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Comment by tim333 | Hacker News Reader

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 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. Do they ping tiny strings at each other and how do they know which way to aim? Maybe some string person can enlighten me.

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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 physics - the energy of a photon is quantized as E=nhf , (Energy = integer * planck's constant * frequency). And this seems to scale all the way down - it works for photons, it works for electron orbitals, and it comes into play dealing with the virtual particles which are exchanged in force interactions.

So however you describe reality, whatever you do, your abstraction pretty assuredly needs to somehow recover the vibrational importance, which implies certain kinds of "geometry". You get "strings" because strings are one of the most fundamental structures which can hold a vibrational mode, and importantly, they kind of neatly explain the quantization as standing waves - closed strings can only setup a standing wave at certain frequencies depending on their length, same with open strings (the wave needs to be zero at the ends of the "string" or it'll lose energy).

Of course this is all my very ad hoc handwavey explanation of it, but the point is, there's a lot of very basic physics which works quite well in the model. It did not, and does not, just come from nowhere even at this very high level.

>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 particles at it and get an interference pattern on a screen on the other side. You can calculate how close the interference stripes will be using λ = h/p and this works not only for point particles like electrons but more complicated ones like helium atoms or C60 molecules. How do you explain that with strings? There's definitely something going on like the amplitude state of the universe changes according to the difference in momentum for different particle paths but I see no way you can explain it using strings.

> It's a fundamental mistake to assume that these are "real" strings being talked about.

>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 further and saying that some theory X isn't correct because it doesn't make sense to ME, a non-professional physicist, is a step too far. Be more humble.

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.

Fair enough but is my description of two slit interference patterns wrong and is there any way you can explain the result with string theory?

You can explain it with any quantum mechanical theory. Talking about strings here is a red herring. That's why people are calling you out.

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...

>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, reputations, funding, and paper mills. Which, given the way that academia works at the moment, became self-sustaining.

Some interesting math has fallen out of string theory, but it should never have been allowed to hold back other approaches to quantum gravity to the extent that it has.

Considering the amount of time and paper involved, there's a huge wall of maybe-perhaps-if but very little solid physics to show for the effort.

Incidentally, that blog is a real find - some of the clearest explanations of hard concepts I've seen anywhere.

It reminds me a little of the phenomena of efficient market theory in economics / finance. Academics were drawn to it partly because it enables them to do a lot of fancy mathematics whereas if you look at inefficiencies like the stuff that went on in the movie The Big Short then the academics don't really have much of an edge against people working in the field. So much academic stuff goes 'assuming efficient markets', blah blah... which is not actually wrong but maybe a misallocation of resources from looking at bubbles and crashes which could have helped avoid the whole 2006 episode.

I agree the blog seems very good.

It gets more complicated, because there are various `strengths' of efficient market hypotheses around. The weaker ones are obviously true, but the stronger ones are more suspect.

Abstruse Goose also has some deep wisdom about string theory. I particularly like this one:

http://abstrusegoose.com/424

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.

Particles themselves are just models of localized field quantizations. It's a bit analogous to how a person is just a quantification of the molecules they comprise. You can gain and lose new molecules by the millions, but you're still the same person -- like the crest of a wave.

Anyway, particles repel because that is the nature of the fields they exist in. Electrons don't have to do anything 'to' each other to repel, they just have to interact with the electromagnetic field. The string model simply employs the word 'string' to describe some components of the field.

Quantification or quantization? (Autocorrect?)

Quantization. I don't use autocorrect, so it was probably my brain's auto-typing.

Strings are supposed to act like Leptons / quarks / etc. Like how quantum mechanics averages out when your taking about planets. The problem is they are like epicycles in that they can describe any shape. Much like how Epicycles are effectivly taking a fourier transform of an orbit and can thus describe any shape, String theory can describe any possible universe.

Why are this comment and the parent comment downvoted? As someone who doesn't know about string theory it's hard to tell.

> 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 quantum fields, if you look at it another way). And you can make any particle (or quantum field) out of strings, so string theory is just the next level down, so to speak, where all of the particles--the ones that exchange other particles, and the ones that get exchanged--are just different vibration states of strings.

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

> Do photons quantize and transmit the magnetic force?

The magnetic force is just an aspect of the electromagnetic force ("interaction" is the word more commonly used in quantum field theory), so yes.

> Are charged particles constantly sending a continuous stream of photons out in all directions?

Virtual photons, yes; they aren't observed directly, only their effects--what we see as the electromagnetic interaction between charged objects--are observed. At least, that's one way of (heuristically) looking at what is happening. This way of looking at it has limitations, but it can be helpful.

> 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.

> /s/magnetic/electric

Same answer as I gave before.

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.

I've got a theory that string theory is more of a sociological phenomena than real science.

I've got to say, that comes across as awfully dismissive toward a whole lot of very thoughtful people. I'm not entirely sure what you mean by it. Certainly all of the string theorists I've known (it's my profession) have talked as if they believed their work was involved in a "genuine attempt" to model reality.

Maybe a physicist can make a living by just "doing math and writing papers" without any expectation of making meaningful progress toward understanding the world, but the people who really drive the field and get noticed are almost invariably folks who dream of changing the world, of being the next Hawking or Witten or even the next Einstein. If someone like that doesn't have the a pretty solid hope that what they're working on is likely to be truly relevant to reality, they work on something else.

I think that others have already more or less answered your electron question. I might answer it this way: one of the great triumphs of 20th century physics was the realization that the details of how physics works on very small scales (or equivalently, very high energies) get very predictably "blurred out" when phenomena are measured at longer scales (or lower energies). The formal process involved is called "renormalization", and the punchline here is that essentially any ultimate theory of nature (whether that's string theory or something else) will reduce to an ordinary quantum field theory (with "renormalizable" fields) once you get a few orders of magnitude below its intrinsic scale.

That means in particular that any "stringy" physics (or any "loopy" physics, or even any simpler "grand unification" physics) will inescapably be completely washed out and undetectable when electrons interact from a few cm apart. All you need to understand is "simple" quantum electrodynamics, in which the two electrons exert a repulsive force on each other by way of their interactions with the surrounding electromagnetic field: interactions that can be described as being mediated by exchange of virtual photons as force-carrying particles.

For that calculation, it's not at all important to know that (e.g.) each electron is an extremely tiny string in a specific vibration mode, nor that they (more or less) emit and absorb virtual photons by pinching off into new tiny strings or in a different specific vibration mode and then joining back up with them in a uniquely determined way. (This would be a good place for me to note that nobody knows exactly which scenario in string theory would correspond to our world, so nobody actually knows exactly what vibration mode corresponds to an electron. But we know a lot of ways in which things like that might work.) My point here is just that most of the questions you've asked are really quantum field theory questions: the string theory connection is almost entirely unimportant in that regime.

And that, to put it succinctly, is the problem. In the pursuit of a Theory of Everything, you wind up with a Theory of Anything. If there's no particular reason why things are the way they are in this universe, then you're reduced to the simpler observationally-verifiable model anyway since the elegant overarching framework is essentially useless. It becomes a philosophy of the ought rather than a description of the is. A theory that predicts everything predicts nothing.

The reality sting theory try to describe is more general than the reality we can observe. It's like finding the primes for what is possible. The meaning of the primes on the next level up is moot.

Say, you shuffle a deck of cards, and shuffle really well. Now you could spend forever by drawing cards from the deck and analyzing the sequence and trying to think of theories how to predict the next card. But the is no ultimate reason behind why the deck was shuffled into this order and not some other.

Perhaps the shape of natural laws (the four fundamental interactions) and the values of natural constants have been arrived at by a similar process. Perhaps there is a multiverse of different universes with different variations of these natural laws, and we just happen to live in this one.

If this is how our universe came to be, shouldn't we be ready to accept it, instead of searching meaning where there is none?

Then again, this is just an idea. And not really even falsifiable. So it's difficult to say if this is even a scientific idea, in the strict sense.

Or perhaps Einstein was right, perhaps God didn't play dice (I am really misusing this phrase here), and there is an underlying mechanistic model which explains everything.

Who knows.

The deck of cards analogy is sort of getting to the anthropic principle -- the natural laws could have come out any number of ways, but most of the other shuffles wouldn't result in us being here to contemplate them.

>most of the questions you've asked are really quantum field theory questions: the string theory connection is almost entirely unimportant in that regime

My issue with the two electrons repelling scenario is that in normal quantum field theory it's modeled, I think, as the exchange of virtual photons and given that we don't really understand what a photon is and that they have odd spread out kind of properties that seem to allow that sort of interaction between distant things I can accept that that happens even if we don't understand how it fully. When you get to "emit and absorb virtual photons by pinching off into new tiny strings" and similar ideas though I just can't see it. My hunch is electrons and photons are in their base nature more abstractly mathematical and attempts to model them as bits of stuff will fail.

I'll be honest: high energy physics isn't really an area where "hunches" carry a lot of weight, at least if those hunches aren't grounded in a pretty thorough understanding of particle physics and general relativity.

The language of "pinching off into new strings" is of course largely an analogy, one which captures some of the mathematical features of string interactions reasonably well while probably obscuring others. What's really going on underneath that analogy is just as "abstractly mathematical" as you could ask for: a (boundary?) conformal field theory defined on the 1+1-dimensional string world sheet, which allows just a single unique self-consistent mode of interaction. It is complicated, but honestly, so is standard quantum field theory when you really dig into it, and if you're familiar with the underlying math and physics this description is surprisingly elegant.

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