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My understanding was that has always been the basis for string theory the math works out very nicely and it is so beautifully self consistent, it is elegant, ma

My understanding was that has always been the basis for string theory the math works out very nicely and it is so beautifully self consistent, it is elegant, mathematically sound and ornate, it has everything anyone could ever want from a theory of everything, except for having any actual testable thesis, making any real predictions, and actually providing any real direction to anything besides funding committees.

erdos4d 5y ago
Perfect for long careers built on publication output.
ChrisLomont 5y ago
It has made some nice post-dictions: things spring out of that we do see, things not built into the model to start, which also lends credence.
prvc 5y ago
Without understanding any of the details whatsoever: if it does provide a simpler explanation of known phenomena only, shouldn't it then be adopted by Occam's Razor?
- Out_of_Characte 5y ago
  Any theory has to have predictability, meaning your theory is more relyable in explaining every future phenomenon than the current working theory. without that your theory is as good as claiming 'god' or divine intervention at every corner.
- ndsipa_pomu 5y ago
  With a similar lack of knowledge, I believe that although conceptually simpler, the maths is much harder to work with.
- pfortuny 5y ago
  Yes but it does nothing of the sort…
  - prvc 5y ago
    Ah... there's the rub.
- mypastself 5y ago
  Prior to reading Brian Greene’s The Elegant Universe, I was unfamiliar with the details, but under the assumption that the string theory is sound. Greene is one of its chief popularizers (as well as a minor researcher), and writes with great clarity on the topic. I enjoyed the book. Yet I ended up becoming agnostic on the string theory after reading it. There seem to be some genuine contributions to mathematics, but those are side products. The theory has yet to make any correct predictions regarding physics and our understanding of the universe, and it is likely completely unfalsifiable. To this layman, a lot of it seem like a bunch of extraordinarily smart people twisting their minds (and our conception of the universe) into a pretzel attempting to make post hoc explanations of existing phenomena.
- naasking 5y ago
  > if it does provide a simpler explanation of known phenomena only, shouldn't it then be adopted by Occam's Razor Yes, but it doesn't describe known phenomena only, it describes things we haven't seen, things we can't ever see, and can be tweaked so much that it can accommodate phenomena that we know can't be true.
ogogmad 5y ago
The maths isn't rigorous and well-defined AFAICT. There aren't any definitive equations either, as far as I know. However, there are some cool geometric observations like AdS/CFT. There are some very polemical critics of string theory like Peter Woit and Sabine Hossenfelder, who suggest that it's a complicated philosophy that started off simple and neat, encountered some problems, and then grew in complexity and vagueness.
- bopbeepboop 5y ago
- drdeca 5y ago
  Well, the math for QFT isn’t on as clear cut foundations as it could be either, is my understanding. (No one has proven that there is a 3D QFT for anything more than U(1), iirc? Or maybe even for U(1) ? Idr. There’s a prize for showing one iirc.) I don’t think that contradicts the claim of the mathematical beauty motivating things.
  - ogogmad 5y ago
    There aren't any definitive equations of string theory AFAICT. For the Standard Model, there are. This is on top of the lack of rigour that's already in QFT. The result is a theory that isn't really mathematics as mathematicians understand it, and nor is it physics as many physicists understand it.
marcosdumay 5y ago
> math works out very nicely and it is so beautifully self consistent AFAIK, nobody knows if it's self consistent yet. Beauty is on the eye of the beholder. But I count "unsolvable" as a very ugly trait.
pontus 5y ago
The entire point of string theory not being testable is not specific to string theory but rather to quantum gravity. Any theory of quantum gravity will only deviate from our current understanding (general relativity) at the Planck Scale. So, if one has an issue with string theory not being testable, one actually has an issue with pursuing any version of quantum gravity. The interesting thing about string theory that sets it apart from all other theories of quantum gravity is that it's actually not just a theory of gravity. Because of this, there is actually hope that string theory could produce nontrivial testable predictions at energy scales much lower than the Planck Scale. However, it turns out that teasing out these predictions is very nontrivial, primarily because of a structure called the string landscape. Basically it turns out that the equations of string theory, while being tidy at high energy, produce a multitude of solutions at low energy and, unless you know which solution to look at, making definitive predictions is hard. Normally the way around a situation like that is to make some observations and try to constrain which solution we should look at. Unfortunately our current best understanding of the landscape is only one-way; we can't currently constrain which solution to look at based on observational evidence. It's sort of like a one-way hash. If we can invert this 'hash function', we could in principle make measurements to constrain which solution we're in and at that point string theory would be falsifiable.
- tsimionescu 5y ago
  The bigger problem is that some of String Theory's few predictions have in fact been falsified. Supersymmetry has been predicted twice already, once at LHC energy levels and once before. Those predictions turned out wrong, but instead of abandoning the theory, it was easily tweaked to make a new prediction at a slightly higher energy level that LHC can predict. The very fact that such tweaks can be made is a known problem with string theory as a component of physics.

erdos4d 5y ago

Perfect for long careers built on publication output.

ChrisLomont 5y ago

It has made some nice post-dictions: things spring out of that we do see, things not built into the model to start, which also lends credence.

prvc 5y ago

Without understanding any of the details whatsoever: if it does provide a simpler explanation of known phenomena only, shouldn't it then be adopted by Occam's Razor?

Out_of_Characte 5y ago
Any theory has to have predictability, meaning your theory is more relyable in explaining every future phenomenon than the current working theory. without that your theory is as good as claiming 'god' or divine intervention at every corner.
ndsipa_pomu 5y ago
With a similar lack of knowledge, I believe that although conceptually simpler, the maths is much harder to work with.
pfortuny 5y ago
Yes but it does nothing of the sort…
- prvc 5y ago
  Ah... there's the rub.
mypastself 5y ago
Prior to reading Brian Greene’s The Elegant Universe, I was unfamiliar with the details, but under the assumption that the string theory is sound. Greene is one of its chief popularizers (as well as a minor researcher), and writes with great clarity on the topic. I enjoyed the book. Yet I ended up becoming agnostic on the string theory after reading it. There seem to be some genuine contributions to mathematics, but those are side products. The theory has yet to make any correct predictions regarding physics and our understanding of the universe, and it is likely completely unfalsifiable. To this layman, a lot of it seem like a bunch of extraordinarily smart people twisting their minds (and our conception of the universe) into a pretzel attempting to make post hoc explanations of existing phenomena.
naasking 5y ago
> if it does provide a simpler explanation of known phenomena only, shouldn't it then be adopted by Occam's Razor Yes, but it doesn't describe known phenomena only, it describes things we haven't seen, things we can't ever see, and can be tweaked so much that it can accommodate phenomena that we know can't be true.

ogogmad 5y ago

The maths isn't rigorous and well-defined AFAICT. There aren't any definitive equations either, as far as I know. However, there are some cool geometric observations like AdS/CFT. There are some very polemical critics of string theory like Peter Woit and Sabine Hossenfelder, who suggest that it's a complicated philosophy that started off simple and neat, encountered some problems, and then grew in complexity and vagueness.

bopbeepboop 5y ago
drdeca 5y ago
Well, the math for QFT isn’t on as clear cut foundations as it could be either, is my understanding. (No one has proven that there is a 3D QFT for anything more than U(1), iirc? Or maybe even for U(1) ? Idr. There’s a prize for showing one iirc.) I don’t think that contradicts the claim of the mathematical beauty motivating things.
- ogogmad 5y ago
  There aren't any definitive equations of string theory AFAICT. For the Standard Model, there are. This is on top of the lack of rigour that's already in QFT. The result is a theory that isn't really mathematics as mathematicians understand it, and nor is it physics as many physicists understand it.

marcosdumay 5y ago

> math works out very nicely and it is so beautifully self consistent AFAIK, nobody knows if it's self consistent yet. Beauty is on the eye of the beholder. But I count "unsolvable" as a very ugly trait.

pontus 5y ago

The entire point of string theory not being testable is not specific to string theory but rather to quantum gravity. Any theory of quantum gravity will only deviate from our current understanding (general relativity) at the Planck Scale. So, if one has an issue with string theory not being testable, one actually has an issue with pursuing any version of quantum gravity. The interesting thing about string theory that sets it apart from all other theories of quantum gravity is that it's actually not just a theory of gravity. Because of this, there is actually hope that string theory could produce nontrivial testable predictions at energy scales much lower than the Planck Scale. However, it turns out that teasing out these predictions is very nontrivial, primarily because of a structure called the string landscape. Basically it turns out that the equations of string theory, while being tidy at high energy, produce a multitude of solutions at low energy and, unless you know which solution to look at, making definitive predictions is hard. Normally the way around a situation like that is to make some observations and try to constrain which solution we should look at. Unfortunately our current best understanding of the landscape is only one-way; we can't currently constrain which solution to look at based on observational evidence. It's sort of like a one-way hash. If we can invert this 'hash function', we could in principle make measurements to constrain which solution we're in and at that point string theory would be falsifiable.

tsimionescu 5y ago
The bigger problem is that some of String Theory's few predictions have in fact been falsified. Supersymmetry has been predicted twice already, once at LHC energy levels and once before. Those predictions turned out wrong, but instead of abandoning the theory, it was easily tweaked to make a new prediction at a slightly higher energy level that LHC can predict. The very fact that such tweaks can be made is a known problem with string theory as a component of physics.