• Question: Is the speed of light really constant?

    Asked by callumsmith1 to Claire, Kate, Matt, Rob, Sam on 25 Jun 2013.
    • Photo: Sam Geen

      Sam Geen answered on 25 Jun 2013:

      Every experiment so far says ‘yes’! We don’t know why, but it seems to hold true. The weird thing is that the speed of light is the same no matter how fast you’re moving – move at half the speed of light, and light still travels at the speed of light. This makes relativity do very weird things.

    • Photo: Claire Lee

      Claire Lee answered on 26 Jun 2013:

      Yes! It’s really really strange!

      If you are on a train going 50 miles per hour, and you throw a ball forward at 10 miles an hour, someone on the ground watching you go past would see the ball fly forward at 60 miles per hour (50 + 10).

      But, if you were on the train and shot a laser beam forward at the speed of light, c, someone on the ground would still see the laser beam moving at c (not 50 + c!)

      And, if you could go on a train that was travelling at the speed of light, and shot the laser, that person would *still* see the laser travelling at c, not (c+c)!

      Crazy universe we live in!

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