How did the expression begin?
这种说法是怎么来的呢？
No one seems to know for sure. But an official of the American space agency, NASA, says the expression just grew. It grew, he says, because rocket scientists probably are the most intelligent people around.
没人确切知道，但美国宇航员一位官员说，这个说法刚出现。他说，出现这种表达是因为火箭专家可能是最聪明的人。
Not everyone would agree.
并不是每个人都同意这种说法。
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