String theory predictions

Discussion in 'Physics & Math' started by ronan, May 15, 2008.

  1. ronan Only Consciousness Exists Registered Senior Member

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    433
    Hello

    I hope I post in the right forum, I heard that for some people string theory (ST) is not part of science because it does not make predictions

    I have just one question at first:

    Let (A) be one quantum theory (QT) experiment (for example the double slit experiment)
    Let (B) be one general theory of relativity (GTR) experiment (prediction about something in the sky)

    We know/assume:
    the result of (A) can be predicted by (QT) but not by (GTR)
    the result of (B) can be predicted by the (GTR) but not by (QT)

    Does (ST) can predict both (A) and (B) by using only (ST) equations ?

    Can you give me some reference in the same time if you know the answer

    Thank you
     
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  3. BenTheMan Dr. of Physics, Prof. of Love Valued Senior Member

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    ronan---

    The predictions of string theory are hard to pin down, but it DOES make definite predictions, in spite of what you may have head.

    There is not a direct answer to your question, but this is a good point for discussion.

    As someone who actually works in the field, I can tell you that there IS no solid prediction in string theory that can be tested.
     
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  5. ronan Only Consciousness Exists Registered Senior Member

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    I think that some predictions of (ST) are not predictable (economically or theoretically) because many (ST)assumptions are below plank' s scale

    But the predictions I am talking are not below, they are the one predicted by (QT) and (GTR)

    What I am asking then is:
    Does theoretically (ST) can predict (QT) result and (GTR) result and does this theoretical assumption have been tested (which is possible)?
     
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  7. AlphaNumeric Fully ionized Registered Senior Member

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    String theory can predict the Einstein Field Equations with it's postulates of the postulates of special relativity and quantum field theory.

    It predicts an extreme derivation from the inverse square law of gravity at small distances due to predicting compact spaces.

    Compact spaces come from the prediction of a particular number of dimensions in the universe, something no other theory has managed.

    The required existence of branes implies the existence of gauge groups, ie bosons and conserved charges. No previous field theory had a requirement of such things.

    Unfortunately, those things are not really precise enough. But the point is that they address fundamental questions currently aimed at GR and QFT. Why are there 3 spacial dimensions at large? We know our current point-quantisation of fields fails for gravity. We know our concept of relativity fails to be naively quantised. And then there's other issues such as universal cosmology. Before, different areas of physics needed different theories, we just couldn't get one which had a finger in every pie. Now it seems we do. String theory has something to say about pretty much everything in high energy physics/cosmology. It's the first theory to be in such a position. Current research goes into doing things like "Okay, so it can describe gauge fields. It needs gauge fields. Which gauge fields? Does it exclude particular ones? Why?". Maybe, with work, it'll turn out it excludes all gauge groups other than the one which unifies the 3 standard model forces and gravity? Or "Okay, so M theory has 11 dimensions. Does this exist as an ultimately unstable state which decays into a different setup, like 4 large dimensions and 7 small? If so, how and why." Then you'd have a description of why the universe is 4 dimensional and perhaps what the BB really was.

    Perhaps the problem is that string theory addresses too much. If it addressed one issue, everyone would be working on the same thing and it'd have been developed or destroyed by now. With so many avenues of research, even with an army of physicists and mathematicians going at it, it's slow going. Ben and I are in roughly the same area of work but even we don't do stuff similar enough to make it important we read one another's work to keep up with our field (or rather, fields).
     
  8. ronan Only Consciousness Exists Registered Senior Member

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    433
    Do you know some references that say that (ST) predict the same results than (GR) and (QFT) in their respective experiment (example: double slit experiment for (QFT)) and (sky observation for (GR))?
     
  9. Fraggle Rocker Staff Member

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    24,690
    The purpose of science is twofold:
    • To explain the present and past behavior of the natural universe as a closed system;
    • To predict the future behavior of that closed system.
    A theory is an assertion that:
    • Provides both that explanation and that prediction;
    • Is derived logically from empirical observations of present and past behavior;
    • Has been tested and peer reviewed without being falsified; and
    • Whose probability of ever being falsified has been judged by an enduring consensus as so low that it can safely be accepted as "true beyond a reasonable doubt."
    String Theory does not actually violate any of these definitions, so there's no reason to say it's "not part of science." It merely fails as yet to satisfy all of them. Therefore, it should not properly be called a "theory," specifically because it is not predictive and because it has not been established as "true beyond a reasonable doubt."

    I have railed at length about the poor status of communication between science and the general public. As the Linguistics Moderator I put the blame on science's amazingly inadequate and imprecise terminology. It's as though science were a secret medieval guild, and we are all bound by oath not to disclose our secrets to laymen, and to help us keep that oath our elders do not provide us with language that makes it easy to even talk to laymen.

    String "Theory" has not achieved the status of a theory and is nothing more than a hypothesis. When we tell laymen that hypotheses like this one are "theories," it sets them up to doubt our real theories like evolution, on the grounds that "it's only a theory." In fact a theory is the ultimate achievement of scientific scholarship. A theory has been found to be "true beyond a reasonable doubt" and indeed of all the myriad theories of the "hard sciences" that have been established over the past 500 years, only a handful have been falsified. And generally that falsification requires further elaboration of the theory rather than complete rejection, e.g. the continuum from Newton's Laws to Special Relativity to General Relativity.

    We should be calling this "the String Hypothesis" or "the String Model of the Universe."
     
  10. BenTheMan Dr. of Physics, Prof. of Love Valued Senior Member

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    Fraggle---

    I heartily disagree. I think your definition of ``theory'' is not quite adequate. For example, the idea of consensus can't be right. String theory DOES have testable predictions---specifically the universe is ten dimensional. Further, this prediction CAN be tested, in principle.

    As AN also pointed out, string theory predicts the existence of extended non-Abelian symmetries in space-time...this is a prediction of the theory.

    As a comparisson, I will offer the example of Quantum Field Theory. What are the predictions of QFT? Should we demote QFT to ``Quantum Field Hypothesis''?
     
  11. BenTheMan Dr. of Physics, Prof. of Love Valued Senior Member

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    Mod Note:

    No trolling please!
     
  12. Fraggle Rocker Staff Member

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    I didn't mean to say that String Theory does not make predictions. In order to become a theory, a hypothesis must make predictions that are tested against the subsequent behavior of the natural universe and found to be fulfilled. I gather from what you've said that the predictions of String Theory have not yet been tested. This means that it is still only a hypothesis.

    I strongly disapprove of the convention of calling a hypothesis a theory when it does not yet satsify the complete definition of the term. The predictions of relativity and (to a lesser extent) evolution have been fulfilled so they get to be called theories. But we don't want to turn around and use the same word to describe a hypothesis whose predictions have not been fulfilled. If we do that, laymen will start to think that everything we call a "theory" is as weak as this one.
    Absolutely. I demand integrity in scientific terminology or science is going to continue to be under attack by laymen looking for ways to discredit it. There's no excuse for imprecision in science in something as important as its language.
     

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