The origin of irreversible behavior is a persistent theme in physics. Since the fundamental microscopic laws, including both Newton’s laws and quantum mechanics, are reversible (except for the weak interactions), the fact that most macroscopic systems behave irreversibly has long been recognized as an important issue.
The problem of understanding macroscopic irreversibility was solved more than 100 years ago by Ludwig Boltzmann, who recognized that systems evolve toward more probable states, namely, those that have a larger number of microscopic configurations for a given macroscopic state. This is such a powerful tendency that on the macroscopic level, fluctuations that go against it are so improbable as to be negligible. The result is a probabilistic explanation of macroscopic irreversibility and the second law of thermodynamics. (See the article by Joel Lebowitz in Physics Today, September 1993, page 32.)
Nevertheless, Boltzmann did not explain the microscopic chaotic dynamics that leads...
