Fluctuation theorem

The fluctuation theorem describes how systems far from equilibrium sometimes spontaneously move backward or decrease in disorder for brief moments, even though they generally increase in disorder over time. It quantifies the likelihood of these rare reversals compared to their forward progression, providing a precise way to understand fluctuations in systems like gases, fluids, or chemical reactions. Essentially, it helps us understand the balance between entropy increases and occasional decreases, revealing that while the overall trend is toward disorder, small, temporary reversals can and do happen with calculable probabilities.