B Is string theory dead or still valid

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It's loosing momentum...

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

As Ive 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

Science Advisor
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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.
 
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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

Gold Member
565
500
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.
 
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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.
 

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