3 ms·

I've read (elsewhere, I guess) that some 95% of the Milky Way's mass is estimated to be dark matter. If there are only 700g of it nearby, it can't be distribute

I've read (elsewhere, I guess) that some 95% of the Milky Way's mass is estimated to be dark matter. If there are only 700g of it nearby, it can't be distributed the same way normal matter is. How can that be, since it interacts with normal matter gravitationally? Does the solar wind blow it away, or something like that? I've also seen an article not long ago showing 'visualizations' of dark matter around a spiral galaxy, and it was mostly in teardrop-shaped lobes above and below the galaxy's center and aligned on the axis, rather than distributed through the disk. I didn't think of it at the time but now that I do, it seems like that distribution also indicates that light from the stars is pushing the dark matter away.

cdumler 7y ago
The reason why normal matter forms disks is because of electromagnetic repulsion: electromagnetic atoms naturally resist being in the same place as another atom. There becomes a tension between the repulsion to not stack up and gravity to compress things together. Since angular momentum is conserved, the matter will spin and flatten out: ie, a galaxy. If dark mater is a particle, it rarely interacts with anything, including itself; so, it cannot collapse. Most of the particles will be in a constant state of free fall throughout the galaxy. Only if the particle just happens to have a nearly matching velocity would it get trapped in a star or planet. Even then, it would still be wobbling around with nothing to touch.