Following on from the recent thread about Hershel finding less dark matter but more stars, we have this one …
Gas rich galaxies confirm prediction of modified gravity theory
Quote:
|
Modern cosmology says that for the universe to behave as it does, the mass-energy of the universe must be dominated by dark matter and dark energy. However, direct evidence for the existence of these invisible components remains lacking. An alternate, though unpopular, possibility is that the current theory of gravity does not suffice to describe the dynamics of cosmic systems.
|
.. so, enter Modified Newtonian Dynamics (MOND);
Quote:
Using recently published work that he and other scientists had done to determine both the mass and flat rotation velocity of many gas rich galaxies, McGaugh compiled a sample of 47 of these and compared each galaxy's mass AND rotation velocity with the relationship expected by MOND. All 47 galaxies fell on or very close to the MOND prediction. No dark matter model performed as well.
…
Almost everyone agrees that on scales of large galaxy clusters and up, the Universe is well described by dark matter - dark energy theory. However, according to McGaugh this cosmology does not account well for what happens at the scales of galaxies and smaller.
"MOND is just the opposite," he said. "It accounts well for the 'small' scale of individual galaxies, but MOND doesn't tell you much about the larger universe.
..
Almost everyone agrees that on scales of large galaxy clusters and up, the Universe is well described by dark matter - dark energy theory. However, according to McGaugh this cosmology does not account well for what happens at the scales of galaxies and smaller.
..
"If we're right about dark matter, why does MOND work at all?" asks McGaugh. "Ultimately, the correct theory - be it dark matter or a modification of gravity - needs to explain this."
|
As he says, sounds a bit like playing around with models to fit the 'sweet spot' of observations. His last question (underlined) is a good one, though .. but there again, Newtonian Gravitation has always had sweet spots anyway.
The 'Darkness' remains for the moment, but MOND may be a possibility for ultimately superseding it.
Cheers