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"Maxwell was a famous scientist who discovered electromagnetic waves.
But only theoretically; he could not prove it. It was proven by Heinrich Hertz 20 years
later. But Maxwell put forward a theory saying that in the world there must be something
called electromagnetic waves. There is a famous second law of thermodynamics which states
that in each system, energy must be constant. But Maxwell said, imagine two spaces:
between the two spaces you have a door with a little slit. One space filled with gas is very
hot, and the other is very cold. According to the law of thermodynamics, when such a door is
opened, both spaces will be of equal temperature. But Maxwell could mathematically prove that
the hot space would become hotter, and the cold space would become colder. So this was a
riddle, a paradox: Maxwell's daemon.(...) But then along came Zurek, a scientist, who wrote
an article in 1984, "Maxwell's daemon, Szilard's engine and Quantum measurement." He solved
the paradox in such a way that it could even obey the second law of thermodynamics. He said,
this daemon is doing work - Somebody is doing work. Even when he just counts molecules, this
also uses energy, this also uses information. So when something is becoming hotter, and
something is becoming colder, we can exactly measure this difference of energy, and we can
say this is an amount of information, that is energy which the daemon uses for himself.
So we could explain it even within the second law of thermodics. He calls this daemon
'Quantum daemon.'" Peter Weibel, "Ways of Contextualisation," Place, Position,
Presentation, Public,(ed. Ine Gevers), De Balie, Amsterdam, 1991-1992, pp.232-3.
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