• Question: Why can we never travel at the speed of light?

    Asked by to Nat, Nate, Roberto, Sam on 25 Jun 2014. This question was also asked by .
    • Photo: Nate Bastian

      Nate Bastian answered on 25 Jun 2014:


      This is a result of Einstein’s famous equation, E=mc^2. Energy and mass are equivalent. The faster you go, the more energy you have, and by equivalence the more mass you have. When you have more mass, it’s harder to get that mass moving (i.e., is it easier to push a bike or a car?). As you approach the speed of light, the mass of the object increases exponentially, meaning that you need more and more energy to make it go just a little bit faster. In the end, it would take an infinite amount of energy to go even a bit faster, when you are at the speed of light.

    • Photo: Roberto Trotta

      Roberto Trotta answered on 25 Jun 2014:


      When an object with mass bigger than 0 approaches the speed of light, three things happen: time slows down, distances in the direction of travel become smaller and its mass increases.

      All of those effects become bigger and bigger the closer you get to the speed of light. So if your mass at rest is say 100 kg, if you are travelling at 99% of the speed of light your mass becomes 700 kg. If you are travelling at 99.9% of the speed of light, it becomes 2.2 tons. And at 99.999% of the speed of light, it becomes 70 tonnes. So the faster you go, the more difficult it is go go any faster because your mass increases. If you reach the speed of light (which is impossible), your mass would be infinite!

      [Technical note: the mass does not actually increase exponentially, as Nate says, but still quite fast]

    • Photo: Natasha Stephen

      Natasha Stephen answered on 25 Jun 2014:


      I think the boys have answered this one perfectly 🙂

    • Photo: Sam Connolly

      Sam Connolly answered on 25 Jun 2014:


      Yup not much to add! The faster you go, the more energy you need to go even faster, so you can never get to light speed!

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