• Question: its a bit of a cofusing question but if there were twins on earth and one went into space and travelled at the speed of light for the length of time that a year is on earth, but the other twin stayed on earth for a year would the twin that went into space come back younger than the twin that stayed on earth? thanks :)

    Asked by jessicaf to Jo, Mark, timcraggs on 24 Jun 2010 in Categories: .
    • Photo: Joanna Buckley

      Joanna Buckley answered on 24 Jun 2010:

      Hiya jessicaf… you’ve just named the twin paradox, an experiment in special relativity 🙂

      It is quite difficult to get your head around but hypothetically that’s exactly what would happen. Scientists have verified this by sending clocks up into satellites and measuring the differences between time on earth.

    • Photo: Mark Lancaster

      Mark Lancaster answered on 24 Jun 2010:

      Yes that’s true – it’s called the “Twins Paradox” – but it has the Paradox since from the viewpoint of the moving twin it is the other twin that is moving so the other twin should age slower …. it’s a tricky one – so the usual get out of this contradiction is to that to go somewhere and come back involves accelerating and decelerating (while you turn around) and it is the acceleration that differentiates the two twins – look up Twins Paradox on google and you’ll find some pretty whacky theories

    • Photo: Tim Craggs

      Tim Craggs answered on 24 Jun 2010:

      Hehe! It is a classic question, Jessica. The thing is that the twin who went into space, could not travel at the speed of light all the time and then return to earth, because in order to return to earth they would have to turn around and come back!

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