Word: greate
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Dates: during 1990-1999
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Einstein's general theory of relativity transformed space and time from a passive background in which events take place to active participants in the dynamics of the cosmos. This led to a great problem that is still at the forefront of physics at the end of the 20th century. The universe is full of matter, and matter warps space-time so that bodies fall together. Einstein found that his equations didn't have a solution that described a universe that was unchanging in time. Rather than give up a static and everlasting universe, which he and most other people believed...
This turned out to be one of the great missed opportunities of theoretical physics. If Einstein had stuck with his original equations, he could have predicted that the universe must be either expanding or contracting. As it was, the possibility of a time-dependent universe wasn't taken seriously until observations were made in the 1920s with the 100-in. telescope on Mount Wilson. These revealed that the farther other galaxies are from us, the faster they are moving away. In other words, the universe is expanding and the distance between any two galaxies is steadily increasing with time. Einstein...
...reason general relativity broke down at the Big 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...
...been President of the United States for 12 of the most tumultuous years in the life of the nation. For many, an America without Roosevelt seemed almost inconceivable. He had guided the nation through democracy's two monumental crises--the Great Depression and World War II. Those who watched the coffin pass were the beneficiaries of his nation's victory. Their children would live to see the causes for which he stood--prosperity and freedom, economic justice and political democracy--gather strength throughout the century, come to dominate life in America and in much of the world...
...will thank God on their knees a hundred years from now that Franklin D. Roosevelt was in the White House," the New York Times editorialized at the time of his death. "It was his hand, more than that of any other single man, that built the great coalition of the United Nations. It was his leadership which inspired free men in every part of the world to fight with greater hope and courage. Gone is the fresh and spontaneous interest which this man took, as naturally as he breathed air, in the troubles and the hardships and the disappointments...