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Asked by sevvalA to Heather, Helen, Hugh, Jane, Julian on 11 Nov 2014.
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Helen Johnson answered on 11 Nov 2014:
About 2 and a half seconds. We predict moon is actually getting a little further away from us all the time, because of what are called ‘tidal forces’. Scientists can reflect this laser off the mirror on the moon, and measure how long the signal takes to get back to us. Since we know the speed of light, we can then work out the distance to the moon. This is proof that the moon is getting a tiny bit further away each year!
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Julian Onions answered on 11 Nov 2014:
It takes about a second for light to get to the moon, and similarly a second or so to come back.
Putting it into a calculator, I come up with 2.562 seconds for a round trip reflection.
Using this you can measure accurately the distance to the moon, and hence find it is moving away slowly. -
Hugh Osborn answered on 11 Nov 2014:
The distance to the moon is 400,000km and the speed that light takes is 300,000km per second.
As time is distance divided by velocity, that gives (2 x 400,000)/(300,000).
A nifty trick is to cancel the zeros from top and bottom of a fraction, so that leaves (2 x 4)/3.
That means it takes 8/3 seconds or (2.666 seconds). Pretty quick, eh!?See; maths is useful for something 😛
Comments
sevvalA commented on :
i love all of your answers thank you especially hugh osborn