• Question: How fast is the speed of light compared to the speed of sound?

    Asked by asiansupreme to Anil, Blanka, Cees, Emma, Mike on 27 Jun 2012.
    • Photo: Emma Trantham

      Emma Trantham answered on 27 Jun 2012:

      The speed of light is much faster than the speed of sound.

      Sound moves at 343 metres per second (thats about 770 miles per hour!)

      The speed of light is a little trickier.

      In a vacuum it is roughly 300 000 000 metres per second (so nearly 900 000 times faster than sound!)

      However, when light moves through air or glass it gets slowed down a little bit so light moving through glass moves at 200 000 000 metres per second which is still 580 000 times faster than sound. (I admit to having to look that last number up! As I said, it gets quite complicated!)

    • Photo: Blanka Sengerova

      Blanka Sengerova answered on 27 Jun 2012:

      I’d have to have looked this up, too, Emma! One of the interesting results of the differing speed of light and sound is that supersonic planes (travel faster than sound) are seen to fly past you first and you only hear the sound a few seconds later. The same effect also causes the difference between the time that you see a flash of lightning, with thunder only following a few seconds later – the closer you are to the centre of the storm, the closer the two effects are together.