Couldn't it be a good emitter, but redirect the heat in a focused way? (beam of RF)
The sibling already mentioned the axioms of thermodynamics that forbid it. Another way to see that this is forbidden is Etendue https://en.wikipedia.org/wiki/Etendue#Conservation_of_etendu...
Re:The strength of the strong force
by survirtual on Wednesday August 17, 2022 @02:11PM
(#32499753)
Any thoughts on this? (discussion on temperature of a black hole)
Re:The strength of the strong force
by OkayPhysicist on Wednesday August 10, 2022 @01:21PM
(#32415508)
Nope. That would violate the 2nd Law of Thermodynamics.
Re:The strength of the strong force
by survirtual on Tuesday August 16, 2022 @01:56PM
(#32486378)
Why?
Couldn’t one build a dyson sphere around a blackhole? Wouldn’t the blackhole have properties of a Bose–Einstein condensate given the matter at the center cannot vibrate?
It would be the coldest temperature possible. Heat moves downhill, you deposit heat into a singularity and have a shell around it.
That aside, at even a scale of a single dyson sphere, something tells me when a civilization has the power to bend spacetime, the rules of possibilities begin to change. I think it is unwise to operate with so much certainty in the face of possibilities.
A really cool outcome of statistical mechanics and thermodynamics is that what you suggest is impossible. The dyson sphere can be as amazing as you want, using every single trickery permitted by physics, but at some point it will enter thermal equilibrium with its host start (or pipe that heat somewhere else where you would still be able to see its thermal radiation). Inherently, if they are optimized to be good absorbers, they will have to also be thermal emitters. There is no such thing as "recycle all spectrum".
Tangentially related to the fact that a "perfectly black body", i.e. a perfect absorber, is also the perfect emitter of thermal radiation of its own.