Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

What good is string theory?

  1. Nov 12, 2009 #1

    When quantum mechanics was established it allowed us to do things that we could not do before.

    What would string theory allow us to do? Lets say that string theory was confirmed -- tests showed the projections string theory made were correct and now string theory was accepted. What would it allow us to do that we can't do now? What good would it do us?

  2. jcsd
  3. Nov 12, 2009 #2
    General Relativity (gravity) = Apples
    Quantum Mechanics (submicroscopic physics) = Oranges

    String Theory brings them together. It's a quantum mechanical model that incorporates gravity, where QM and Relativity were never able to work together before.

    It's a bit more complicated than that, but that's about the gist of it.
  4. Nov 12, 2009 #3
    String theory says that the universe is a seamless whole spread out among several dimesions rather than a sea of quantum particles. So, according to String Theory, any interaction involving either of the four fundamental forces can be described by one single set of laws. In the same way that Kaluza was able to unite GR and electromagnetism by the addition of a fifth dimension, String Theory hopes to unite GR with the other two nuclear forces by the addition of extra spatial dimensions.
  5. Nov 12, 2009 #4
    Correct, as well as adding (though not uniquely) the presence of "superparticles".
    And in response to ernestpworrel's comment about extra-dimensions, string theory uses the "M-theory" concept, in that there are 11 dimensions, rather than Kaluza's 5.
  6. Nov 13, 2009 #5

    Thanks for your replies! Everything stated I already know.

    So scientists will have 'closure' and everything will be tied together.

    But besides that... how would it improve technology. What problems would this knowledge help us with in practical terms (consumer goods, space exploration, faster PCs, cure the common cold, smaller Ipods)?

    What good is it to the average (non-scientist) person?

    Don't get me wrong, I'm with you... wanting 'to know'. But, there should be 'some' answer.

  7. Nov 13, 2009 #6


    User Avatar
    Science Advisor

    Due to additional dimensions, perhaps we could travel long distances through shortcuts in higher dimensions. It's pure SF at the moment, but who knows ...
  8. Nov 13, 2009 #7


    User Avatar
    Science Advisor

    It depends on the solution of the theory we are living in; perhaps we can create a tunnel to the "next" brane, perhaps we can tune the strength of gravity, I don't know.

    I do not see any realistic aplication as everything is right at the Planck scale

    (OK, large extra dimension could change this; we will be able to create black holes at the LHC and destroy the earth much more effectively :-(
  9. Nov 13, 2009 #8
    Try to think of what Planck would have answered if asked what his considerations on heat and radiation are good for. Would he have guessed "iPhones !" ?

    String theory is a logical possibility in our quest to understand what's "out there". We have only very few things in life comparing in value.
  10. Nov 13, 2009 #9
    Black body radiation was a real problem.

    String theory does not proceed from any real problem. It's a mathematical physics exercise extremely advertised but resulted in nothing since proceeded from nothing physical. It is like taking some mathematical postulates and deriving consequences, theorems, etc. They exist within the mathematical framework but not reflect and are not obliged to describe something physical. String theory is not a "logical possibility"; rather it is practising mathematical logics.
    Last edited: Nov 13, 2009
  11. Nov 13, 2009 #10
    From somebody who does not believe in renormalisation, I must say I am not surprised.
  12. Nov 13, 2009 #11
    The string theory proceeds from believing-in-renormalizations researchers (believers in bare masses, counter-terms, running cut-offs, and other non physical stuff and its patches) but who failed to apply it in QG - this theory is not renormalizable. So the believers added the cut-off by hand. The higher, the better. Plank length in the coordinate space. Nobody can verify it. But even that does not work. Because everything is thought out, then patched and re-patched. And this all is presented as TOE.

    I believe in reasonable physics and mathematics, according to my own experience.
    Last edited: Nov 13, 2009
  13. Nov 13, 2009 #12


    User Avatar
    Gold Member

    I wouldn't take that way. Blackbody radiation was a weird fundamental problem experimentally observed expecting to be explained, just like dark matter and dark energy are today.

    String Theory, or anything that involves anything that involves quantum gravity, are not based on any observed data, but on the inconsistencies of mathematical models.
  14. Nov 13, 2009 #13

    Ah, So because you can't actually see the Planck length, it isn't there? Well we can't actually see the so-called "Dark Side of the Moon", so it must also not be there. And if we're going to go there, let's say that evolution doesn't happen because we can't actually SEE it.

    Here's an experiment that you can add to you "own experience. Put your foot in a shoe. When it disappears, try convincing me that it's there.

    Sorry to put it to harshly, but saying that something cannot exist just because you cannot see it is to completely rule out quantum mechanics, also.
  15. Nov 13, 2009 #14
    My foot in and out of a shoe is quite different from the Plank-length stuff (strings). Max Plank developed a unit system from known universal constants including G and ћ. The length unit obtained was quite weird and followed from no physical problem. Do you know what is the size of a Hydrogen-like atom with G, me, and mp instead of e2?

    Please give us an estimation of this "Bohr-Plank" quantum radius. I am afraid that gravity is always classical, no quantum gravity effects can be separated from other, stronger interaction effects.
    Last edited: Nov 13, 2009
  16. Nov 13, 2009 #15
    I do not understand why you cited one my phrase and attacked another one.

    I admit that there are things that I had no opportunity to see but it does not mean I should believe in any assertions.
    Last edited: Nov 13, 2009
  17. Nov 13, 2009 #16
    Reading these posts makes me wish I found this forum ages ago :D
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook