By: Aaron Bergman
What is your definition of a macrostate outside of thermodynamic equilibrium?
View ArticleBy: Sean
An equivalence class of microstates under some coarse-graining. Again, in practice, it might be convenient to define your coarse-graining by reference to macroscopic observables that are not defined...
View ArticleBy: Neil B
Fubaris you get the issue of what goes wrong in the “time” reversed world. I suppose you are also right about experiencing such a world, since the processes are relative to the beings there and they...
View ArticleBy: David
Maybe I’m stupid but i don’t understand why entropy increases or decreases when the total content of the universe does not change. Why are Ice-cubes more ordered than water. The total energy and...
View ArticleBy: wolfgang
>> But, I would argue (and I’m happy to hear other points of view, as the matters are by no means settled), entropy is not one of them. And I would agree with you. Temperature (mean kinetic...
View ArticleBy: Sean
wolfgang– I don’t want to gloss over that at all; calculating the entropy of a system in which gravity is important is something we don’t know how to do, and that’s a problem. However, we have fairly...
View ArticleBy: Aaron Bergman
Temperature (mean kinetic energy) may not be well defined for a system out of equilibrium, but entropy certainly is. If entropy would only be defined for a system in equilibrium, we would not need the...
View ArticleBy: wolfgang
> it’s only defined for equilibrium states. So you are saying that e.g. entropy is not defined for a black hole, because a black hole (radiating into the universe) is not in equilibrium ?
View ArticleBy: links for 2009-01-03 < kulturbrille:amanuensis
[...] Richard Feynman on Boltzmann Brains | Cosmic Variance | Discover Magazine This one-wayness is interrelated with the fact that the ratchet [a model irreversible system discussed earlier in the...
View ArticleBy: What is The Universe | DesiPundit
[...] was reading a fascinating discussion at Cosmic Variance on Boltzmann Brain Paradox and what Feynman made of it. The paradox raises questions about the state of the Universe, why is the beginning...
View ArticleBy: Low Math, Meekly Interacting
Greg, thank you very much for your clear reply to my question, it was very helpful. I hadn’t considered the possibility that one could use the paradox, perhaps by itself, to argue the universe must...
View ArticleBy: tomate :: Gravitation and thermodynamics :: January :: 2008
[...] some discussion over the web (here, here, here and here) about thermodynamics and gravitation, a discussion that comes out pretty regularly. [...]
View ArticleBy: tomate :: Gravitation and thermodynamics :: January :: 2009
[...] some discussion over the web (here, here, here and here) about thermodynamics and gravitation, a discussion that comes out regularly. I [...]
View ArticleBy: what age did you stop beleaving in the religion you where raised with? -...
[...] Originally Posted by Sparrow I can pinpoint the exact moment I lost my religion. Our very own Scotticus hit me up with a fact: Life is a state of disequilibrium. Everything clicked and I lost my...
View ArticleBy: what age did you stop beleaving in the religion you where raised with? -...
[...] Life is a state of disequilibrium. Everything clicked and I lost my soul. Thanks, Dr. Scotty! Richard Feynman on Boltzmann Brains | Cosmic Variance | Discover Magazine I <3 [...]
View ArticleBy: Sean Peters
You can get a universe like ours that way, but you’re overwhelmingly more likely to get just a single galaxy, or a single planet, or even just a single brain — so the statistical-fluctuation idea seems...
View ArticleBy: Leonardo
The low degree of entropy is not a consequence of the Boltzmann hypothesis (we are in a low entropy region), but a consequence of the nature of entropy itself. Entropy also generates order. Out of...
View ArticleBy: Fritz Lorenz Doerring
Decay is obvious and visible, and experiential. Multiverse is not in our present sphere of experience. Might it ever become so? Wait: Be patient! It may be a long time. Fritz
View ArticleBy: Carl Lumma
The Boltzmann brain paradox assumes a fixed (and rather naive) prior: that all regions of spacetime are independent. Bayesians would like us to consider the weighted probability over all priors. That’s...
View ArticleBy: Moninder Singh Modgil
There is a simple vacuum solution of Einstein’s field equations, obtained from Minkowski universe by the replacement- t -> sin t Geodesics in this universe (which I refer to as the “Periodic...
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