英語(yǔ)聽(tīng)力文摘517 地球同步衛(wèi)星（一）
Some of the best devices in science have been anticipated by science fiction writers years before they existed. Occasionally a writer comes up with an idea that can be put into practice within their lifetime!
Such is the case with the geostationary satellite, first imagined by Arthur C. Clarke. Clarke, famous for writing “2001: A Space Odyssey,” also wrote a scientific article titled “Extra-Terrestrial Relays” in 1945. In it, he proposed a satellite that would remain motionless in the air, rather than passing by overhead. Such a “fixed” satellite would be useful for relaying television and radio signals, helping ships navigate, and a host of other things.
But how to do it? After all, heavy machinery can’t just float. Most satellites handle this problem by being blasted into orbit around the planet. But in order to be in orbit, you have to be constantly moving. Can you think of a way around this?
How about putting a satellite into orbit both in the same direction as the planet rotates–and at the same speed! The result is a satellite that is, in fact, orbiting the planet. But the ground underneath it turns at the same rate as the satellite orbits, so the satellite is always above the same spot of ground. From our perspective on the earth, a geostationary satellite seems fixed in one spot.
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