As a reasonable guess, they might, on an average, be 100 light years away. a light year is the distance which light travels at 186,000 miles per second in one year, namely 6 million million miles.
据合理推算，外星人离我们平均距离也有100光年之远(1光年是光以每秒186,000英里的速度在一年内走的距离即6万亿英里)。
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