• Question: If string theory requires the testing of planck lengths to be proved which is impossible to do(to my knowledge), why is it being considered as a theory to explain phenomena? Won't we be left with another theory that may seem valid in many circumstances (if it is correct) but can never actually be proved to work universally?

    Asked by sebstrug to Ben, Clare, Ezzy, Mario, Sam on 15 Mar 2012.
    • Photo: Elizabeth Pearson

      Elizabeth Pearson answered on 14 Mar 2012:


      Oooh, good question. One of the main flaws in string theory is that it can’t be proved. Most of the science community doesn’t think string theory is the way to the theory of everything but it’s very elegant and has gotten a lot of press so it seems to be sticking around.

    • Photo: Mario Campanelli

      Mario Campanelli answered on 15 Mar 2012:


      there is no such a thing as a string theory. there are thousands of theories based on the string idea, that there is no pointlike structure of spacetime, but none of them manages to describe our universe. Quantisation of gravity is a problem that challenged very bright minds for almost a century now, and up to now all these efforts failed. Clearly a theory, string-inspired or not, able to describe general relativity in quantum terms, would be an enormous success, and its experimental proof would be that it is able to describe our world (even if you would also like to predict something new, and this is so far not the case; however without a complete theory it is hard to say anything)

    • Photo: Clare Burrage

      Clare Burrage answered on 15 Mar 2012:


      It’s one of the problems with string theory that it doesn’t make concrete predictions that we can test. The only way we know to test it for sure is, like you say, to look at planck lengths and energies. We’re a long way off being able to do this in the lab, but we might be able to learn something by looking at the very early universe, when the size of the universe was at the Planck scale.
      Even if we can’t test it, studying string theory can show us new ways in which our universe can behave, for example that there might be extra dimensions. So even if it doesn’t turn out to be the way our universe works it’s still useful to study sting theory.

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