A physicist's a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter's made (particle physics) to the behavior of the material Universe as a whole (cosmology). Education Most material a student encounters in the undergraduate physics curriculum's based on discoveries and insights of a century or more in the past. Alhazen's intromission theory… (More on Physicist)