Re:Entropic Gravity
by SiempreViernes on Monday September 02, 2019 @06:16AM
(#20858062)
It explicitly (almost) doesn't interact with normal matter, so it cannot be illuminated: it's dark because the light just goes right trough it, the same way space is dark because it doesn't scatter light.
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However, for a long time the main competing theory for WIMPs was MACHOs (yeah, really), basically "familiar" dim, compact objects such as brown dwarfs and black holes, scattered around in the galactic halo. However, gravitational microlensing surveys have found that the observed density of MACHOs is far too low to make up a significant fraction of dark matter.