Question: What is superstring theory? [Mark]

Mark Jackson answered on 8 Mar 2014:

Go get an apple. Now look at it and imagine zooming in about a billion times – you’ll be seeing individual atoms. We learned quite a while ago that atoms are made of particles called protons, neutrons, and electrons. The protons and neutrons, we have learned, are each made up of three quarks. As far as we know, the quarks and electrons are ‘elementary’ in the sense that we don’t know of anything smaller into which they can be decomposed.

One theory – and I emphasize theory, because this is not proven – is that if you zoomed in on the electrons or quarks about a billion, billion, billion times these would actually be tiny strings vibrating at the speed of light. What is this string made of, you ask? Pure energy. The quark-string would be vibrating at a slightly higher frequency than the electron-string, giving it more mass. The other elementary particles (photon, neutrino, Higgs Boson, probably gravitons) could be described similarly.

But why would anyone believe such a thing in the first place? For about a hundred years physicists have been trying to combine the two basic ideas in physics – quantum mechanics and gravity. As we currently understand them, their equations don’t allow them to be combined. But in the string theory not only can you combine them, but you have to! This is such a cool idea that a number of physicists, including myself, are working on ways to prove whether the string theory is true or not. Usually this is done at particle accelerators such as CERN, but we are trying to be more creative and use the Big Bang as an experiment!

A video of me explaining this a bit more is at http://www.youtube.com/watch?v=pMXVK8ecD1I

Now eat the apple.