B Is string theory dead or still valid

[Fra]

To me, it becomes a bit suspicious how every time something initially bad for string theory turns out to be good. Just sayin'.

I think this is another manifestation of "duality". There is no such thing as, good or bad, it is all just a matter of choice of background context ;-)

/Fredrik

 

[phyzguy]

It seems to me that the name "string theory" is a misnomer. A theory in physics is a model where I can do calculations and compare the results of these calculations withe experiment. SInce this isn't (yet) the case in string theory, I think it would be more appropriate to call it the "string concept" or the "string idea".

 

[PeroK]

It seems to me that the name "string theory" is a misnomer. A theory in physics is a model where I can do calculations and compare the results of these calculations withe experiment. SInce this isn't (yet) the case in string theory, I think it would be more appropriate to call it the "string concept" or the "string idea".

... or "string thing"?

 

[haushofer]

It seems to me that the name "string theory" is a misnomer. A theory in physics is a model where I can do calculations and compare the results of these calculations withe experiment. SInce this isn't (yet) the case in string theory, I think it would be more appropriate to call it the "string concept" or the "string idea".

Well, string theory is a 2-dimensional (superconformal) quantum field theory. But quantum field theory in itself is a paradigm, not a theory. So I guess that's where the bad naming starts.

Regarding experiments: I think people doing AdS/CFT would disagree. String dualities are testable.

 

[phyzguy]

Well, string theory is a 2-dimensional (superconformal) quantum field theory. But quantum field theory in itself is a paradigm, not a theory. So I guess that's where the bad naming starts.

Regarding experiments: I think people doing AdS/CFT would disagree. String dualities are testable.

Quantum Field Theory can do detailed calculations that can be compared to experiment in exquisite detail. Things like scattering amplitudes and the electron or muon magnetic moment. It's not at all like string theory in that respect.

Can you name a "string duality" that has been tested against observations?

 

[ohwilleke]

Didn't someone invent a bunch of dimensions in order to make the theory compatible with other theories but are the extra dimensions right or correct.

String theory has never been established to be a valid description of the real world. But, it isn't dead. A plurality of theoretical physicists in the world are still working on it.

 

[Islam Hassan]

String theory has never been established to be a valid description of the real world. But, it isn't dead. A plurality of theoretical physicists in the world are still working on it.

Well as Niels Bohr might say, ST —or any other theory for that matter— cannot describe the actual, real, underlying world of particle physics, it can only say something about it.

In that sense ST has said a lot, a whole whole lot over 40+ years now. Maybe too much for some people’s taste.

The day all that can be tied to a feasible experimental set-up, ST will explode. I would think cosmology is a better candidate to provide that experimental link one day than HEP/particle physics...maybe with the Webb space telescope and some high-resolution soundings of black holes?...IH

 

[Dr. Courtney]

Didn't someone invent a bunch of dimensions in order to make the theory compatible with other theories but are the extra dimensions right or correct.

The question, "Is string theory dead or still valid?" highlights a common failure of science education that instills (or allows) folks to frame scientific questions as false dichotomies when it comes to the validity of theories.

It is more complicated than "dead or still valid."

Scientific theories are never really proven, but given a long enough track record of making testable predictions that are later confirmed, one can say a theory is well supported and validated. String theory never came anywhere near this.

Scientific theories can also be disproven by experimental results that contradict their predictions. String theory has not really suffered this fate either, since there have not been many (or any) real predictions within the abilities of modern experiments to test them.

The ups and downs of string theory have been more like a scientific popularity contest falling in and out of favor (and funding) rather than really meeting the fundamental scientific tests of validity or testability.

https://blogs.scientificamerican.com/cross-check/why-string-theory-is-still-not-even-wrong/

 

[FactChecker]

Can you name any testable predictions made by M-theory and tell us how the results compare to observations? I would not consider it "valid" until it is an actual theory where one can do calculations and compare the results to observations. I do not think that this is yet the case.

I have always thought that a statement like this deserved some discussion. Clearly the theory agrees with many facts that were already known. The difference between those earlier-known facts and later-confirmed predictions is just the timing of the development of the theory. Of course, one must be sceptical of theories that were rigged to agree with already known facts, but I think there should be better criteria applied than the simple timing of the development of a theory. Some theories fit very simply into earlier accepted theories while others seem like "Rube Goldberg" contraptions.

 

[MathematicalPhysicist]

It's undead.
A zombie!

 

[phyzguy]

I have always thought that a statement like this deserved some discussion. Clearly the theory agrees with many facts that were already known.

Can you give an example of a known fact that is derivable from string theory and explain how it is derived from the set of string theory assumptions?

 

[FactChecker]

Can you give an example of a known fact that is derivable from string theory and explain how it is derived from the set of string theory assumptions?

I have no expertise on this subject, so I can not. My question / comment is a general one that keeps occurring to me when the issue comes up. I just assumed that there were some constraints on the theory. If there are no constraints at all, either to fit facts already known or to predict results, then I don't know what the purpose of the theory is. It never occurred to me, till you asked, that the theory may not fit any already known facts.

 

[phyzguy]

I have no expertise on this subject, so I can not. My question / comment is a general one that keeps occurring to me when the issue comes up. I just assumed that there were some constraints on the theory. If there are no constraints at all, either to fit facts already known or to predict results, then I don't know what the purpose of the theory is. It never occurred to me, till you asked, that the theory may not fit any already known facts.

You are the third person in this thread who has made the claim that string theory makes testable predictions, and the third person who has been unable to name one when I challenged them. I think, as I said in post #32, that string theory is not a "theory" in the sense that we usually mean. It is more a set of ideas that might some day be concise enough to allow predictions to be made.

 

[FactChecker]

an

You are the third person in this thread who has made the claim that string theory makes testable predictions, and the third person who has been unable to name one when I challenged them. I think, as I said in post #32, that string theory is not a "theory" in the sense that we usually mean. It is more a set of ideas that might some day be concise enough to allow predictions to be made.

Sorry if I wasn't clear. Let me clarify my earlier post. Are you saying not only that it can not make predictions of new things to be verified, but also that it does not fit and support any already tested facts? That would be a strong statement that you are making and it leaves the obvious question: What motivated the theory if it can't explain anything we already know and can't predict anything new. The difference between the two cases is only the chronology of the facts being verified versus the development of the theory.

 

[cosmik debris]

What motivated the theory if it can't explain anything we already know and can't predict anything new.

It looks pretty?

Cheers

 

[phinds]

What motivated the theory if it can't explain anything we already know and can't predict anything new.

The early developers thought it eventually WOULD make testable predictions. Even after forty years of none such some of them apparently have still not changed their minds.

 

[mitchell porter]

In this thread, @JorisL was the actual string theorist.

You can see how the mainstream of string theory thinks it could apply to reality, at last year's string phenomenology conference.

 

[rootone]

String theories have not been shown to be either true or false.
A lot of things are like that.

 

[MathematicalPhysicist]

String theories have not been shown to be either true or false.
A lot of things are like that.

So they are metaphysics theories.

 

[Islam Hassan]

It looks pretty?

Cheers

That would seem to be one very big attraction. Despite the complex maths vs Occam’s razor, ST would seem to have some very elegant mathematics behind it.

String theorists are betting that it is a big, huge, comprehensive and immensely complex version of Dirac’s equation out of which anti-matter miraculously ‘plopped’ out, that its elegant maths predict boatloads of unsuspecting physics...that its mathematics are an Oracle...IH

 

[Mehe]

It's loosing momentum...

Regarding physics I am just a layman, so please bare with me :)

As I've understood the string theory is just a mathematical theory (metaphysics), which has not been confirmed directly or indirectly in any targeted experiments.
Before LHC went online there where high hopes that string would be confirmed by it (e.g. the loss of energy when colliding particles, which would confirm the extra dimensions).
But for now, I guess, its still the best contender for a unified theory.

So, the search for a unified theory is still up for grabs, if anyone is bored

 

[haushofer]

I wouldn't use the word "metaphysics", but "paradigm". Technically, string theory is a quantum field theory of strings (and branes), so in the hierarchy of paradigms string theory is a subset of quantum field theories.

 

[George Jones]

please bare with me :)

But we are a family-oriented forum.

 

[bobob]

String theory isn't exactly dead, but it's languishing out in the landscape (or swampland). I'll give my personal opinion here since the lack of any real experimental predictions makes my opinion no better or worse than anyone else's. In all likelyhood, some of the work done on string theory will turn out to be useful, but whether or not that part which is useful has much to do with string theory is a crap shoot. For one thing, no one really understands string theory (of which there are many that have been slurped up into M theory). There are still physicists working on string theory, but I think that number is shrinking due to an inability to calculate anything remotely in reach of any real experiment. In addition, the problem of the landscape is a rather crippling result.

I think that what most physicists would like to think in lieu of anything definite to the contrary is that the universe is unique in the sense that the there is some underlying physical principle that leads to a universe with the forces and particles we observe rather than the lanscape in which this univere is but one of a gazillion possiblities, that just happened to produce this universe (followed by some who have followed that idea down the rabbit hole of multiverses.) The second most desirable theory is one which leads to our universe as just one of many possibilities, but that makes it very clear that it HAS to be that way for universe to exist. This is far less satisfying, but better than string theory and the landscape which allows zillions of possible universes without being able to show that the theory could actually lead to the one we are living in (e.g., the standard model doesn't follow from string theory, or if it does, no one has yet been able to start with string theory and obtain the standard model in some limit.)

So, string theory has lost a bit of it's glamour as a theory of everything and although it isn't dead, it's not exactly going anywhere in a hurry and without some sort of a miracle breakthrough, the amount of attention it receives and the number of students who will be heading off to study string theory is likely to dwindle. I doubt it will ever die completely, but only because the mathematics and formalism developed will be useful in other contexts.

Or, to put it another way, doing a thesis on string theory is probably a lot less likely to get someone a job than it used to.

 

[pinball1970]

String theory isn't exactly dead, but it's languishing out in the landscape (or swampland). I'll give my personal opinion here since the lack of any real experimental predictions makes my opinion no better or worse than anyone else's. In all likelyhood, some of the work done on string theory will turn out to be useful, but whether or not that part which is useful has much to do with string theory is a crap shoot. For one thing, no one really understands string theory (of which there are many that have been slurped up into M theory). There are still physicists working on string theory, but I think that number is shrinking due to an inability to calculate anything remotely in reach of any real experiment. In addition, the problem of the landscape is a rather crippling result.

I think that what most physicists would like to think in lieu of anything definite to the contrary is that the universe is unique in the sense that the there is some underlying physical principle that leads to a universe with the forces and particles we observe rather than the lanscape in which this univere is but one of a gazillion possiblities, that just happened to produce this universe (followed by some who have followed that idea down the rabbit hole of multiverses.) The second most desirable theory is one which leads to our universe as just one of many possibilities, but that makes it very clear that it HAS to be that way for universe to exist. This is far less satisfying, but better than string theory and the landscape which allows zillions of possible universes without being able to show that the theory could actually lead to the one we are living in (e.g., the standard model doesn't follow from string theory, or if it does, no one has yet been able to start with string theory and obtain the standard model in some limit.)

So, string theory has lost a bit of it's glamour as a theory of everything and although it isn't dead, it's not exactly going anywhere in a hurry and without some sort of a miracle breakthrough, the amount of attention it receives and the number of students who will be heading off to study string theory is likely to dwindle. I doubt it will ever die completely, but only because the mathematics and formalism developed will be useful in other contexts.

Or, to put it another way, doing a thesis on string theory is probably a lot less likely to get someone a job than it used to.

Lee Smolin made a video outlining a couple of predictions made by the theory that did not pan out. I have searched but cannot find it. I'll keep looking but think was related to cosmological constant.

 

[jlcd]

Modern Physicists are still following the footsteps of Einstein in his latter years. Remember he spent nearly 40 years working on unification of forces without success. Einstein only knew gravity and electromagnetism then. Quarks wouldn’t even be discovered until a decade after his death. Electroweak unification took a few more years after that. There’s no realistic way to discover a unified field theory without taking those things into account.

String theorists and most physicists nowadays are in similar situation. They thought they have taken into account all forces of nature or dynamics and tried to build unified theory out of it. They still miss key phenomena exactly like Einstein did.

Half a century from now, when it will finally be discovered. Then all things will fall into place and we will finally have the theory of everything (whether it is string theory or other more elegant theory we do not know yet).

However, I worry whether in 2070 the world will be in a state of tranquility or chaos. https://edition.cnn.com/2019/06/04/health/climate-change-existential-threat-report-intl/index.html

If climate change indeed causes existential threat and wars break out. There may be no robust scientific institutions and infrastructure and resources to focus on it. Or even if it was discovered in 2070 it may be too late. The theory will itself include the physics that will address the balance of Gaia and make Earth a pristine beauty it once was (for example as ilustration something related to the magnetic field and stuff in the sun that causes strange readings and even dip in frequency). Today should be the best time for the Theory of Everything that can improve the lives of very human being on Earth but unfortunately physicists see the world only through biased lens. I only hope they discover it sooner so instead of a dark dystopian future, we will have a golden age of physics and the best era ever in our civilization. The decision whether humanity lives or perishes is in our hands.