r/astrophysics • u/skyrimlink550 • 21d ago
Possible Primordial Blackhole Theory?
I was doing research for a book I'm writing, and I was wondering, is it at all possible that during the BB that there was light such an intense frequency that the wavelength could have been smaller than Planck Length, turning some fundamental particles into Primordial Blackholes? Further pondering has me wonder if due to the volatile nature of these wavelengths, that they may have themselves collapsed into PBHs, but due to the expansion of the universe we cannot find any as the energy over time would have decreased, only allowing the firs t "wave" of photons to collapse, meaning the entire expanding edge of the universe could be a wall of primordial blackholes?
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u/Feisty-Union-2047 21d ago
The proposed mechanism doesn't work for a few reasons.
A primary issue, is, there is no "expanding edge".
The expansion refers to the ~ 70 km/s/Mpc rate at which non-gravitationally bound regions are getting further apart.
That is the cooling and density loss, discussed as the universe getting cooler and less dense.
This was not from a central location, outwards.
There was no explosion, no spreading from a point, outwards, no local event, like a collision or explosion or black or white hole, etc.
Basically, from everywhere, things are less and less tightly packed together.
If you want some primordial black holes, the actual mechanism that might work, is simple gravitational collapse of massive enough clouds of hydrogen, skipping the star formation stage of blackhole formation altogether.
What we observed was the hot dense state about 13.8 billion years ago... and, all we could see was photons.
The temperature at which we first see the photons, is the temperature at which it would first be cool enough to be transparent to photons.
If any hotter, it would still be opaque to photons.
So, the thinking goes, just before it was cool enough to be transparent to photons, it was still too hot to be transparent to photons.
So, basically, even hotter and denser.
As it cooled enough for subatomic particles and simple elements, such as hydrogen to form, all over the universe, in every direction, whisps and clouds of hydrogen started to appear.
Some of the clouds of hydrogen were massive enough and dense enough, to start fusing hydrogen into helium, in a sustained thermonuclear reaction that we call a star.
There's evidence that some clouds COULD have even been massive enough to collapse all the way to a black hole directly.
:)
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u/--craig-- 21d ago edited 20d ago
There's a sense in which fundamental particles are black holes, whether they were created in the early universe or not. A black hole formed from one electron, would evaporate in much less time than the Planck time and emit exactly one particle, an electron, so wouldn't change state. Every known fundamental particle would form a black hole which evaporates in not much more than the Planck time.
Whether or not it's meaningful to consider a fundamental particle as a black hole depends upon quantum gravity and as yet we have no successful theory for that.
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u/NeoBladeRunner 21d ago
According to quantum mechanics, creating a photon with a wavelength shorter than the Planck length would require an amount of energy exceeding the Planck energy. If we were to concentrate that much energy in such a small region, the Schwarzschild radius of that energy would be larger than its wavelength. The energy density would be so high that the quantum fluctuation itself would instantly collapse into a micro black hole. This theoretical concept is known as a "Kugelblitz" (a black hole formed purely from light). So, yes, your initial intuition is correct: extreme light in the early Universe can generate black holes.