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I'm in a similar boat, but I've always felt the opposite! I've always felt the second law is kind of a shoe-in and maybe even shouldn't be a law at all. The f

I'm in a similar boat, but I've always felt the opposite! I've always felt the second law is kind of a shoe-in and maybe even shouldn't be a law at all. The first and third laws, "energy is never created or destroyed" and "for every action there's an equal and opposite reaction" are always true! To my knowledge, no process is ever allowed to break either law. (With exceptions for cosmological process like the expansion of the universe that we really don't purport to understand.) The second, "entropy can only increase" isn't! That's right, I said it. The processes it describes (a cup unshuttering, or coffee unmixing, or particles all finding their way into the same side of a box) are totally legal process, albeit statistically unlikely. If you restrict your system to few enough particles (say, n=3), random processes that decrease entropy are not only possible, but something that happens with regularity! Now, I make no claims to be right here. I suspect that Eddington fellow probably knows what he's talking about. But, this has been a longstanding thorn in my understanding of physics, so I'd be interested if anybody has any interesting insights!

elashri 2y ago
> With exceptions for cosmological process like the expansion of the universe that we really don't purport to understand That's not accurate, expansion of the universe (that the standard model of cosmology describes) does not violate conservation of energy. It makes it a little different from the classical view. In classical mechanics, energy conservation is a well-defined concept in a static or non-expanding spacetime. However, in an expanding universe, especially one described by general relativity (like ours), the energy of the universe is not necessarily conserved in the traditional sense, because the global energy of the universe is difficult to define when spacetime itself is dynamic (expanding) So GR does not require global conversation of energy in the same way classical (here classical means strictly newtonian mechanics) mechanics does. This dynamic nature of the spacetime allows for energy to appear to "change" due to the expansion. It is more complicated when you add things like dark energy to the equation. One interesting aspect is the phenomenon of cosmological redshift. As the universe expands, light travelling through space is redshifted. This means that ita wavelength increases and its energy decreases. This "loss" of energy from light is not violating conservation of energy. It is rather consequence of the expansion itself. Now lets back to dark energy which is driving the accelerated expansion of the universe, the energy associated with the vacuum of space remains constant per unit volume, but as space itself expands, the total energy associated with dark energy increases. This again does not violate the laws of physics because energy conservation is more complex in general relativity than in Newtonian mechanics. And of course the local energy conservation works in a well-defined way if you take a localized region of the spacetime.

elashri 2y ago

> With exceptions for cosmological process like the expansion of the universe that we really don't purport to understand That's not accurate, expansion of the universe (that the standard model of cosmology describes) does not violate conservation of energy. It makes it a little different from the classical view. In classical mechanics, energy conservation is a well-defined concept in a static or non-expanding spacetime. However, in an expanding universe, especially one described by general relativity (like ours), the energy of the universe is not necessarily conserved in the traditional sense, because the global energy of the universe is difficult to define when spacetime itself is dynamic (expanding) So GR does not require global conversation of energy in the same way classical (here classical means strictly newtonian mechanics) mechanics does. This dynamic nature of the spacetime allows for energy to appear to "change" due to the expansion. It is more complicated when you add things like dark energy to the equation. One interesting aspect is the phenomenon of cosmological redshift. As the universe expands, light travelling through space is redshifted. This means that ita wavelength increases and its energy decreases. This "loss" of energy from light is not violating conservation of energy. It is rather consequence of the expansion itself. Now lets back to dark energy which is driving the accelerated expansion of the universe, the energy associated with the vacuum of space remains constant per unit volume, but as space itself expands, the total energy associated with dark energy increases. This again does not violate the laws of physics because energy conservation is more complex in general relativity than in Newtonian mechanics. And of course the local energy conservation works in a well-defined way if you take a localized region of the spacetime.