History of Black Holes: Formation and Timing After the Big Bang

[PhilKravitz]

When were the first black holes formed? How long after the big bang until black holes could form?

 

[zhermes]

That's an excellent question, and one that's being actively studied. Thus there isn't an exact, known answer.

It is generally believed that the first stars ("population III" stars) formed about a million years after the big bang, these stars would have been much much larger than stars now, and most likely would have collapsed directly to early black-holes within a few million years after their formation (such large stars don't survive very long).
It is possible that these early, high-mass, black-holes grew gradually and became what are now the super-massive black holes at the center of galaxies.

It is also possible that in the first seconds of the universe, micro-black-holes were formed, but they would have disappeared soon afterwords.

 

[PhilKravitz]

It is also possible that in the first seconds of the universe, micro-black-holes were formed, but they would have disappeared soon afterwords.

Why would black holes formed in the first few seconds be micro in mass? Would any be macro in mass? What is the physics that makes early black holes only micro?

 

[zhermes]

Why would black holes formed in the first few seconds be micro in mass? Would any be macro in mass? What is the physics that makes early black holes only micro?

Remember that you start out with only fundamental particles, then protons, neutrons and electrons... and basics you're left with only those for a hundred million years (until the first stars are formed). Still, in the first small fractions of seconds, the energy of these particles were large enough that they could collide with each other---creating energy densities high enough to form a micro-black hole (with total mass roughly on the order of a proton or so).

 

[PhilKravitz]

Is it the amount of inhomogeneity that matters or the size of common particles? Even today the basic particle is a hydrogen atom with size 2E-10 meters. At 1E-6 seconds after the big bang neutrons and protons formed with size 1E-15 meters.

Why was the early universe so smooth that black holes could not form? I am not doubting that it was only wonder what was the physics behind it being so.