探索频道 Cosmos 宇宙的边疆14
By sixteen hundred, the long forgotten ideas of Aristarchus had been rediscovered. Johannes Kepler constructed elaborate models to understand the motion and arrangement of the planets---the clockwork of the heavens. And that night, he dreamed of traveling to the moon. His principal scientific tools were the mathematics of the Alexandrian library and an unswerving respect for the facts, however disquieting they might be. His story and the story of the scientists who came after him, are also part of our voyage. 70 years later, the sun-centered universe of Aristarchus and Copernicus was widely accepted in the Europe of the enlightenment. The idea arose that the planets were worlds governed by laws of nature and scientific speculation turned to the motions of the stars. The clockwork in the heavens was imitated by the watchmakers of Earth, precise time keeping permitted great sailing ship voyages of exploration and discovery which bound up the Earth. This was a time when free enquiry was valued once again.
250 years later, the earth was all explored. New adventurers now look to the planets and the stars. The galaxies were recognized as great aggregates of stars, island universes, millions of light years away.
In the 1920s, astronomers had begun to measure the speeds of distant galaxies.
(what time is it? 7:15, Well, lights off. please).
They found that the galaxies were flying away form one another. To the astonishment of everyone, the entire universe was expanding. We had begun to plumb the true depths of time and space. The long collective enterprise of science has revealed a universe some 15 billions years old, the time since the explosive birth of the cosmos---the Big Bang.
The cosmos calendar compresses the local history of the universe into a single year. If the universe began on January 1st, it was not until May that the Milky Way formed. Other planetary systems may have appeared in June, July and August, but our sun and earth, not until mid-September, life arose, soon after. Everything humans have ever done occurred in that bright speck at the lower right of the cosmic calendar. The Big Bang is at upper left in the first second of January 1st, 15 billions years later, is our present time, the last……
