Physics World  October 26, 2018 “Feynman’s ratchet” is a microscopic heat engine that converts thermal fluctuations into work when connected to two heat sources at different temperatures. It is a way of showing how the second law of thermodynamics cannot be violated. Until now no-one has built such a tiny ratchet because of significant technical challenges that include how to prevent convection from washing out thermal fluctuations. An international team of researchers (USA – Purdue University, University of Maryland, China) has built a ratchet using a 780 nm-diameter ball of silicon dioxide confined to a 1D optical trap set up […]