String Theory, summarized
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Bikewer
Penultimate Amazing
There were a number of physicists maintaining that string theory was more of a philosophy...
I just read Kaku's book on the subject, and he seemed to think we'll be seeing some concrete evidence before too long.
I just read Kaku's book on the subject, and he seemed to think we'll be seeing some concrete evidence before too long.
TV's Frank
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Well, he's Kaku, a string theorist, so of course he'd say that! Also, he has no idea exactlty how that evidence would come about, which is something a lot of stringers have a hard time coming up with...
String theories predict different properties from the Standard Model for the Higgs boson and other particles that should be seen at the energies the LHC and ILC will reach. It should be possible to tell if they are at least on the right lines ones these accelerators are working.
HeavyAaron
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I've been curious for a while. How did it get to be the "String Theory" instead of the "String Hypothesis"? Or if you like, the set of string theories instead of the set of string hypotheses?
Aaron
Aaron
Great question. It might have been facilitated by the way the actual words sound together (there must be a term for that).
"String Theory" sounds better "string hypothesis" (or in the other direction, "the law of string").
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HeavyAaron
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I think you're wrong on two counts:
1) That's not the criteria for establishing what is or is not theory.
2) More advanced mathmatics than is presently available are required to fully model string theories.
At least, both of those are true to my best remeberence.
Aaron
Apparently they're still working on putting together M-theory and seeing what it predicts, so they're not in right now will get back to us later.
I believe that it is called a theory because of a few factors. Its completeness. It succeeds in fitting the Standard Model. It has sufficient support from a sufficient number of prominent physicists.
On the other hand, it makes no testable hypotheses that are not predicted by other theories. For example, Supersymmetry is the theory that predicts the different properties from the Standard Model for the Higgs boson and other particles. String theory is just sufficiently mathemetically elegent that it also describes Supersymmetry.
Basically the only reason anyone has faith in string theory is the mathematical elegance. Until someone can produce a verifiable prediction from the theory it will remain a theory. Or until someone can prove that it has one or more fatal mathematical inconsistencies.
On the other hand, it makes no testable hypotheses that are not predicted by other theories. For example, Supersymmetry is the theory that predicts the different properties from the Standard Model for the Higgs boson and other particles. String theory is just sufficiently mathemetically elegent that it also describes Supersymmetry.
Basically the only reason anyone has faith in string theory is the mathematical elegance. Until someone can produce a verifiable prediction from the theory it will remain a theory. Or until someone can prove that it has one or more fatal mathematical inconsistencies.
I'm currently reading a book on the failure of String Theory, called "The Trouble with Physics" by Lee Smolin, who himself taught string theory for some years.
There is also a blog by Peter Woit called "Not Even Wrong" which is also the title of his (rather more mathematical) book
Strictly speaking, string theory is a conjecture or a hypothesis, and not a theory. It's unlikely that ST has a mathematical flaw, but as Smolin and Woit both point out, its a failure at making any testable predictions which is why they contend it should not be considered a physical theory.
Edited to add:
Here's a review of Peter Woit's book which gives a good non-technical overview of the problem with String Theory: http://sciencewriter.org/2006/10/peter-woits-book/
There is also a blog by Peter Woit called "Not Even Wrong" which is also the title of his (rather more mathematical) book
Strictly speaking, string theory is a conjecture or a hypothesis, and not a theory. It's unlikely that ST has a mathematical flaw, but as Smolin and Woit both point out, its a failure at making any testable predictions which is why they contend it should not be considered a physical theory.
Edited to add:
Here's a review of Peter Woit's book which gives a good non-technical overview of the problem with String Theory: http://sciencewriter.org/2006/10/peter-woits-book/
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Because they have plenty of evidence supporting them. String theories predict exactly the same as the Standard Model for everything we have observed so far, otherwise we wouldn't consider them at all. The reason people criticise them is because they only predict differences at energies we can't reach yet, so so far it has been impossible to test them. Or at least impossible to test them against the Standard Model. There is a lot of public misunderstanding over this. Just because it is impossible to tell two theories apart does not mean the newer one is useless, it just means we need to wait until we are able to test between them, which in this case is fairly soon.
This is what I was talking about. It actually doesn't make any predictions that are testable at any energy level which are not also predicted by other theories. The Standard Model is also considered a theory, so it is not the basis for all other tests. It is simply the best theory we have at the moment that is both testable and describes the universe in which we live.
The major flaw of string theory (and M-theory which is a comprehensive version of string theory based upon its inconsitencies) is that it doesn't simply describe our universe. It is a mathematical model which potentially describes infinite universes.
The majority of the predictions of string theory are untestable because the theory itself prevents us from testing them. For example, M-theory predicts that the entire universe is tied to a 3-plane (AKA a membrane) floating around in some unknown and unknowable superverse (I made that word up). This presents a problem because string theory doesn't allow us to leave our universe to find out if it's true or not.
So, until another Einstein comes along and cracks string theory (or creates a better theory), it is unverifiable. We cannot show that it is true or false. It is a faith. A mathematical religion. It's as impossible to prove as the existance of a Deity. Thus we have string theory believers, string theory agnostics, and string theory athiests.
A side question. What exact education would one need to make an informed opinion on string theory? What math education, what physics education, what other education?
HeavyAaron
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When you have two hypothesis that predict the observations with equal accuracy you assume the simplier pending further observations. IMHO String Theories fail the simpliar tests. I suppose you could argue that they are more elegant. But it doesn't look that way to me. Of course, I don't have all the math skills required to fairly evaluate that.
Aaron