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  3. At present, it seems impossible to visit the satellites of other stars in search of life. Our present theories of physics indica

At present, it seems impossible to visit the satellites of other stars in search of life. Our present theories of physics indica

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问题     At present, it seems impossible to visit the satellites of other stars in search of life. Our present theories of physics indicate that it is impossible to move at a speed greater than that of light. Even at such a speed it would take many years to reach the nearest star that might have planets. Most of such stars are many lifetimes away.
    Perhaps someday we shall invent ways of traveling or sending messages that will allow man to find other living things in the universe.
    Even more interesting is the possibility that they may find us. If the steady-state theory of the universe is correct, there must be many "solar systems" that are much older than ours.
    On some of these, intelligent life may have evolved long ago. If so, these creatures might be exploring the universe today.
    Serious scientific projects in recent years have been studying the risks with radio telescopes, hoping to find signals sent by such intelligent beings. It has been suggested that the puzzling quasars(类星体) might be the wakes(航迹) left by spaceships traveling faster than light.
    Thus far, we have found no definite evidence of other intelligent life in the universe. Perhaps we never shall. Yet the search and the hope will remain an exciting possibility for the future.
Today we can’t visit other stars because _____.
选项 A、they have no planets and satellites
B、we can not travel at the speed of light
C、we need further research in physics
D、they are beyond our traveling distance
答案D
解析
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