A physicist is a scientist whose job is doing physics (and usually gets paid for it too!). Physics is a field of science that explains how nature fundamentally behaves using mathematical laws. Physicists come in many forms and shapes. Some are theoretical and some are experimental (and some are a mixture!). Theoretical physicists like their pen and paper to work out the laws of physics. Experimental physicists are more hands on and enjoy playing with their shiny equipment to test new theories.