311–315 of 315 posts
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Minor correction: The accelerating expansion of the universe implies the existence of dark energy, not dark matter.
This is not a minor correction simply because they both contain the word "dark". It would have been slightly more correct to confuse the terms dark matter and dark chocolate. Dark energy is an entirely different kettle of fish.
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> Fascinatingly, it is known that the interaction of the dark matter with the Earth is so weak that there would be no "clumping" of it around the Earth at all! Would I be right in thinking that also puts severe limits on how much it interacts with itself? Because my intuition would be, if you loose normal matter into a gravity well, it will clump, even if it doesn't interact with the source of the gravity. Am I infer…
> Because my intuition would be, if you loose normal matter into a gravity well, it will clump, even if it doesn't interact with the source of the gravity. Am I inferring correctly? Now I have a little of Newton for you: look at our Solar system: you see the planets, and even more interesting, all the small asteroids circling around the Sun? Can you answer why don't they all fall to the Sun, but move in the orbits? T…
Sweet of you to bring me Newton. Always a welcome gift.
But I think you misunderstand where my question is pitched.
The solar system is rather clumped, you see. A little Aristotle for you. :)
In all seriousness, the more dark matter is around, the less it can have mutual interactions, before it would clump, surely? Assuming such forces exist, there is a nonzero probability that two particles of dark matter will approach close enough that non-gravity forces will be significant, And they will no longer act under an ideal Newtonian gravity. Dust clouds coalesce into suns, given time. Can dark matter have its own dark-only version of the electromagnetic force? Or is that ruled out by the lack of clumping? Or is there just too little of it to make a conclusion on that? My question was entirely consistent with ol' Issac.
I have no chops whatever in this field, but it's fun to think of experiments we might do: If I understand current theory, dark matter only interacts with itself and with ordinary matter through gravity. Hence the importance of Vera Rubin's observations [1] that some galaxies were rotating too darned fast to hold together based on the ordinary matter we could see. Gotta be something invisible generating more gravitati…
Your experiment has several fundamental flaws. Firstly, dark matter is weakly interacting (even with itself) which is why it doesn't "clump" the way atomic matter does. The only "clumping" of dark matter happens on galactic scales, because the typical speeds of dark matter particles are in the range of orbital speeds around galaxies. Our measurements of the dark matter mass in galaxies don't have nearly enough precis…
Earlier quoted context omitted.
> Because my intuition would be, if you loose normal matter into a gravity well, it will clump, even if it doesn't interact with the source of the gravity. Am I inferring correctly? Now I have a little of Newton for you: look at our Solar system: you see the planets, and even more interesting, all the small asteroids circling around the Sun? Can you answer why don't they all fall to the Sun, but move in the orbits? T…
> Now I have a little of Newton for you Sweet of you to bring me Newton. Always a welcome gift. But I think you misunderstand where my question is pitched. The solar system is rather clumped, you see. A little Aristotle for you. :) In all seriousness, the more dark matter is around, the less it can have mutual interactions, before it would clump, surely? Assuming such forces exist, there is a nonzero probability that…
My "feeling" is, it's not "intuitive enough" to "guess" any answer without a lot of computing:
https://www.quantamagazine.org/coder-physicists-are-simulati...
We think we're quite sure in our observations, so that helps, but to be able to claim how the simple laws can exactly produce what we see, we have to do a lot of work. Just like what Newton figured out was not provable before without all the computations:
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I believe it’s generally believed that dark matter clumps near galaxies because it interacts through gravity. So would it be reasonable to say that it should clump together near massive objects in the solar system?
DM usually forms a halo as it orbits the center of mass of whatever it orbits (galaxy, globular cluster), and because it doesn't interact otherwise, it cannot slow down, cannot shed momentum, so it is likely mostly not a disk, but a big sphere, and probably a shell around galaxies.