# Is string theory wrong?

1. May 20, 2014

### Hossam Halim

Hello,
Is string theory or M theory wrong ? Isn't it the theory of everything ? Should we continue our research to reach the true theory of everything ? If so, why physicists still research on string theory ?!!

2. May 20, 2014

### phinds

String theory at this point is not right OR wrong, it is simply a hypothesis that has no experimental evidence but which would explain a lot of stuff very nicely if it DOES turn out to describe reality.

Why would you want to abandon the search for a theory of everything? Do you not care about knowledge?

3. May 20, 2014

### Hossam Halim

I meant we should search for the theory of everything with different thinking and to leave string theory as there are 2 experiments falsify it

4. May 20, 2014

### George Jones

Staff Emeritus
Which two experiments falsify string theory?

5. May 20, 2014

### phinds

As George requested, you MUST back up such a statement with citations otherwise it is just an unsubstantiated personal theory.

6. May 21, 2014

### Hossam Halim

Google this : ( string theory fails test )

7. May 21, 2014

### ZapperZ

Staff Emeritus
Sorry, but this is insufficient.

When you are trying to back up your argument, you must provide proper citation. Asking people to search for the source to support your point should not be done. Google search will turn up both valid and dubious sources. Which one did you use?

Please provide clear, valid references as soon as possible, or this thread will be closed.

Zz.

8. May 21, 2014

### Hossam Halim

9. May 21, 2014

### PAllen

All of these are of the following nature:

- Had they been found, they would have added support to (but not confirmed) string theory
- Not finding them does not even remotely disprove string theory

All of the sources you provide are of dubious reliability, or strongly biased.

10. May 21, 2014

### ZapperZ

Staff Emeritus
Please re-read the PF Rules that you had agreed to. Pay attention to the type of sources that we consider as valid.

Not knowing your background, I will assume that you are not familiar with how things are done in science. Valid sources require a DIRECT citation of either well-established standard text/references, or a publication in our accepted peer-reviewed journals. Personal websites and blogs (even by Woit) do not constitute as valid sources. If you used this, then you are using 2nd, 3rd, or even 4th hand news.

This may be an "ordinary" forum, we are try to adhere to the higher standards on the quality of discussion. This means that references and sources must be of the same standard. This hopefully will prevent discussions at the level of tabloid journalism where dubious sources and any and all garbage are in. It also forces YOU to pay attention to where you are getting your information, and hopefully, educate you on how science is practiced.

Zz.

11. May 21, 2014

### ChrisVer

As already pointed out, string or M theory are just theories - they haven't been disproved or confirmed, because they exist far away from our experimental reaches, and their phenomenological results haven't been found yet (however that's a very difficult way to "disprove" the theory, more oftenly, you are just going to disprove one model out of the theory or something like that).

I'd quote Feynman for the "theory of everything" thing, because asking whether we should search or not for a "theory of everything" is more a philosophical question... we are just exploring nature, if there happens to be a "theory of everything" so be it, if there doesn't so be it- we are just seeking for our own answers.

I don't think physicists at the moment do research on string theory (Glashow's viewpoint?). That's something mathematicians or string theorists do. Physicists are trying to find phenomenological results out of it.

12. May 21, 2014

### micromass

Here you go:

13. May 21, 2014

### Ilja

Would it really explain at least something?

There is an old joke, that according to string theory our universe is exceptional: It is the only one which string theory is unable to explain.

The main problem with string theory is that the focus of research capabilities on string theory leaves no place for any other, independent search for a theory of everything.

14. May 21, 2014

### Bill_K

I was going to post a joke about String Theory, but there were too many of them.

Judging by your indirect references, the two results you're referring to are:

1) The LHC failed to find evidence for Supersymmetry. This only means that the mass of any supersymmetric partners would be beyond the reach of the LHC, about 1 TeV. There were good reasons for hoping that Supersymmetry would show up at relatively low energies, but even though it did not, it's still a reasonable possibility at higher energy.

2) The LHC failed to find micro black holes. This would have been evidence for large extra dimensions, a somewhat far out idea.

String Theory does not really have anything to say about physics at LHC energies, so these two results neither confirm or invalidate it.

15. May 21, 2014

### phinds

Now that's just silly. No one area of study precludes any other area of study.

16. May 21, 2014

### ChrisVer

Although Supersymmetry is a very nice theory, it's even more elusive than string theory...
Because we always expect to find it at some scales, yet it always avoids our detection hahaha.., At least you know that for strings the energies are unreachable and you only search for evidences of it, however for susy you know very much less (even the mass of Higgs is within the limits of MSSM+radiative corrections (<130GeV).
Nevertheless, don't forget some historical facts. When people first proposed the top quark, they were expecting to find it at ~50-70GeV (sorry I don't remember the exact energy). Of course, it finally appeared at ~170-175 GeV.

Of course there are searches outside string theory... However, during several eras in physics, there are some reasons why people like a theory more than others- because it seems more consistent/predictive. That was one of the reasons QCD dropped away string theory for some decades. But again it's a matter of personal view (some people like string theorists, some others don't consider them to be physicists- as I stated above Glashow belongs to the 2nd group).

Also the person who will come and tell you that he has the theory that describes everything, either his theory is wrong or he won't be a physicist hahahaha (joke)

Last edited: May 21, 2014
17. May 21, 2014

### Staff: Mentor

Now that's just naive.

I said that tongue in cheek, but Lee Smolin has argued (in his book The Trouble with Physics, among other places) that the stronghold of string theory has has stifled research in other theories of quantum gravity, through funding and tenure.

18. May 23, 2014

### MathematicalPhysicist

What are the limits on the mass of supersymmetric partners?

I mean, in the future we might have a faster particle accelerator, and they may argue the same argument as you do now, that we need a faster accelrator.

If they don't have some falsifiable limits on the bounds of the masses, then it's not even a theory.
It may even postulate that the energies are infinite, in which case you can never really know if the theory is right or wrong.

19. May 23, 2014

### PAllen

String theory makes very definite predictions about physics at the Planck energy. That is still like zero compared to infinite energy. However, it might as well be infinite compared to current technology.

20. May 23, 2014

### MathematicalPhysicist

What is the interval of required energies?

I understand that 1 Tev is in the lower end.

21. May 23, 2014

### craigi

Although string theory has taken many twists and turns and many physicists have concerns about the amount of research effort put into it, which could be directed towards other theories of quantum gravity, I think this has been over exaggerated in popular writings, recently.

It's popular to note that string theory has been in development for decades and hasn't yet been confirmed by experiment, but it's also important to note that it hasn't been excluded by experiment either. In fact, to disprove it at low energies, where almost all observational data is gathered, would involve disproving QFT itself, which would be much more problematic.

Amongst other things, string theory has given us the AdS/CFT correspondence, which although it is still conjecture, is widely accepted in theoretical physics and has found uses in our understanding QFT and black holes.

Is string theory a ToE? I'd say probably not because it doesn't tell us how the vacuum of our universe is selected, but it's certainly a useful mathematical description, which could form a subset of, or a limiting case of, a ToE.

Last edited: May 23, 2014
22. May 23, 2014

### ChrisVer

The limits for mass particles don't come from Supersymmetry I guess, they come from the models of Supersymmetry. So models can of course be wrong-
I remembered the value- when the top quark was proposed (right after the discovery of bottom), the models we made proposed that it should have a mass of roughly 17GeV... they didn't find it there, so they said it must be around 30, 40, 50GeV the most.... The top quark appeared at 170GeV, and from that we get some lesson. Firstly, the nature will show itself up as it is and not as we want it to be. And secondly, we don't know why the top quark must be so heavy.

23. May 23, 2014

### ChrisVer

Well, since supergravity is the extension of string theory at lower energies, and since sugra gives us the susy breaking mechanism that allows $E_{vacuum}$ to take zero (or almost zero-as we measure it today-) value, isn't that a possible answer to how it's chosen?

24. May 23, 2014

### MathematicalPhysicist

Wait a minute, how do they know that it's a top quark before detecting it?

I mean presumably it has some properties that were detected and thus they concluded that it's a top quark. What properties are they looking for in supersymmetry that were'nt detected yet?

I mean this enterprise of research can last for decades (unless people who fund this research will be fed up with no experimental results).

This reminds me of the bet:
http://longbets.org/12/

Just less than 6 more years to go.

25. May 23, 2014

### ChrisVer

Some I guess didn't expect such a big divergence to the quarks' masses... And since they found the bottom at ~4GeV, they wouldn't expect the next one to be at 170GeV. And models probably were built to give them this result too.. of course they failed, but also we knew there should be the 6th quark after finding the 5th... That's how it works....
We weren't bored of quarks or leptons,and chose to bring about their superpartners to have more fun... SuSy fixes some problems which are pretty strong, as the gauge hierarchy problem (of course next to SuSy there are more candidates)

At the moment?
They are looking at LHC for enough missing energy (that will be LSP leaving the detectors).
http://physics.aps.org/synopsis-for/10.1103/PhysRevLett.112.201802

Or cosmological searches, for WIMPs maybe...