>>3260
>Is the void between galaxies filled with black holes? If so, wouldn't we detect them?
There might actually be black holes floating around the intergalactic space. Simulations predict that when galaxies collide, the central black holes sometimes get ejected. We wouldn't detect them, as they wouldn't interact with pretty much anything as intergalactic space is even more empty than plain interstellar space. Perhaps we could notice them through gravitational lensing if they were really massive.
You also need to understand though that galaxies are much more densely spaced than stars in a galaxy relative to their size. Our galaxy is about 30 kiloparsec in diameter, and the closest major galaxy, The Andromeda, is about 780 kiloparsec away. To give you a clue on how close that is, if you scale everything down to planet scale, the Moon is relatively further away from the Earth than this distance on the galactic scale.
>If CERN created a black hole somehow, would it tether to earth and gobble it up, or fly off into space as the planet continues to move through the galaxy? Can a small black hole even sustain itself? Think about it, we only see black holes forming out of the largest stars.
Well, if we use Hawking radiation derivation of black hole evaporation, we can calculate the predicted black hole lifespan before it disappears as:
t[s] = 8.40716E-17 M[kg]^3.
A black hole that survives for a second (if it doesn't swallow anything) would have to weigh about 200 tons. CERN currently operates at 13TeV collisions, which is about 2.3E-23 kg, a black hole of such low mass would have lifespan of only 1.0E-84 second, which is way too low for anything.