5
$\begingroup$

I understand that space was compressed to a single point and that during the big bang all points within that expanded away from each other at phenomenal speeds. I also have heard that during this the universe wasn't the same everywhere, as in small quantum fluctuations that expanded to macroscopic scales.

Would this mean that higher density than normal areas could create massive black holes? Maybe not as big as the ones today but perhaps large enough to solve some of the problems with super massive black holes being observed in a short amount of time after the big bang

I am not asking "why didn't the universe turn into a singularity?" I am asking "Could the variable density afterwards create many singularities which could explain for the problems associated with super massive blackholes?".

$\endgroup$
  • 2
    $\begingroup$ Possible duplicate of Why did the big bang not just produce a big black hole? $\endgroup$ – Sir Cumference Mar 28 '17 at 17:54
  • 3
    $\begingroup$ It's really not the same question, though it's related. The linked question(s) are about the entire observable universe being well inside the schwarzchild radius of that much mass. Big bang theory does raise that paradox. This question is about after the initial expansion, were there large primordial black holes that formed during the expansion out of sufficient density, that became the centers of galaxies. I've read an article here or there, that it's been proposed, but I don't know enough to answer the question. $\endgroup$ – userLTK Mar 29 '17 at 0:06
  • $\begingroup$ I agree with userLTK, this question is distinctly different from the question posted by Sir Cumference. $\endgroup$ – zephyr Mar 29 '17 at 15:23
  • 3
    $\begingroup$ A small correction of "space was compressed to a single point". I think observable universe was compressed to a point (nearly enough), while the universe can be regarded as "infinite" during the Big Bang as it is today. $\endgroup$ – kubanczyk Mar 29 '17 at 15:47
  • $\begingroup$ Well, thats kind of the same thing isnt it? If you take infinite space but just decrease the amount of that space between all points, you still have an infinite plane... Just a very high density (in this case VERY high density) $\endgroup$ – Terran Mar 29 '17 at 16:08
1
$\begingroup$

Arxiv prodives Haiman 2012 paper The Formation of the First Massive Black Holes. The leading theory, based on WMAP, is that the first perturbations resulted in dark matter halos, which were the first gravitational concentrations of matter.

the first nonlinear objects in the universe were born inside ∼ 10^5 M⊙ dark matter halos at redshifts of z ∼ 20−30

The non-linear objects do not refer precisely to black holes. The key part for us:

[...] question of how the first SMBHs were assembled. It is worth emphasizing that this is an unsolved problem – indeed, it is not entirely clear even whether the first nonlinear objects in the universe were stars or black holes, and whether galaxies or their central black holes formed first.

The article proceeds to tell a very wide range of theories, but the summary is - we are quite clear about simulating the early dark matter halos but we really don't know how to clearly show whether/how it led to SMBH formation.

I'd like to emphasize what is (maybe) obvious: SMBH requires a very concentrated gravity. We assume that a very early universe despite being dense didn't have enough gravity. All theories are generally about how density dropped far down and in what ways could it start to grow again, but now only inside the concentrations (i.e. when the gravity started to affect universe, the density was much lower that inside stars or black holes).

$\endgroup$
  • $\begingroup$ If it helps at all: gravity relates to the energy density gradient as opposed to the density per se. For example if you're at the centre of the Earth gravitational potential is low and the energy density is high, but there's no gradient and no gravity. Ditto if you're midway between two stars. $\endgroup$ – John Duffield Mar 31 '17 at 12:14
  • $\begingroup$ @JohnDuffield that's for Newtonian gravity, but not in GR. $\endgroup$ – Walter Apr 1 '17 at 17:41
1
$\begingroup$

The problem of early SMBH formation arises because of the Eddington limit: accreting matter heats up, radiates, and the radiation pressure limits further accretion. The problem is particularly acute if the SMBH is spinning fast, because then the innermost stable circular orbit (ISCO), which sets the inner edge of the accretion disc, is closer to the hole and the accreting matter heats up much more before passing the event horizon. However, SMBHs may actually not spin much (as a result of randomly orientated infall events), when the formation of observed SMBHs at high redshifts are not a problem.

$\endgroup$
  • $\begingroup$ I think supermassive black holes don't spin at all. $\endgroup$ – John Duffield Mar 31 '17 at 12:10
  • 1
    $\begingroup$ @JohnDuffield Think what you want, but they may spin, it's one of their properties (the others are mass and charge). If they accrete matter, they also accrete its spin (and charge), so may spin up if preferentially accreting material of the same angular-momentum orientation. $\endgroup$ – Walter Mar 31 '17 at 17:24
  • $\begingroup$ I know that's what people say Walter. But I've read the Einstein digital papers, some of the things I see there don't square with some of the things I read in modern texts, and I find myself siding with Einstein. $\endgroup$ – John Duffield Apr 1 '17 at 16:47
  • 1
    $\begingroup$ Einstein erred more often than you might think. $\endgroup$ – Walter Apr 1 '17 at 17:39

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.