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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

#101

Post by eggy »

TheOtherHobbes wrote: post #71
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…

>I've got a theory that string theory is more of a sociological phenomena than real science. Yes. I have a friend with a PhD in physics, and he says that a generation of string theory people basically just shouted everyone else down in a rather obnoxious way. Other critics (e.g. Lee Smolin) have said similar things, albeit slightly more politely. At some point it stopped being science and became more about careers, r…

Yes, I am glad about this blog too.

Lee Smolin's 2006 book 'The Trouble with Physics' first alerted me to this, since I am not a string theorist, and I like to read about the applied physics going on instead. I would like to read the theoretical math, but my mind can only deal with beginning grad-level math at most. Nonetheless, I like to burn some wood and try at times. I just don't want to waste it on what is seeming to be more and more of a rabbit hole.

Re: Why not string theory? Because enough is enough

#102

Post by iofj »

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.

Think of it this way :

"I have solved all of math, physics, and everything else ! Look ! My theory is simply the assembly programming language. Any problem can be expressed in it and anything that we can predict we can predict using some assembly language".

You wouldn't consider this to actually predict anything, right ? Despite the statement being perfectly true. Change any prediction into the assembly program printing it out. Done/done. So the critique of string theory is that it is such a form of assembly language. It is a general principle, that can express nearly any algorithm.

So generally one considers that any theory, for it to be a theory, has to predict things unrelated to why it was originally designed, with no changes (or at the very least, very minimal changes). Quantum theory, for instance, was designed to solve a particular problem relating to electrons, but turned out to solve the ultraviolet catastrophe (and dozens of other problems).

Re: Why not string theory? Because enough is enough

#103

Post by erikpukinskis »

tormeh wrote: post #98
erikpukinskis wrote: post #44

Earlier quoted context omitted.

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."

Supervised learning is what I'm talking about and it's not a solution to the frame problem. The human handler knows roughly the answers they looking for, and the machine learns details. The machine isn't discovering a new idea, it's just learning how to perform well inside a very small, well defined game that a human made.

Re: Why not string theory? Because enough is enough

#104

Post by justifier »

tim333 wrote: post #66
XorNot wrote: post #14

Earlier quoted context omitted.

It's a fundamental mistake to assume that these are "real" strings being talked about. String theory is about the idea that reality is best modeled as, notionally, strings - i.e. the mathematics looks a bit like them if you sort of squint and look at it really hard. But there's a really good reason strings are a compelling here: because near as we can tell, vibrational frequency is really important to particle physic…

>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 think attempts at popularising of a lot of science is hindered by language compression

for instance, calling one element hydrogen and another helium from a natural language perspective seems to imply they are completely different things when in reality they are essentially the same thing differently configured that interact with the universe in completely different ways

as for strings, my understanding is they are particles considered with consequence

from the wiki(o):

> The starting point for string theory is the idea that the point-like particles of quantum field theory can also be modeled as one-dimensional objects called strings.

so zero dimensional objects, or particles, modeled as one dimensional objects, or vectors, or lines, or.. erm, strings?

string theory is concerned with interactions, map these interactions through point-likes: . . . ; and you get a string : .-._. ;

like how animation has individual, often disparate, frames but our eyes model the scene as a fluid, consistent, connected string of motion (i)

but these are mathematical models stead something you can tie your shoe with (ii)

from this explanation strings explaining the double slit makes sense because 'particles should act this way, why do they reliably act a different way' is answered by saying 'interactions'

that said, i dislike the probabilistic explanation of quantum mechanics which seems entwined with double slit explanations and as such my hope is future science will show the outcome of the double slit is a consequence of bad assumptions about the experiment and its equipment stead some underlying universal expression of quantum mechanics

https://www.youtube.com/watch?v=qDii69YCh_Q

(o) https://en.wikipedia.org/wiki/String_theory#Strings

(i) https://en.wikipedia.org/wiki/Nude_Descending_a_Staircase,_N... nsfw? art

(ii) https://en.wikipedia.org/wiki/A_rose_by_any_other_name_would...

Re: Why not string theory? Because enough is enough

#105

Post by lmm »

logicallee wrote: post #100
Trombone12 wrote: post #77

Earlier quoted context omitted.

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 ge…

> 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?

Models like e.g. the heliocentric solar system, or even relativity, weren't developed that way - they were developed by noticing flaws or incompatibilities in existing models, and proposing a better explanation for them. (The much-touted "experimental verification" of relativity in an eclipse was a nonsense - the errors were as large as the measurements - but it didn't matter; the theory was elegant enough to be obviously correct).

String theory is mostly still at the fiddling-with-the-epicycles-and-thought-experiments stage. But at least it has a model that contains a) standard QM and b) a graviton. None of the competition has even got that far (and there's little reason to think they ever will in most cases).

Re: Why not string theory? Because enough is enough

#106

Post by dnautics »

ellyagg wrote: post #13
dnautics wrote: post #10

"[A]cademia is currently organized so that it invites communal reinforcement, prevents researchers from leaving fields whose promise is dwindling, and supports a rich-get-richer trend." A really awesome quote there. (Perhaps a bit self-serving for me).

(Perhaps a bit self-serving for me). So you think she's biased in pointing out that academia has systemic biases?

sorry, that parsed poorly.

It's a bit self serving for me. I operate a science nonprofit outside of traditional academia.

Re: Why not string theory? Because enough is enough

#107

Post by [deleted] »

lmm wrote: post #105
logicallee wrote: post #100

Earlier quoted context omitted.

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 ge…

> 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? Models like e.g. the heliocentric solar system, or even relativity, weren't developed that way - they were developed by noticing flaws or incompatibilities in existing models, and proposing a better explanation for them. (The much-touted "experimental v…

[deleted]

Re: Why not string theory? Because enough is enough

#108

Post by Gibbon1 »

jerf wrote: post #96
yoha wrote: post #61

Earlier quoted context omitted.

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 ser…

Whack realization of the day for me at least.

Epicycles --> Taylor series.

Re: Why not string theory? Because enough is enough

#109

Post by pdonis »

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

> /s/magnetic/electric

Same answer as I gave before.

Re: Why not string theory? Because enough is enough

#110

Post by wolfgke »

zamalek wrote: post #49
narrator wrote: post #42

Earlier quoted context omitted.

This sounds like the scientific equivalent of "overfitting" in machine learning. The point of a theory is not to predict the training set well, but to generalize well to new cases. This is what string theory fails at.

NNs are modeled after the human brain. It's not an immensely crazy to point out that we could be overfitting ourselves by continuously exposing ourselves to a single theory.

The successful backpropagation algorithm works completely different from anything that has been observed in the human brain up to now.
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