He knew that 'everything is in a state of flux' much earlier than anyone else - his contemporaries still thought that the world was made of fire or cheese or mice. He was so out there that nobody knew what he was talking about, but all agreed with his sentiment that he was cleverer than anyone else. Good for bringing into a conversation about chaos principles in nature. This equation was invented by Einstein in the early part of this century. It concerns the energy you get from the complete annihilation of a quantity of matter.
E stands for energy.
Yes - it does. M is the mass, ie. C squared is the velocity of light. Since C 2 is such a huge number, it stands that the amount of energy released is immense. Since everything has loads of energy it is also why mystics claim a pebble is as alive as you are.