- #1
- 24,775
- 792
Lieutenant Dax (at the moment newcomer, 5 posts) presented some thoughts/questions about BSM theorizing, string in particular, in hopes of getting some useful or enlightening response from us. I'm taking a chance by copying her initial post(s) here out of context so people can focus on them without it getting mixed up with a more technical discussion.
Please contribute your thoughts on the issues she is raising and let's try to answer any specific questions, if we can.
==first Dax post==
Here is my view. Feel free to squash it if there's reason to.
Isn't the main criticism of String Theory nothing at all to do with falsifiability, use of abstract mathematical trickery, or usefulness?
(It is clear that an unfalsifiable idea may become falsifiable at technology improves. Weird mathematics is not a sign of overstretching ourselves, as was pointed out with regards to hilbert spaces in QM, for example. And nobody doubts the usefulness of string theory and AdS/CFT in pure mathematics for example).
Isn't the primary criticism of string theory that it introduces features uncalled for? What do I mean, well we usually formulate a quantum field theory with 4 space time dimensions and point particles because that is exactly what we observe in nature. Forgive me for being "old-fashioned", but usually we develop a scientific theory by making observations first, then drawing conclusions. We chastise literalist creationists for doing things the opposite way around.
Of course, sometimes theory matures so fast that it gets a little ahead of experiment. String theorists often cite Dirac's theory and the prediction of the positron as proof that it's acceptable to jump the gun. I disagree. While it is clear that Dirac was inspired and a genius to bring special relativity together with quantum mechanics, he didn't introduce anything exotic. No strings, bells, whistles, extra dimensions or any other peculiar entities. His theory assumes point particles and four dimensions, since there was no experimental evidence that anything more than this exists (and there still isn't, as far as I know).
It's also tempting to claim that Planck introduced, seemingly as a random fudge, the quantum in order to explain the unexplainable. "See, there you have it, that's what string theorists do!" they claim. Except that Planck did what he did because there was no other way to explain the data. He knew it felt like a fudge and he felt bad doing it, but it worked well because there was no alternative, and experiment quickly supported the idea (in fact, the experimental proof for the existence of the photon already existed, it was just languishing without explanation).
Then there is the claim that Einstein developed special and general relativity "just by thinking about it", divorced from experiment. String theorists seem to use this idea (which is highly questionable anyway) to validate the claim that they're actually "discovering" new physics all the time. Ed Witten is particularly fond of making this claim, suggesting that by writing equations down we are actually discovering things. But you don't discover things with theory, you explain things with theory. You discover things with experiment. Surely experiment (observation) is the arbiter of truth.
In any case the comparison with Einstein's approach is flawed. Special relativity follows from the requirement that electromagnetism produces invariant results in different reference frames coupled with the constancy of the speed of light, an experimental observation. General relativity follows from these things but obviously not straightforwardly otherwise it wouldn't have taken him another ten years, but general relativity is as devoid of exotic concepts as it can be. Curved space time is a necessity, and was quickly confirmed experimentally, just as Planck's hypothesis was.
Another claim I've noticed that string theorists make is that it does in fact originate from experiment, because it was proposed to explain the strong force (another attempt to parallel the introduction of the quantum, for example). However, this hypothesis was rejected in favour of QCD which (unsurprisingly in my view) in based on point particles and four dimensions, nothing uncalled for and nothing unobserved. So what is the continuing motivation for studying string theory as a candidate for explaining nature (as opposed to just mathematical interest)?
It may finally be tempting to say that unification is the motivation, but although it looks compelling, there is not yet any proof that all the forces are unified. Making the coupling strengths match at the appropriate energy scale required altering the standard model so I remain unconvinced. Physics may or may not be unified. It is my firm belief that experiment will tell us whether or not all of the forces are unified together, and how they are (we don't even have a grand unified theory minus gravity yet!).
Isn't it also clear that Einstein, if we wish to follow his career with interest (which string theorists understandably like to), was far more successful in his early years. What distinguished his early career? In his younger years, he studied experimental results, unsolved problems and he reaped large results from listening to nature. In his later life, he tried to dictate to nature, and he made little progress. The rest of the physics community viewed him as an old timer who'd lost touch. And yet the string theorist community choose to imitate the later half of his career. The fact that Einstein tried to find a unified theory seems to provide some sort of validation for thousands of physicists to engage in a global effort to do so, when in my view his failure actually teaches the opposite lesson.
Isn't this the key, then: experiment is king. Theory is (or should be) subservient, in my view. The predictability of theory is surely meaningless unless the theory has its origins in observation in the first place; an experiment sandwich with theory in the middle. Why do I say that? Because without some form of experimental constraint both in the formulation and confirmation of a theory, there are literally an infinite number of ways to solve the same problem (isn't that the fundamental reason why there are so many string vacua?) There are probably an infinite number of (unconstrained) uses for a paper clip.
In my view, because I view the origin of a theory as just as crucial as its later validation, string theory doesn't even fit the usual definition of an empirical theory, which originates from experimental observations, by definition. The standard model fits this description well, and contains within its parts some of the most spectacularly verified predictions ever produced. Isn't it rather unfortunate that the Standard "Model" is a true theory, but String "Theory" is actually just a model? (Isn't that also a source of enormous confusion when discussing it?).
It's worth noting that although it's acceptable for a (real) theory to get ahead of experiment for a little while, this uncomfortable no-man's land does not typically last long. Never has it lasted for 30 years! Dirac's theory would have been discarded long before 30 years had passed. Before anyone claims that our technology has become so limited that we've reached an impasse, consider that there is currently an enormous list of unsolved problems in physics that are far more deserving of our attention. If our technology (ability to make experimental observations) is so limited/limiting, then how did it produce such an enormous list of unsolved observations?
Far fewer unsolved problems led to two huge revisions in our understanding of physics in the early 20th century, so we could probably learn a lot about the universe just by taking the approach of the young Einstein, to sit down and try to explain them by developing or revising a theory. We may even learn some things about high energy physics. If string theory is pure mathematics then put it in the mathematics department, surely. This is not a trivial issue; it actually takes up lots of PhDs and funding which the funding councils assume is used to advance physics, not mathematics.
Am I old-fashioned, behind the times and hopelessly naive? I'm not being belligerent, I genuinely want to know why I have the view I do. Did the entire physics community decide in the 1980s that we could change the way we discover new science, and I haven't realized the new "sophisticated" way of doing things? Or is the claim of sophistication and beauty just a cover to play in a sand box?
==endquote==
https://www.physicsforums.com/showthread.php?p=2980716#post2980716
Please contribute your thoughts on the issues she is raising and let's try to answer any specific questions, if we can.
==first Dax post==
Here is my view. Feel free to squash it if there's reason to.
Isn't the main criticism of String Theory nothing at all to do with falsifiability, use of abstract mathematical trickery, or usefulness?
(It is clear that an unfalsifiable idea may become falsifiable at technology improves. Weird mathematics is not a sign of overstretching ourselves, as was pointed out with regards to hilbert spaces in QM, for example. And nobody doubts the usefulness of string theory and AdS/CFT in pure mathematics for example).
Isn't the primary criticism of string theory that it introduces features uncalled for? What do I mean, well we usually formulate a quantum field theory with 4 space time dimensions and point particles because that is exactly what we observe in nature. Forgive me for being "old-fashioned", but usually we develop a scientific theory by making observations first, then drawing conclusions. We chastise literalist creationists for doing things the opposite way around.
Of course, sometimes theory matures so fast that it gets a little ahead of experiment. String theorists often cite Dirac's theory and the prediction of the positron as proof that it's acceptable to jump the gun. I disagree. While it is clear that Dirac was inspired and a genius to bring special relativity together with quantum mechanics, he didn't introduce anything exotic. No strings, bells, whistles, extra dimensions or any other peculiar entities. His theory assumes point particles and four dimensions, since there was no experimental evidence that anything more than this exists (and there still isn't, as far as I know).
It's also tempting to claim that Planck introduced, seemingly as a random fudge, the quantum in order to explain the unexplainable. "See, there you have it, that's what string theorists do!" they claim. Except that Planck did what he did because there was no other way to explain the data. He knew it felt like a fudge and he felt bad doing it, but it worked well because there was no alternative, and experiment quickly supported the idea (in fact, the experimental proof for the existence of the photon already existed, it was just languishing without explanation).
Then there is the claim that Einstein developed special and general relativity "just by thinking about it", divorced from experiment. String theorists seem to use this idea (which is highly questionable anyway) to validate the claim that they're actually "discovering" new physics all the time. Ed Witten is particularly fond of making this claim, suggesting that by writing equations down we are actually discovering things. But you don't discover things with theory, you explain things with theory. You discover things with experiment. Surely experiment (observation) is the arbiter of truth.
In any case the comparison with Einstein's approach is flawed. Special relativity follows from the requirement that electromagnetism produces invariant results in different reference frames coupled with the constancy of the speed of light, an experimental observation. General relativity follows from these things but obviously not straightforwardly otherwise it wouldn't have taken him another ten years, but general relativity is as devoid of exotic concepts as it can be. Curved space time is a necessity, and was quickly confirmed experimentally, just as Planck's hypothesis was.
Another claim I've noticed that string theorists make is that it does in fact originate from experiment, because it was proposed to explain the strong force (another attempt to parallel the introduction of the quantum, for example). However, this hypothesis was rejected in favour of QCD which (unsurprisingly in my view) in based on point particles and four dimensions, nothing uncalled for and nothing unobserved. So what is the continuing motivation for studying string theory as a candidate for explaining nature (as opposed to just mathematical interest)?
It may finally be tempting to say that unification is the motivation, but although it looks compelling, there is not yet any proof that all the forces are unified. Making the coupling strengths match at the appropriate energy scale required altering the standard model so I remain unconvinced. Physics may or may not be unified. It is my firm belief that experiment will tell us whether or not all of the forces are unified together, and how they are (we don't even have a grand unified theory minus gravity yet!).
Isn't it also clear that Einstein, if we wish to follow his career with interest (which string theorists understandably like to), was far more successful in his early years. What distinguished his early career? In his younger years, he studied experimental results, unsolved problems and he reaped large results from listening to nature. In his later life, he tried to dictate to nature, and he made little progress. The rest of the physics community viewed him as an old timer who'd lost touch. And yet the string theorist community choose to imitate the later half of his career. The fact that Einstein tried to find a unified theory seems to provide some sort of validation for thousands of physicists to engage in a global effort to do so, when in my view his failure actually teaches the opposite lesson.
Isn't this the key, then: experiment is king. Theory is (or should be) subservient, in my view. The predictability of theory is surely meaningless unless the theory has its origins in observation in the first place; an experiment sandwich with theory in the middle. Why do I say that? Because without some form of experimental constraint both in the formulation and confirmation of a theory, there are literally an infinite number of ways to solve the same problem (isn't that the fundamental reason why there are so many string vacua?) There are probably an infinite number of (unconstrained) uses for a paper clip.
In my view, because I view the origin of a theory as just as crucial as its later validation, string theory doesn't even fit the usual definition of an empirical theory, which originates from experimental observations, by definition. The standard model fits this description well, and contains within its parts some of the most spectacularly verified predictions ever produced. Isn't it rather unfortunate that the Standard "Model" is a true theory, but String "Theory" is actually just a model? (Isn't that also a source of enormous confusion when discussing it?).
It's worth noting that although it's acceptable for a (real) theory to get ahead of experiment for a little while, this uncomfortable no-man's land does not typically last long. Never has it lasted for 30 years! Dirac's theory would have been discarded long before 30 years had passed. Before anyone claims that our technology has become so limited that we've reached an impasse, consider that there is currently an enormous list of unsolved problems in physics that are far more deserving of our attention. If our technology (ability to make experimental observations) is so limited/limiting, then how did it produce such an enormous list of unsolved observations?
Far fewer unsolved problems led to two huge revisions in our understanding of physics in the early 20th century, so we could probably learn a lot about the universe just by taking the approach of the young Einstein, to sit down and try to explain them by developing or revising a theory. We may even learn some things about high energy physics. If string theory is pure mathematics then put it in the mathematics department, surely. This is not a trivial issue; it actually takes up lots of PhDs and funding which the funding councils assume is used to advance physics, not mathematics.
Am I old-fashioned, behind the times and hopelessly naive? I'm not being belligerent, I genuinely want to know why I have the view I do. Did the entire physics community decide in the 1980s that we could change the way we discover new science, and I haven't realized the new "sophisticated" way of doing things? Or is the claim of sophistication and beauty just a cover to play in a sand box?
==endquote==
https://www.physicsforums.com/showthread.php?p=2980716#post2980716