Jennifer Ouellette has a great post up at Twisted Physics all about the origins of the idea of black holes. Apparently it can all be traced back to an English scientist called John Michell who, in 1783, wrote a paper about trying to measure the mass of stars. Michell was using Newtonian physics that treats light as particles. A particle of light leaving a star should therefore behave similarly to a ball leaving the Earth – it would need to achieve escape velocity. And Michell then wondered what would happen if the star’s gravitational field was strong enough to prevent any light from leaving.