Demons are not big fans of laws. The demon we’re going to talk about
today has only one purpose in his purpose in his life, and that’s to
subvert one of the basic laws of nature, to ensure the universe never
reaches equilibrium. Oooooh, scary.
Or maybe not.
The second law of thermodynamics says that the entropy of an isolated
system can never decrease. According to it, “over time, differences in
temperature, pressure, and chemical potential tend to balance out in
an isolated physical system.”[wikipedia]
So, basically, the law says that if you bring two bodies of different
temperature into contact together and isolate them from the rest of
the universe, the hot side will heat up the cold and the cold side
will cool down the hot and they will come to the same temperature. For
example, if you have a closed chamber and you inject a gas of two
different temperatures into it, the molecules of the gas will disperse
so the temperature of the chamber will be the same in every area of
the chamber. The hotter molecules of the gas aren’t going to gather in
one corner, the cooler molecules in another. Nope, everything will
Unless, of course, you get demonic forces involved.
And so, on December 11, 1867, a demon was born. A Scottish physicist
named James Clerk Maxwell, found a way to violate the second law and
wrote about it in a letter to a friend. He expanded on the theory in
his 1870 book Theory of Heat.
Maxwell imagined that same closed chamber of gas we talked about
earlier, but with a few changes. He put a wall in the chamber, making
two rooms, with a little door just big enough to let molecules pass
from one side to the other. At that door, Maxwell placed a super
smart, super fast demon.
Because this demon just wants to break laws, specifically the second
law of thermodynamics, the demon opens the door to let all the hot molecules to one side and all the cold molecules to another (Of course we all know that gas molecules bounce around, so the demon just waits
until a hot molecule bounces toward the door and opens it.).
So, in a closed chamber, through demonic interference, you get bodies
of two different temperatures. Thanks, Maxwell’s demon!
By the way, it wasn’t Maxwell who named his demon. He called the
creature a “finite being.” The guy who identified it as a demon was
William Thompson, who was eventually ennobled as the First Baron
Kelvin by Queen Victoria. Maxwell hated that the being in his chamber
got called a ‘demon.’ Like any smart person, he realized that messing
around with supernatural forces is a really bad idea.
Tomorrow: Maxwell’s Demon debunked. And the debunking debunked.
- Maxwell, BBC “In Our Time” Thu, 2 Oct 2003
- William Thomson, 1st Baron Kelvin, wikipedia
- Maxwell’s Demon, wikipedia