5 ms·

As far as I understand the main problem of string theory is that it has been carefully constructed to fit all the physics we know about, and has not actually pr

by tinco 5y ago

As far as I understand the main problem of string theory is that it has been carefully constructed to fit all the physics we know about, and has not actually predicted anything we didn't already know about that we could experimentally verify. So in a practical sense string theory has been quite useless. If indeed it is true that string theory predicts this effect, and the effect can be experimentally verified (afaik this was dubious at best) then that would be a huge boon for string theory.

tsimionescu 5y ago
Well, string theory has actually predicted Supersymmetry, which so far seems not to exist (though it is always possible to say it exists only on some higher energy than we can detect right now).
- qubex 5y ago
  As I understand it, supersymmetry was taken as a concept and baked into the strings concept, to come up with superstrings. So it’s not really a prediction as much as it is baked-in by the prevailing notions of the time.
xvilka 5y ago
It's possible to test string theory experimentally, just the amount of energy required is far too big for any foreseeable future. With a bruteforce approach, at least.
tzs 5y ago
> As far as I understand the main problem of string theory is that it has been carefully constructed to fit all the physics we know about. Doesn't string theory have a lot fewer tunable parameters than the standard model? > and has not actually predicted anything we didn't already know about that we could experimentally verify I don't like that argument for a couple of reasons. First, it depends on the timing of when we discover things. If the experimentalists had taken longer to discover some things a theory that we would criticize today as not predicting anything we don't already know about would be a theory that would be celebrated for its predictions if it had just been posed earlier. I think a better thing to look at is if a theory can correctly calculate things that weren't built into the theory. I remember reading [1] that string theory correctly calculated some things concerning black holes that none of the people who had developed string theory to that point knew about. Second, I don't like it from a philosophical point of view. It suggests that if say some pre-Newton gravity theorist had just included enough epicycles, science should have rejected Newtonian gravity because it would not have explained anything that the epicycle theory didn't. [1] Probably either in Brian Greene's "The Elegant Universe" or Lawrence Krauss' "The Greatest Story Ever Told--So Far". Possibly Greene's "The Fabric of the Cosmos", but that seems unlikely. I distinctly remember reading it, and my copy of "The Fabric of the Cosmos" is an audiobook. The other two are Kindle books.
- tinco 5y ago
  > I think a better thing to look at is if a theory can correctly calculate things that weren't built into the theory. I remember reading [1] that string theory correctly calculated some things concerning black holes that none of the people who had developed string theory to that point knew about. Well if that's true, then string theory definitely isn't useless, so I'd be interested in the specifics. This prediction from string theory wasn't explained by any of the accepted physical models? > Second, I don't like it from a philosophical point of view. It suggests that if say some pre-Newton gravity theorist had just included enough epicycles, science should have rejected Newtonian gravity because it would not have explained anything that the epicycle theory didn't. Well yeah, but why not reject Newtonian gravity if everything observable can be predicted by the epicyclical view? The goal is not to generate pretty models, the goal is to make accurate predictions of the physical universe, ideally through the simplest model we can come up with just to guard against overfitting. Anyway, it's not that I (or anyone, I don't have any physics authority certainly :P), am rejecting string theory, it's just that as far as I understand string theory hasn't had any real use to our physical models. I certainly don't have an alternative to string theory.

by tinco 5y ago

tsimionescu 5y ago

Well, string theory has actually predicted Supersymmetry, which so far seems not to exist (though it is always possible to say it exists only on some higher energy than we can detect right now).

qubex 5y ago
As I understand it, supersymmetry was taken as a concept and baked into the strings concept, to come up with superstrings. So it’s not really a prediction as much as it is baked-in by the prevailing notions of the time.

xvilka 5y ago

It's possible to test string theory experimentally, just the amount of energy required is far too big for any foreseeable future. With a bruteforce approach, at least.

tzs 5y ago

> As far as I understand the main problem of string theory is that it has been carefully constructed to fit all the physics we know about. Doesn't string theory have a lot fewer tunable parameters than the standard model? > and has not actually predicted anything we didn't already know about that we could experimentally verify I don't like that argument for a couple of reasons. First, it depends on the timing of when we discover things. If the experimentalists had taken longer to discover some things a theory that we would criticize today as not predicting anything we don't already know about would be a theory that would be celebrated for its predictions if it had just been posed earlier. I think a better thing to look at is if a theory can correctly calculate things that weren't built into the theory. I remember reading [1] that string theory correctly calculated some things concerning black holes that none of the people who had developed string theory to that point knew about. Second, I don't like it from a philosophical point of view. It suggests that if say some pre-Newton gravity theorist had just included enough epicycles, science should have rejected Newtonian gravity because it would not have explained anything that the epicycle theory didn't. [1] Probably either in Brian Greene's "The Elegant Universe" or Lawrence Krauss' "The Greatest Story Ever Told--So Far". Possibly Greene's "The Fabric of the Cosmos", but that seems unlikely. I distinctly remember reading it, and my copy of "The Fabric of the Cosmos" is an audiobook. The other two are Kindle books.

tinco 5y ago
> I think a better thing to look at is if a theory can correctly calculate things that weren't built into the theory. I remember reading [1] that string theory correctly calculated some things concerning black holes that none of the people who had developed string theory to that point knew about. Well if that's true, then string theory definitely isn't useless, so I'd be interested in the specifics. This prediction from string theory wasn't explained by any of the accepted physical models? > Second, I don't like it from a philosophical point of view. It suggests that if say some pre-Newton gravity theorist had just included enough epicycles, science should have rejected Newtonian gravity because it would not have explained anything that the epicycle theory didn't. Well yeah, but why not reject Newtonian gravity if everything observable can be predicted by the epicyclical view? The goal is not to generate pretty models, the goal is to make accurate predictions of the physical universe, ideally through the simplest model we can come up with just to guard against overfitting. Anyway, it's not that I (or anyone, I don't have any physics authority certainly :P), am rejecting string theory, it's just that as far as I understand string theory hasn't had any real use to our physical models. I certainly don't have an alternative to string theory.