美国科学60秒 SSS 2013-01-08

This is Scientific American 60 second Science, I am Karen Hopkin, this will just take a minute. There are in fact 100 billion galaxies, each of which contains something like a 100 billion stars. Well, Carl Sagan would have loved to get the latest est

发表于:2018-12-02 / 阅读(92) / 评论(0) 分类 Scientific American(一)月
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