Word: coulds
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Dates: during 1990-1999
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General relativity completely changed the discussion of the origin and fate of the universe. A static universe could have existed forever or could have been created in its present form at some time in the past. On the other hand, if galaxies are moving apart today, they must have been closer together in the past. About 15 billion years ago, they would all have been on top of one another and their density would have been infinite. According to the general theory, this Big Bang was the beginning of the universe and of time itself. So maybe Einstein deserves...
...Bang was that it was not compatible with quantum theory, the other great conceptual revolution of the early 20th century. The first step toward quantum theory came in 1900, when Max Planck, working in Berlin, discovered that the radiation from a body that was glowing red hot could be explained if light came only in packets of a certain size, called quanta. It was as if radiation were packaged like sugar; you cannot buy an arbitrary amount of loose sugar in a supermarket but can only buy it in 1-lb. bags. In one of his groundbreaking papers written...
...Heisenberg in Copenhagen, Paul Dirac in Cambridge and Erwin Schrodinger in Zurich, who developed a new picture of reality called quantum mechanics. No longer did tiny particles have a definite position and speed. On the contrary, the more accurately you determined the particle's position, the less accurately you could determine its speed, and vice versa...
...Einstein could never accept that the universe was at its heart a cosmic crapshoot, so that today his papers on unified field theory seem hopelessly archaic. But the puzzle they tried to solve is utterly fundamental. In simply recognizing the problem, Einstein was so daringly far-sighted that only now has the rest of physics begun to catch up. A new generation of physicists has at last taken on the challenge of creating a complete theory--one capable of explaining, in Einstein's words, "every element of the physical reality." And judging from the progress they have made, the next...
...seven dimensions in addition to the by now familiar four (height, width, length and time). It also requires the existence of an entirely new class of subatomic particles, known as supersymmetric particles, or "sparticles." Moreover, there isn't just one string theory but five. Although scientists could rule out none of them, it seemed impossible that all of them could be right...