• Question: Does mass only begin to increase when you are travelling close to the speed of light, or does mass begin to increase as soon as you travel?

    Asked by blatantlyninja to James, Marcus, Martin, Rob, Suzanne on 20 Mar 2012.
    • Photo: Suzanne McEndoo

      Suzanne McEndoo answered on 20 Mar 2012:

      It increases as soon as you begin to travel, but the increase is very, very small when the speeds are far from the speed of light. The factor involved in the change of mass is v^2/c^2 (so the square of your velocity divided by the square of the speed of light). If v is small compared to c, this ratio will be extremely close to zero, hence we don’t see any effects like mass increases when we travel in cars.

      In planes, the changes due to special relativity are still very tiny, and a human being wouldn’t notice them, but if you put an atomic clock on a plane, the time stretching effect due to the speed of the plane will mean that the atomic clock that flew is out of synch with a clock on the ground.

    • Photo: Marcus Gallagher-Jones

      Marcus Gallagher-Jones answered on 20 Mar 2012:

      As soon as you begin to accelerate your energy begins to increase but the amount is incredibly small. Since mass and energy are interconnected it could also be said that your mass increases. It’s a little tricky but the key thing to remember is this mass/energy equivalence.

    • Photo: Robert Thompson

      Robert Thompson answered on 20 Mar 2012:

      Yes I agree, amazingly small. Hopefully we will never feel the effect. Because if we start trveling close to the speed of light I think there are other things we need to worry about. Like surviving.

    • Photo: Martin Zaltz Austwick

      Martin Zaltz Austwick answered on 21 Mar 2012:

      Well, we are travelling quite fast through space, around the sun… but although we’re constantly accelarating towards the sun, we’re not getting any faster or slower, so our mass-energy isn’t changing.

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