3 ms·

Just sew the end of time up to the beginning of time and the electrons never need to turn around.

• pdonis 13y ago
  There are mathematical descriptions of universes like this, but their predictions don't match our observations of the actual universe. For example, the Godel universe contains closed timelike curves through every event, but it predicts that we should see distant galaxies rotating with respect to nearer stars, with the rotation getting faster the farther away the galaxies are. We don't observe that.
  • samograd 13y ago
    Why do we have to think that this electron is moving through spacetime? With the 9(?) other dimensions that String Theory has given us, I would think that it could be passing through any subset of them. My impression is that thinking this electron curve is moving through spacetime ignores a lot of modern physics.
    • pdonis 13y ago
      When Wheeler and Feynman originally came up with this model, string theory was still decades in the future. Also, string theory even today is speculative; a lot of physicists think it's a good theory, but it is experimentally untested, because nobody can think of a way to test it; we can run plenty of experiments that are consistent with string theory, but they're also consistent with lots of other theories. We don't know how to run experiments that will help us to distinguish between string theory and the others. And in any case, the point of the model is to describe observations of electrons that we can make directly; those observations don't involve extra dimensions even if there are any. They directly involve the four dimensions we can directly observe, three spatial dimensions plus time, i.e., spacetime. Even if there were string theory machinery "behind the scenes", so to speak, it would still have to be describable at some level as electrons moving through spacetime.