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View Full Version : What are your thoughts on MOND & TeVeS



DyerWolf
2006-Aug-11, 04:00 PM
From what I've read, many people are comfortable with the DM hypothesis. However, DM and DE sound awfully close to 'the ether' to me - kind of a convenient fudge/hunch to make the numbers work.

However I just read an article on MOND / TeVeS which seems like it might answer the problems of galactic rotation without having to resort to mysterious, unseen, undetected matter/energy.

What are your thoughts?

cmsavage
2006-Aug-11, 06:57 PM
First off, you need to be aware of the reasons we believe dark matter exists. The galactic rotation curves are the most well known, but are not the only reason (and were not even the first). Dark matter can be observed from velocities of galaxies in a cluster, gravitational lensing (http://www.bell-labs.com/news/1997/january/15/1.html), CMB anisotropies (http://map.gsfc.nasa.gov/m_ig/060913/CMB_ILC_Map75BK.jpg), big bang nucleosynthesis, and structure formation. Many of dark matter's effects were predicted before being subsequently observed (we would have expected some of these observations to be quite different without dark matter).

Originally, dark matter was never required to be an exotic form of matter. Neutrinos, neutron stars, and brown dwarfs (super-Jupiter objects) were all possibilities: either very dim or difficult to detect objects that could thus be considered "dark". Most of these are now ruled out as the dominant component of dark matter (they can still contribute to the dark matter) and more exotic candidates are now leading the charge.

Most astronomers/cosmologists are reluctant to consider MOND to be a strong competitor to dark matter for multiple reasons. MOND cannot explain all the observations (above) that dark matter has, in which case, if MOND were true, you might need something like dark matter to exist anyways to explain those observations. Another issue is the non-relativistic nature of the MOND theory: it is (was) mainly an ad-hoc change in the theory of gravity with little theoretical basis. That has changed with the intruction of TeVeS, a relativistic version of MOND, for which now people are taking it a bit more seriously. However, MOND/TeVeS still needs to make unique predictions of something we can subsequently observe, which dark matter has been doing for decades.

Nereid
2006-Aug-11, 07:22 PM
We already have a thread devoted to discussion of MOND (http://www.bautforum.com/showthread.php?t=44142); please join it! :)