#science #physics #ideas The Biggest Ideas in the Universe | 10. Interactions

#science #physics #ideas The Biggest Ideas in the Universe | 10. Interactions 83,500 viewsMay 26, 2020 1.5K DISLIKE SHARE DOWNLOAD CLIP SAVE Sean Carroll 154K subscribers The Biggest Ideas in the Universe is a series of videos where I talk informally about some of the fundamental concepts that help us understand our natural world. Exceedingly casual, not overly polished, and meant for absolutely everybody. This is Idea #10, "Interactions." Last time we dipped a toe into quantum field theory, seeing how quantizing fields leads to particles. Now we let the particles interact with each other, and see how the results are characterized by Feynman diagrams. My web page: http://www.preposterousuniverse.com/ My YouTube channel: https://www.youtube.com/c/seancarroll Mindscape podcast: http://www.preposterousuniverse.com/p... The Biggest Ideas playlist: https://www.youtube.com/playlist?list... Blog posts for the series: http://www.preposterousuniverse.com/b... Background image: https://www.ecopetit.cat/ecvi/JwTib_w... #science #physics #ideas #universe #learning #cosmology #philosophy #quantum #fields #feynman 149 Comments rongmaw lin Add a comment... Chip Hill Chip Hill 1 year ago Thanks for hitting the technical complexity sweet spot. These are great videos! 43 Werner Van Belle Werner Van Belle 1 year ago Great series you made here. I love how you take care of the details but still stay sufficiently on the surface 4 Maria Penfold Maria Penfold 1 year ago Great series! Are you going to do a "Lenny" and write a Theoretical Minimum based on this series? That would be great and something good would come out of lockdown. 4 B aa B aa 1 year ago "The Biggest Ideas in the Universe" series is fantastic! They are timeless content. This format of explaining one concept is great. soulremoval soulremoval 1 year ago thank you so much, this was extremely helpful and insightful. 2 James Stewart James Stewart 1 year ago Thanks Sean, QED is the stuff happens where the stuff happens is not particularly emphasised in a quantum chemistry course so this extreme introductory non-lecture was not only intriguing but also had me scrubbing the timeline. 1 Lars Alfred Henrik Stahlin Lars Alfred Henrik Stahlin 1 year ago You're getting better at this youtube business Sean! Totally lured me in with that tasty blue rather irrelevant CGI thumbnail! ...Glad you did. I love this series and I loved you latest book. And the one before that taught me a lot too. Like philosophy and the universe for dummies. I feel like I'm getting more and more inspired to learn calculus, differential equations and all that the more stuff you put up. Greetings from Sweden 1 Shalkka Shalkka 1 year ago I was more excited to go from particle diagram to understand how the wavelike nature of interactions works. Could one try to tell the story using the mode decompositions of the incmoing particles. Like electron momentum right encounters anti-electron momentum left plus other configurations like electron momentum north encounters anti-electron momentum going left. But maybe it's the case that the mathematics is not particularly elegant or that summed back up version is not very packety? It also feels that the feyman diagramms are in effects the "modes" of the interaction with added vertex being analogous to considering an increase of an energy quanta. If one tried to solve a hamilton with an interaction term in it would it have quantised solutions? With QED it should be enough to have most essential things handled with a electron-antielectron system. I was looking to understand the conditions where they keep circling each other vs annhilation vs flying far apart from each other. Because both partcile have uncertainty in position and momentum it seemed to be possibe to set up a situation where that wave-indeterminacy decides which of the three types of outcomes happens. And I had an incling that "time to decay" via a quantum uncertain path would be something I don't understand and could gain more insight on. I also feel that the construction of understanding fields via particles was a red herring in that it's applicability is already hit. When we start rolling our spherical cows we are going to get in trouble with cow-tipping. Part of the job of a particle physcicis was to come up with new hamiltoninan. However the interaction term seemd to be just combine all fields via multiplication and a scalar. There doesn't seem to be much room to make it any other way. Or is it rather a more general function f(e-,e+,y) that could in principle do more fancy stuff? Or is the complication hidden in the definition of what the fields are (complexity of combining the fields vs how rich the field ontology is) 1 Nartana Premachandra Nartana Premachandra 1 year ago Hello Sean, I have a question: how can a particle or field be completely free or not entangled? I can’t envision that as everything interacts with everything else all the time. Thank you so much for these lectures; I have all your books and the lectures help to elucidate them. 2 Nathan Moynihan Nathan Moynihan 1 year ago I think it was John Wheeler who gave Feynman the idea that the positron is an electron moving backwards in time. 6 Chavdar Danchev Chavdar Danchev 1 year ago Question: How do we ensure that the sum of the probabilities for all variations of interactions converges to 1? If it exceeds 1 do we have to think of other version of alpha? 1 John Rendle John Rendle 4 months ago Such a pleasure to watch your lectures….I’m a radiologist and you’ve given me a Eureka moment re PET and the fact that you get two photos rather than one in positron-electron interactions. Thank you! Naimul Haq Naimul Haq 1 year ago Hawking demonstrated the most interesting interaction of QF, using a blend of GR and QM, when explaining radiation and calculating entropy of BH. A pair production of virtual particle and anti-particle from the QF, makes the anti-particle fall into the BH while a real particle is ejected into space. Implying the QF can simulate conscious intelligent 'observer', collapsing the field to produce particles (Adam Becker' question, can QF simulate/define cosmic consciousness). 1 Gareth Williams Gareth Williams 1 year ago The two lowest order electron>γ 1, which means the probability will be bigger than 1. What am I misunderstanding? QUESTION 2: - 44:52 "d^3x represents dxdydz" My question is, is this related to the notation we use for 3rd derivative, where the differential operator has d^3 in the numerator? Or is this just the same notation used to mean different things in different contexts? 2 John Walker John Walker 1 year ago Thank you sir, nice lecture. vinm300 vinm300 4 months ago This series will be the best thing on YouTube for decades. NGC 7635 NGC 7635 10 months ago Sean: There is only one diagram we can draw for this Sean 5 minutes later: There is an infinite amount of diagrams we can draw for this Jeff Bass Jeff Bass 1 year ago (edited) Another question...I believe you mentioned in an earlier video that vacuum entanglement is different from particle entanglement (since you have the idea that spacetime emerges from vacuum entanglement). How can these two things be separate if particles are just excitations in fields? TetonGemWorks TetonGemWorks 1 year ago These are great videos, but I'm failing this class.... Won't stop watching and rewatching. Just love listening to the Professor explain thing, go on tangents, the whole thing. Eigenbros Eigenbros 1 year ago (edited) I've always wanted to know more quantum field theory without taking a course on it. much appreciated Sean 4 element4element4 element4element4 1 year ago I feel that one of the deepest ideas in physics is the Wilsonian renormalization group theory. Not only does it give a way to think about the connection between high energy microscopic and low energy macroscopic theory, it gives a deep understanding of phase transitions, the space of quantum field theories, universality (the robustness and fundamentalness of low energy effective theories) etc etc. In particular, it gives a possible answer of the infinities quantum field theory implying that they should most likely be considered as effective theories rather than be seen as fundamental. I think there generally lacks a good exposition of these important ideas in theoretical physics for the general public. I can imagine that a version of Kadanoff block spin would give some intuition. Paul C. Paul C. 1 year ago Reminder : at 41:00 This video, (no. 10 - Interactions) is where the "Lagrangian" & "Lagrange Density" is discussed & explained. Fully. 4pharaoh 4pharaoh 1 year ago (edited) Much More on Alpha Please! I'm sure α is a Big Idea. 1 Álvaro Rodríguez Álvaro Rodríguez 1 year ago (edited) It would be very cool to see the field depiction of an electron and a positron, as to understand what you mean by “electronness “. In a more detailed way, in prior depictions particles were lobes in a wave, no matter if they were pointing up or down. So... I guess it all boils down to what defines charge in the electron field. Note: by depiction I mean literally a drawing. Álvaro Rodríguez Álvaro Rodríguez 1 year ago (edited) Now fields interact with each other?? I feel that if I don’t understand how, I’m going to grow a giant moustache and pretend I live in the XIXth century, just to keep what’s left of my sanity. PS: the level of math you introduce is very satisfying. If it depends on me, the more the better. 3 Calvin Grondahl Calvin Grondahl 1 year ago I am old so these videos are as relaxing as music... playful and honest. Carl Sagan in 1980 was also reassuring and fun. 1 J Cowan J Cowan 1 year ago Is there a Field Theory (classical or quantum) that uses Special Relativity? Field configurations defined in spacetime coordinates rather than R3 real coordinates? How about higher dimensional space (rolled-up dimensions?) yak yak 1 year ago "The positron can be thought of as an electron moving backwards in time..." The way this was stated makes me think that people don't think positrons are actually electrons moving backward in time. Is that correct? 2 Paps Aebus Paps Aebus 1 year ago Does an electron lose energy in the interaction 22:46? Or does the energy conservation simply not apply in this scenario?🤔 1 Rafaella Zanchet Rafaella Zanchet 1 year ago so if the reason for every electon having the same mass and charge is because they are vibrations in the same field,does it mean that every particle have its own specific field? Does the field defines the particles or the opposite ? Or is it both simultaneously and they are different ways of expressing the same thing ? karmel lewis karmel lewis 1 year ago i think one future problem may be that there is no small metric for the density or energy level , if i had to guess id say those measurements are based on the individual doing the measurement,. once again thank you. great informational video* Colin MacLaurin Colin MacLaurin 1 year ago (edited) at 23:00, I think the Feynman diagram with one electron in, and an electron and photon out, is unphysical. Energy is not conserved, which is most easily seen from the centre-of-mass frame of the "in" electron. Instead, as Carroll says later, the two diagrams should be mirror images of one another. Edit: But I guess it's fine as a single vertex of a larger diagram Projjwal Dubey Projjwal Dubey 1 year ago @Sean Carroll. Thanks Prof, if you happen to see my gratitude. Wonderful series. 1 Matt Rodriguez Matt Rodriguez 1 year ago Thank you Sean for the video. 1 judy churley judy churley 1 year ago If some particle 'decays into...' does that imply that it was made up of those decay constituents? Or that it has changed the interacting fields in some way that those 'decay constituents' come into being in he relevant fields? John Healy John Healy 1 year ago I enjoyed the wrap-up to your chat #10 Interactions. (transcript quote) so we are left with both this wonderfully accurate calculational device of Feynman diagrams and this somewhat unnatural formalism of quantum field theory. we don't know what to do about that. we didn't ... I'm not gonna reveal what to do about that. We still don't know what to do about the energy density of empty space. But we're thinking, and it might be that we do in one way or the other have to replace quantum field theory. But in the mean time it is absolutely the best way we have of understanding nature currently available. (end quote) The "what to do about the energy density of empty space" is what intrigues me. As well as ways to do 3D visualizations of localized field interactions, like a electron vibration and "reverse" vibration (positron) annihilating. Leland Beaumont Leland Beaumont 1 year ago Is there anything analogous to Feynman diagrams that can be used to diagram philosophical arguments or texts? Isabel AB Isabel AB 1 year ago I truly wish I remembered enough mathematics to do justice to this wonderful knowledge. Thank you 1 lilit vehuni lilit vehuni 1 year ago The electron splits into another electron and photon. The new electron must be at a lower energy level, since it lost a photon worth of energy. Is this correct? Paul C. Paul C. 1 year ago (edited) Reminder : at 41:00 This video, (no. 10 - Interactions) is where the "Lagrangian" & "Lagrange Density" is discussed & explained. Fully. Michael J Morrison Michael J Morrison 1 year ago Enjoying your lectures....we are so lucky that corona seems to have you with us -a very real silver lining! So.... my question....Is gravity emergent and if so can it be manipulated by affecting entropy in a particular volume of space or even specifically here on Earth? Too Crash Too Crash 1 year ago (edited) Thank you. I hope to understand more. Christine LaBeach Christine LaBeach 1 year ago I'm imagining a particle that is like a tiny sphere with a surface that is wavey. Don't know if that's right. yewenyi yewenyi 9 months ago If electrons move forward in time and positrons move backwards in time, does that mean that at the no bang two universes were created. On with our matter moving forwards in time and one with antimatter moving backwards in time? Jurassic Fart Jurassic Fart 1 year ago These sci fi backgrounds look cool as hell 7 Erik Dahlgren Erik Dahlgren 1 year ago I have bought Seans book and its good. Sean is pushing the limits. 1 TimboJohn TimboJohn 1 year ago Would an Eternalist look at a Feynmann diagram as not going from right to left or left to right, but just *being there*? 3 Swan Swan 10 days ago A piece of gold! Yoda Jimmy Yoda Jimmy 1 year ago Why I keep watching all his videos even when I skip most of the part? 1 Pavlos Papageorgiou Pavlos Papageorgiou 1 year ago (edited) I'm a little lost on how many degrees of freedom we're talking about. You explain that we can decompose any field as a collection of waves, waves have modes, modes have energy levels, and the Nth energy level corresponds to N particles. That's for a classical field and on top we have the wave function. That sounds like "for each" is expanded too many times. Is there a way to count the infinities? For example there's an R^3 infinity of k plane waves, then a Z infinity of coefficients of each mode? then you take the set of all of the above to make Ψ? I don't know. Roughly how large is everything? EDIT: And I'm guessing part of the answer is that this "how big" doesn't change with many worlds because the the wave function is already there. It's implied by what you say here that you, an object, is not defined locally anyway. We're all defined holographically as components of the vibration modes of the whole universe. All versions of us. In a way that should make Many Worlds more plausible, or at least no less plausible than expressing everyday things that way. James Jacobberger James Jacobberger 1 year ago Sorry if this was asked already. So, is a hydrogen atom the superposition of an electron wave and proton wave function (which is the superposition of quark and gluon wave functions) that travel through space-time together? Somehow, I think the answer is no. Amere Mortal Amere Mortal 1 year ago (edited) What is actually real? Is it just the connections between things? 1 Rodrigo Serafim Rodrigo Serafim 1 year ago 49:20 "an electron, a positron and a photon..." walk into a bar. electron turns to the positron and says 'i'm feeling negative', positron asks responds 'are you positive?', photon interjects 'can you guys see where this is going?' 2 Jason ols Jason ols 1 year ago (edited) So droplets of energy called particle are suspended in a cloud called electron and agitated by a wind called photon? Jeff Bass Jeff Bass 1 year ago I'm sure it's hidden in all the Lagrangian stuff, but where in the fields do these interactions take place...like, do the interactions always happen where both the electron field and positron field have relatively large values? Peter Ebel Peter Ebel 1 year ago Sean, I know this is kinda the wrong place to ask, but it's been bothering me since I saw the Big Idea video on Space. In your two dimensional example of space, you drew a cylinder, which I cannot help but notice is a three dimensional object. It seems to me, the (small) circular dimension is in fact two dimensions. That makes no sense to me. Is this something that can be explained to the lay person? Charles Carter Charles Carter 1 year ago What if all the missing antimatter is in the future? 1 Prakash Huded Prakash Huded 1 year ago (edited) How is the electron field different from electric field? Or How are they related? Henrik Scheel Henrik Scheel 1 year ago Can you explain how a Quantum computer works? Soul DFS Soul DFS 1 year ago Rad, every video gets better! Travis Cook Travis Cook 1 year ago 55:00 The reasons given for why Wheeler's 'one electron universe' is wrong don't actually logically falsify the theory.. Just because the [same underlying] 'field description' works as an explanation for why all the electrons are the same mass and charge, doesn't mean it's the right one and Wheeler's is wrong. That's like saying the 'round globe theory' is wrong because the flat earth 'theory' has a working alternative explanation for the motion of the 'heavenly bodies' (or the geocentric/ptolemaic model explanation for planetary motion, etc.) And the fact that electrons can turn into other particles doesn't falsify it either because whatever the electron turns into can still be the 'one electron/particle' just undergoing 'transformation'. I'm not saying the 'one electron universe' theory is correct, but are there other more compelling reasons why it's wrong? Blackie Black Blackie Black 1 year ago How did I get this far into the series when I suck at math? 1 bjarke nielsen bjarke nielsen 1 year ago The field is up and down. 18 squared. 324 group 18 periodic system is All gassens together is 324. From 1 to 18.. So the field is up +up- and down+down-.. Alfian Gunawan Alfian Gunawan 1 year ago this is a completely new concept for me nathanisbored nathanisbored 1 year ago i think the reason you keep 'slipping' and calling these lectures is because you secretly want historians to refer to these videos as the Carroll Lectures 6 John Długosz John Długosz 1 year ago Do you mean lepton number rather than fermion number for conserving electron-ness? Joshua Pasa Joshua Pasa 1 year ago I thought QM was about unifying fields and particles? So does QFT give a multi-variable function depending on x and phi? (Probability that x will have a certain field value phi). Is that what he is saying? I'm just confused because its probabilities of probabilities. Czeckie Czeckie 1 year ago If I grow up to be a particle physicist, what fields will I be inventing? Standard model is bunch of interacting fields and they are all described, right? So is my job to imagine some new interactions and new particles and see what happens even though I have no indications from experiments there are any other fields? Clearly, I am confused about why should anyone invent new fields when it seems we've got them all. Paps Aebus Paps Aebus 1 year ago What about Gauge Invariance? 2 Samuel J Samuel J 1 year ago YES! Just in time for my particle physics exam tomorrow!!! 2 FirstRisingSouI FirstRisingSouI 1 year ago If Feynman diagrams are just visualizations of series expansions, not real things happening in physical reality, why teach them to a general audience? 1 Steven Mellemans Steven Mellemans 1 year ago Center of mass of a two photon system ? :-) karabo mothupi karabo mothupi 1 year ago Beautiful Splicex JMS Splicex JMS 1 year ago Shoutout to Greg Gutfeld who I believe has been watching your videos. 1 Calin Werlein Calin Werlein 1 year ago I always wonder how you can top it...what's next...Sean Caroll is the best sherpa you can get (free!!) on the way to the summit of Everest of Physics...but you still have to climb high on your own feet... Riki Mitchell Riki Mitchell 1 year ago re 10:00 outgoing dispersive wavefront combined (additive/subtractive) harmonic spectra Joao Joao 1 year ago Stopping everything to watch the new video! =) 28 Valdagast Valdagast 1 year ago (edited) TIL: Physicists desperately need to adopt new alphabets to steal letters from. I suggest Chinese ideograms (not strictly letters, but never mind). Evgenii Neumerzhitckii Evgenii Neumerzhitckii 1 year ago 18:00 Hola, wait a minute! Particles traveling backwards in time? Say what? 1 qr6QRbMBG6hjGpZhnWqG qr6QRbMBG6hjGpZhnWqG 9 months ago Such an amazing physicist and communicator. Such a terrible arrow head drawer. 23:15 :D Keith butler Keith butler 1 year ago I wonder what his neighbours think when he calls "Taliban !" : ) Rattus Norvegicus Rattus Norvegicus 1 year ago I feel like Ogre watching this... "What if C A T really spells dog?" 3 karabo mothupi karabo mothupi 1 year ago My mind is in a superposition of understanding and not understanding Potonicml Potonicml 1 year ago We live in a field called a black hole, it's totally free. Jesse Montano Jesse Montano 1 year ago Interactions?? Nice!!!!! Parveen Farook Parveen Farook 1 year ago Love you from India sir Bolek Szewczyk Bolek Szewczyk 1 year ago Neat spherical-cyberpunk cow in the background! 13 Joshua A Martin Joshua A Martin 1 year ago hmmm, the energy of "empty" space.............I have an idea, should I email?comon you must get a laugh out of some of them :) Michal C Michal C 1 year ago I'm the spherical cow everyone is talking about. 5 Sabin Ripan Sabin Ripan 1 year ago Who the hell hits the dislike button and what does he do here? Mot Mot Mot Mot 1 year ago 25:20 was a bit of hand-waving? 1 Michael Lorden Michael Lorden 1 year ago Sir it’s turtles all the way down!! 4 Mattias Sollerman Mattias Sollerman 1 year ago aggresively nodding along 3 Mauro Cruz Mauro Cruz 3 months ago 33:22 MathAdam, ADHD MathAdam, ADHD 1 year ago Does this comment count as an interaction? mr cash cashiers mr cash cashiers 1 year ago the earth is flat 1 pizzacrusher pizzacrusher 1 year ago Why name your cat Taliban? Greyback Greyback 1 year ago Hi if you don't know tomorrow there will be a debate review on "capturing Christianity" YouTube channel of your debate with William L.C maybe you would be interested in it George Keeling George Keeling 1 year ago I got distracted by Taliban! Rewind 1 minute. Shaun Krueger Shaun Krueger 1 year ago I wonder what sort of person clicks on a theoretical physicist's lecture during a pandemic and gives it a thumbs down. Must have been an anti-Everettian. #science #physics #ideas The Biggest Ideas in the Universe | Q&A 10 - Interactions 44,888 viewsMay 29, 2020 Sean Carroll 154K subscribers The Biggest Ideas in the Universe is a series of videos where I talk informally about some of the fundamental concepts that help us understand our natural world. Exceedingly casual, not overly polished, and meant for absolutely everybody. This is the Q&A video for Idea #10, "Interactions." I talk about the circumstances under which it's okay to use Feynman diagrams and think of fields as being particle-like vs. wave-like, and am a bit more precise about locality and the infinite number of degrees of freedom in a field theory. My web page: http://www.preposterousuniverse.com/ My YouTube channel: https://www.youtube.com/c/seancarroll Mindscape podcast: http://www.preposterousuniverse.com/p... The Biggest Ideas playlist: https://www.youtube.com/playlist?list... Blog posts for the series: http://www.preposterousuniverse.com/b... Background image: https://www.ecopetit.cat/ecvi/JwTib_w... #science #physics #ideas #universe #learning #cosmology #philosophy #quantum #fields #feynman 87 Comments rongmaw lin Add a comment... Mina Ghavimi Mina Ghavimi 1 year ago I absolutely love these videos, exactly what I was looking for, explaining laws if physics to non-physicists. Thanks Sean for taking the time to educate the public, I have read all your books. Not saying I understood them all well, but From Eternity to Here completely changed my perspective about the universe and how it works. 4 Manuel Martín Manuel Martín 1 year ago (edited) I love these videos. I learned some math on my engineering degree but not enough to read QM for myself without being overwhelmed. I'm very curious about the general ideas behind "real life" physics but I don't really have time to learn all the math. In practice these means that most of these ideas are behind a math "paywall" for me. Luckily these videos allow me to make some headway into these subjects and that makes them very fun and interesting. This type of content is very difficult to find elsewhere. I know the DrPhysicsA channel which uses a very similar format and is a little more heavy on math, sadly he isn't active since 2014. Khan Academy also uses this format for more elementary stuff. What makes these videos different from the usual divulgative content is that they include a small amount of math, Nowadays I find I'm rarely able to learn anything new from the normal content that is 100% based on verbal analogies. 7 John Davis John Davis 1 year ago Thank You !! Please keep this as an ongoing series. You give understanding to the once unknown; again heartfelt thanks. 1 Joao Joao 1 year ago Great video Sean! I've watched nearly all the videos for nom physical graduates in the YouTube and yours are the best ones, by far! 1 Andrey Bashkin Andrey Bashkin 1 year ago A chuckle at "uninteresting infinities", full blast of laughter at a "simple minded QFT". Love the whole series! 1 Jim's Mind Jim's Mind 1 year ago QM feels very much like an emergent phenomena from some more elegant theory we haven't fully conceived of yet. I think Einstein's concerns about it are still valid today. I sometimes think some of the maths put us on the wrong track of understanding, although it works, the implications are difficult to come to terms with. Enjoyed the series so far and wondering where it goes next. 5 Pierre Alain Cotnoir Pierre Alain Cotnoir 1 year ago Thanks from an old one (near 70), that follows (after having read your last book) those videos since the beginning of september, trying to listen one subject each day. One suggestion: if you kept it, it would be useful to be able to download your writing of the virtual blackboard for reviewing. Stumpy Mason Stumpy Mason 1 year ago Thank you again for another great episode musicalcacti musicalcacti 1 year ago Love the YouTube content professor! 1 Kai Henningsen Kai Henningsen 1 year ago I'm sure he already said that in another video, but there's an important conceptual difference when thinking about "spooky action at a distance" in the field context. Remember, in that context, the wave function is not about particle states, but about field configurations. Now, the superposition means that we have several different field constellations (One with, say, A up and B down and one with A down and B up). When we measure that field at one point in space, we effectively select one of those configurations - it then follows immediately that measuring at the other place now must have a pre-determined outcome. You can't measure two different configurations. (Or in many worlds, measuring different configurations can only happen on different, non-interacting branches.) No longer quite so spooky, in my opinion. Also, just wanted to say "lockdown mullet". Brian Cannard Brian Cannard 1 year ago "Eventually we will figure this stuff out!" Thanks Sean, keep inspiring next generations! Moreno Sanguanini Moreno Sanguanini 1 year ago Is it possible that vertical particles pop up due the result of space inflation? Aaron Watson Aaron Watson 1 year ago I've always heard that total energy E is given by: E^2 = p^2*c^2 + m_0^2*c^4. Can you explain why you write E^2 = p^2 + m^2? I'm assuming your m is rest-mass energy and your p is some clever energy variant of momentum? Where does this come from? markweitzman's wannabe a theoretical physicist school markweitzman's wannabe a theoretical physicist school 1 year ago Sean seems to skirt over the fact that the perturbation expansion is in fact an asymptotic expansion - but they are still useful even though they don't converge even for electrodynamics. TimboJohn TimboJohn 1 year ago The equation for the "mass shell" appears to be analogous to the Pythagorean Theorem. What's that about? 2 Barefoot Barefoot 1 year ago (edited) Okay, I actually do have a question on this one... If "electronness" as we're calling it in our simplified code, (lepton number in the real world) is a preserved quantity, and an electron neutrino can carry "electronness", what happens when the anti-electron neutrino spontaneously changes flavor? Obviously the answer is "lepton number is only approximately conserved, and neutrino oscillation is exactly one of the things that violates it", but... if it is violable at all, in a way that, it seems to me, in no way involves an external influence that would explain that violation, then why is it conserved at all, even approximately? D. Glasby D. Glasby 1 year ago Darn, I was hoping Sean would apply for membership in the Luxuriant Flowing Hair Club for Scientists. Joe Taber Joe Taber 1 year ago What if the only real locality is measurement locality, entanglement, and dynamical locality is an emergent property of measurement-locality? Maybe entanglement would "prop up" space into three dimensions and be "propagated" by entanglement with and in the quantum vacuum. John Długosz John Długosz 1 year ago 52:40 "My box is getting worse and worse" That's what happens to my Amazon deliveries sometimes, too. Adithyaa Anand Adithyaa Anand 1 year ago 12:31 [e+'s arrow] Thank you for clarifying that. I was worried you might deem that question dumb enough to give a clarification to... Soul DFS Soul DFS 1 year ago “Backyard Einstein” 😆 that’s why I love you man! I was dying! Never cease to amaze me!!! 1 eefaaf eefaaf 1 year ago I was so hoping you'd say "I'm 110% sure you can't have a probability greater than 1" 6 Steve White Steve White 1 year ago (edited) wow. mindblowing. no wait .. mind expanding! Ronald L. Johnson Ronald L. Johnson 1 year ago less hair more science ;) just kidding, just started another one of my favorite shows...i know grade a content is forthcoming ;) 1 bmoneybby bmoneybby 1 year ago You have to fight through the shitty part of growing your hair out. Then after 1 year, the same people who thought it looked like trash will tell you how good it looks. It's empowering you just have to see it through, see yourself how you really look. Which is sexy my friend haha. Think like a rock star. Cause you are haha Sully Sullivan Sully Sullivan 1 year ago one thing I didn't understand, aren't there still infinite possible wavelengths even if you set a minimum scale? aren't there an infinite number of wavelengths BETWEEN any two wavelengths? Jainal Abdin Jainal Abdin 1 year ago Different modes with infinite number of energy states contributing to the vacuum energy being infinite seems analogous to the Ultraviolet Catastrophe problem for a black body emitting an infinite amount of energy? Maybe we need to quantise a further level for modal energy states? Are different energy states from modes across different fields interacting and are in some form of superposition, and when the vacuum energy is measured, we get the expected value? Eliézer José da Silva Rios Eliézer José da Silva Rios 1 year ago If Feynman diagrams can add more than 1 how can I be sure my below one adding is correct ? R C R C 1 year ago While enjoying every episode and the companion Q&A, I am also interested and observant of the curiously effective method of teaching being employed by Sean Carroll. In my opinion, these videos should be regarded as the 21st century social media Feynman Lectures. If there was homework and smaller groups with graduate assistants working with the students, then this would be functionally equivalent to an undergraduate overview course in physics. All my opinions of course. While I truly love to learn physics, I also love to learn about learning. This is a perfect storm. 2 twinner42 twinner42 1 year ago Quarantine hair growth is irrelevant if you've been growing it out for years already like me. remogaggi82 remogaggi82 1 year ago I liked the long hair! Either way you are awesome Sean. A Kumar A Kumar 1 year ago Love the haircut, your a star 🌟 1 Sean Dimmock Sean Dimmock 1 year ago When’s the quantum textbook coming!!!!! Michael Smith Michael Smith 1 year ago Haha. I feel the same exact way about my hair. Still debating if I should get it cut. dk6024 dk6024 1 year ago Thanks for the late post; I needed to get some work done, today. blaganger5 blaganger5 1 year ago Loved your longer hair, was very 70's-ish! J.D. Luke J.D. Luke 1 year ago (edited) At about 31:46 as you drew electron number, I started to become one with the universe. Then you apologized for making it too complicated, but that little addition of colored flows to the diagram was a brilliant insight for me. I could suddenly intuit (and I am very much an intuitive thinker) more about quantum fields and the various values flowing through them far better than I ever have before. Thank you. 1 QuantumZoflyne Yotaphi QuantumZoflyne Yotaphi 1 year ago I like the interaction part about the haircut 😂🖖🏻 2 LasVegasGames LasVegasGames 1 year ago Why is the Hamiltonian integrated over space and not spacetime, or does such a Hamiltonian exists which is integrated over spacetime? Bhadra Bhadra 1 year ago I doubt you could do slob you're far too cool.... and no offence but thank you for helping me wind down and sleep in the evenings. Love from the UK XxX John Bach John Bach 1 year ago Just finished 'Something Deeply Hidden', I made it to where you mention the reference to the title of the book! It's a perfect quote for the title (I feel good in spotting it since I suspect many readers would either have missed it or not gotten that far). For your next books, please make the references to the titles even more Deeply Hidden - I will enjoy the challenge of looking for them! len horn len horn 1 year ago you’re explanation on cutting your hair is the first thing i’ve half understood in your series Deep Recce Deep Recce 1 year ago Hahaha..we dont give a damn about your hair Professor, its what inside your head that we are all here to learn and be WoW..🤭🤭🤭 1 Boris Petrov Boris Petrov 1 year ago Degrees of freedom --- Penrose uses them as his argument that "string hypothesis" is -- mere fashion.... I don't understand anything here ;-)) Raymond Luxury-Yacht Raymond Luxury-Yacht 1 year ago Surely you could pull off the "mad professor" look with your hair! Valdagast Valdagast 1 year ago Internal pressure? You mean dark energy causes haircuts? Randy LaMonda Randy LaMonda 1 year ago Why isn’t the Higgs bozon the same thing as a graviton bobdole57 bobdole57 1 year ago I still haven't gotten my hair cut. I look like Paul Mccartney from Let It Be Quantum Delusion Quantum Delusion 1 year ago Internal pressure? You’re sure Jennifer didn’t have some influence? 10 NOVA longclaw NOVA longclaw 1 year ago I need you to take 12 steps back and start again. 8 Platonist Music Platonist Music 1 year ago Looking like a slob here, but then again, i probably did before the lock down as well. lmao Joshua A Martin Joshua A Martin 1 year ago pause and google.........