沸沸逻辑第39题求教！

coocooper · 发表于 2010-10-19 04:41:21

Quasars-celestial objects so far away that their light takes at least 500 million years to reach Earth--have been seen since 1963. For anything that far away to appear from Earth the way quasars do, it would have to burn steadily at a rate that produces more light than 90 billion suns would produce. But nothing that burns at a rate that produces that much light could exist for more thatn about 100 million years.
If the statements above are true, which one of the following must also be true on the basis of them?
A. instruments in use before 1963 were not sensitive enough to permit quasars to be seen.
B. light from quasars first began reaching Earth in 1963.
C. Anything that from Earth appears as bright as a quasar does must produce more light than would be produced by 90 million suns.
D. nothing that is as far from Earth as quasars are can continue to exist for more than about 100 million years.
E. No quasar that has ever been seen from Earth exists any longer.

这个题目的答案是E，我选的是D，请问为什么选E啊？

coocooper · 发表于 2010-10-19 10:53:57

up up

Bichenfei928 · 发表于 2010-10-19 12:55:40

Quasars需要500M才能到达地球，但是文中又说那种强度的星体只能持续100M，那就是说光在达地球的过程中Quasars已经灭忙了，所以我们现在看见的光是500M前就传过来的，现在Quasars已经不存在了

coocooper · 发表于 2010-10-19 20:32:03

make sense, thanks..

沸沸逻辑第39题求教！

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