In the book Reinventing Gravity (see the column above) the author points out that if there is Dark Matter around spiral galaxies then you might expect to find it around other shaped galaxies also ... but there are some that would behave differently if Dark Matter were present... so the fact that they behave the way they do says Dark Matter isn't present, which says ... well ... I think we will discover what it says real soon...
The fact that an equation cranks out good predictions in the area we can test does not mean that it will be doing it correctly elsewhere (err .. that is in the areas we cannot test at the moment ..). I do embedded software so I use extrapolated and interpolated equations a lot, they are good enough but I know better that they are not the "real" thing :-0
If one has selected the career of being an astronomer, and being well paid for it, one must deliver interesting reports from time to time, otherwise those large paychecks may cease. So discover a huge pile of almost undetectable stuff at a distance so great that nobody will ever be able to prove or disprove it within your lifetime. And if you are wrong, well, it seemed reasonable at the time. Just think what we might develop if all of these great minds did not waste every day investigating things that are too far away to matter.
What instrument can look at a battery or capacitor and determine if it is charged or not charged? Mass should be only slightly different but at a distance in space how do you tell what potential energy is there? Dark energy.
If it turns out that dark matter is "fool's gold" then so must dark energy be. If both are really just components of a fudge factor needed to make an incorrect cosmological theory fit our observations, then cosmology is in for an enormous upheaval when dark matter/energy is finally debunked.
The universe is said to be 74% dark energy and 22% dark matter, leaving only 4% for the matter & energy we actually can observe. 96% is one heck of a fudge factor!
On the ether thing, I disagree. A quasi-newtonian interpretation of ether predicted that the interference fringes in the Michelson-Morley would move. The experiment therefore disproved that understanding of ether. However, Einstein did not provide an alternative! He simply showed that, if you use light to measure the universe (which we do, even the lengths of our rulers are established by electromagnetic phenomena), that the Michelson-Morley experiment would fail, because of the Lorenz-Fitzgerald contraction. I think you will find that if you re-interpret ether in that context that it is no longer contradictory. It got dropped not because it was invalid, but because it no longer contributed anything. In an Einsteinean context, Ether can't be measured. That doesn't mean it doesn't exist, just that it is operationally meaningless. A flowing medium for Electromagnetic forces may still be there. We just can't detect it because we are making our measurements using it. Like trying to measure the velocity of water using that same water as a reference. You always come up with zero. That doesn't mean the water isn't moving, it just isn't moving with respect to itself.
I'm not an astrophysicist (and I don't play one on TV)..but... I have been following string theory for a while and this is my opinion on dark matter.
It seems to me that the multidimensional universes that vibrate (credit: Dr Kaku on TV) and when they touch you get an interaction between them (in short, the big bang). Now if you think of frequency/math analysis, when two frequencies interact, you get the sum and the difference between them. Think about these multidimensional universes as gigantic polynomials that interact.
When polynomials interact, the differences provide the first 4 dimensionís which we normally call length, width, height and time.
In my humble opinion, the upper level dimensions (5+) should be counted as the dark matter. This would account for possibly some mass that doesn't interact well with the lower 4 dimensions. Remember that some equations have missing terms in them (ax+bx^2+0x^3+dx^4... or 0ax+bx^2+cx^3...) which could also be the case.
As I said, this is my opinion only, I have no proof and about the only thing that I could back this up with is by comparing it to frequency analysis.
So this is how I look at the universe and try to understand it with my small mind.
As a resident physicist, you gotta be careful knocking established theories like that. First, dark matter isn't even that strange, compared to dark energy, which according to its own theory comprises 90% of the mass of the Universe, and is so significant that it changes the entire geometry and dynamics of the Universe, by causing its expansion.
Secondly, those theories have been quite extensively peer reviewed. They may not be perfect, but they are the best explanation of the known facts. If the facts were explainable better by the actions of little green men, the Little Green Men theory would be the one to beat---it doesn't make sense to argue over philosophical merit if the math works out! People still argue about the philosophical underlying of quantum mechanics but the math is solid and we crank out practical results day in and day out.
Bottom line is, the only criterion is the theory's predictive powers. Ether theory didn't fail because ether was strange, but because it predicted a doppler shift in the speed of light, which failed to appear in the Michelson-Morley experiment.
max, you're not alone. I really dislike the ideas of "Dark Matter" and "Dark Energy." They feel like fudge factors made manifest. Or, worse: the place where God is allowed to creep back into what has, so far, been a wonderfully, purely, materialstic Universe.
One of the things I've been trying to get an answer to is this: do astrophysicists allow for the fact that when they look deeper and deeper into the universe, finding that wonderful, changing red shift of objects moving away from us at different speeds--faster speeds the further away they are, IIRC--do they allow for the fact that not only is that data coming from a far distant source, but a far OLDER source?
So, regardless of which direction you're looking out at, if you see light that is 14 billion years old, with some huge red shift in its spectrum (vs. the expected gaps, etc., that make the red shift mean what it means), of COURSE there's going to be a high velocity associated with it. It's as close to the BIG BANG as you can get. And if the universe is SLOWING, wouldn't you expect the early speeds to be high, and the current speeds to be lower?
Maybe there ARE answers to this question out there (links, please? Pretty please?) and I'm just too slow to realize it....