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Does heat death occur in a closed system? (Assuming you can theoretically have some sort of "closed system".

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    $\begingroup$ FWIW: here's some psychologists explaining the dress color perception: redd.it/2xbfxp $\endgroup$
    – Andrew S.
    Commented Feb 27, 2015 at 7:29
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    $\begingroup$ Not necessarily in a closed system because heat can be exchanged, but in an isolated system yes. And Wired had an article on the dress. $\endgroup$
    – lemon
    Commented Feb 27, 2015 at 7:33
  • $\begingroup$ The dress is in a superposition of all four. $\endgroup$
    – Hritik Narayan
    Commented Feb 27, 2015 at 8:18

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There is a degree to which this is just terminology, but in cosmology a distinction is somtimes made between the Heat Death and the Big Freeze. The Big Freeze is the point at which the universe reaches absolute zero, while the Heat Death is the point at which the entire universe has a constant temperature. These are not necessarily the same thing, because a de Sitter universe possesses a cosmological horizon and this will emit Hawking radiation. That means a de Sitter universe will never cool to absolute zero - only to the temperature of the Hawking radiation. However the distinction I make here is far from standard and you'll see the two terms being used interchangeably.

The point of all this is that a closed system is never going to cool to absolute zero because obviously if it's closed heat can't escape from it. However it can attain a state of uniform temperature. So it can attain a state of Heat Death, but only for a subset of commonly used meanings of the term Heat Death.

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  • $\begingroup$ Interesting insight.. so my only other question is, does entropy increase in a closed system? I'm aware that you said it will reach "heat death" (aka consistent temperature), just to be clear "consistent" means evenly distribute and lowest value obtainable (because of entropy increasing)? $\endgroup$
    – Albert Renshaw
    Commented Feb 27, 2015 at 13:45
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    $\begingroup$ Yes, the entropy will increase in a closed system up to some maximum value determined by the construction of the system. By uniform temperature I mean that the temperature is the same everywhere in the system. $\endgroup$
    – John Rennie
    Commented Feb 27, 2015 at 14:42
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    $\begingroup$ Entropy can decrease in a closed system sometime,for example you can decrease the entropy of your house using refrigerator but doing that you finally increase the entropy of the system(house) plus the sorrounding(entropy of the universe).we cannot take the whole universe as a system,there must be a sorrounding. $\endgroup$
    – Paul
    Commented Feb 27, 2015 at 15:16

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