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Why not string theory? Because enough is enough

backreaction.blogspot.com

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Re: Why not string theory? Because enough is enough

#91

Post by tremon »

yoha wrote: post #61
throwaway43 wrote: post #18

Earlier quoted context omitted.

It's called adding epicycles : http://rationalwiki.org/wiki/Adding_epicycles

I mostly agree, but I'd argue that epicycles actually made useful and testable predictions, although we found a simpler description later on. The article underlines a lack of refutable theories. Thus, I think [1] is a better analogy. [1] http://rationalwiki.org/wiki/The_Dragon_in_My_Garage

Perhaps off-topic, but I really like the classification of that article:

This might be Skepticism but we're not sure

Re: Why not string theory? Because enough is enough

#92

Post by tim333 »

macspoofing wrote: post #83
tim333 wrote: post #66

Earlier quoted context omitted.

>really good reason strings are a compelling here: because near as we can tell, vibrational frequency is really important to particle physics I can give a sort of counter argument. Fair enough the relationship between frequency and energy and also wavelength and momentum are fundamental to physics. But consider maybe the classic experiment where you demonstrate that, where you have a barrier with two slits and fire p…

>I can give a sort of counter argument. You can't because you clearly have an incredibly shallow understanding of string theory (I do too). For one thing, you're completely stuck on the metaphor of the 'string' and you're trying to apply it to a very shallow understanding of Quantum Mechanics and complaining that it doesn't make sense. Okay. I think it's cool to talk about fundamental research but taking it one step…

Yup I don't understand it. I'm not convinced others really do either though.

Re: Why not string theory? Because enough is enough

#93

Post by dwc »

colordrops wrote: post #16

The author says that he "became more convinced [string theorists] are merely building a mathematical toy universe." The explanation for his conclusion was that they kept revising string theory in order to fit observations. I know little of string theory, so I am probably misreading his meaning, but isn't that how all science works? Create a model, then revise it when you get more data.

Theories serve multiple purposes. A theory can be useful to make calculations about things you already know. Or to make predictions about things you don't yet know. String theory has been adapted over time to be able to calculate things we already know. But we already had that without string theory. But the predictive part is where string theory really falls down. It's track record there is abysmal.

On the other end of the predictive spectrum there's Einstein. Somebody fiddles with the equations and says, "if this is right then there could be black holes!" And then... they find black holes. It seems that every few years there's some confirmation of an odd corner case that shows the predictive power of Einstein's theories.

That string theory can calculate the known might still be useful, if it's a more convenient way to get the results than other theories. Plain old Newtonian physics is still hella useful today, for instance, even for space missions. AFAIK, string theory is not more convenient.

Take this with a grain of salt, because I haven't kept up on what string theory has been doing lately. As a matter of personal triage I stopped following it until such time as I heard that someone predicted something interesting with it, and it was confirmed in observation or experiment. If that happened then I missed it, and would love to hear about it.

Re: Why not string theory? Because enough is enough

#94

Post by thaumasiotes »

stephengillie wrote: post #12
pdonis wrote: post #7

Earlier quoted context omitted.

> you have two electrons in space a few cm apart and the accelerate away from each other due to the charges repelling. I'm not sure how that is supposed to happen if everything is strings. At the level of quantum theory, you don't have charges repelling. You have charged particles, like electrons, exchanging other particles--photons in the case of the electromagnetic force. So really it's all particles (or all quantu…

Do photons quantize and transmit the electric force? Are charged particles constantly sending a continuous stream of photons out in all directions? I'm genuinely curious and haven't had luck finding this with Google - neither sites that confirm this, nor those that deny it. Edit: /s/magnetic/electric

> I'm genuinely curious and haven't had luck finding this with Google - neither sites that confirm this, nor those that deny it.

Wikipedia talks about this. https://en.wikipedia.org/wiki/Force_carrier .

> The electromagnetic force can be described by the exchange of virtual photons.

Re: Why not string theory? Because enough is enough

#95

Post by auntienomen »

tim333 wrote: post #92
macspoofing wrote: post #83

Earlier quoted context omitted.

>I can give a sort of counter argument. You can't because you clearly have an incredibly shallow understanding of string theory (I do too). For one thing, you're completely stuck on the metaphor of the 'string' and you're trying to apply it to a very shallow understanding of Quantum Mechanics and complaining that it doesn't make sense. Okay. I think it's cool to talk about fundamental research but taking it one step…

Yup I don't understand it. I'm not convinced others really do either though.

There's a minimum threshold of understanding required to make intelligent commentary on topics like this. Muddled pop-sci and half remembered undergrad material doesn't cut it.

Re: Why not string theory? Because enough is enough

#96

Post by jerf »

yoha wrote: post #61
throwaway43 wrote: post #18

Earlier quoted context omitted.

It's called adding epicycles : http://rationalwiki.org/wiki/Adding_epicycles

I mostly agree, but I'd argue that epicycles actually made useful and testable predictions, although we found a simpler description later on. The article underlines a lack of refutable theories. Thus, I think [1] is a better analogy. [1] http://rationalwiki.org/wiki/The_Dragon_in_My_Garage

The characteristic of metaphorical epicycles is that the make simple, testable predictions that are then wrong, which are fixed with another epicycle.

Another more subtle aspect of epicycles, real ones this time, is that they are too powerful and can be used to prove anything. You can predict the motion of the planets with epicycles, it's just that the required series is very long or infinite. And with very long series of cycles, you can "predict" anything: https://youtu.be/QVuU2YCwHjw?t=25s Thus, one of the problems with epicycles both real and metaphorical is that they are indeed not refutable. Because epicycles can predict anything, they aren't that useful; they exclude far less than meets the eye at first.

It isn't hard to see that characterist showing up in string theory. The theory has for a very long time had problems with excluding possibilities, and each new metaphorical "epicycle" seems to come with more parameters than the last, rather than fewer. Now, this isn't unique to string theory since all the current theories seem to have that problem, but then, the point is, why does this problematic theory have so much more support and money than the other problematic theories?

Re: Why not string theory? Because enough is enough

#97

Post by Aelinsaar »

tim333 wrote: post #3

I've got a theory that string theory is more of a sociological phenomena than real science. It started as a genuine attempt to model how the nucleus was held together and then continued because it's a good area to do maths and write papers rather than because it models reality. One thing I don't get, which may be down to my own stupidity - take maybe the simplest interaction in physics - you have two electrons in spa…

The issue with string theory isn't an inability to explain what standard QM can explain, it's the problem that so many formulations of it may not be falsifiable. Making predictions along aside another falsifiable, real theory, without offering falsifiable predictions yourself... that's where String theory finds itself for the most part.

There are still some formulations that haven't been ruled out by observations such as LHC data, but not many, and they're not necessarily the ones that were anyone's darlings.

Re: Why not string theory? Because enough is enough

#98

Post by tormeh »

erikpukinskis wrote: post #44
visarga wrote: post #30

This is probably a naive question: can we input a bunch of particle interactions into a deep learning system and train it to predict the probability of future interactions? It would be like a "black box version" of physics. If we can predict, then we can find a more elegant mathematical notation and a more intuitive physical interpretation. Machine learning can observe and learn patterns that are more complex than hu…

I don't think so. I wish the Frame Problem[1] got talked about a little more, because it's one of the fundamental challenges for intelligent beings/systems. I think we'd see fewer grandiose claims about AI if people spent a little more time pondering it. But I'm getting ahead of myself. You can think of the Frame Problem as the problem babies have when they first enter the world. You've got eyes that can look anywher…

That's been solved by the most basic approach to ML: Supervised learning. A simplistic way to describe it would be that you say to the ML algorithm: "Here's two states, one at time N and one at time N+1. Your task is to predict the state at N+1 given the state at N. We have a bazillion of such state-pairs that you can test and refine your model on. Go nuts."

Re: Why not string theory? Because enough is enough

#99

Post by eli_gottlieb »

seanmcdirmid wrote: post #37
visarga wrote: post #30

This is probably a naive question: can we input a bunch of particle interactions into a deep learning system and train it to predict the probability of future interactions? It would be like a "black box version" of physics. If we can predict, then we can find a more elegant mathematical notation and a more intuitive physical interpretation. Machine learning can observe and learn patterns that are more complex than hu…

The idea that the universe runs on a simple program with simple rules hasn't failed us so far. All we have to do is figure out what that simple program is with our capability for abstract symbolic thinking and reasoning; machines are presently very bad at this while humans are less bad at it.

>The idea that the universe runs on a simple program with simple rules hasn't failed us so far.

Uhhhh... yes it has. The universe has myriad levels at which a simple program works. If the universe "really" runs on a simple program with simple rules, it's got so large a parameter space that even knowing the program itself is mostly useless to us.

https://arxiv.org/abs/1303.6738

Re: Why not string theory? Because enough is enough

#100

Post by logicallee »

Trombone12 wrote: post #77
colordrops wrote: post #16

The author says that he "became more convinced [string theorists] are merely building a mathematical toy universe." The explanation for his conclusion was that they kept revising string theory in order to fit observations. I know little of string theory, so I am probably misreading his meaning, but isn't that how all science works? Create a model, then revise it when you get more data.

You misunderstand, first: it is not the case that new observations about the world forced the changes. Instead, it is mostly observations about the internal properties of string theory which has forced modifications. After it was proposed as a self-consistent theory of quantum gravity it was realized it wasn't self-consisten because it had ghosts, which was then fixed by adding 22 dimensions. But this is a problem be…

Don't the "best" models make surprising predictions that we go out of our way to design experiments to collect data for - and find that they are, in fact, accurate?

Has string theory made a single prediction anyone went out of their way to test, finding it accurate?

I don't have a problem with shoveling in a bunch of dimensions. If it's shovelled in carefully so as not to predict anything that can be tested, I can get that entertainment from watching flat Earth videos though.

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