Is String Theory really a theory?

  • #26
marcus
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whydoyouwanttoknow said:
So, um, the answer is that it's not a theory?
Read jeff's post.
jeff is our unofficial string-spokesman here at PF
he says it is a "Research Program", as opposed to a theory
he indicates he believes, for various reasons, that it is a very promising program

String may in time become a well-developed scientific theory and
make unequivocal predictions of definite numbers that can be tested
In which case it will be possible to prove wrong.

the criterion of a scientific theory is that it bets its life on predicting
the outcome of future measurements
(if it can accomodate any future measurement it has no meaning as science----it is more of a daydream or a poem)

So when String becomes clear enough and definite enough that it could be shot down or refuted by some empirical observation it will be a scientific theory and it will be running the daily risk that this entails.

General Relativity was published in 1915 and by 1919 there was the first test, which could have invalidated it but didnt, and it continues to be testedeven today with things like Gravity Probe B satellite, and it could be found to be off by even a little----in the sixth decimal place, like----at any time but it hasnt yet. That is a theory.
 
  • #27
marcus
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jeff said:
... that string theory is somehow pathological - it clearly isn't - but rather that they need to stop trying to make huge conceptual leaps and instead work towards making more incremental and hence surer progress.
Yes
there was a good, lengthier, post by Lubos Motl to this effect
He said that the "string cosmology" stuff was premature
He said young researchers in the field should be advised not to
work on the more optimistic speculative things (I think he meant
"colliding braneworlds" and stringy multiverses and such) but instead
to grapple with basic problems. the post contained warnings and
he used the word "premature" more than once. I will try to find it
unless someone else can come up with a link.

In that same post, Lubos mentioned the need for "background-universal"
string models. Sounds encouragingly like background independent

On hearsay, I believe also that Lubos is very strong in rejecting Anthropery.

If we could filter out the voices of silliness we could hear the reasonable voice of string more clearly.

[edit: this blog has a pointer to a relevant Lubos post, and I see Peter was agreeing with Lubos there]
http://www.math.columbia.edu/~woit/blog/archives/000028.html
 
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  • #28
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Sol2 said:
What are your thoughts on probing dimenisons in context of what I have shown in regards to the graviton(energy in energy out-where has it gone if not equal?) in regards to the colliders? Do you have another explanation?
Peter gave a response and was honest. If Jeff is suppose to be the official spokesperson, then he obviously hasn't given much here in PF to consider in regards to strings.

As a laymen I like to understand the experimental approach as well. Given indications here, from what has so far been considered(dimensions), although labelled whacky by a large segment, has something it is deriving itself from?

No? Yes?

The original question is still being poised, from the start of this thread. Is there scientific validation being looked at in the colliders?
 
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  • #29
jeff
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Sol,

What's your first language?
 
  • #30
Gza
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I'm entering grad school within under two years, and still trying to figure out what I want to specialize in. I have been pretty fascinated by string theory and got a chance to take an undergrad class in it, which furthered my interest, but I am worried about what the state of it will be by the time I am a few years into research. If it hasn't given testable results in this many years, how many more years will people continue to hold onto it? Also, what fields are you guys currently specializing in?
 
  • #31
marcus
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Gza said:
... Also, what fields are you guys currently specializing in?
I'm a physics watcher and my special area of interest currently is Quantum Gravity Phenomenology.
This combines recent invovations in theory (extensions of special relativity to more than one invariant scale) with developments in instrumentation and satellite observatories such as GLAST, and PLANCK gammaray burst astronomy, ultra-high-energy-cosmic-ray, UHECR, astronomy, and other.

The latest conference on this was WS-2004 in Poland February 4-14
on the subject "Quantum Gravity Phenomenology"
Talks by a dozen or more experts included several people doing observational work

http://ws2004.ift.uni.wroc.pl/html.html [Broken]
click on "lectures"

Steve Carlip, Roger Penrose and Carlo Rovelli were on the program committee: choosing the lecturers and which topics to cover.
Lee Smolin and Jerzy Kowalski-Glikman were among the theorists giving talks.
Observationalists Piran and Lipari gave talks on UHECR and Gamma Ray Burst astronomy.
The talks by these and other observational astronomers were
plentiful and of special interest. In (Loop especially) Quantum Gravity the trend is now to get busy with predicting and testing.
One wants to find LQG signatures in the spikes of gammaray bursts, for instance.
GLAST, the first gammaray array sensitive enough to see such things is not scheduled to fly until 2007 but in the meantime the observationalists are sort of "warming up" by doing whatever they can do with the instruments they have.

So that is a central interest for me. Exciting things are happening in Quantum Gravity, including the beginnings of prediction and testing, and i like to keep track of that.

I also have an interest in (Loop especially) Quantum Cosmology---basically the consequences of removing the big bang and black hole singularities by quantizing the relevant GR models.
 
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  • #32
arivero
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marcus said:
I'm a physics watcher and my special area of interest currently is Quantum Gravity Phenomenology.
I keep wondering why you (and some other people which seems to have both the time and the interest) do not upgrade from "watcher" to "student" or something so.
 
  • #33
arivero
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whydoyouwanttoknow said:
So, um, the answer is that it's not a theory?
Hmm it depends. There is a "naive string theory", or "promised string theory", which was to have some nice properties (background-free to name one) letting us to justify mathematically the properties of the smallest elements of Nature. Such entity is not a theory but a goal. In pursuing it, the string practicioners were able to build a theory of perturbation for kaluza klein space-times with a matter content fixed by the theory. They did it twenty years ago; since then, the scientific discussion is about the utility of such object.
 
  • #34
marcus
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arivero said:
I keep wondering why you (and some other people which seems to have both the time and the interest) do not upgrade from "watcher" to "student" or something so.
a student may mature into a researcher and do original research in the chosen field

a watcher may aspire to gain historical perspective on the human quest for knowledge and perhaps to arrive at a journalistic account

it is a private-language distinction---I dont want to force it on anyone else and I am happy to be thought of as a student

Alejandro, have a good walking tour in the spanish country.

when you get back, here is a request

Could Meteor or you supply the original-language quote from Alfonso
(probably in 13th century Castilian)
"If I had been present at the creation, I would have given some useful hints on the ordering of the universe."

that guy was as smart as a cat, if he really said that,
and very right they called him Alfonso Sagio or whatever it was.
 
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  • #35
Nereid
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marcus said:
String may in time become a well-developed scientific theory and make unequivocal predictions of definite numbers that can be tested In which case it will be possible to prove wrong.

the criterion of a scientific theory is that it bets its life on predicting the outcome of future measurements (if it can accomodate any future measurement it has no meaning as science----it is more of a daydream or a poem)

So when String becomes clear enough and definite enough that it could be shot down or refuted by some empirical observation it will be a scientific theory and it will be running the daily risk that this entails.

General Relativity was published in 1915 and by 1919 there was the first test, which could have invalidated it but didnt, and it continues to be testedeven today with things like Gravity Probe B satellite, and it could be found to be off by even a little----in the sixth decimal place, like----at any time but it hasnt yet. That is a theory.
[nitpick]A scientific theory *also* has to be consistent with all historical observations and experimental results (within its domain of applicability).[/nitpick]

This can be a truly awesome mountain to climb; many new theories do it by showing that they are consistent with well-established existing theories they hope to go beyond, to within the limits of experimental error, 'in the limit' of the domains of applicability (or best current tests) of those current theories.
 
  • #36
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As far as evidence goes for String theory-- there is some evidence for it just not as solid as we would like. For example as Ed Witten points out one of the biggest pieces of evidence for String Theory is gravity-- a postdiction that String theory requires. I am not talking about the graviton which would provide much more "proof" (especially if it were at the moment of disapearence into the extra dimensions) but there seems to be some evidence. Also as many people feel is the weakness is string theory but many people feel the evidence is in the beauty of the equations... they have to be right there just too elegant to be wrong.
 
  • #37
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Tom McCurdy said:
... many people feel the evidence is in the beauty of the equations... they have to be right there just too elegant to be wrong.
entertaining blog about this-----a mathematician's view of alleged mathematical beauty

"Beauty, Fashion, and Emperors"

http://www.math.columbia.edu/~woit/blog/archives/000064.html

comments contain a classic impertinence from Murray Gellmann:
"If I have seen farther than other it is because I am surrounded by dwarves."

IMO it is too easy to imagine that many people thought the Ptolemaic system was beautiful.

so I am dubious of the "elegance" argument. I suspect if next year unexpectedly some real experimental corroboration appeared everybody would instantly stop the "elegance" talk and get down to business.
 
  • #38
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Woit's blog is good, but just for a little equal time here, try Jacques Distler's blog (the occasional math is set up for Mozilla).
 
  • #39
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Well, I think that is not correct to say that string theory does not make testable predictions,for example predicts particles with exotic values of electric charge, for example (1/5)*e or (1/13)*e, particles that have not been yet detected, but it's not less true that is a theory with more than 30 years of development, it's like a never-ending path, while the quantum revolution took place practically in 5 years, and special and general relativity were worked in 10 years. I don't like the barroque picture that string theory offers of the world, it seems to me much intrincated, but I have very much to learn, and maybe the theory can grow on me. Don't know.
 
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  • #40
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The definition of a scientific "theory" usually means a model that has been very successful with testible predictions. Examples: Special Relativity, the theory of evolution, the big bang theory, etc. With that definition, the answer is no and isn't debatable.
 
  • #41
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Does anywone know if there has been any news supporting strings since fabric or even elgant universe that could explain it or link it to a non mathmatical based site. I haven't had calc yet.
 
  • #42
selfAdjoint
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I am pretty sure there aren't any newer popularizations of string theory than the books you mention. It's really tough to do even simple quantum mechanics without calculus. You read ten different books (or web sites) and they give you ten different verbal descriptions, and you can't tell if the differences are real or just stylistic.
 
  • #43
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So, um, the answer is that it's not a theory?
LOL! Depends who you ask. Hm, kind of kidding.

No, it is a hypothesis (potential explanation) and not a theory if, as is most common, you define a theory as needing to be able to make testable predictions. After an experiment, we collect and analyze the results and then compare the results to the prediction made by the hypothesis. If this happens "enough" times (when enough people are convinced), the hypothesis is instead called a theory. String "theory" makes no predictions we can put to the test as of now, but so many people worked so much on it that it seemed unfair to call it a mere hypothesis.

The most favored/accepted hypotheses and theories are established by "consensus." Unfortunately at any time most big theoretical ideas in physics are unlikely to be correct. This has been the case for most of scientific history, except for when someone makes a large leap of progress, leaving behind plenty of details to be worked out by others and keep them busy.

String theory went backwards...it's an inside-out abomination. (lol)

Short answer: No, it's not a real theory as of now, anyway. (But it could be.)
 

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