[ailideex]

> Would they be able to capture enough energy so their star would be indistinguishable from the ambient temperature of space?

You would still see infrared:

https://en.wikipedia.org/wiki/Fermi_paradox#Conjectures_abou...

> Such a feat of astroengineering would drastically alter the observed spectrum of the star involved, changing it at least partly from the normal emission lines of a natural stellar atmosphere to those of black-body radiation, probably with a peak in the infrared.

https://en.wikipedia.org/wiki/Technosignature

> A Dyson sphere, constructed by life forms dwelling in proximity to a Sun-like star, would cause an increase in the amount of infrared radiation in the star system's emitted spectrum. Hence, Freeman Dyson selected the title "Search for Artificial Stellar Sources of Infrared Radiation" for his 1960 paper on the subject.[4] SETI has adopted these assumptions in its search, looking for such "infrared heavy" spectra from solar analogs. From 2005, Fermilab has conducted an ongoing survey for such spectra, analyzing data from the Infrared Astronomical Satellite.[5][6]

[Misdicorl]

Only if the 2nd law of thermodynamics holds. When speculating about advanced civilizations building Dyson spheres, why not speculate about the bedrock of science as well?

There are (probably) other paths to avoiding this conundrum as well. Spitballing here, but perhaps the 'satellites' in this case can be pairs of orbiting black holes which emit the waste heat in a band we don't detect (gravitational waves).

[pharke]

I always forget about the concept of gravitational engineering, probably because it's just a bit scary to think about the unknowns involved. If you could mass produce small black holes and position them you could pretty easily construct giant lenses capable of redirecting the output of a star to anywhere you please. That's more than a little terrifying.

[ailideex]

> Only if the 2nd law of thermodynamics holds. When speculating about advanced civilizations building Dyson spheres, why not speculate about the bedrock of science as well?

If the person I replied to qualified their comment with "lets assume laws of physicis is not relevant" then sure...

[Misdicorl]

Except when discussing technologically hyper advanced civilizations, the 2nd law of thermodynamics is a (vaguely) reasonable place to expect our laws to break.

The 2nd law is an observed fact with very shaky theoretical underpinnings (I am not talking about the behavior which has very strong underpinnings). It appears to be an emergent behavior rather than a fundamental one. It is a surprising fact given what else we know about the universe. It breaks the time symmetry of the other laws of physics. This is akin to learning that even though the laws of physics dont break position and rotational symmetries, there is a preferred direction and spin. In fact there is a preferred spin- all neutrinos are left handed. There are huge research efforts to understand why or if there are corresponding right handed particles. Broken symmetries mean big things because as far as we can tell the universe is ruled by what symmetries exist and in what ways they are broken.

[pharke]

You're ignoring the point I was making about capturing the infrared waste heat. It seems counterintuitive for a civilization to go to the effort of encasing their star in a shell of satellites while dumping energy as waste heat. Surely there must be some way of utilizing that energy and my conjecture was that advances in the efficiency of the Seebeck effect might lead to a way to fully utilize that waste.