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What if dark matter is just the clumping up of particles that don’t interact?
by posix_compliant 6y ago
What if dark matter is just the clumping up of particles that don’t interact?
- thisiscorrect 6y agoWhy would the clump if they don't interact?
- can16358p 6y agoI think that meant something like don't interact with our "ordinary matter" in a way that we know.
- rurban 6y agoGravity still attracts them. They do have mass
- magicalhippo 6y agoBut without interacting they have no means to shed the energy they gain when attracted to other matter, so they won't clump like normal matter.
- Google234 6y agoThey interact with normal matter and themselves via the force of gravity...
- magicalhippo 6y agoBut gravity is (effectively) a conservative force. For the most part a dark matter particle attracted to another particle will just convert all the kinetic energy it gained during the attraction back to potential energy as it whizzes past and away from the other particle. Normal matter particles can radiate away photons when they hit each other, ie friction, leading to a non-conservative interaction. This allows them to shed their energy and clump in a way dark matter can't.
- rurban 6y agoNo, gravity is different to all other forces. First it's not really a force, then it's attracting and distant. We don't even have a proper theory for it yet.
- magicalhippo 6y agoSure gravity is different from the other forces. That changes nothing about what I said, because we do have a proper theory for it: General Relativity. General Relativity matches a vast number observations with stunning precision. Of course General Relativity is not the final answer, we know that. But that does not mean we know nothing about gravity, or that we somehow can't use our current theory to make predictions. Dark matter as a concept assumes General Relativity is good enough, and takes it as-is. Without modifying gravity we need some other way to explain the discrepancies like galactic rotation curves, and so for dark matter we add in some new, so-far unseen, particles. We also know they have to interact very weakly with normal matter besides gravity, otherwise we'd would already have noticed them in existing observations and experiments. Based on this we can make predictions. What would happen if we have some matter that only interacts gravitationally buzzing around? Well as mentioned in my previous post such matter can't cool down and clump like normal matter, so instead it would be spread out in diffuse blobs around galaxies. And when we model galaxies with such dark matter halos we find that indeed, that might explain galaxy rotation curves. It also makes other predictions which also seem to match other observations. So overall dark matter looks like a pretty good candidate. The alternative of course is to assume there aren't dark matter particles, but rather that GR has to be replaced or modified in some non-trivial way. There are many people working on that. However they're so far struggling, because it turns out to be very difficult to change or replace GR without failing to match existing observations. So that seems to indicate that GR is a pretty darn good theory of gravity.
- steve76 6y agoGravity tends to present as action at a distance. It's just what happens when you say velocity must be relative and does not work with one object alone. I would say gravity is more of a description of the object, what it's really doing, than what produces gravity. Particles tend to present as little tiny building blocks. Einstein looked at Planck's resolution of Newton's Law of Cooling, and said you have a start, you have an end, you have a particle. So now a particle can be a little bit of charge-up needed to make an ember radiate from red to orange, nothing really inside the flame itself. No more absolute right way to tick-tock a clock. Radiate heat, your clock ticks faster, your dumping heat by making a slow ticking dark clock fast and your fast ticking bright clock slow regardless of convective medium. Uncertainty tends to present as a limitation. It's actually very powerful. Everything has an infinite degree of freedom for the fastest path to thermal equilibrium. Spacetime tends to be elevated, even mystical. I see it as a coarse concept, like how probability strips away all sense of weights or lengths or measures. A real gravity application would be popping things in and out of existence. I think of what we could do with matter waves or chemicals or quantum biology or particle beams in orbit. Encircle the Earth, or the Sun, and turn that into a microstate to a cosmic macrostate. Or what we could do with cosmic variance, inflation and parallax. We know this very bright object is here. Everything else from a long distance away thinks it's somewhere else. --- --- --- They mocked the guy for thinking about small black holes. They really would love me. Part of me thinks everything up there is just where a much lesser amount of material down here decided to dump their heat, and that telescopes are disruptive. Point a telescope the right way, and you get them caught in the cross fire, dissolve them or even create them. They really only become real when things from the Earth land on them. Sounds crazy but reminds me of empiricism.
- _nosewings_ 6y agoThat's essentially the leading theory. They're called WIMPs.
- posix_compliant 6y agoThanks for the search term, I'll look into it.
- unnah 6y agoIf this new primordial black hole theory works out, then doesn't that mean that MACHOs beat WIMPs once again?
- Rury 6y agoThese theories aren't necessarily at odds with one another. Could very well be a combination of both MACHOs & WIMPs among other things...
- Google234 6y agoI would guess that Axions are currently the leading candidate.
- wiml 6y agoAs a general category of theories that's called "cold dark matter" — it needs to interact with something in order to clump up / cool off, but perhaps not in a way that's very visible to us. A wikipedia excursion will net you a handful of such theories and their pros and cons.
- danwills 6y agoWhat if dark matter is actually a secondary effect (a-la-turbulence) of the flow of space that gravity causes? (I know the idea that space can flow is a fringe idea, but it seems thinking broadly/laterally in this area is not a terrible idea?)
- GuB-42 6y agoThat would be a modified theory of gravity. I don't know about the idea of turbulence but modified gravity is serious science. It is just not the preferred explanation right now. An important reason is that AFAIK, none of these theories are currently able to match the observations without the dark matter they intend to eliminate.
- arminiusreturns 6y agoI've had a theory for years now that it is the opposite: eg that gravity is a second tier effect at shorter distance of normal matter consolidating in order to seek breaking through black holes into dark matter. So some form of entanglement as two universe membranes collide (aka the big bang) means "real matter" in this universe was but is no longer dark matter (this would only work in a dual universe system instead of a multiverse system I posit) but due to all matter entering via a single membrane collision point it is all some form of entangled (quantum or otherwise), so in this theory black holes aren't the dark matter, but the gateway for normal matter to become dark matter, transitioning back to the other universe. In this theory, dark matter would then be concentrated in the areas of our universe with sparse amounts of normal matter, a theoretically testable hypothesis at some point in the future. I'm no physicist, theory was developed while doing Einstein inspired imagination visualization/simulation of the big bang. I know it's probably so wrong in so many ways it's not worth a normal physicist to respond to, just thought I'd share. If I were correct, which I'm probably not, it would mean there are no "primordial black holes" that existed since the moment of the big bang, but rather as time went on the black holes were created and increase in number (also being part of what causes this universe to expand)
- deleted 6y ago[deleted]