Episode 18: Clifford Johnson on What's So Great About Superstring Theory
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- เผยแพร่เมื่อ 14 ต.ค. 2018
- Blog post with show notes and transcript: www.preposterousuniverse.com/...
Patreon: / seanmcarroll
String theory is a speculative and highly technical proposal for uniting the known forces of nature, including gravity, under a single quantum-mechanical framework. This doesn't seem like a recipe for creating a lightning rod of controversy, but somehow string theory has become just that. To get to the bottom of why anyone (indeed, a substantial majority of experts in the field) would think that replacing particles with little loops of string was a promising way forward for theoretical physics, I spoke with expert string theorist Clifford Johnson. We talk about the road string theory has taken from a tentative proposal dealing with the strong interactions, through a number of revolutions, to the point it's at today. Also, where all those extra dimensions might have gone. At the end we touch on Clifford's latest project, a graphic novel that he wrote and illustrated about how science is done.
Clifford Johnson is a Professor of Physics at the University of Southern California. He received his Ph.D. in mathematics and physics from the University of Southampton. His research area is theoretical physics, focusing on string theory and quantum field theory. He was awarded the Maxwell Medal from the Institute of Physics. Johnson is the author of the technical monograph D-Branes, as well as the graphic novel The Dialogues. - วิทยาศาสตร์และเทคโนโลยี
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Aw yea. I've been waiting forever to hear Sean really get into string theory.
Please do an interview with Leonard Susskind!
I second this.
Yeees!
Two of my heroes coming together, yes please :’)
Absolutely. And it seems like he might be open to doing something like this?
Please do an interview with Maldacena.
I cannot imagine better way of spending some time on youtube
Keep going, thanks for taking the time beside work to record this.
Thanks for keeping the ball rolling Sean! Always a pleasant surprise to see your episodes pop up and reguardless of the amount of viewers I would say you probably have one of the stronger and more appreciative/supportive base followings where +90% of your viewers are genuinely plugged in and listening to learning and enjoying your entire episodes beginning to end. So thanks again bro keep doing you!
I actually asked my mom to buy me The Elegant Universe when I was twelve. It was the first book I enjoyed reading. A book that wasn't an absolute chore to get through.
Damn!! Why can't these things be longer? Sean, you need to have special two hour episodes with guys like this PLUS subsequent Parts 2, Part 3 ...
Sean, thanks for the lecture. Will listen during the day.
Thank you very much, Sean.
Hey! I saw you on Sam's comment section and now you're here too!
Thanks for the upload! I enjoy your work greatly :)
As always it was wonderful. Keep making podcast Dr. Carroll.
This was great. A bit over my head some parts, but I'll definately come back for a second round when I'm more informed. I hope I'd hear more from Clifford Johnson in the future.
Love the podcast, channel deserves more subs!
Very interesting episode, keep up the awesome work!
Its wonderful to have physics discussed by someone who sounds just like Cliff Richard, and who's called Cliff! We'd like to have a romp through those useful mathematical technologies (techniques?) to cope with higher dimensions one day, preferably with some graphics. Thanks for all the string!
The Elegant Universe documentary sparked my interest in science. I brought it home from the library one day, and never returned it lol. Then I dug it up again when I had my daughter. Some people had their babies watch Little Einstein videos, I had my daughter watch The Elegant Universe over and over and over. If she was fussy it would calm her right down. That documentary is very special to me in more than one way!
Talking about science is fun! Thanks, Sean.
Great podcast! Thank you sean 😁
Great podcast! But it also made me think that having Peter Woit or Lee Smolin would be really interesting - along the lines of "What's Not So Great About String Theory". Anyways, will keep listening either way ;)
I really enjoyed that, thanks. I confess I'm not able to fully comprehend it, but I loved it nevertheless.
Great interview.
I'm reading the book on D-branes for my thesis - it's right up there with Polchinski's text.
My mom bought me "The Elegant Universe" when I was a young teenager and it was one of the few books I enjoyed reading.
It bothers me when Sean calls the Phenomenal world the Real world. I guess you could say that I Kant stand it.
Sean and Brian are my heroes
If 26 dimensions go down to 10 by adding a new type of particles (fermions), maybe adding a third type would help those dimensions go down to our observed 3. But I guess that possibility is already ruled out.
You're a fantastic interviewer, you let the interviewee explain himself as much as possible, not such a common thing.
Great interview. Becoming more and more difficult to justify intellectual resources being expended on Superstring/brane theory. Does it even satisfy theory status in being unable to predict anything that is currently if ever experimentally proven...
You can not fix a broken theory by adding extra dimensions.
Astronomer Jill Tarter reportedly remarked that the Drake equation was a wonderful way to organize our ignorance. I sometimes think about that quote in reference to string theory. i know it's too harsh an idea, although, in M Theory, some say the M is for Magic. However, string theory helps organize our questions with regard to vacuum states, dimensions, etc., and trying to explain string theory to the masses (like me) is similar to trying to summarize the plots in Game of Thrones in an hour.
Ps, Mindscape is an effective anecdote to "Transgressing the Boundaries: Toward a Transformative Hermeneutics of Quantum Gravity" by Sokal.
Positive and negative cosmological constant may have to do with SUSY, and may reveal more about matter phases.
Good one SC, tks
Espectacular!!
Would be nice to hear something about the time. Why we can create mass from energy and energy from mass, but we cannot do the same with time and energy. Create time or convert it to energy. Why photon does not experience time, how? How much time existed at the time of big bang. If it has not existed then where it came from. If photon does not experience time, maybe it is time. So many interesting topics...
Thank you for interesting podcast, dr Carroll. Despite decent education (chemist) this theoretical physics is too far beyond my understanding. Do you think you could do some review type video about current state of the string theory with all pros and cons? From what I read it seems that the theory predicts things which are later not observed and because of this mismatch with reality the theoretical physicists update the theory, but again fail to match reality. From what I understand the string theory needs supersymetry but no supersymetrical particles have been found at LHC yet. What keeps people in, for lack of better expression, believing that ST is correct so they spent their prime on working on it?
I find ST quite interesting but somehow it seems to me that it is more some kind of intelectual excercise then connection to the reality we live in.
Once you start bringing on theologians, please bring Ed Feser or David Bentley Hart.
Professor Carroll, will you be doing any public speaking events anytime soon? I missed you with Sam Harris.
This is more like it!
More like this!!
[In quantum theory] “the distinction between reality and our knowledge of reality has become lost,... “
Edwin Jaynes
Do probabilities belong to objects or events in the physical world or do they only belong to a human brain observing and acquiring knowledge about the behavior of such phenomena. To address this question let’s Imagine throwing a die that lands with the number one showing on its upper surface. It is difficult to believe that the die knows that it should land in that manner on approximately one sixth of the times it is tossed. For that to occur, the die would have to keep track of all its prior outcomes to ensure that the one-up event occurs on approximately one sixth of the times. In contrast, a human brain has a memory that can, and does, keep track of these repeated events and can eventually estimate the subjective probability of the one-up result. Perhaps we could argue that it’s not the die, per se, but rather it is the laws of physics that determine the probability. The laws of physics include the action of forces, friction, and angular momentum etc., but they don’t count or keep track of which face of the die will end up on the top surface on any throw. Most Importantly, every throw of the die is totally independent from, and not related in any way to any prior or future throw. Just like the die by itself, the laws of physics do not keep track of, or calculate, the probability of any one event. The concept of probability is strictly a human construction invented by Pierre de Fermat and Blaise Pascal in the seventeenth century. Human brains can, and do, subjectively compute the likelihood of possible outcomes based on past experiences, and can modify these likelihoods on the basis of future observations. In addition, a human brain can also classify an event, like the sound of gun shot, as “surprising” (a low subjective probability) in one context (a supermarket), or “expected” (a high subjective probability) in another situation (a shooting range). That is, probability is not only subjective and personal, it is also context dependent (a conditional probability), that is continuously updated by an individual’s personal experiences. This computation and update of conditional probabilities has also been mathematically modeled by Thomas Bayes in the middle of the eighteenth century. Probability theory and Bayesian statistics are useful tools for simulating how humans acquire knowledge from observing the physical world around them: that is, epistemological in origin. They are not, however, attributes that belong to physical objects or events :that is, they are not ontological in origin. So treating the probability of an event’s occurrence as if it belongs to the external physical world is a serious misattribution.
The Schrödinger wavefunction is not reality itself, but only a mathematical description of what a human can know about reality before it is observed (or interacts with the macro world). Within an hour there is a 0.5 probability of Schrödinger’s cat being alive (it is either alive or not alive, not both) but when observed by the experimenter her subjective probability becomes 1 (or 0). No superimposed cats, no faster than light messages and no multi worlds
The lack of someone claiming first is odd
2:17 Did he just call physicists "smart cookies?" hahaha!
I think all the physicists ignore "too much" or more than they should, Gödel's Incompleteness Theorem. It was no small thing Einstein himself thought Of Gödel as the best time spent when he took those walks with him talking about these subjects. I can't remember exactly how he described him, but he saw him as having achieved a higher understanding of it all, Einstein was LEARNING from Gödel. He is the most underrated man in these areas of knowledge, and the most damagingly ignored one.
This talk unlike several other speakers was not clear. Maybe Dr Carroll needs to redirect him more to clarify the speaker
I wish they would talk about the language barrier in explaining these non-ordinary realities, after all Language is for the everyday "common" reality, a tool of survival.... will it be expanded MUCH into these new areas, is it the right tool for that, or is even math the right tool? Will they invent another one, another META-language to work with these topics....
I think Feyman did something like that with his wiggly arrows and things, a condensation of A LOT OF MATH, or even an ENTITY, which they all agreed on as being correct, into a single symbol.
The language barrier: the main issue with that, which I think is still solvable, is that those things have to still de explained or described with Language, and really, even if we adopt the best WORDS or sounds of all languages into this one to describe new things, or symbols that best describe those new things, how much can we expand this one language before it BECOMES ANOTHER no one ordinary can understand.... Oh, it this has already happen to some extent with it, when explaining these topics!!
I didn't know that Christopher Walken was a guest on this show
Yep
we need some new math... both for strings and quantum mechanics
This was the only podcast I could not keep up with. I am an idiot :(
If learned 1 new thing or youre thinking was challenged. Worth it.
interesting, very interesting
Love the podcast! But! Sometimes I fall asleep and get brutally woken up by that ending music.. Can you tone it down or turn it off please? It doesn't really serve any purpose :)
Cn someone tell me whether this guys accent is American or British? I literally can't tell wtf
His accent is English but has very slightly been adulterated with an American slant, presumably by him living in California.
I turned off Mia khalifa for this
Dude, you can do both at the same time.
Good, she's ugly.
I have no idea what that is and don't care
Christopher Frasher just turn on private mode before you google her
Mia will wait for you.
Beware the ides of October...
Leonard Susskind!
Had high hopes for this episode when I saw the title, unfortunately could not follow much of it all - please could Sean revisit the subject with Brian Greene ? as he is a much better communicator than this guest
Electric Universe Theory! If misinterpretation of the red shift has occurred, would cosmologists ever admit it? And how far down the wrong path will you go? Make up dark matter to try and balance the equations. Or neutron stars? Dr. Carroll, if you read this comment, can you possibly give this a unbiased review, or does it just get your dander up?
Brooklyn isn't expanding!
get Hofstadter on :)
Bosonic!
are you a string theorist? no I'm afraid not.