EDIT: Let’s cool it with the downvotes, dudes. We’re not out to cut funding to your black hole detection chamber or revoke the degrees of chiropractors just because a couple of us don’t believe in it, okay? Chill out, participate with the prompt and continue with having a nice day. I’m sure almost everybody has something to add.
We observe patterns of behavior – orbits, movement, gravitational lensing – that are exactly what we would see if, for example, there were great clouds of matter or other galaxies in those places. But we don’t see the hydrogen gas. We see non-uniform distributions of dark matter mass that imply there is not simply some consistent calculation error, but rather that there is dark matter that is not uniformly distributed. Again, read up on the Bullet Cluster because it shows a VERY clear example of what I am talking about, where the regular, electromagnetically-interacting matter behaves one way but the apparent shadow of dark matter behaves in a different way that is consistent with lack of electromagnetic interactions.
We’ve also discovered things like ultradiffiuse galaxies – likely remnants from ancient collisions – that have apparently been stripped of their dark matter. MOND cannot explain these observations because these galaxies essentially behave in a Newtonian manner that would be impossible in a MOND framework.
Why does stuff clump together? For all non-dark matter, the answer is electromagnetism. Outside of the extreme cases of neutron stars and black holes, where gravity overwhelms and defeats electromagnetism and the nuclear forces theoretically take over to create degeneracy pressure, electromagnetism is the reason things clump. Absent electromagnetism, what would cause clumping? Essentially nothing, stuff would whizz straight through other stuff and go into orbits. Potentially HUGE orbits, which is why there’s so many theories around dark matter “halos”. Maybe if there were DIRECT collisions of theoretical DM particles, that might cause an energy-releasing event – this is one of the things current dark matter detectors are looking for and may yet find within the upcoming years.
Yep, and more than a handful Many that make specific predictions we can test for and so are testing for. For example, you could look at axions, which are a theoretical particle predicted by an entirely different theory that may be a good fit for the dark matter particle.
Which would still not rule out anything else…
That non-uniformity though, yes, this is a good point for a “dark matter exists” hypothesis. Although I would still word it differently: Not “We see non-uniform distributions of dark matter mass” but “We see a non-uniform mass-like effect”. I’ve learned that keeping the terms as neutral as possible, or it might exert too much pressure on the thought process to go in just one direction.
Which is basically an extreme case on “not uniformly distributed”.
That is acceptable. I was not “selling” MOND here (or any other theory), btw, I’m just wondering what kind of possibilities are there to explain all those observations. “An invisible mass nobody has observed except for it’s gravity effect” sounded a bit thin of a leg to stand on there, while incomplete models are a rather widespread phenomenon.
Gravity? I mean, we are talking about something that has gravity. Did planets form because of electromagnetism?
Indeed. Try that with the wannabe-sciences like economics…
Well, at least they share the common trait of not being found yet… ;-)
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I don’t have a bias against new particles. For me as a non astrophysicist, just another theory having a big hole was simply more likely. And the theory of gravity breaks anyway when it approaches quantum theory, why shouldn’t it be broken elsewhere, too?
But I can easily accept the information given here, primarily the case with uneven distribution, which is a good case for something being there. Now you just have to nail the particle down.
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