We don't know if any alien civilizations exist.

我们不知道如果任何外来文明的存在。

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To assume alien civilizations will be friendly and welcome us with open arms seems grossly naïve.

如果认为外星智慧生命会非常友好的敞开胸怀欢迎我们，那真是天真的想法。

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Cosmologists use this Kardashev Scale to predict the technical advancement of future and alien civilizations.

宇宙学家使用“卡尔达舍夫等级”来预测未来的技术进步以及外星文明。

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So Arizona State University physicist and astrobiologist Paul Davies says we might not be hearing alien civilizations because they have transcended their broadcasting stage.

VOA: standard.2010.04.16

"We could look for beacons." "It could be that there are alien civilizations that have simply created something a little bit like a lighthouse that sweeps the plane of the galaxy, goes bleep, and it's there to attract attention, or it's a monument, or an aesthetic symbol or even a religious symbol.

VOA: standard.2010.04.16

These efforts are notable because so few other attempts have been made to craft a message to alien civilizations.

FORBES: How To Talk To Aliens

Forty-two radio dishes, each 20 feet in diameter, were powered up on Oct. 11, to scope out galaxies, black holes, and--maybe, just maybe--alien civilizations.

FORBES: Magazine Article

So when Fischer says we should be "the alien civilizations that explore other worlds, " I say: With Kepler or without, it's only a matter of time until we find signs of life on other worlds.

CNN: Kepler or not, we'll find life in space