Quantum Reality: Beyond the New Physics

by Nick Herbert

Einstein showed that although the number of atoms striking the Brownian particle from each direction is equal on the average, the fluctuations away from this average lead to unbalanced forces in random directions. In any random process, the relative fluctuations from an average value is inversely proportional to the square root of the number of samples—the smaller the sample, the bigger the fluctuations. For a large particle, the bulk pressure of the surrounding atoms is indeed evenly balanced, but for a small particle, the fluctuations in the number of impinging atoms is sufficient to propel it in an unpredictable direction with a predictable force. Einstein showed how this random force would vary with temperature and particle size. If atoms existed, Einstein’s model of Brownian motion would allow you actually to count the number of atoms striking a Brownian particle by measuring how far it drifts in response to these fluctuation forces.