A perpetual motion machine is a hypothetical machine that can do work infinitely without an external energy source. This kind of machine is impossible, as it would violate either the first or second law of thermodynamics or both. ...That was dad. Filled with an energy for life that felt like it would never stop. He loved everything he did and once he made a decision would rush towards it with conviction, joy and determination. I remember Sundays .. music at full volume … Holt's the planets or the fifth dimesion … swimming at Bradford on Avon… digging the vegetable garden... building dry stone walls the summer we moved to Applegarth with his students helping and sitting down to Sunday lunch … Sunday evening when a quiet would decend and he would sit at the dining room table with student papers spread out or something he was working on ready for the working week. He'd arrive home after walking back from the university into the kitchen where his glasses would immediately steam up. His joy in making things, painting and music shaped my life with a belief I could create anything. The last few years as his eyesight failed we painted together scenes from past holidays. The motions of planets may appear perpetual, but are actually subject to many processes that slowly dissipate their kinetic energy so they will not keep moving forever. I miss you Dad so much. Carl Sagan said 'We're made of star stuff'. The stars are even brighter tonight with you there too.