> <i>Well, the demon needs to have information about the motion of the atoms, otherwise it does not know when to open the door. The interesting thing about Maxwell’s demon is that it tells us entropy is somehow the opposite of information, you can use information to decrease entropy.</i><p>It's the first connection between the laws of physics and the process of computing, although it's a modern reinterpretation (the original interpretation only argued measurements by the demon requires energy). An interesting implication is: all computers in this universe must generate heat because information is lost in the logic circuit. However, if we can construct the logic circuit in such a way that all information is preserved at the output (i.e. reversible) [0], this computer only needs an infinitesimal amount of energy to operate.<p>Also a fun fact: Do you know that the term "daemon" for background processes was originally named after Maxwell's demon? [1]<p>[0] <a href="https://en.wikipedia.org/wiki/Reversible_computing" rel="nofollow">https://en.wikipedia.org/wiki/Reversible_computing</a><p>[1] <a href="https://en.wikipedia.org/wiki/Daemon_(computing)#Terminology" rel="nofollow">https://en.wikipedia.org/wiki/Daemon_(computing)#Terminology</a>