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this post was submitted on 22 Dec 2023
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I'm no astrophysicist - I just design computer chips. But this issue of "We need dark matter" came up with rotating galaxies, didn't it? So I'd look into that direction if there is a potential connection. Classic bug hunting technique.
The Bullet Cluster, among several other systems, are very strong evidence that dark matter is actual baryonic matter that does not experience significant (or any) electromagnetic interactions. What we see when we look at these kinds of systems is that there is all evidence of STUFF there, but we cannot see the stuff. It's not an indication of a poorly-performing math model missing a function term.
It would be like if we saw ripples in the water like we know exist around a rock. But we don't see a rock. Sure, MAYBE we just fundamentally need to rewrite our basic rules of fluid mechanics to be able to create these exact ripples. But the more probable explanation is that there's a rock we can't see, and falsifying that theory will require just HEAPS of evidence.
The evidence we have suggests overwhelmingly that there is actual stuff that has mass that we simply do not have the tools to observe. Which isn't all that surprising given that we are only JUST starting to build instruments to observe cosmological phenomena using stuff other than photons of light.
How would you know the difference? All the evidence of "STUFF" being there is obviously gravity based, as no other factors are involved. So that "STUFF" has a number of parameters that can be determined from the postulation of it's existence: It should be baryonic to have the mass, and it should be stable, or one would probably observe energetic events related to state changes. Another point is: if it has mass, why does it not just clump together? I guess one can also rule out that it is charged, or one might see electromagnetic interactions. Did I miss a key parameter? Did I misunderstand anything here?
So do you know of any 3 (or maybe even 5 or 7) quarks baryon that would fit the pattern? The amount of combinations is limited, and CERN and others have created so many different particles over time that something of that kind that is actually stable should have made an appearance? Or are there any theoretical works on what kind of particle this could be, matching the pattern?
And, by the way, I would not call it a "poor performing" math model, as it covers quite a lot of the world we can observe. I deliberately used the term "incomplete".
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... ;-)
For myriad reasons, the answer to this is an emphatic yes.
Gravity may attract particles towards each other, but the force that actually causes them to interact with each other is almost entirely electromagnetism. The collisions of grains of cosmic dust are caused by electromagnetic fields interacting with each other. As is the gradual loss of kinetic energy -- the friction -- that allows some amount of potential energy to get converted to heat, allowing the particles to slow down and, as you described it, clump.
Absent electromagnetism, the actual particle nuclei would need to directly hit each other to cause an interaction via the nuclear forces, which is VERY improbable in the vastness of space. Improbable doesn't mean it wouldn't happen, but in this case it does mean the universe is way too big and young. Without electromagnetic interactions, particles just form orbits. Which again, that's what a "dark matter halo" is. It's all the dark matter stuff orbitting around a galaxy's center of mass because it doesn't get easily trapped in the center. It's all the dark matter in a gravitational system constantly whizzing back and forth across the center of mass since there's no electromagnetic force to rob them of the potential or kinetic energy and stop them from heading back out.
And, conveniently, these halos are just what our observations seem to indicate dark matter is doing in a typical galaxy. The observations and theory align well
OK, I can accept that. Good luck hunting down whatever this dark matter is made of, then.
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.
Sounds like the retired engineer that has a theory cliché.
Modifying the theory of gravity to fit the data might be useful even if it's just for modelling purposes. But it doesn't make a theory for sure.
I am also an (non retired) engineer, but alas I have no theory of my own :)))
No, I'm just wondering about the reasoning for something that has not been observed except for it's gravity effects. I mean, physics has loads of incomplete models, so for me, just another incomplete model looks more likely than some phantom particles that nobody can explain.
The problem is that most writing on that topic is incomprehensible even for me. And I'm not even part of the non-science crowd - my specialization is just elsewhere.