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  • You may have heard physicists describe the moon as being 1.3 light-seconds away, or the

  • sun as 8 light-minutes away, and thought "what is this nonsense? Measuring distances with

  • time?"

  • But actually, we measure distances using time almost every day. How far is it from your

  • house to the store? About ten minutes. And how far is it from New York to Boston? About

  • four hours. Los Angeles to Sydney? 14 hours.

  • But of course, what we really mean is that the store is ten bike-minutes from your house,

  • New York is 4 car-hours from Boston, and Sydney is 14 plane-hours from LA. In fact, using

  • time to measure distances is so useful that I only know the distance from LA to Sydney

  • in plane-hours, not miles or kilometersthough I suppose I could figure it out by

  • multiplying 14 plane-hours by the 550-miles-per-hour speed of a plane to get roughly 7500 miles.

  • But Sydney is also 5 sailboat-weeks from LA, 7 humpback-whale months from LA, 5 message-in-a-bottle

  • years from LA, and 0.04 light-seconds from LA. On the other hand, the moon is 18 airplane-days

  • away, 6 car-months away, and 15 whale-years away. Which means, in fact, that a whale might

  • swim as far as the distance to the moon over the course of its lifetime .

  • And if that's not crazy enough, sometimes we even measure times in distance! How long

  • is a movie? 8,000 feetof film! And MinutePhysics? 30 meters.

You may have heard physicists describe the moon as being 1.3 light-seconds away, or the

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A2 la sydney plane whale distance measure

How far is a second?

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    Fu Jung Lai posted on 2012/12/20
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