Visualizing the numbers we work with


chewie and han solo star wars lightspeed

Let’s face it — engineers see a lot of numbers in their everyday jobs.  While generally comfortable with math and numbers, I doubt many of us take the time to actually visualize what those numbers actually mean.

The speed of light is a great example.  Every engineer knows that it’s 299,792,486 m/s^2.  In more common (for us Americans) terms, it’s about 186,000 miles per second.  But how fast is that, exactly?

Well, the moon is a good example.  While really close to Earth in astronomical units, it would be a pretty long walk to reach there, if such a journey were possible.  But humans have been to the moon and around the far side.  It’s as far as we’ve ever managed to travel in one journey.  So how far is it, in relation to the speed of light?

Enter Wikipedia.  This handy illustration below shows you the amount of time it takes for a light signal to travel that distance.  Remember, it’s the furthest from Earth we’ve ever gotten.  The delay illustrated here was something that NASA engineers had to come to terms with during the original Apollo tests.  And for future missions, with ground control issuing many control and command parameters, NASA has to synchronize clocks between the two systems and account for the signal propagation lag.

This animation shows a beam of light traveling from the Earth to the Moon; a trip that takes approximately 1.26 seconds. It took the Apollo astronauts 3 days to get there, traveling at about 100,000 miles per hour (remember light travels at 186,000 miles per SECOND). Still pretty impressive for a species that has a maximum recorded running speed of only 23 miles per hour (Usain Bolt).

speed of light from earth to moon

Source: Wikipedia

Next time you are working with numbers that humans don’t typically encounter in their own frame of reference, take the time to appreciate how truly astronomical those numbers can be.

Category: Engineering & Design, Interesting Stuff

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One Response

  1. Anonymous says:

    M/s^2 us a unit of acceleration not speed. I’m also a bit confused that it takes light 1.26 seconds to reach the moon, traveling at a (universally) constant speed of 186,000 mps i make that a distance of 234360 miles which would take a capsule travelling at 100,000 mph just over 2 hours and 20 minutes to cover, so what were they doing for the other 2 days and 21 hours and 40 minutes?

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