Albert Einstein (1879-1955) was one of the top minds in physics in the 1900s, if not since Newton himself. He was widely regarded as the definition of genius. His theories in physics made possible the atom bomb, which can destroy a whole city in a moment. He was a kindly, humble man who rarely combed his hair and often had a sad look on his face.
Einstein discovered the theory of relativity. He came out with it in two parts: special relativity in 1905 and general relativity in 1915.
He came up with his theory while riding the train to work at the patent office in Berne, Switzerland. He looked at the town clock and wondered what would happen if he moved away from it on a beam of light. He asked the kind of simple questions a child would ask. But then he would tirelessly follow the physics and the numbers to the breaking point till he found the answer.
The most famous bit of his theory is this:
This means that matter (m) can be converted into energy (E). Energy is the force needed make something move faster or change its course. The c is for how fast light moves. In an atom bomb matter is converted into energy at an incredible rate. Which is how such a small thing can destroy a city. It is also how the sun and the stars shine.
The theory also says that nothing can move faster than light. And as you move faster time slows down. But for time to slow down by a lot, you need to be going almost as fast as light itself.
This leads to the Twin Paradox: one twin stays on Earth while the other goes to the stars in a ship that moves almost as fast as light. When he gets back from the stars he will find that his twin brother is much older than he is. Because what had seemed like months on the ship was years on Earth.
Just as matter and energy are two sides of the same coin, so are space and time. Gravity, which we know as the force that pulls things down to earth, is a fold in space. The gravity of the earth is like a deep well in the structure of space.
When the second world war broke out in 1939 Einstein knew the Germans could use his theories to build an atom bomb and win the war. He wrote a letter to President Roosevelt to tell him the horrible news. Taking no chances America built the bomb.
When Einstein died they burned his body but kept his brain. His genius had become a legend by then. But when they looked at his brain, it seemed completely ordinary. Years later, however, when they knew more about brains, they noticed that the part that thinks about space and number is larger than most people’s. He was probably born that way.