This was a really fascinating link, and it illustrates some things I already mostly knew very very well and introduces some things I didn’t in very creative ways, but it doesn’t actually explain what entropy is- the author explicitly states several times that he hasn’t gotten to entropy yet, that it’s all primer, spread over several posts, and I’ve read through the whole thread and he never ultimately gets to entropy before running out of steam. Or caloric, I suppose. It supports the stuff people are saying here about perceiving the Sun in terms of a Hot Sun/Cold Space system, but it actually contradicts what’s being said about an increase in entropy resulting in an increase in information, and meshes with a lot of how I currently conceive of physical information.
Essentially, information requires unevenness. In order for a thing to exist in a pattern, that thing must vary between at least two states. In a system with maximum entropy, everything is “flat”. Entropy cannot increase because energy is evenly distributed and has no impulse to move around any further. So there’s nowhere to record information- it’s like trying to write your name with a fountain pen on the surface of a pool of ink.
Assuming you’re talking about something like a thermal gas–it’s flat macroscopically, but not microscopically. Microscopically, it’s highly disordered and uneven. As such, it contains a great deal of information (although it may not be useful to you).
Contrast with something like a perfect crystal. Again flat macroscopically, but microscopically as well. It cannot contain any information unless the pattern is disturbed–and that must necessarily increase the entropy.
Sun
state 1. protons neatly contained in a hot ball
state 2. helium nuclei + photons and neutrinos eventually shooting into space
state 2 has higher entropy than step 1
Earth
state 1. various elements somewhat randomly distributed in a rocky ball
state 2. rocky ball with highly organised organic molecules all over the surface
state 2 has lower entropy than state 1
Sun-Earth
state 1. frigging huge ball of protons and tiny rocky ball
state 2. frigging huge ball of protons, plus huge, but comparably tiny amount of helium, plus actually tiny rocky ball with insignificant amounts of highly organised organic molecules all over the surface, and an insignificantly lower number of photons speeding into space, oh, and neutrinos.
