When a few weeks ago someone in a waterpark jumped into my left side and cracked a rib, I literally got a crash course in human anatomy. I didn't really appreciate just how often we use our torso muscles, which I was now painfully made aware of with every move. I could neither cough, nor run, nor laugh without wincing. Sneezing was the worst, turning over in bed a nightmare. I also had to notice that one can't sing with a cracked rib. And so, in my most recent song, I've left the vocal track to Ed Witten.
If you want to know more about the history of string theory, I can recommend watching the full lecture, which is both interesting and well delivered.
The rib has almost healed, so please don't expect Ed to become a regular, though he does have an interesting voice.
Can you recommend a good book as an introduction to string theory? Something above the mostly-qualitative popular-science stuff but not a technical monograph for experts already familiar with at least some aspects of it.
No, sorry - there it is again, the gap in the literature between pop sci and textbooks. But the first some chapters of both Polchinski and Zwiebach are not too demanding. I'd suggest you have a look at this and just see how far you get.
Thanks :) Yes, that would be nice, but I'm afraid I am not much of a graphics designer... Though I've recently looked into some software options, for the videos I almost exclusively use background material from other people under a creative-commons licence (see the links below my video on the youtube page).
In this case, I used (besides the Witten lecture) some documentaries about string theory and the multiverse, which I've patched together. This kind of works, but the storyline that comes out is inevitably one born out of necessity and not out of want. Best,
Well, the story is that I wrote this track last year already, but the lyrics didn't quite come together. I have one verse, but then I got stuck with the second one. I quite liked the way the violins came out though, so in the end I scraped out my verse (the second actually) and put in Witten (which also solved the problem of having to come up with a decorative video). Feel free to suggest new lyrics if you want :) Best,
It would be too repetitive. I'm lacking some insights there as to how properly use and sweep the synths, not to mention that my drums and percussions are pretty monotonic (I'm sure there are some plugs to fix this, if I had a thousand dollars too much). So Witten is there to distract from my lack of software and audio mixing skills ;)
"Witten is there to distract from my lack of software and audio mixing skills" Aren't there apps to automatically do counterpoint, improvisation, and warping (Youtube ?v=-ciFTP_KRy4)? Kreator isn't Julliard, but it works.
Witten, "string theory has repeatedly forced physicists...into directions we didn't anticipate and frequently didn't work." No quantum gravitation delivers even Newton. ("Obvious" particle theory, then Yang and Lee.)
Gravitation assumes the Equivalence Principle, excluding it from violation. Physics demands mirror-symmetry; failure, then unending parameterizations. Chirality is emergent (another sin). Opposite small shoes violate the EP. P3(1,2)21 space groups quartz unit cells are 0.113 nm^3. D_3-4,7,11-trioxatrishomocubane (TOTHC, 8 homochiral centers of 11 skeletal atoms) is 0.117 nm^3 (van der Waals). Eötvös experiment, left-handed versus right-handed quartz; racemic TOTHC cryogenic molecular beam rotational temperatures, are definitive. Physics has exhausted its assumptions. Look, falsify, correct, then quantize gravitation. Music is chords not scales.
Philip, Francis has been reviewing this summer most of books in string theory at the level that you ask. It is in Spanish, but I think that using Google translator you could get most of it.
This is the last entry of the blog, which is precisely a review of a string theory book.
dear Professor Hossenfelder, Thank you. I read the FAQ but could I query something. The FAQ Is String Theory Testable has an answer that begins like this "The all-time favorite. Yes, it is. There is really no doubt about it. The problem is that it is testable in principle, but at least so far nobody knows how to test it in practice. The energy (densities) necessary for this are just too high." I feel confused, because isn't everything testable in principle, in principle? I mean, I could say there's a world of green dwarfs in Andromeda. That's testable. I can't think of anything that isn't. I'm just wondering what I'm supposed to think about string theory.
"Francis has been reviewing this summer most of books in string theory at the level that you ask. It is in Spanish, but I think that using Google translator you could get most of it.
This is the last entry of the blog, which is precisely a review of a string theory book."
Thanks for the tip. There seems to be at least one other review of a string-theory book on that blog. I'll have a look around. I have some basic knowledge of Spanish. It's not one of the languages I'm actively trying to improve (5 of those are enough!), but is on the list of "when I have time or a good reason". Probably neither will come to pass, but the blog is a more attractive way (to me) of practicing Spanish than, say, reading about Mexican recipes (one of my children is looking forward to eating burritos this week and if they taste good to him that's good enough for me).
Spanish is, though, the language my wife is most actively trying to improve (she speaks 5 fluently and 1 quite well (better than Spanish), even though she has just one native language, so improving Spanish makes sense for her), so if I get stuck I can ask her. I don't think she'll become interested in string theory, though. (Stranger things have happened, though. Ed Witten started out with degrees in history and linguistics before passing through economics and maths before arriving at physics at the ripe old age of 22, only to become a professor at Princeton at the ripe young age of 28.)
I did a follow-up question after thinking awhile, but it must have got lost somewhere. So asking again, how can string theory be testable even in principle when the extra dimensions can be folded in an infinite number of different ways?
Ok, first a better example for untestable came to my mind. The "hypothesis" that "god exists" isn't testable because it doesn't make predictions.
About string theory. The question you asked wasn't whether all of string theory is testable. You can't test whether causally disconnected parts of the universe exist pretty much by definition of 'causally disconnected'. But that isn't the point. String theory makes predictions that are testable in principle and that, if we could reach the energies to observe them, would quite obviously reveal themselves. The problem is of course that we can't reach the necessary energies, thus it's a predictability "in principle" but not "in practice".
Hope that clarifies it. Then there are string-theory based models that are testable (for example string cosmology and some brane-world models) but these make extra assumptions that may or may not be part of string theory. Ie, if you find something these models predict it would speak for string theory, but if you don't find, it doesn't speak against it. Best,
dear Professor Hossenfelder, I understand the distinction you are making and would agree that 'god exists' is in a lot worse shape than String Theory. But at the same time, every assertion of that kind, predicts at least its own truth. If at some future point we can get to an energy level that is totally beyond contemporary science at the moment, we can't rule out that there'll be a test for God.
How much nearer actually is a test for string theory than that? I thought it was so far beyond what is possible that there's no way to even begin to see a roadmap. If that's true then no one can say which is nearer.
When you say parts of string theory can be tested, is that because those parts don't rely on extra dimensions? Because the extra dimensions can be folded up in an infinite number of ways so I don't understand how a situation like that can be tested. If one doesn't work out, it's a case of move to another, and another. There's no end so it can't be tested? Or is that confused?
I think we're talking past each other. You have to make a prediction for how "god" would make itself noticeable at high energies and then it would be testable. But there isn't any such prediction. There is such a prediction from string theory, ergo it is testable.
The many ways that you can compactify the extra dimensions all correspond to slightly different realizations of string theory, but they all have in common that fundamentally the thing is still a string, and in all of these cases you'd see string excitations and/or stringballs. There are also lots of calculations for string scattering at high energies.
dear professor Hossenfelder, it's not that I am not studying what you say, but I feel this needs finer distinctions, for me to be able to understand and accept. You seem to be saying that testability in the scientific sense is satisfied purely if it can be defined, even if the means of testing is effectively impossible for science in its current form.
I didn't think that was true because the meaning of falsifiability would be really diminished. A theory that can define a test, that can't be tested for 100 years, with that status could claim to be science and just carry on for 100 years. What if it fails test after 100 years...science could be ruins.
I also have trouble with what you say about the dimensions. Surely the point is that if there is an infinite number of possibilities, albeit all of them are strings with standard attributes, if we find one that works, how do we know whether that's just a coincidence? Two very different paradigms could easily describe the same phenomena, yet one of them be totally wrong.
If a theory is hard to vary, and gives back a lot more than it needs put into it, that's a reason to think it's conceptually on the right track. I can't see how you could know that if a theory was massively easy to vary. Then there's the psychological issues. If people work on a theory for decades, they're not going to give it up while there's wriggle room. And infinite ways to fold the dimensions is a permanent guarantee of wriggle room.
I'm sorry about this...I'm sure I'm wrong....but I can only say what I currently think is right. I'll be very grateful if you can understand where I am at, and then help me walk to the right understanding.
You asked whether string theory is testable, not whether it's falsifiable. I've made all the distinctions you ask for. I've told you several times now it's testable in principle, though not in practice. Falsifiability is meaningless anyway, it only works in the simplest cases, in practice its what I like to call "implausification" that happens.
Regarding the extra dimensions, as I said, it doesn't matter exactly how they look, they have the common feature that you can excite string states in them once you reach high enough energies. If we find one that works, then that works and what does it matter whether it's a coincidence. What does that even mean, I don't understand the question.
Yes, sure, people work on something for decades then they don't want to give up, etc, I have written about the cognitive biases that promote this trend many times. I am coming to think you didn't quite understand my video was sarcastic. Best,
ok thanks for the chat. I felt I was asking whether there's any scientific legitimacy in a status of "testable in principle" if the test is technically impossible.
"Regarding the extra dimensions, as I said, it doesn't matter exactly how they look, they have the common feature that you can excite string states in them once you reach high enough energies."
I'm confused. Are you saying the landscape is not a problem?
"If we find one that works, then that works and what does it matter whether it's a coincidence. What does that even mean, I don't understand the question."
It matters because if you are picking a solution all predictive potential is gone. As mentioned by Andrew Strominger, the discover "As the constraints on [these] solutions are relatively weak, it does seem likely that a number of phenomenologically acceptable . . . ones can be found. . . . While this is quite reassuring, in some sense life has been made too easy. All predictive power seems to have been lost. "
I knew your video was a tease. I was only asking you because you seemed approachable. Thanks for the chat anyway.
Let's go back to "what should I read to get into String Theory". In my view you start with Chapter one of Green, Schwarz & Witten. That chapter is not string theory, but it is what you have to know to get into it. There are no shortcuts. You read GSW. You learn about anomaly cancellations at D=26. You learn about Calabi-Yau manifolds. There are no shortcuts.
Can you recommend a good book as an introduction to string theory? Something above the mostly-qualitative popular-science stuff but not a technical monograph for experts already familiar with at least some aspects of it.
ReplyDeleteNo, sorry - there it is again, the gap in the literature between pop sci and textbooks. But the first some chapters of both Polchinski and Zwiebach are not too demanding. I'd suggest you have a look at this and just see how far you get.
ReplyDeleteVery well! But why only closed strings? The ordinary matter is made of the open strings, isn't it? Could you add some D-branes, please? :)
ReplyDeleteBrilliant. Better without the vocal, though, I reckon.
ReplyDeleteI mean, better without the Witten vocal. I like your Bjork-like vocal.
ReplyDeleteIvan,
ReplyDeleteThanks :) Yes, that would be nice, but I'm afraid I am not much of a graphics designer... Though I've recently looked into some software options, for the videos I almost exclusively use background material from other people under a creative-commons licence (see the links below my video on the youtube page).
In this case, I used (besides the Witten lecture) some documentaries about string theory and the multiverse, which I've patched together. This kind of works, but the storyline that comes out is inevitably one born out of necessity and not out of want. Best,
B.
Andrew,
ReplyDeleteWell, the story is that I wrote this track last year already, but the lyrics didn't quite come together. I have one verse, but then I got stuck with the second one. I quite liked the way the violins came out though, so in the end I scraped out my verse (the second actually) and put in Witten (which also solved the problem of having to come up with a decorative video). Feel free to suggest new lyrics if you want :) Best,
B.
If you just took Witten out, a really good dance track.
ReplyDeleteIt would be too repetitive. I'm lacking some insights there as to how properly use and sweep the synths, not to mention that my drums and percussions are pretty monotonic (I'm sure there are some plugs to fix this, if I had a thousand dollars too much). So Witten is there to distract from my lack of software and audio mixing skills ;)
ReplyDelete"Witten is there to distract from my lack of software and audio mixing skills" Aren't there apps to automatically do counterpoint, improvisation, and warping (Youtube ?v=-ciFTP_KRy4)? Kreator isn't Julliard, but it works.
ReplyDeleteWitten, "string theory has repeatedly forced physicists...into directions we didn't anticipate and frequently didn't work." No quantum gravitation delivers even Newton. ("Obvious" particle theory, then Yang and Lee.)
Gravitation assumes the Equivalence Principle, excluding it from violation. Physics demands mirror-symmetry; failure, then unending parameterizations. Chirality is emergent (another sin). Opposite small shoes violate the EP. P3(1,2)21 space groups quartz unit cells are 0.113 nm^3. D_3-4,7,11-trioxatrishomocubane (TOTHC, 8 homochiral centers of 11 skeletal atoms) is 0.117 nm^3 (van der Waals). Eötvös experiment, left-handed versus right-handed quartz; racemic TOTHC cryogenic molecular beam rotational temperatures, are definitive. Physics has exhausted its assumptions. Look, falsify, correct, then quantize gravitation. Music is chords not scales.
Philip, Francis has been reviewing this summer most of books in string theory at the level that you ask. It is in Spanish, but I think that using Google translator you could get most of it.
ReplyDeleteThis is the last entry of the blog, which is precisely a review of a string theory book.
http://francis.naukas.com/2015/08/18/resena-an-introduction-to-string-theory-and-d-brane-dynamics-por-richard-j-szabo/#more-33536
"string theory has repeatedly forced physicists...into directions we didn't anticipate and frequently didn't work"
ReplyDeleteI might have misheard this, but I think he said "frequently didn't WANT"
sorry to bother you but I think it was here that I first heard that string theory can't predict. Doesn't that mean it isn't legitimate science?
ReplyDeleteLucy M: Please refer to the FAQ.
ReplyDeletedear Professor Hossenfelder,
ReplyDeleteThank you. I read the FAQ but could I query something. The FAQ Is String Theory Testable has an answer that begins like this "The all-time favorite. Yes, it is. There is really no doubt about it. The problem is that it is testable in principle, but at least so far nobody knows how to test it in practice. The energy (densities) necessary for this are just too high."
I feel confused, because isn't everything testable in principle, in principle? I mean, I could say there's a world of green dwarfs in Andromeda. That's testable. I can't think of anything that isn't.
I'm just wondering what I'm supposed to think about string theory.
There's a green dwarf in Andromeda but it doesn't couple to any particle we can observe isn't testable.
ReplyDeleteI feel like you've answered my question but I don't understand. Sorry - I shouldn't be bothering you with my level of knowledge.
ReplyDelete"Francis has been reviewing this summer most of books in string theory at the level that you ask. It is in Spanish, but I think that using Google translator you could get most of it.
ReplyDeleteThis is the last entry of the blog, which is precisely a review of a string theory book."
Thanks for the tip. There seems to be at least one other review of a string-theory book on that blog. I'll have a look around. I have some basic knowledge of Spanish. It's not one of the languages I'm actively trying to improve (5 of those are enough!), but is on the list of "when I have time or a good reason". Probably neither will come to pass, but the blog is a more attractive way (to me) of practicing Spanish than, say, reading about Mexican recipes (one of my children is looking forward to eating burritos this week and if they taste good to him that's good enough for me).
Spanish is, though, the language my wife is most actively trying to improve (she speaks 5 fluently and 1 quite well (better than Spanish), even though she has just one native language, so improving Spanish makes sense for her), so if I get stuck I can ask her. I don't think she'll become interested in string theory, though. (Stranger things have happened, though. Ed Witten started out with degrees in history and linguistics before passing through economics and maths before arriving at physics at the ripe old age of 22, only to become a professor at Princeton at the ripe young age of 28.)
I did a follow-up question after thinking awhile, but it must have got lost somewhere. So asking again, how can string theory be testable even in principle when the extra dimensions can be folded in an infinite number of different ways?
ReplyDeleteLucy M,
ReplyDeleteOk, first a better example for untestable came to my mind. The "hypothesis" that "god exists" isn't testable because it doesn't make predictions.
About string theory. The question you asked wasn't whether all of string theory is testable. You can't test whether causally disconnected parts of the universe exist pretty much by definition of 'causally disconnected'. But that isn't the point. String theory makes predictions that are testable in principle and that, if we could reach the energies to observe them, would quite obviously reveal themselves. The problem is of course that we can't reach the necessary energies, thus it's a predictability "in principle" but not "in practice".
Hope that clarifies it. Then there are string-theory based models that are testable (for example string cosmology and some brane-world models) but these make extra assumptions that may or may not be part of string theory. Ie, if you find something these models predict it would speak for string theory, but if you don't find, it doesn't speak against it. Best,
B.
dear Professor Hossenfelder,
ReplyDeleteI understand the distinction you are making and would agree that 'god exists' is in a lot worse shape than String Theory. But at the same time, every assertion of that kind, predicts at least its own truth. If at some future point we can get to an energy level that is totally beyond contemporary science at the moment, we can't rule out that there'll be a test for God.
How much nearer actually is a test for string theory than that? I thought it was so far beyond what is possible that there's no way to even begin to see a roadmap. If that's true then no one can say which is nearer.
When you say parts of string theory can be tested, is that because those parts don't rely on extra dimensions? Because the extra dimensions can be folded up in an infinite number of ways so I don't understand how a situation like that can be tested. If one doesn't work out, it's a case of move to another, and another. There's no end so it can't be tested? Or is that confused?
Lucy M,
ReplyDeleteI think we're talking past each other. You have to make a prediction for how "god" would make itself noticeable at high energies and then it would be testable. But there isn't any such prediction. There is such a prediction from string theory, ergo it is testable.
The many ways that you can compactify the extra dimensions all correspond to slightly different realizations of string theory, but they all have in common that fundamentally the thing is still a string, and in all of these cases you'd see string excitations and/or stringballs. There are also lots of calculations for string scattering at high energies.
Best,
B.
dear professor Hossenfelder, it's not that I am not studying what you say, but I feel this needs finer distinctions, for me to be able to understand and accept. You seem to be saying that testability in the scientific sense is satisfied purely if it can be defined, even if the means of testing is effectively impossible for science in its current form.
ReplyDeleteI didn't think that was true because the meaning of falsifiability would be really diminished. A theory that can define a test, that can't be tested for 100 years, with that status could claim to be science and just carry on for 100 years. What if it fails test after 100 years...science could be ruins.
I also have trouble with what you say about the dimensions. Surely the point is that if there is an infinite number of possibilities, albeit all of them are strings with standard attributes, if we find one that works, how do we know whether that's just a coincidence? Two very different paradigms could easily describe the same phenomena, yet one of them be totally wrong.
If a theory is hard to vary, and gives back a lot more than it needs put into it, that's a reason to think it's conceptually on the right track. I can't see how you could know that if a theory was massively easy to vary. Then there's the psychological issues. If people work on a theory for decades, they're not going to give it up while there's wriggle room. And infinite ways to fold the dimensions is a permanent guarantee of wriggle room.
I'm sorry about this...I'm sure I'm wrong....but I can only say what I currently think is right. I'll be very grateful if you can understand where I am at, and then help me walk to the right understanding.
Lucy,
ReplyDeleteYou asked whether string theory is testable, not whether it's falsifiable. I've made all the distinctions you ask for. I've told you several times now it's testable in principle, though not in practice. Falsifiability is meaningless anyway, it only works in the simplest cases, in practice its what I like to call "implausification" that happens.
Regarding the extra dimensions, as I said, it doesn't matter exactly how they look, they have the common feature that you can excite string states in them once you reach high enough energies. If we find one that works, then that works and what does it matter whether it's a coincidence. What does that even mean, I don't understand the question.
Yes, sure, people work on something for decades then they don't want to give up, etc, I have written about the cognitive biases that promote this trend many times. I am coming to think you didn't quite understand my video was sarcastic. Best,
B.
ok thanks for the chat. I felt I was asking whether there's any scientific legitimacy in a status of "testable in principle" if the test is technically impossible.
ReplyDelete"Regarding the extra dimensions, as I said, it doesn't matter exactly how they look, they have the common feature that you can excite string states in them once you reach high enough energies."
I'm confused. Are you saying the landscape is not a problem?
"If we find one that works, then that works and what does it matter whether it's a coincidence. What does that even mean, I don't understand the question."
It matters because if you are picking a solution all predictive potential is gone. As mentioned by Andrew Strominger, the discover "As the constraints on [these] solutions are relatively weak, it does seem likely that a number of phenomenologically acceptable . . . ones can be found. . . . While this is quite reassuring, in some sense life has been made too easy. All predictive power seems to have been lost. "
I knew your video was a tease. I was only asking you because you seemed approachable. Thanks for the chat anyway.
Thanks, Javier. Phillip I've written more than 10 book reviews on string theory and still do...
ReplyDeletehttp://francis.naukas.com/?s=rese%C3%B1a+teor%C3%ADa+de+cuerdas
Let's go back to "what should I read to get into String Theory". In my view you start with Chapter one of Green, Schwarz & Witten. That chapter is not string theory, but it is what you have to know to get into it. There are no shortcuts. You read GSW. You learn about anomaly cancellations at D=26. You learn about Calabi-Yau manifolds. There are no shortcuts.
ReplyDelete