Comments by "Lepi Doptera" (@lepidoptera9337) on "Is string theory still worth exploring? | Roger Penrose and Eric Weinstein battle Brian Greene" video.

  1. True... but no offense... we haven't even solved Ising spins, yet, so it's not like other fields of physics haven't met their theorist's breaking points early and often. The mathematicians have the ultimate example for that phenomenon in the Collatz conjecture. It doesn't take much at all to come up with very hard to solve problems. Should these things suck all the air out of the room? No, not really. I think we can agree about that.
    3
  2. All teens are arguing with their dads and they always take the opposite opinion. Sound of one hand clapping. ;-)
    2
  3. No, not outside, but probably inside of black holes. The problem is that we can't do experiments in there...
    2
  4. Yes, and in that sense string theory is not science. It's a hell of a ride in mathland, though.
    2
  5. Yes, the key word there is "believe", which only idiots will use in conjunction with science and mathematics. String theory is quite well defined in its function, it just didn't lead to the kind of structural breakthrough in science that some people were hoping for. We had situations like this before, e.g. with Bohr's model of the atom. It was a step in the right direction, but it didn't quite get us there.
    2
  6. The universe is randomly accelerating stuff to really high energy, but that is not enough to do serious vacuum spectroscopy with that stuff. It has to hit other stuff in a well defined interaction volume and the resulting scattering process has to be surrounded by a nearly 4pi detector system. Without the last two conditions all we are getting are tons of by-products that don't contain the actual physical information we are after. We do have those detector systems... large cosmic ray shower experiments are doing just that. They have their uses, but they can't replace an accelerator.
    1
  7. String theory seems to lead to branes naturally. There is probably a correspondence.
    1
  8. Yes. It is still a pre-geometry model, even though it desperately tries to get away from that, but I don't think it ever did.
    1
  9. Currently it's not even that. A hypothesis has to be testable. String theory is simply to general relativity what quantum field theory is to special relativity. It's a necessary piece of mathematical machinery that, unfortunately, didn't manage to tame the QFT landscape. It just replaced it with something of similar size. The great hope that gravity might restrict the universe to this one and no other has, so far, not materialized.
    1
  10. Sabine is a Karen and so is Weinstein. They are both suffering from roughly the same personality disorders. ;-)
    1
  11. If you were, then you would be reading scores of really, really boring CERN papers. You aren't, are you?
    1
  12. If you are expecting something like a personal jetpack, then I have to disappoint you. If you are happy with food for thought, then string theory is a smorgasbord that will keep you eating for centuries. I have a feeling that you are more the jetpacky than the thougthy kind of person. Am I wrong about that?
    1
  13. Witten doesn't have to participate in things like these. He has serious work to do.
    1
  14. The quantum field theory landscape is, unfortunately, of similar size as the string landscape. That is widely unknown, but it is probably due to an actual correspondence. The real problem with QFT and string theory are not risky predictions. The real problem is that neither is taking any serious risks at all. They are both based on geometric representations of the Poincare group. We are still working through the mathematical consequences of Galileo's ship, which was the first modern description of relativity (at least as far as I know). This means we are still gnawing on a bone that we were thrown around 1630.
    1
  15. One can quantize gravity the ordinary way starting with a second order tensor field on a flat background just fine. It's a myth that one can't. It just doesn't lead anywhere. String theory starts at the other end and asks if one can quantize the free action on a Riemann manifold that satisfies general relativity. Lo and behold, one can. And again, it doesn't seem to lead anywhere, either. This is a strong indication that we are missing an element that is neither contained in quantum field theory nor in general relativity. We do not have any experimental evidence what that could be.
    1
  16. Weinstein is not a great thinker, though, and Penrose is aged out.
    1
  17. There is nothing stochastic about quantum mechanics. So, no. ;-)
    1
  18. If you want tools to test string theory, then start saving for a solar system size accelerator.
    1