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“我们是宇宙中唯一的文明生物吗?”、“有没有外星人?”这些问题不仅困扰着科学家,也引起越来越多的人的兴趣。理论上说,宇宙中除了我们人类以外,完全可能存在其他文明生物,而且其文明程度可能比我们还要发达。我们不妨对宇宙略加推算一下:银河系估计有4000亿颗恒星。如每10颗恒星有一颗拥有行星,就会有400亿颗恒星拥有行星。这400亿颗恒星如果各有10颗行星,就会有4000亿颗行星。这当中又有几颗适
“Are we the only civilized creatures in the universe?”, “Are there any aliens?” These issues not only plague scientists but also attract more and more people’s interest. In theory, it is entirely possible that there will be other civilizations besides the human being in our universe, and its civilization may be more developed than ours. We may wish to reckon a little more about the universe: the Milky Way is estimated at 400 billion stars. If there is one planet for every 10 stars, 40 billion stars will have planets. If there are 10 planets in each of these 40 billion stars, there will be 400 billion planets. How many of these are suitable?