5 ms·
It's interesting to note that applying the second law of thermodynamics to the whole universe, even if we didn't know about expansion, yields one of the biggest
by simiones 4y ago
It's interesting to note that applying the second law of thermodynamics to the whole universe, even if we didn't know about expansion, yields one of the biggest disconnects between prediction and observation since the ultraviolet catastrophe. If the second law applied to the whole universe, we should expect the Big Bang to have been quickly followed by a heat death. Having the entire universe we see today become so extraordinarily well organized from an initial glob of hot uniform plasma would have an inexpressably small probability. It seems far more likely to say that, for as yet un-determined reasons, the second law can't apply to the universe as a whole, only to certain subsets of it.
Might also suggest that the problem of black hole entropy is not actually settled, and that black holes could in fact simply reduce entropy instead of emitting Hawking radiation.
Also, it's interesting to note that expansion of the universe actually "breaks" the first law of thermodynamics: energy is not actually being conserved, new energy is being created. This can happen because the first law of thermodynamics only applies in a fixed size space, while in the expansion model we believe that space itself (the coordinate system, as it were) is expanding.
- reedjosh 4y agoI love this perspective. Not all physical laws have been proven in the grand scale of the universe, yet we narrow mindedly assume every one of these laws always hold -- I mean they're laws right!? -- and then we base all theories on what could be misconceptions. And realizing this makes theoretical physics much more interesting as there are so many more possibilities to how reality works than what's proscribed. I also wonder how much of our dogmatic adherence to these laws are preventing us from progressing.
- simonh 4y agoIs new energy really being crated by the expansion of space though? I know the vacuum energy increases, but would the increased negative gravitational potential energy cancel it out?
- spiralx 4y agoYes, the net energy of the Universe is zero.
- marcosdumay 4y agoAFAIK, if you count dark energy, then yes. The lost gravitational energy is much smaller. But if you stay with the understood kinds (that are certainly energy), then no, they stopped increasing a long time ago and are decreasing now.
- panda-giddiness 4y agoFor those curious, the assumption that the universe began in a low entropy state is known as the past hypothesis [1]. [1] https://en.wikipedia.org/wiki/Past_hypothesis https://en.wikipedia.org/wiki/Past_hypothesis