Abstract: The contradiction between temporal reversibility of Newton mechanics and irreversibility of thermodynamic process has long been one of the most frequently debated problems in physics and philosophy. This paper retrospects the historical conflicts of opinions on irreversibility through the H theorem introduced by L. Boltzmann. Recent progresses of the study on this issue are also discussed. In the frame of modern ergodic uheory and chaotic dynamics, the contradiction between microscopic reversibility and macroscopic irreversibility can be well understood and answered.

Key words: irreversibility, stochasticity, entropy, ergodicity