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Is it even meaningful to say that the universe - everything - has an entropy? Isn't it not even meaningful to talk about the entropy of something that is in a n
by pizza 5y ago
Is it even meaningful to say that the universe - everything - has an entropy? Isn't it not even meaningful to talk about the entropy of something that is in a non-equilibriated state? People point to experiments about gas particles bouncing off the walls of closed boxes to prove how entropy is always increasing, but it really makes no sense to transfer that to the whole universe.
I have been much more convinced that the universe, starting from a maximally structured configuration, tends to even greater structure, as Julian Barbour wrote about in the Janus Point. Structure emergence, as opposed to catastrophic mixing. My perspective used to be like yours but it has become: the game is only starting.
- alisonkisk 5y agoHow can there be greater than maximal structure?
- pizza 5y agoI might have messed up that wording.. basically as I understand it the universe started out pretty much homogeneous and uniform, minor deviations became magnified into seeding the structure that exists today, and basically some mix of inflation + gravitation will create additional structure forever, as measured by a value called the "shape potential" C = l_rms/l_mhl of a spatial configuration of particles [0]. l_rms is the root-mean-square length of the system and l_mhl is the mean-harmonic-length. He makes this argument that there are many potential geometric configurations that the universe could have started out as but he believes it started from the one that has the maximum shape potential, iirc. [0] https://physics.aps.org/featured-article-pdf/10.1103/PhysRevLett.113.181101 https://physics.aps.org/featured-article-pdf/10.1103/PhysRev...
- bengarrr 5y agoEntropy IS always increasing. Water is always gonna flow downhill. Its not possible to go from maximally ordered to even more ordered, except in some kind of highly localized phenomena. But it is possible that it can return to that maximally ordered state after it reaches a maximally unordered state. This is the idea Roger Penrose has for the big bang is that it is the state of the universe immediately succeeding the heat death of the universe, at a certain point maximally unordered and maximally ordered can look the same, at least mathematically.
- pizza 5y agoI'm not really talking about things that violate energy conservation or statistical mechanics. I'm talking about how the uniformity of the state during the big bang lead to something clumpier. Structure formation. And I still find it suspect to apply the concept of thermodynamical entropy, something defined for isolated systems at thermal equilibrium, primarily, to even make sense at universe-scale.
- bengarrr 5y agoStructure is not entropy though unless I am missing what you are saying. The arrangement of macro level objects like a supercluster has less to do with entropy and more to do with dark matter/energy or what ever that stuff is. Also I dont follow the reasoning that this concept of entropy is incorrectly being applied to the universe... energy is energy I have never heard that the thermodynamics only applies to isolated systems in equilibrium.
- rendall 5y ago> Is it even meaningful to say that the universe - everything - has an entropy? The overarching approach to possible lack of meaning applies whether the universe increases entropy, sheds it, or maintains static equilibrium forever and ever and ever. It's kind of beside the point, really. Read entropy here as a metaphor for creeping existential despair or random chaos, whichever makes more sense to you.