Persistence Pays Off in Defining History of Diffusion

摘要

Everyone knows that the smell of a cooked breakfast is sure to reach someone sleeping in a distant room of the house. That enticing information is carried mostly courtesy of air currents, but even if the air were dead still, the news would still arrive--in days or weeks rather than minutes. Billions of collisions with air molecules would ultimately convey the aroma of the long-cold breakfast to the far comers of the house. This process of diffusion is one of the basic modes of transport by which nature shifts material and heat from one place to another, and physicists thought it held few surprises.