Feifei 39

Outsider1988 · 发表于 2010-6-19 22:35:07

39. 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 than 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 billion 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

答案是E
我觉得E是对的，可是觉得D也不错啊

sweety9 · 发表于 2010-6-26 11:22:44

我也觉得D是对的，有没有高手来解答一下？

frankning007 · 发表于 2010-7-6 14:30:35

D是说距离地球跟Quasar一样远的（星球）都不能存活超过100万年，这太绝对了，Quasar存活不超过100万年是因为剧烈的燃烧（90万个太阳的量），不是因为跟地球之间的距离太远

这道题有蛮多人问过的，以后多搜搜论坛（关键字“fei 39）就有了

Feifei 39

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