Guest Editorial

The world of science, and especially the world of particle physics. is populated by thought experiments. These are helpful in dealing with issues that go beyond our intuitive abilities. For example. Einstein’s EPR Paradox suggested that the Copenhagen Interpretation of quantum mechanics couldn't he accurate. Unfortunately for Einstein. his paradox ultimately proved Bohr’s theory was. in fact, correct.

Laplace‘s Demon is another thought experiment inspired by Newton's revolution. lt deals with the issue of free will vs. determinism. The idea is that if there were an entity with full knowledge regarding the state of every particle in the universe. then every action could be perfectly predicted - no free will. lt‘s hard to imagine a future experiment to settle this issue. but who knows?

Now, on to Maxwell’s Demon. This is like Laplace's, but in this case a demon would know the speed and trajectory of every particle within a box. A barrier would separate the box into two compartments. A door in the barrier would allow the demon V to allow passage whenever a particle of a chosen quality heads toward the door. it would have the option of stopping it or letting it through.

Let's assume the box is filled with two types of particles: one high temperature and one low temperature, in a state of high entropy (i.e., well mixed). The hypothetical power possessed by the demon means that it can separate particles with high temperature on one side and low temperature on the other.

"But who cares?" Good question. What this means is, in violation of the second law of thermodynamics, the entropy of a system can be reversed (assuming a demon like this existed). Therefore. a critical tenet of physics would be violated.

Again, you ask, "so what?" Even though theoretical, this logic can be projected on the overall universe. This would have a major impact on our understanding of time and quantum entanglement. Time moving backward would be possible.

To be fair, others have tried to negate the theory. “About 1950 the French physicist Leon Brillouin exercised the demon by demonstrating that the decrease in entropy resulting from the demons actions would he exceeded by the increase in entropy in choosing between the fast and slow molecules."(Encyclopedia Britannica). But here again, this negation is hypothetical as well. Who knows how much energy the demon‘s actions would require?

On the positive side. scientists believe Maxwell's Demon might lead to important technological breakthroughs as well as new frontiers in information science. In the words of James Clerk Maxwell “The second law of thermodynamics has the same degree of truth as the statement that if you throw a tumblerful of water into the sea, you cannot get the same tumblerful of water out again." Ironically, the Maxwell Demon suggests that you can.

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