it should be theoretically pursued to see if it can be mated with general relativity (and subsequently purged of these conflicts with observation). I do not, however, believe that there is sufficient evidence to even tentatively consider it real (or probable, for that matter). The conflicting observations are very damning to MoND, and hence it should only be considered as a theory to be further evolved and then tested (and possibly falsified] by observations after it is fully formulated, if that will ever happen. In conclusion, MoND may someday be a contending theory for how to explain certain observed galactic phenomena, but currently it is only a preliminary theory with conflicting observational results.
“The truths of religion are never so well understood as by those who have lost the power of reasoning.” --Voltaire |
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Lars_H
SFN Regular
Germany
630 Posts |
Posted - 07/29/2002 : 04:14:35 [Permalink]
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Not my area of expertise either, but I don't see anything wrong with Mond yet.
They are going at the problem from an unconventional way and everything, but it is still solid science from what I have heared. It is to early and I know to little about it to make any kind of jugdemnt about it. I think it needs some more looking into even if it does do away with all the fancy theories that have been made in connection with dark matter.
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Wiley
Skeptic Friend
68 Posts |
Posted - 07/29/2002 : 11:58:18 [Permalink]
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There are cases where MOND fails:http://arxiv.org/abs/astro-ph/0105184
My main problem with MOND is that there is no reasoning behind it. Why would very small accelerations deviated from classical Newtonian dynamics? Until this is answered MOND will be of limited use. If we don't know why something works, we don't know it's range of validity.
However, my gut feeling is that when a unified theory of quantum gravity emerges, it will have modify Newton in a similar manner.
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Cosmic string
New Member
USA
37 Posts |
Posted - 07/29/2002 : 19:07:09 [Permalink]
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| Thanks for the link, Wiley. I think that finding may sway me toward [4)unlikely] if any more similarly damning observations are made. |
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NubiWan
Skeptic Friend
USA
424 Posts |
Posted - 07/29/2002 : 19:18:55 [Permalink]
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",.. with the lack of substantial, observed dark matter."  Hmm.. "observed dark matter,"  enough for me, bub-bye...
"If we believe absurdities, we shall commit atrocities." -Voltaire |
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Cosmic string
New Member
USA
37 Posts |
Posted - 08/01/2002 : 18:00:10 [Permalink]
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I guess I should have waited before posting this topic...
New analysis of detailed CMB observations using the VSA found that the spectral (thermal) 'map' of the CMB could only be accounted for if there were (and are) substantial amounts of both dark matter and dark energy.
“The truths of religion are never so well understood as by those who have lost the power of reasoning.” --Voltaire |
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Topic Locked
