On this day in physics: On 11 January 1787 William Herschel, discovered the first two moons of Uranus, Titania and Oberon, roughly six years after he discovered the planet itself. The names were given 65 years later by Herschel's son. Word of the Day: Matter is the stuff around you. It is anything that has takes up space and has mass. This definition is designed to exclude energy such as light, or the motion of particles, such as sound. The majority of matter is made up of atoms, which are made of protons, neutrons, and electrons. Protons and neutrons are then of course made up of up and down quarks. There are four states of matter. The state with the lowest energy is a solid. Next is liquid. Next is gas. Finally, the least commonly known state of matter is a plasma. Matter behaves distinctly different in each state. Killer Resource: Wolfram Online Integrator.