Maxwell’s demon is a famous thought experiment proposed by physicist James Clerk Maxwell to challenge the Second Law of Thermodynamics, which states that the total entropy of an isolated system can never decrease.
The Thought Experiment:
Imagine a tiny “demon” controlling a door between two chambers of gas. The demon opens the door only to allow faster (hotter) molecules to go to one side and slower (cooler) ones to the other, seemingly creating a temperature difference without doing work — decreasing entropy and violating the second law.
Implications:
- It sparked debates about the connection between information, entropy, and energy.
- Later analyses showed that the demon itself must use energy and gain information, which increases entropy and preserves the second law.
- It led to insights in statistical mechanics, thermodynamics of computation, and information theory.
Maxwell’s demon remains a powerful conceptual tool to explore the limits of physical laws and the role of information in physics.