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String theory and m theory

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I just watched a video on String theory and they mentioned something about M theory, can anyone explain how they are related at least just a little bit?

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Ok, first string theory, There is a field of physics called particle physics that describe the shitload of different particles that exist. This is more like biology than physics. They divide them in different groups and give them different names. For calculation they use a system called the "standard model" which is very good at predicting the different features of the different particles. Now the problem is that the standard model is not compatible with anything else (quantum field theory, quantum gravity, theory of relativity etc). So these particle physicists invented the "string theory" that tries to connect it all.

The problem is that their only interest is in keeping the standard model. They don't care a bit about string theory giving completely BS results and explanations for the rest of physics. As long as their beloved standard model works they don't give a rats ass that it means that for it to work, you have to introduce seven or eight new dimensions in the world.

A load of crap, if you ask me.

Now as for "M-theory", I had to google it and found this. Apparently M-theory is a form of a patch that makes different flavours of string theory work together. It's a typical string theory. Instead of questioning how reasonable it is to have a set of contradicting theories, they just slap on another dimension to make it work together.

And all this is just theory and speculation. There has been no evidence at all supporting any string theories.

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Denoir, I'm dying to know, and I'm sure others are too. What do you do for a living, where were you educated and how the hell do you know about this stuff! wow_o.gif

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I'm an electrical engineer. I'm currently doing my master's thesis on neural networks. I was educated at the Royal Institute of Technology in Stockholm. smile_o.gif

I know this stuff because I've taken a couple of mandatory courses in modern/quantum physics. Plus I was recently at a lecture given by Stephen Hawking on the string theory.

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I'm an electrical engineer. I'm currently doing my master's thesis on neural networks. I was educated at the Royal Institute of Technology in Stockholm. smile_o.gif

I know this stuff because I've taken a couple of mandatory courses in modern/quantum physics. Plus I was recently at a lecture given by Stephen Hawking on the string theory.

Oh, O.K., tounge_o.gif ,I suppose a young wipper snapper like myself aspires to have such knowledge. I'm in my final exams at the moment, Physics exam Friday. Then no more physics till Uni......wohooo! wink_o.gif

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Hey denoir your university isnt listed at his site yet and neither is that lecture ...

http://www.hawking.org.uk/info/iindex.html

All his lectures are pasted there as well , i read the guys got a motor neurone disease but his research looks very good i must say , for a person with so many trouble in his life. sad_o.gif

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It hasn't been updated. Did you miss this part?:

Quote[/b] ]Up and coming lectures will be announced here - check back often to find out what is planned.

Professor Hawking is currently planning a trip to Sweden in August

Concretely, here's the lecture in question.

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It hasn't been updated. Did you miss this part?:
Quote[/b] ]Up and coming lectures will be announced here - check back often to find out what is planned.

Professor Hawking is currently planning a trip to Sweden in August

Concretely, here's the lecture in question.

No i did say 'YET' ....

I d/lded all his lectures on the website make for an interesting read when your free  biggrin_o.gif

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A load of crap, if you ask me.

Well, I wouldn't go so far as that tounge_o.gif.

Now the problem is that the standard model is not compatible with anything else (quantum field theory, quantum gravity, theory of relativity etc).

First of all, the Standard Model is itself a quantum field theory, and through that virtue it is compatible with the special theory of relativity. The Standard Model is an excellent description of three of the four fundamental forces of physics, i.e. the electromagentic, weak and strong force (gravity being the fourth).

The fundamental problem arises when combining the Standard Model (or any quantum theory) with Einsteins Theory of Gravity. This hasn't been solved yet and String theory is a possible way out.

The problem is that their only interest is in keeping the standard model. They don't care a bit about string theory giving completely BS results and explanations for the rest of physics. As long as their beloved standard model works they don't give a rats ass that it means that for it to work, you have to introduce seven or eight new dimensions in the world.

In a sense, it is essential to keep the Standard Model because it explains our world so well. In fact, most physicists think the major problem of the Standard Model is that it is so good!! There does not seem to be any room for improvement. The only hard facts for physics beyond the Standard Model currently are neutrino oscillations and of course gravity (which has not been in the scope of particle physics because at the level of single particles, gravity is negligible).

It is generally agreed that the Standard Model is not the final answer, because it is constructed just to work and not from some fundamental idea. E.g., in the Standard Model, one can not calculate the masses of particles, they have to be put in by hand. This does not mean that the Standard Model is wrong, though. Every new theory must incorporate the Standard Model.

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HOW THEY RELATE TO OFP:

String Theory:

The first explanation given as to why a public variable hasn't been working. (i.e. "Dude1: My publicVariable script doesn't work in MP! Dude2: Are you passing a string?")

M Theory:

The main explanation given as to why your script/function/mission doesn't work in general. It usually involves a little guy who's name ends in "urphy". His full name cannot be uttered due to the enormous amount of bad luck associated with it. Therefore, this theory of explanation is designated "M".

Side Note: While this is only a theory, several theories also by the "M" have been proven and designated as "Laws".

ghostface.gif  

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...

Hehe, yes sir dr Spinor sir. Typically my luck that the probably only particle physicist in the community happens to see this thread  wink_o.gif

Quote[/b] ]In a sense, it is essential to keep the Standard Model because it explains our world so well. In fact, most physicists think the major problem of the Standard Model is that it is so good!!

It's only particle physicist that think that. Objectivly looking, it's not a very good physical model as it's not founded on any general theory. It's just a method for calculation and categorization. The particle zoo that is a direct effect of it's lack of general theory is a good example of why it's bad physics.

As for string theory, it's very arbitrary since there is no empirical evidence to support it. From a more general point of view it's also not very appealing to accept a theory that has been tailor made to look good for one small area but that largely ignores its consequences in the rest of the physics. While it is an improvement in particle physics, it entirely destroys the simplicity and elegance of the general theory of relativity. String theory tries to force space-time, energy and intrinsic properties into a complete mess, just so that they can keep their little standard model clean. IMO that's not good physics.

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Quote[/b] ]It's only particle physicist that think that. Objectivly looking, it's not a very good physical model as it's not founded on any general theory. It's just a method for calculation and categorization. The particle zoo that is a direct effect of it's lack of general theory is a good example of why it's bad physics.

The main goal of a physical theory is not to be founded on some profound idea (although, that would be nice) but to make falsifiable predictions that can be tested in experiment. In that regime, the Standard Model (SM) is extremely succesful, because with it, one was able to predict certain particles and their properties before they were dicovered. Also, calculations in the SM agree with experiment to a very high degree.

Anyway, it is not really true that the SM is only a classification scheme. It is based on the most profound theoretical idea yet tested called gauge symmetry. Taking gauge symmetry for granted, it is absolutely necessary to introduce the forces as they are observed. It is not necessary to put them in by hand. This was a major theoretical step forward.

Also, the particle zoo observed is not a result of the SM. It's simply what is seen in experiment.

Just to make sure, I also think that the SM is not the final word. I'm quite sure there is a better theory, but the experimental hints and evidences (and everything in physics hinges on them) are not enough yet.

Quote[/b] ]As for string theory, it's very arbitrary since there is no empirical evidence to support it.

No doubt about it, and I would still classify string theory more as mathematics than physics.

Quote[/b] ]From a more general point of view it's also not very appealing to accept a theory that has been tailor made to look good for one small area but that largely ignores its consequences in the rest of the physics.

I don't know to much about string theory history but AFAIK, string theory was not tailor made, but was dicovered accidentally and its nice properties (and some not so nice ones) were dicovered later.

Quote[/b] ]While it is an improvement in particle physics, it entirely destroys the simplicity and elegance of the general theory of relativity.

Yeh, but why should the general theory of relativity be so sacred. GTR deals with stuff on large scales like planets, stars and galaxies. It is not tested on the small scale. On the other hand particle physics is succesful on small scales. In a way, it is quite natural that upon combining them there arise problems. In fact, IMHO, this is the most outstanding problem in physics at the moment.

Quote[/b] ]String theory tries to force space-time, energy and intrinsic properties into a complete mess, just so that they can keep their little standard model clean. IMO that's not good physics.

I say again, it is absolutely necessary to keep the Standard Model clean because it explains the observations to such a high degree that it is very improbable that it is completely wrong. Take gravity as an analogy: Newtons theory of gravity is not wrong, it is an approximation (for small velocities and mass densities) to Einsteins theory.

In the same sense, both the Standard Model and General Relativity might become approximations to some more fundamental theory, might that be string theory or something else.

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So in short....String theory is another attempt...or at least working towards a TOE? (Theory Of Everything)

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Yup (although, "Theory for Everything" sounds a little too ambitious to me), its an attempt to unify all known forces in one scheme. It is even claimed that String theory will explain all particles and their properties like masses.

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/waits for denoir and bn880 to yak about it.

Heh, no way not me, I'm not arguing with Denoir until I have solid proof he is right. tounge_o.gif lol

I'm staying out of this one for sure. smile_o.gif I think such a discussion could carry on for years and cartainly never bring a solution, though it will inform a lot of people, so it's pretty good.

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Anyone interested in this area of physics living in the UK might like to watch Channel 4 on Sun @ 8pm, 2nd part of a three part series on TOE.

*Goes to C4 to collect advertising revenue!*

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Anyone who wants it explained visually, click here!

-Post

That was the show I watched, except on tv smile_o.gif

So what about those "membranes"? How do they relate to the whole theory?

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The main goal of a physical theory is not to be founded on some profound idea (although, that would be nice) but to make falsifiable predictions that can be tested in experiment.

True, but you can't have it both ways. If you're designing a theory of everything then you have to have a core belief that there is some nice idea behind it and you can't stay attached to a practical method like the standard model. While the string theory gives nice results for the standard model the effects on the macro scale ain't pretty. And if you have the ambition of making a grand unified theory, then it better be based on a nice general idea. Otherwise you have not achieved anything.

Quote[/b] ]Yeh, but why should the general theory of relativity be so sacred. GTR deals with stuff on large scales like planets, stars and galaxies. It is not tested on the small scale. On the other hand particle physics is succesful on small scales. In a way, it is quite natural that upon combining them there arise problems. In fact, IMHO, this is the most outstanding problem in physics at the moment.

Yeah, but there is a scaling issue that isn't equivalent. You can't falsify general relativity by looking at the small scale since the effects are too small to measure. You do get however troubeling issues if you try to apply quantum mechanics to GR.

Quote[/b] ]

I say again, it is absolutely necessary to keep the Standard Model clean because it explains the observations to such a high degree that it is very improbable that it is completely wrong. Take gravity as an analogy: Newtons theory of gravity is not wrong, it is an approximation (for small velocities and mass densities) to Einsteins theory.

Yeah, let's look at that. I present to you the denoir's theory of everything that unites newtonian mechanics (NM) and quantum mechanics (QM). No GR needed. And it's done the string theory way.

Quote[/b] ]

A: I've discovered a way to unite newtonian gravity and mechanics with quantum mechanics,

B: Bullshit. NM is continuous while QM is discreete, you can't combine them.

A: Yes I can, I just add another dimension. In normal 4-d space-time it looks like the particles jump discreetly between energy levels but actually they continue their real path in that new dimension.

B: What about Schrödinger's equation and the randomness?

A: No problem. I just add another dimension to fix that. That's where the hidden variables are hidden.

B: Ok, what about the problem with __ (insert problem here)?

A: That's no problem. It's all solved in and because of a new dimension n+1

And that's string theory in a nutshell for ya. Have a problem? Introduce a new dimension. Don't be bothered that it does not make any physical sense. On the contrary, the less common sense there is, the better. Everybody loves relativity and quantum mechanics because of their oddness, right? They'll just adore this one. Add some mathematical quirks as well, just to be sure..

The string theory is exactly like that. They wanted a nice theory for the standard model and they wanted to make it general. Unfortunately the problem has always been that quantum mechanics doesn't go very well with general relativity. So their solution was to focus on one and make a nice solution for it and entirely ignore the effects on the others. And all the plumbing and all the patches were made by introducing new dimensions:

Listen fellas' how's this for a solution: we add another dimension!

Now while that is a sound mathematical solution, it does not make any sens physically. These people keep forgetting that physics isn't creative writing but that you have to base your theories on observed data.

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So does that mean OFP's wheeled vehicles with missiles bug could be fixed by adding another dimension? tounge_o.gifwink_o.gif

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Quote[/b] ]True, but you can't have it both ways. If you're designing a theory of everything then you have to have a core belief that there is some nice idea behind it and you can't stay attached to a practical method like the standard model.

Sure, a fundamental theory has to have a profound basis. The Standard Model never aimed for this. I think you don't have a proper feeling of what the Standard Model actually is. It is not just a huge bunch of rules and calculation method just created to explain the experiments. It is a very concise and mathematical consistent theory that (using proper mathematics) fits on a sheet of paper, and which happens to explain 99.9% of all particle physics phenomena.

The only thing that prevents the Standard Model from being fundamental is that you have to insert certain parameters like the electron mass by hand. A fundamental theory should be able to explain these.

Quote[/b] ]Yeah, but there is a scaling issue that isn't equivalent. You can't falsify general relativity by looking at the small scale since the effects are too small to measure.

You can test gravity at smaller scales. I think, currently, gravity is tested down to the millimeter scale and efforts are being made to go down further. In fact, this can be a test of stringy theories because additional dimensions would change gravity at small distances.

Quote[/b] ]You do get however troubeling issues if you try to apply quantum mechanics to GR.

Hehe, but who's fault is it? By virtue, QM is a theory for small scales. Almost all its effects are washed out on large scales. Hence, no interference between GR and QM at large scales. At small scales, QM is tested to a very high degree, GR is not.

Quote[/b] ]Listen fellas' how's this for a solution: we add another dimension!

Now while that is a sound mathematical solution, it does not make any sens physically. These people keep forgetting that

physics isn't creative writing but that you have to base your theories on observed data.

Yeah, but this is how many physical theories start. Again, take the Standard Model as example: With it, one was able to predict the existence of the top quark and was even able to calculate its mass before the top was actually discoverd.

If you take string theory for granted, you are stuck with additional dimensions. Why not? It is a prediction of this theory and efforts are being made to test this, either by checking gravity, as mentioned above or through effects at particle colliders, like the Large Hadron Collider that is being built at the moment. Maybe nothing is found, but if it is, it would really be a revolution in physics.

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Quote[/b] ]True, but you can't have it both ways. If you're designing a theory of everything then you have to have a core belief that there is some nice idea behind it and you can't stay attached to a practical method like the standard model.

Sure, a fundamental theory has to have a profound basis. The Standard Model never aimed for this. I think you don't have a proper feeling of what the Standard Model actually is. It is not just a huge bunch of rules and calculation method just created to explain the experiments. It is a very concise and mathematical consistent theory that (using proper mathematics) fits on a sheet of paper, and which happens to explain 99.9% of all particle physics phenomena.

The only thing that prevents the Standard Model from being fundamental is that you have to insert certain parameters like the electron mass by hand. A fundamental theory should be able to explain these.

I never said anything about the standard model having that aim. I said that string theory had and if they want to keep their credibility they have to let go of their attachment for the standard model.

And unfortunately I've had some experiences with the standard model in two courses that I took (high-energy physics and plasma physics) - apart from the basics that was covered in our QM course.

Why did I not like it?

1) The idea of having six quarks + six leptons plus the four force carriers seems more like biology than proper physics to me. It's phenomenology and not a nice general model like for instance GR or electromagnetic field theory. This is a vague argument, yes, but I'm a believer of symmetry in the nature and I have a hard time believing that anything could be so ugly as the standard model. Why are there three generations of matter?

2) It can't predict particle masses. This is a good indicator of an incomplete theory. The mass patterns of the particles have no correspondence whatsoever to the categorization that the standard model predicts.

3) Can you say "dark matter"?

So why do physicists like the standard model and by extension string theory? Unfortunately physics has been split into smaller and smaller areas with physicists specializing in their own very narrow domains. In practice it means that they don't have a general overview.

All physicists don't like the string theory. Particle physicist do since it's convenient for them and they don't bother to check if there is anything else out there beyond their CKM matrices. It works perfectly with their primary tool: the standard model, and that's all they want to know.

Cosmologists for instance generally loath the string theory and think it's a load of drivel. You should check out what people like Stephen Hawking think of the string theory. (IMO his theories of quantum singularity physics is equally whacked, but that's another story).

Having said that, I don't deny that the standard model is a very successful model in terms of predicting experimental results in particle/high-energy physics. Sort of reminds me of all the different theories we had in the end of the 19th century before QM entered the scene (you know, Balmer series etc). They were all very successful at predicting experimental results but they lacked a fundamental theory.

Quote[/b] ]You can test gravity at smaller scales. I think, currently, gravity is tested down to the millimeter scale and efforts are being made to go down further. In fact, this can be a test of stringy theories because additional dimensions would change gravity at small distances.

Millimeter scale? Hehehe. Call me when you get down to 6.62e-34 J/s. Then we can talk on small scale. Millimeter scale is no different than interplanetary distances for QM.

Quote[/b] ]If you take string theory for granted, you are stuck with additional dimensions. Why not?

Because there is no reasonable motivation for introducing those dimensions apart from patching things up to work with GR. String theory is like a badly conditioned function fit. It goes nicely through the points that represent the SM but gives horrible results elsewhere. THe problem with string theory is that it's exclusivly built around the standard model, as if that was the only relevant theory in the world. String theory does not give a rat's ass about the results it brings to the rest of the physics.

And I guess that's what bothers me - it's a very narrow minded theory. No matter how good the SM is for particle physics, there is more to the world then just the standard model. And building a theory of everything exclusivly around the standard model is well, plain wrong.

Quote[/b] ] like the Large Hadron Collider that is being built at the moment.

A bit offtopic, but I've always wondering how the hell they manage to get funding for such projects. Huge accelerators that cost billons of euros to build that not so seldom only serve to track down one or two hypothetical particles. Where's the relevance in finding a new quark that's charmed, strange and up. Whoa, what a discovery. What is the value for man kind in that? I don't get the value of this reductionist approach to physics. There's a shitload of data already on elementary particles. Stop building bloody accelerators and take a paper and a pencil and make a proper theory about them instad. Invest the money in telescopes or something.  rock.gif Or even better in pencils and papers for theoretical physicists. wink_o.gif

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I once visited an accelerator in Hamburg/Germany (called DESY; Deutsches(German) Electron SYnchrotron, iirc). And they said that there are in fact some interresting/side effects/products from those accelerators. One I remember was the Synchrotron radiation, that they used as a light source to create very small structures, e.g. for micro- or nanotechnology. The quality of this light was much better then the usual lasers. (but don't quote me on that, the visit was ~12 years ago...)

While only remotely related to this topic, the speed of light beaten!?

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