- #1
Feynstein100
- 162
- 16
I have a thought experiment in mind. Crudely speaking, the second law of thermodynamics implies that there is only a finite amount of change possible in the universe. Once this limit is reached, no more change can occur. The key thing here though is reversibility. If changes were reversible, then the entropy change would be zero and we could stay at the same entropy level indefinitely.
Considering only the Solar System, the sun is burning up its mass and converting it to energy, which then spreads out across the Milky Way and the rest of the universe. Again, according to the second law, once energy gets spread out, it cannot be concentrated again without expending more energy. So what if we stopped the energy from spreading out? Let's say we have some kind of Dyson sphere but instead of enclosing just the Sun, it encloses the entire Solar System. This hypothetical Dyson sphere is made out of ideal mirrors that reflect all of the Sun's energy without absorbing any of it, i.e. now all of the Sun's energy comes back to it and doesn't get spread out. What would happen in this theoretical scenario?
Would this cause the entire Solar System to be in a reversible state? The sun emits energy. This energy gets reflected back to the sun, and then re-emitted by the sun again, closing the loop. Of course, fusion would no longer occur but that's kind of the point. The sun is no longer burning itself up, and yet still shining.
Although, any closed system should eventually reach an equilibrium temperature across its entirety. So will that happen in this case too? Will the entire Solar System reach some equilibrium temperature and then not change anymore? Which, ironically, is heat death. I'm not sure what would happen. My mental simulation of this is kinda stuck lol. Could anybody help me out here?
Considering only the Solar System, the sun is burning up its mass and converting it to energy, which then spreads out across the Milky Way and the rest of the universe. Again, according to the second law, once energy gets spread out, it cannot be concentrated again without expending more energy. So what if we stopped the energy from spreading out? Let's say we have some kind of Dyson sphere but instead of enclosing just the Sun, it encloses the entire Solar System. This hypothetical Dyson sphere is made out of ideal mirrors that reflect all of the Sun's energy without absorbing any of it, i.e. now all of the Sun's energy comes back to it and doesn't get spread out. What would happen in this theoretical scenario?
Would this cause the entire Solar System to be in a reversible state? The sun emits energy. This energy gets reflected back to the sun, and then re-emitted by the sun again, closing the loop. Of course, fusion would no longer occur but that's kind of the point. The sun is no longer burning itself up, and yet still shining.
Although, any closed system should eventually reach an equilibrium temperature across its entirety. So will that happen in this case too? Will the entire Solar System reach some equilibrium temperature and then not change anymore? Which, ironically, is heat death. I'm not sure what would happen. My mental simulation of this is kinda stuck lol. Could anybody help me out here?