光行进的速度是每纳秒一英尺，很简单的经验法则了。
Light travels basically a foot in a nanosecond. Simple rule of thumb.
光的传播速度为299，792千米/秒，是凭借加速所不可能超越的。
That speed, beyond which it is impossible to accelerate, is 299,792km a second.
光的传播速度为299，792千米/秒，是凭借加速所不可能超越的。
That speed, beyond which it is impossible to accelerate, is 299,792km a second.
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