Hermann von Helmholtz is all over the place. His father was a close friend of Fichte. He pulls together the work of Sadi Carnot, Émile Clapeyron and James Prescott Joule to propose the conservation of energy, after discovering that no energy is lost in muslce movement. He is thought to be the first person to speculate on the heat death of the universe. He invents the opthalmoscope. His students include Heinrich Rudolf Hertz, Max Planck, A. A. Michelson and William James.