Word: einstein
(lookup in dictionary)
(lookup stats)
Dates: during 1990-1999
Sort By: most recent first
(reverse)
...very important consequence of relativity is the relation between mass and energy. Einstein's postulate that the speed of light should appear the same to everyone implied that nothing could be moving faster than light. What happens is that as energy is used to accelerate a particle or a spaceship, the object's mass increases, making it harder to accelerate any more. To accelerate the particle to the speed of light is impossible because it would take an infinite amount of energy. The equivalence of mass and energy is summed up in Einstein's famous equation E=mc2, probably...
...consequences of this law is that if the nucleus of a uranium atom fissions (splits) into two nuclei with slightly less total mass, a tremendous amount of energy is released. In 1939, with World War II looming, a group of scientists who realized the implications of this persuaded Einstein to overcome his pacifist scruples and write a letter to President Roosevelt urging the U.S. to start a program of nuclear research. This led to the Manhattan Project and the atom bomb that exploded over Hiroshima in 1945. Some people blame the atom bomb on Einstein because he discovered the relation...
...Einstein was aware of this difficulty in 1907, while he was still at the patent office in Bern, but didn't begin to think seriously about the problem until he was at the German University in Prague in 1911. He realized that there is a close relationship between acceleration and a gravitational field. Someone in a closed box cannot tell whether he is sitting at rest in the earth's gravitational field or being accelerated by a rocket in free space. (This being before the age of Star Trek, Einstein thought of people in elevators rather than spaceships...
...return to Zurich in 1912 Einstein had a brainstorm. He realized that the equivalence of gravity and acceleration could work if there was some give-and-take in the geometry of reality. What if space-time--an entity Einstein invented to incorporate the three familiar dimensions of space with a fourth dimension, time--was curved, and not flat, as had been assumed? His idea was that mass and energy would warp space-time in some manner yet to be determined. Objects like apples or planets would try to move in straight lines through space-time, but their paths would appear...
With the help of his friend Marcel Grossmann, Einstein studied the theory of curved spaces and surfaces that had been developed by Bernhard Riemann as a piece of abstract mathematics, without any thought that it would be relevant to the real world. In 1913, Einstein and Grossmann wrote a paper in which they put forward the idea that what we think of as gravitational forces are just an expression of the fact that space-time is curved. However, because of a mistake by Einstein (who was quite human and fallible), they weren't able to find the equations that related...