What is light? It’s photons that are little packets of visible energy. They don’t weigh anything, they are quanta (a tiny quantity). There have been different ideas about light, whether it is made up of waves or particles (called a wave particle duality). Probably the most interesting physicist to read is Richard Feynman, he died several years ago. But his book QED, quantum electro dynamics was quite good in helping me understand it slightly (its too complex for me). I liked his diagrams which helped to visualise the ideas….. Anyway that’s another random thing I’m interested in…