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/sci/ - Science & Math

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9778334 No.9778334 [Reply] [Original]

Black holes growing and hawking radiation.
Guys! Aren't black holes supposed to grow until the heat death of the universe? For instance the cosmic background radiation is still energy right? So can it feed existing black holes even if there are no stars anymore?
I am watching Pbs space time but it is really hard to follow...

>> No.9778384

>>9778334
The radiation is not nearly enough to cause a significant increase in mass and the black hole is constantly losing mass due to emission of wheelchair radiation.

>> No.9778417
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9778417

Black holes doesn't real, they are even incompatible with general relativity because the equations state they can have no mass.

>> No.9778439

>>9778417
That's the most retarded argumentation ever.

>> No.9778449
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9778449

>Aren't black holes supposed to grow until the heat death of the universe? For instance the cosmic background radiation is still energy right? So can it feed existing black holes even if there are no stars anymore?

The temperature of the CMB decreases as the universe ages, and thus so does the energy a body receives. The CMB was emitted as a ~3000 Kelvin blackbody, now it is redshifted to 2.7 K. In the future it will continue to decrease.

Eventually the energy from the CMB big black holes receive will fall below their Hawking radiation and they will start to shrink. It will take a very long time however.

The amount of energy a black hole emits via Hawking radiation depends on it's mass, very tiny black holes could evaporate even in the current universe as they would have Hawking temperatures higher than the CMB. We don't have much reason to believe these small black holes exist however.

Pic related. Observations which infer the change in the CMB temperature as you look back at the earlier universe. Measured with absorption line systems.

>> No.9778458

>>9778439
Einstein's field equations removes the energy momentum tensor (which removes matter), hence black holes cannot exist.

>> No.9778462

>>9778458
That means he’s just wrong, you retard.

>> No.9778470

>>9778417
They have mass.
https://en.wikipedia.org/wiki/ADM_formalism