Physicists here. He's trying to explain everything in terms of a simple blackbody in thermal equilibrium, peacefully radiating its energy away only via thermal

Physicists here. He's trying to explain everything in terms of a simple blackbody in thermal equilibrium, peacefully radiating its energy away only via thermal photons. That's not the reality of the radiation from the sun or moon. Solar physics is an entire branch of physics, and such simple toy models are not even wrong. Sun doesn't just radiate away its existing energy via thermal photons. First, it keeps burning its fuel via a series of nuclear reactions, which by the way keeps pumping energy into the system, essentially acting like a battery (so there's no perpetual motion here). Second, sun emits photons that are much more energetic than the thermal photons from the surface. Some of the radiation is not thermal, and comes directly from different types of nuclear reactions (which provides signatures regarding the kind of reactions happening in the sun) and various other processes.