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Maybe I’m a bit naive here, but I thought finding of many supermassive back holes in the very early universe should be expected, and not a surprise. My chain of

Maybe I’m a bit naive here, but I thought finding of many supermassive back holes in the very early universe should be expected, and not a surprise. My chain of thoughts is following: - Blackholes are collapsed masses. In our phase of the universe, they are normally the results of supernovae but only because today stars are the only source of dense masses. - Because the total mass of the universe is constant and the early universe has a volume of dozen orders of magnitude smaller than the universe in later stage (the universe we normally observe), collapsed masses should happen much more likely than in later stage. - Those masses do not necessarily come from the stars, which are masses with a visible fusion processes but could come directly from mass-lumps, left after the Big Bang. - In fact, I think the idea of a super homogenous universe right after the Big Bang is suspect. Even the CMB is only homogeneous on (very) large scale (3000 mega parsecs), ways too big for blackholes. - Therefore, I think after the Big Bang, there should be a large number of primordial blackholes. - We can only observe blackholes with an accretion disk, but the primordial blackholes with no visible accretion will stay invisible unless there is a collision/fusion in progress. Consequently, we will find a lot more blackholes in the early universe, the more we look. They are super massive because of the bias: only supermassive blackholes with accretion disk were producing radiation, powerful enough so we can detect with our current technology.

andrewstuart 3y ago
Great ideas tend to be obvious in hindsight.
lenkite 3y ago
Lets say the number of actual black holes is even more - several orders more than what is even mentioned here. Would it be enough to account for the "Dark Matter" conundrum ?
- sinuhe69 3y ago
  In fact, primordial blackholes are a candidate for dark matter hypothesis. They are still invisible but at least we could devise a theory to detect them (light focusing/bending for examples)
- andrewflnr 3y ago
  Look up the "MACHO" hypothesis for dark matter. Tl;dr: mostly ruled out via gravitational lensing surveys.
deleted 3y ago
[deleted]
mikhailfranco 3y ago
There remains doubt about CMB inhomogeneity at the smallest scales - basically the error bars at the right of this graph, and the region off the chart to the right, which is yet to be measured: https://en.m.wikipedia.org/wiki/Cosmic_microwave_background#Primary_anisotropy https://en.m.wikipedia.org/wiki/Cosmic_microwave_background#... A naive view would be that a turbulent Big Bang has turbulence all the way down, with many fine-grain clumps and vortices, giving rise to early black holes. Inflation is invoked to create a homogeneous CMB, but that begs the question, and cannot be used to rule out small-scale inhomogeneities.
netbioserror 3y ago
This makes a lot of sense. In those first few seconds, that incredibly hot, dense soup of matter would've immediately "pitted" through with absolutely enormous black holes, and like rain, those black holes were probably the "seeding" nuclei for the remaining matter to clump around and form galaxies. Which suggests that galactic core supermassives are drifting leftovers from the formation of the universe. It might also suggest that after the primordial age, they may not have consumed much matter at all (though we have plenty of evidence of some early supermassives consuming quite a lot at the fringes of the observable universe).
- MaxikCZ 3y ago
  I still dont get it. If during the first few second there was so much matter in so little space that enormous blackholes should form, then why did big bang even happen? In the first instance, there was all the matter in the tinies of space, everything should have immediatelly form a blackhole and bigbang should have not happen
  - netbioserror 3y ago
    Disclaimer: I am a lay man and a physics enthusiast, no more. My thought is that the initial inflationary event of the Big Bang was far more powerful than early gravity’s ability to counteract it, maybe even on the order of the nuclear forces. I’d speculate that the “pits” (“low pressure systems” if we analogize to storms) would have formed in this period. Once expansion slowed, maybe even just a few seconds in, the conditions might have been conducive for the pits to collapse into black holes.
dtgriscom 3y ago
What do you mean by "many" black holes being "expected"? What's "many"? You have to be specific, and to do that you model, and then validate through observation. The article states that more black holes are being observed than the models predict, which is their definition of "many".
tzs 3y ago
> Because the total mass of the universe is constant It isn't [1]: > The point is pretty simple: back when you thought energy was conserved, there was a reason why you thought that, namely time-translation invariance. A fancy way of saying “the background on which particles and forces evolve, as well as the dynamical rules governing their motions, are fixed, not changing with time.” But in general relativity that’s simply no longer true. Einstein tells us that space and time are dynamical, and in particular that they can evolve with time. When the space through which particles move is changing, the total energy of those particles is not conserved. > It’s not that all hell has broken loose; it’s just that we’re considering a more general context than was necessary under Newtonian rules. There is still a single important equation, which is indeed often called “energy-momentum conservation.” It looks like this: μν ∇ T = 0 μ > The details aren’t important, but the meaning of this equation is straightforward enough: energy and momentum evolve in a precisely specified way in response to the behavior of spacetime around them. If that spacetime is standing completely still, the total energy is constant; if it’s evolving, the energy changes in a completely unambiguous way. > In the case of dark energy, that evolution is pretty simple: the density of vacuum energy in empty space is absolute constant, even as the volume of a region of space (comoving along with galaxies and other particles) grows as the universe expands. So the total energy, density times volume, goes up. [1] https://www.preposterousuniverse.com/blog/2010/02/22/energy-is-not-conserved/ https://www.preposterousuniverse.com/blog/2010/02/22/energy-...

andrewstuart 3y ago

Great ideas tend to be obvious in hindsight.

lenkite 3y ago

Lets say the number of actual black holes is even more - several orders more than what is even mentioned here. Would it be enough to account for the "Dark Matter" conundrum ?

sinuhe69 3y ago
In fact, primordial blackholes are a candidate for dark matter hypothesis. They are still invisible but at least we could devise a theory to detect them (light focusing/bending for examples)
andrewflnr 3y ago
Look up the "MACHO" hypothesis for dark matter. Tl;dr: mostly ruled out via gravitational lensing surveys.

deleted 3y ago

[deleted]

mikhailfranco 3y ago

There remains doubt about CMB inhomogeneity at the smallest scales - basically the error bars at the right of this graph, and the region off the chart to the right, which is yet to be measured: https://en.m.wikipedia.org/wiki/Cosmic_microwave_background#Primary_anisotropy https://en.m.wikipedia.org/wiki/Cosmic_microwave_background#... A naive view would be that a turbulent Big Bang has turbulence all the way down, with many fine-grain clumps and vortices, giving rise to early black holes. Inflation is invoked to create a homogeneous CMB, but that begs the question, and cannot be used to rule out small-scale inhomogeneities.

netbioserror 3y ago

This makes a lot of sense. In those first few seconds, that incredibly hot, dense soup of matter would've immediately "pitted" through with absolutely enormous black holes, and like rain, those black holes were probably the "seeding" nuclei for the remaining matter to clump around and form galaxies. Which suggests that galactic core supermassives are drifting leftovers from the formation of the universe. It might also suggest that after the primordial age, they may not have consumed much matter at all (though we have plenty of evidence of some early supermassives consuming quite a lot at the fringes of the observable universe).

MaxikCZ 3y ago
I still dont get it. If during the first few second there was so much matter in so little space that enormous blackholes should form, then why did big bang even happen? In the first instance, there was all the matter in the tinies of space, everything should have immediatelly form a blackhole and bigbang should have not happen
- netbioserror 3y ago
  Disclaimer: I am a lay man and a physics enthusiast, no more. My thought is that the initial inflationary event of the Big Bang was far more powerful than early gravity’s ability to counteract it, maybe even on the order of the nuclear forces. I’d speculate that the “pits” (“low pressure systems” if we analogize to storms) would have formed in this period. Once expansion slowed, maybe even just a few seconds in, the conditions might have been conducive for the pits to collapse into black holes.

dtgriscom 3y ago

What do you mean by "many" black holes being "expected"? What's "many"? You have to be specific, and to do that you model, and then validate through observation. The article states that more black holes are being observed than the models predict, which is their definition of "many".

tzs 3y ago

> Because the total mass of the universe is constant It isn't [1]: > The point is pretty simple: back when you thought energy was conserved, there was a reason why you thought that, namely time-translation invariance. A fancy way of saying “the background on which particles and forces evolve, as well as the dynamical rules governing their motions, are fixed, not changing with time.” But in general relativity that’s simply no longer true. Einstein tells us that space and time are dynamical, and in particular that they can evolve with time. When the space through which particles move is changing, the total energy of those particles is not conserved. > It’s not that all hell has broken loose; it’s just that we’re considering a more general context than was necessary under Newtonian rules. There is still a single important equation, which is indeed often called “energy-momentum conservation.” It looks like this: μν ∇ T = 0 μ > The details aren’t important, but the meaning of this equation is straightforward enough: energy and momentum evolve in a precisely specified way in response to the behavior of spacetime around them. If that spacetime is standing completely still, the total energy is constant; if it’s evolving, the energy changes in a completely unambiguous way. > In the case of dark energy, that evolution is pretty simple: the density of vacuum energy in empty space is absolute constant, even as the volume of a region of space (comoving along with galaxies and other particles) grows as the universe expands. So the total energy, density times volume, goes up. [1] https://www.preposterousuniverse.com/blog/2010/02/22/energy-is-not-conserved/ https://www.preposterousuniverse.com/blog/2010/02/22/energy-...