• Question: Does time move more slowly around something with a large mass, like a planet? My friend said it did but I wasn't sure can you confirm?

    Asked by maximillian to Sara, Drew on 20 Jun 2011.
    • Photo: Sara Imari Walker

      Sara Imari Walker answered on 20 Jun 2011:

      Hi maximillian! Yes time does move more slowly around a large body of mass. The effect is not significant for us to notice around as small a mass as a planet though. You’d have to go near the surface or a massive star or better yet a black hole to really see that effect! Of course YOU as the tester wouldn’t notice any difference. You would think time was moving normally, but an outside observer would see your clock running more slowly. General relativity is pretty weird!!

      Here’s a cool related example. Increasing speed also causes time to slow. So, astronauts and satellites, which orbit the Earth at 17,000 miles per hour actually experience time slightly slower than we do. Its a minuscule effect, their clocks run fractions of of a second slower than ours per year. But its enough for our GPS systems to have to account for relativistic effects! Can you imagine, GPS wouldn’t work without us knowing Einstein’s theories!!

    • Photo: Drew Rae

      Drew Rae answered on 20 Jun 2011:

      Yes, it’s true. Time does slow down, but by a very tiny amount. This was predicted by Einstein, and confirmed by something called the Pound–Rebka experiment. Look this one up – it’s pretty easy to understand, and gives some idea for how it works.

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