Sometimes they give you the speed in miles per hour, kilometers per year, pounds per square foot.

有时候速度的单位是英里/小时,千米/年,英磅/平方米

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And this is a very fast speed, of course, it's about 700 million miles per hour. So, one way to put that in perspective is to think about how long it takes for a light beam to get from earth to the moon. Does anyone have any guesses? Eight seconds, that sounds good.

当然这是一个非常快的速度，它大约是每小时7亿英里,为了更形象化，我们,看看光从地球到月球,需要多少时间，你们猜猜是多少？,8秒，猜的不错。

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