• Question: Why is gravity so much weaker than all the other fundemetal forces? do you belive that it is because gravitons are dispersed through multiple dimension and is this why the graviton has not yet been observed?

    Asked by oshkar to Ben, Clare, Ezzy, Mario, Sam on 11 Mar 2012.
    • Photo: Mario Campanelli

      Mario Campanelli answered on 9 Mar 2012:

      We do not know why gravity is so much weaker, as we do not know why the weak force is weaker than the strong one (even if in some models their couplings converge at high energies).
      We do not know if gravitons exist at all, since there is no such a thing as a quantum theory of gravity. No string theory can describe our universe. We only assume that gravity could be carried by a mediator which is massless (because gravity propagates as 1/r^2, as in Newton’s law) and that has spin 2, because Einstein’s equations have a rank 2 tensor in it. But they are just speculation

    • Photo: Clare Burrage

      Clare Burrage answered on 11 Mar 2012:

      That’s a good question that we don’t know the answer to yet! If we could understand why gravity was so much weaker than the other forces, then we could make a lot of progress towards building a theory which can describe both gravity and quantum physics.
      It’s definitely possible that the explanation is that gravitons are travelling through extra dimensions that the particles that transmit the other forces can’t get into, and that’s why the gravitational force is weaker. But that opens up many new questions, like why are the extra dimensions so tiny, and why are only gravitons allowed into them?

    • Photo: Elizabeth Pearson

      Elizabeth Pearson answered on 11 Mar 2012:

      No one really knows. The best answer I’ve had to this so far has been ‘because of some maths’ but that’s true of a lot of things in physics.

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