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Could String Theory Be the Future of Quantum Physics?

  1. Nov 4, 2013 #1
    I'm a 10th grade high school student, but before you judge me I would like to inform you that I have a 127% (thanks extra credit) in my Advanced Physics class. I was reading the textbook as I usually do in my free time and I stumbled across a section on String Theory, I read through the chapter and I found this theory to be extremely intriguing. I would like to hear your opinions on this String Theory and if it is legitimate enough to work its way into a permenant position in modern physics and become a widely accepted rule of quantum physics.
     
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  3. Nov 4, 2013 #2
    If you click at the top of the "Views" column in this forum, you will see all the discussions that have ever happened here, ranked by the number of views. As you can see, there have been some very long threads about string theory here, in which defenders and critics of string theory have talked at great length.

    In the physics world, string theory is already widely accepted, but it is also widely attacked. It's controversial because it has been around for decades without a clear proof of its correctness.
     
  4. Nov 15, 2013 #3
    Update: String theory is dead. The LHC has excluded any obvious extension to SUSY. The only thing left now is unnatural extensions at higher energies: basically a Hail-Mary pass. But rest assured, as LHC excludes more enerties, the proponents of SUSY will continue to modify their models. Yes, there are still rabid advocates of String Theory, but that is only because these people have invested their entire careers on a psuedo-Science. Without SUSY, there is no String Theory and there is no SUSY.
     
  5. Nov 18, 2013 #4

    bapowell

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    What does string theory have to do with low-energy spacetime SUSY?
     
  6. Nov 18, 2013 #5

    bapowell

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    There are several difficulties with string theory: 1) it has made no falsifiable predictions. This is partly a consequence of the fact that it seeks to describe physics at energies far beyond anything realizable here on Earth. Because we have no experimental constraints on string theory, there are currently a vast, vast number of ways that the extra dimensions might arrange themselves (these ways are referred to as "solutions" of string theory). This problem has given rise to the "landscape" of string theory. 2) there are formidable theoretical stumbling blocks, including a great difficulty in getting inflationary spacetimes out of string theory, not to mention an apparent inability to recover the Standard Model of particle physics (or basic extensions, like MSSM) from string theoretic unifcation schemes.

    The theoretical difficulties might be surmountable, but in my view the biggest issue is the lack of experimental support. In a very real sense, string theory is not only not a theory, it is not a science, in the sense that we generally use science to understand the world through observation and experiment. For now, string theory is an impressive theoretical formalism that proposes a universe built out of string; whether that universe happens to adhere to reality is still an open question.

    Over all, my impression is that professional interest in string theory is waning.
     
  7. Nov 18, 2013 #6

    marcus

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    That impresses me as a fair, thoughtful assessment. What you say about "waning interest" is born out by a decline in numbers of citations to string papers in professional research journals, and in a decline in the number of faculty job offers to string PhDs as a fraction of total hiring in theoretical particle physics. Physics departments in US and Canadian universities are today far less interested in taking on string theorists than they were, say, back in 2001-2004.
     
  8. Nov 18, 2013 #7
    What is the latest thinking on the tension required? The last I recall was on the order of 10^41 kilograms force (you could approximate that by suspending about four Milky Way galaxies).
     
  9. Nov 20, 2013 #8
    I really don't believe in the string theory. I think they are trying to hard to find an explanation to unknown things in the universe. The string theory is kinda like a religion. People create myths and gods to explain the unknown. The "god" in the string theory are the strings and the myth is that its different vibratios form different particles.

    Things are much more simple than it seems, in my opinion.
     
  10. Nov 20, 2013 #9

    bapowell

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    Except that string theory can in principle be falsified, because it is a framework that purports to describe the physical world. Not so for religion.

    So do you think that 0-dimensional points are a more apt physical description of particles?
     
  11. Nov 20, 2013 #10

    bapowell

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    Unfortunately nature doesn't care much for your opinion. Applying aesthetics and a prejudicial sense of simplicity to the world has no promise of leading to correct theories. Have you ever written down the Lagrangian of the Standard Model and managed to fit it on a single sheet of paper?
     
  12. Nov 20, 2013 #11
    Whan I'm saying is that when we eventually find out where everything came from and how everything works, we will be like "hm that makes sense, it is not that complicated". The thing is that the human mind created fantasies about the unknown. A long time ago people use to say that gods were responsible for everything in nature, like gravity, fire, etc. Nowadays we know more about why those things exist and how they happen, so we don't need their gods anymore.

    Our "god" nowadays can be the theory of strings and multiverses. Saying that there is a 11 dimensional hyperspace can be as dogmatic as believeing in chronos, the god of time, for example.
     
  13. Nov 20, 2013 #12

    bapowell

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    Unless it is that complicated (cf. the Standard Model Lagrangian)

    Sure, multiverses and string theory are speculative ideas. My impression, though, is that you don't really understand these things sufficiently well to be dismissing them as misguided dogmatic beliefs. The multidimensional universe arises from string theory as follows: 1) postulate the existence of 1-dimensional objects as particles (this is a hypothesis, just as the supposition that particles are 0-dimensional entities. It is perfectly in line with the scientific method.) 2) Next, study the dynamics of these strings by applying what we know about relativity, quantum mechanics, etc. to the 1-dimensional object 3) You find that Lorentz invariance and mathematical consistency are only achieved in select numbers of dimensions. In other words, these fantastical things like extra dimensions -- that, to the uninformed layman, appear dreamed up like a god -- are in fact a direct consequence of applying known physics to a hypothesis. You can now, in principle, devise experiments to probe the dimensionality of spacetime in an effort to falsify this new-found idea. Isn't this precisely how science is supposed to work? I see virtually zero similarity between the extra dimensions of string theory and an unverifiable, obvious fiction like Chronos.
     
  14. Nov 21, 2013 #13
    For becoming scientific, one would have to add yet another step: 4.) Compare the derived predictions with observation and reject the hypothesis as falsified if there is no agreement.

    Once the 3+1 dimensions we observe are not among the selected numbers, this would have been the end of string theory.
     
  15. Nov 21, 2013 #14

    bapowell

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    Yes, I said this above: "You can now, in principle, devise experiments to probe the dimensionality of spacetime in an effort to falsify this new-found idea. Isn't this precisely how science is supposed to work?"
     
  16. Nov 21, 2013 #15

    Chronos

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    I object ... I think.
     
  17. Nov 21, 2013 #16
    :biggrin:
     
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