10 ms·

Why not string theory? Because enough is enough

189 points by Santosh83 10y ago

kordless 10y ago
> Even with that problem fixed, however, it was quickly noticed that moving the superpartners out of direct reach would still induce flavor changing neutral currents that, among other things, would lead to proton decay and so be in conflict with observation. Dissonance strikes again!
tim333 10y ago
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.
- Retric 10y ago
  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.
  - dcacaac 10y ago
    Why are this comment and the parent comment downvoted? As someone who doesn't know about string theory it's hard to tell.
- pdonis 10y ago
  > 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.
  - stephengillie 10y ago
    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
    - pdonis 10y ago
      > 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.
    - thaumasiotes 10y ago
      > 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 https://en.wikipedia.org/wiki/Force_carrier . > The electromagnetic force can be described by the exchange of virtual photons.
- Retra 10y ago
  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.
  - tamana 10y ago
    Quantification or quantization? (Autocorrect?)
    - Retra 10y ago
      Quantization. I don't use autocorrect, so it was probably my brain's auto-typing.
- Steuard 10y ago
  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.
- XorNot 10y ago
  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.
  - tim333 10y ago
    >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.
    - 10y ago
- TheOtherHobbes 10y ago
  >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.
  - tim333 10y ago
    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.
    - eru 10y ago
      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.
  - semi-extrinsic 10y ago
    Abstruse Goose also has some deep wisdom about string theory. I particularly like this one: http://abstrusegoose.com/424 http://abstrusegoose.com/424
  - 10y ago
- Aelinsaar 10y ago
  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.
stesch 10y ago
Article isn't about TCL.
Steuard 10y ago
Speaking as a professor specializing in string theory, I'd say, "More power to her." I have no idea whether string theory gets too much attention relative to its actual value in modeling the real world, but I think one essential part of finding the right amount of attention for any physical theory is for theorists to make their best judgement about what's worth their time to study. In fact, it's quite comforting to me to see people deciding to focus in other directions: to my eye, that means the system is working (though perhaps the author would argue it's not working efficiently), and I'd hate to see other worthwhile angles of attack wither away purely due to lack of attention. For myself, I got excited about string theory in grad school and decided to go that route, and I'm still finding it fascinating today. (And it still feels worthwhile to keep studying it, though perhaps I'm not quite as optimistic about its ultimate success as I was 15 years ago.)
- tamana 10y ago
  So you feel strong theory connects to reality, and is falsifiable and avoids "piling on epicycles"? Will string theory be more parsimonious than the the more concrete model of physics it tries to model?
  - 4ad 10y ago
    Of course string theory is falsifiable. String theory reduces to quantum field theory in some limit and to general relativity in some other limit. Unlike all the other previous theories, string theory is the theory that has resisted all efforts to falsify it yet. It's a ridiculous misconception floating around that string theory can't make predictions, when in fact string theory is the only theory we have so far that predicts all known observed phenomena.
    - cygx 10y ago
      String theory reduces to quantum field theory in some limit and to general relativity in some other limit. That's nice and clearly shows why string theory research is a worthwhile endeavor, but you only get a gold star once you make an experimentally verified new prediction. There is a reason why people were excited about the discovery of the Higgs boson.
dnautics 10y ago
"[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).
- ellyagg 10y ago
  (Perhaps a bit self-serving for me). So you think she's biased in pointing out that academia has systemic biases?
  - drxzcl 10y ago
    SKDH is as much of a physics insider as they come. So, if anything, she has something to lose.
  - dnautics 10y ago
    sorry, that parsed poorly. It's a bit self serving for me. I operate a science nonprofit outside of traditional academia.
    - deleted 10y ago
      [deleted]
    - ellyagg 10y ago
      Yeah, I realized later it was possible to interpret that sentence another way. I think my downvoter thought I was making a dumb throwaway snark, but I was actually just confused.
      - dnautics 10y ago
        well it's not an expected situation that anyone runs a science nonprofit, so your confusion is understandable.
colordrops 10y ago
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.
- arjie 10y ago
  True, of course. But at some indeterminate point theories start seeming awfully ad-hoc even if they still retain other properties. Let's say I propose that no existing solar panel designs respond to artificial light. Easily falsifiable. Say you perform the experiment and find that panels from First Solar do respond to artificial light. I refine my hypothesis to "no existing solar panel designs respond to artificial light except for First Solar". You find that SunEdison panels do, by testing at your lab in SF. I refine my hypothesis to "no existing solar panel designs respond to artificial light when tested outside San Francisco except for First Solar". You repeat the experiment in San Jose, and I refine my hypothesis again. We're revising the model, keeping it falsifiable, and keeping it consistent with existing evidence. It would not be without merit to claim that this is something of a toy hypothesis, however, and that our time would be better served otherwise.
  - narrator 10y ago
    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.
    - zamalek 10y ago
      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.
      - 10y ago
spectrum1234 10y ago
This ties in with my thinking that there is just too much funding to do research for the sake of research. Let the private sector work on moonshots if they want but more realistically no one should be researching super far out problems. Instead the agile "just in time" approach needs to be used in academia as well as private companies. A good analogy is no one was trying to build electric cars fifty years ago but now they are. But they only are because progress has been made indirectly in other fields to make it worth it now.
- oska 10y ago
  > A good analogy is no one was trying to build electric cars fifty years ago but now they are. People were trying to make electric cars 120 years ago and succeeding. [1] [1] https://en.wikipedia.org/wiki/Electric_car#History https://en.wikipedia.org/wiki/Electric_car#History
  - hugh4 10y ago
    True. On the other hand, nobody was trying to build them fifty years ago.
- MawNicker 10y ago
  Babbage designed a computer almost 200 years ago. We need people to be working on moonshots. A lot of them will fail. When one finally succeeds it pierces the veil of "just in time" capitalistic motivation. The financial incentive is certainly perverse in this case. Everyone sells their ideas up front in a frenzied competition to exist. We need a lot more research for the sake of research. More varied and more useless. We need to find a way for people like Babbage to exist, at scale, while seeking whatever intrinsic motivations drive them. We likely won't be able to know if they're doing anything useful until they're done. Academia needs the ivory tower.
  - archeopterix 10y ago
    But I don't want moonshots, I want moon transit.
- 10y ago
spectrum1234 10y ago
This ties in with my thinking that there is just too much funding to do research for the sake of research. Let the private sector work on moonshots if they want but more realistically no one should be researching super far out problems. Instead the agile "just in time" approach needs to be used in academia as well as private companies. A good analogy is no one was trying to build electric cars fifty years ago but now they are. But they only are because progress has been made indirectly in other fields to make it worth it now.
cygnus_a 10y ago
i vote we change the name. "generalized quantum mechanical phenomena maybe" ... and we can rename quantum gravity to "generalized macroscopic versions of quantum phenomena maybe" then we can add the "maybe" suffix to all the rest of our theories
visarga 10y ago
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 humans can grasp. What if the perfect Physics theory is more complex than humans can understand and possibly quite unintuitive in meaning? Then we won't like it and steer away from it, and that would be a bad thing in the end.
- sidek 10y ago
  So, how many bits are you giving the deep learning machine? If you give it enough bits, you aren't predicting anything -- you're just feeding it experimental data which it more or less spits back out. For an elegant solution, one would need to have deep learning that also optimises on a constrained set of bits. I feel like in this scenario, humans perform much better. The main strength of computer learning is being able to harness a massive dataset and really good storage capabilities. Also, you would need to impose a "consistency" constraint on the computer which would be hard to do. Like a computer might say if (mass > 5) do this; else do that. And that is valid computationally. We do that in our split between gr/qm. But in some sense we feel this is wrong physically. The universe shouldn't run on arbitrary if statements. So I think the answer is just no: the computer algorithms we have today can't handle the problem's constraints.
  - visarga 10y ago
    Enough bits to make it efficient at predicting. When it predicts better than the current theory, it starts getting closer to having enough bits. That's the beauty of ML, you don't need to worry about these details if it gives good accuracy. My intuition was that there could be different ways to explain the laws of Physics that don't look like the current ones which evolved based on human intuition, math and language ability. A non-anthropocentric Physics if you will.
    - 10y ago
woodandsteel 10y ago
The author is taking a different approach called phenomenological quantum gravity that has some promise to be more productive in the long term. http://backreaction.blogspot.com/2013/06/phenomenological-quantum-gravity.html http://backreaction.blogspot.com/2013/06/phenomenological-qu... From what I understand, she and others are trying to understand what empirical differences a quantum gravity theory of any sort would have, and hopefully will come up with one that can be experimentally observed, which in turn would help people figure out what is the correct quantum gravity theory.

189 points by Santosh83 10y ago

> Even with that problem fixed, however, it was quickly noticed that moving the superpartners out of direct reach would still induce flavor changing neutral currents that, among other things, would lead to proton decay and so be in conflict with observation. Dissonance strikes again!

tim333 10y ago

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.

Retric 10y ago
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.
- dcacaac 10y ago
  Why are this comment and the parent comment downvoted? As someone who doesn't know about string theory it's hard to tell.
pdonis 10y ago
> 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.
- stephengillie 10y ago
  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
  - pdonis 10y ago
    > 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.
  - thaumasiotes 10y ago
    > 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 https://en.wikipedia.org/wiki/Force_carrier . > The electromagnetic force can be described by the exchange of virtual photons.
Retra 10y ago
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.
- tamana 10y ago
  Quantification or quantization? (Autocorrect?)
  - Retra 10y ago
    Quantization. I don't use autocorrect, so it was probably my brain's auto-typing.
Steuard 10y ago
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.
XorNot 10y ago
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.
- tim333 10y ago
  >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.
  - 10y ago
TheOtherHobbes 10y ago
>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.
- tim333 10y ago
  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.
  - eru 10y ago
    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.
- semi-extrinsic 10y ago
  Abstruse Goose also has some deep wisdom about string theory. I particularly like this one: http://abstrusegoose.com/424 http://abstrusegoose.com/424
- 10y ago
Aelinsaar 10y ago
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.

stesch 10y ago

Article isn't about TCL.

Steuard 10y ago

Speaking as a professor specializing in string theory, I'd say, "More power to her." I have no idea whether string theory gets too much attention relative to its actual value in modeling the real world, but I think one essential part of finding the right amount of attention for any physical theory is for theorists to make their best judgement about what's worth their time to study. In fact, it's quite comforting to me to see people deciding to focus in other directions: to my eye, that means the system is working (though perhaps the author would argue it's not working efficiently), and I'd hate to see other worthwhile angles of attack wither away purely due to lack of attention. For myself, I got excited about string theory in grad school and decided to go that route, and I'm still finding it fascinating today. (And it still feels worthwhile to keep studying it, though perhaps I'm not quite as optimistic about its ultimate success as I was 15 years ago.)

tamana 10y ago
So you feel strong theory connects to reality, and is falsifiable and avoids "piling on epicycles"? Will string theory be more parsimonious than the the more concrete model of physics it tries to model?
- 4ad 10y ago
  Of course string theory is falsifiable. String theory reduces to quantum field theory in some limit and to general relativity in some other limit. Unlike all the other previous theories, string theory is the theory that has resisted all efforts to falsify it yet. It's a ridiculous misconception floating around that string theory can't make predictions, when in fact string theory is the only theory we have so far that predicts all known observed phenomena.
  - cygx 10y ago
    String theory reduces to quantum field theory in some limit and to general relativity in some other limit. That's nice and clearly shows why string theory research is a worthwhile endeavor, but you only get a gold star once you make an experimentally verified new prediction. There is a reason why people were excited about the discovery of the Higgs boson.

dnautics 10y ago

"[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).

ellyagg 10y ago
(Perhaps a bit self-serving for me). So you think she's biased in pointing out that academia has systemic biases?
- drxzcl 10y ago
  SKDH is as much of a physics insider as they come. So, if anything, she has something to lose.
- dnautics 10y ago
  sorry, that parsed poorly. It's a bit self serving for me. I operate a science nonprofit outside of traditional academia.
  - deleted 10y ago
    [deleted]
  - ellyagg 10y ago
    Yeah, I realized later it was possible to interpret that sentence another way. I think my downvoter thought I was making a dumb throwaway snark, but I was actually just confused.
    - dnautics 10y ago
      well it's not an expected situation that anyone runs a science nonprofit, so your confusion is understandable.

colordrops 10y ago

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.

arjie 10y ago
True, of course. But at some indeterminate point theories start seeming awfully ad-hoc even if they still retain other properties. Let's say I propose that no existing solar panel designs respond to artificial light. Easily falsifiable. Say you perform the experiment and find that panels from First Solar do respond to artificial light. I refine my hypothesis to "no existing solar panel designs respond to artificial light except for First Solar". You find that SunEdison panels do, by testing at your lab in SF. I refine my hypothesis to "no existing solar panel designs respond to artificial light when tested outside San Francisco except for First Solar". You repeat the experiment in San Jose, and I refine my hypothesis again. We're revising the model, keeping it falsifiable, and keeping it consistent with existing evidence. It would not be without merit to claim that this is something of a toy hypothesis, however, and that our time would be better served otherwise.
- narrator 10y ago
  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.
  - zamalek 10y ago
    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.
    - 10y ago

spectrum1234 10y ago

This ties in with my thinking that there is just too much funding to do research for the sake of research. Let the private sector work on moonshots if they want but more realistically no one should be researching super far out problems. Instead the agile "just in time" approach needs to be used in academia as well as private companies. A good analogy is no one was trying to build electric cars fifty years ago but now they are. But they only are because progress has been made indirectly in other fields to make it worth it now.

oska 10y ago
> A good analogy is no one was trying to build electric cars fifty years ago but now they are. People were trying to make electric cars 120 years ago and succeeding. [1] [1] https://en.wikipedia.org/wiki/Electric_car#History https://en.wikipedia.org/wiki/Electric_car#History
- hugh4 10y ago
  True. On the other hand, nobody was trying to build them fifty years ago.
MawNicker 10y ago
Babbage designed a computer almost 200 years ago. We need people to be working on moonshots. A lot of them will fail. When one finally succeeds it pierces the veil of "just in time" capitalistic motivation. The financial incentive is certainly perverse in this case. Everyone sells their ideas up front in a frenzied competition to exist. We need a lot more research for the sake of research. More varied and more useless. We need to find a way for people like Babbage to exist, at scale, while seeking whatever intrinsic motivations drive them. We likely won't be able to know if they're doing anything useful until they're done. Academia needs the ivory tower.
- archeopterix 10y ago
  But I don't want moonshots, I want moon transit.
10y ago

spectrum1234 10y ago

cygnus_a 10y ago

i vote we change the name. "generalized quantum mechanical phenomena maybe" ... and we can rename quantum gravity to "generalized macroscopic versions of quantum phenomena maybe" then we can add the "maybe" suffix to all the rest of our theories

visarga 10y ago

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 humans can grasp. What if the perfect Physics theory is more complex than humans can understand and possibly quite unintuitive in meaning? Then we won't like it and steer away from it, and that would be a bad thing in the end.

sidek 10y ago
So, how many bits are you giving the deep learning machine? If you give it enough bits, you aren't predicting anything -- you're just feeding it experimental data which it more or less spits back out. For an elegant solution, one would need to have deep learning that also optimises on a constrained set of bits. I feel like in this scenario, humans perform much better. The main strength of computer learning is being able to harness a massive dataset and really good storage capabilities. Also, you would need to impose a "consistency" constraint on the computer which would be hard to do. Like a computer might say if (mass > 5) do this; else do that. And that is valid computationally. We do that in our split between gr/qm. But in some sense we feel this is wrong physically. The universe shouldn't run on arbitrary if statements. So I think the answer is just no: the computer algorithms we have today can't handle the problem's constraints.
- visarga 10y ago
  Enough bits to make it efficient at predicting. When it predicts better than the current theory, it starts getting closer to having enough bits. That's the beauty of ML, you don't need to worry about these details if it gives good accuracy. My intuition was that there could be different ways to explain the laws of Physics that don't look like the current ones which evolved based on human intuition, math and language ability. A non-anthropocentric Physics if you will.
  - 10y ago

woodandsteel 10y ago

The author is taking a different approach called phenomenological quantum gravity that has some promise to be more productive in the long term. http://backreaction.blogspot.com/2013/06/phenomenological-quantum-gravity.html http://backreaction.blogspot.com/2013/06/phenomenological-qu... From what I understand, she and others are trying to understand what empirical differences a quantum gravity theory of any sort would have, and hopefully will come up with one that can be experimentally observed, which in turn would help people figure out what is the correct quantum gravity theory.