Or maybe why I can't? Quantum Quantum Quantum Chromodynamics Link to Patreon - one exclusive video per month: / acollierastro I have merch: store.dftba.co...
The video really delivers on its promise, at the beginning of my shower I didn't understand QCD and at the end of my shower I still do not understand QCD.
shoving mathematicians into lockers? well... that's what physicists do on a daily basis because the mathematicians keeps bickering about rigorousness or something
Oh, the flatulence jokes just waiting to be told… :P Just in case it satisfies anyone's curiosity, if we were to be strict with our Greek roots, I believe the topic would be called "quantum geumodynamics" - "gastro-" more precisely comes back to "stomach"!
@@dashoc9430 But cooking is known as "gastronomy" when attempting to sound important. I say they're trying to incite chaos along the lines of cosmologist/cosmetologist. About the only thing those two professions have in common is that they both need proficiency in Photoshop.
@@mal2ksc I don’t know exactly what the OP’s intentions were, but I took their comment to be humorous (and found it funny myself). My comment isn’t meant to negate it, but to complement it. Like the neutron to the OP’s proton, or the side to the their main :)
"You can't explain it to a six year old because it takes 4 years of undergrad and 4 years of grad school-" Ok, so they must be at LEAST 8 years old. Got it.
Takes about sixteen hours to teach all of the coding needed for simulation, though. PDEs, if you cut out the timewasting geometry, accounting math, and trains leaving Chicago, another three months. The real issue is all of QM is just models, and what's behind the models is only vaguely represented by all of QED and QCD, so possibly a six year old, undistracted by all the noise adults have in their heads might be Mozart, and all of us Salieri.
Einstein once said: "I have predicted many things in my life. My theory can predict Mercury's precession. My theory predicts black holes. But the prediction I am most proud off is that 12 year olds will incorrectly attribute quotes to me on the internet."
> sign up for a qcd lecture > Ask the professor if it's really about qcd or if it's just qed > They don't understand > Prepare a half hour CZcams video about the difference between qcd and qed > They laugh "it's a qcd lecture" > Attend > It's all qed
By watching at higher speed, it actually enhances understanding because all points are presented temporally closely together, this mitigates issue like 1) low memory retention (memory fading before all points are presented) and 2) ADHD by focusing all attention at shorter time frame.
@@xponen Thanks! I'd been steadying myself to rip through at 4x -- *or more!* -- so I could not understand QCD even faster than my peers. Now that I know it won't work, I can get ignorant about something else instead. Saved my afternoon!
My favorite quote about quantum mechanics is from CGPGrey: “look, ‘spin’ and ‘whirl around’ don’t mean what you think they mean. In the quantum world, words mean NOTHING, there is only MATH.”
My mental model of the relative complexity: QED: watching 2 or 3 billiard balls run into each other on a nice smooth pool table. QCD: watching a writhing ball of spaghetti the size of the solar system and oh yeah, the spaghetti is moving at nearly the speed of light and is made up of super-powerful magnets.
I think I can summerize QCD. It is a game where a lot of 6 year old quarks spin on thier hands or feet or jump up and down. They wear red, green or blue T-Shirts, some of them are a bit strange but others are charming. Then there are other players which can use glue to catch the quark players. The rules who can catch whom are complicated, you have to consider the color of the shirts, how they are spinning, relativistic effects and the probability of sun shine during the game. The rules are so complicated that there is no way to calculate the exact outcome of the game you can only do some computer simulations. And I forgot to mention that the best players can play as bosons which makes everything more complicated.
The more I listen to Dr Collier, the more I realize I don't know shit about fuck but also the more I enjoy realizing this about myself. Dr Collier is a superhero. Her power is knowledge. Her secret weapon is an anti-crackpot-Dunning-Krueger-syndrome-theorists mischievous smile. Thank you so much.
She easily destroys the false veneer of youtube/online-aquired science knowledge that so many have. Idk I watched a lot of pbs space time and though I at least knew a bit about quantum mechanics, but after watching her stuff I quickly realised that I don't know shit...
One of the problems is that the approach that makes the leap from QED to QCD seem simple and natural is a really mathematically abstract one, where you take *gauge symmetry* as the most important thing that determines the whole theory. Usually when you study electromagnetism in a quantum mechanics class, gauge symmetry comes in kind of late as an advanced topic. If you express electromagnetism as potentials, you can do things to the potentials and simultaneously do something to the phases of the matter wave functions, and it's unchanged even if you do it differently at every point in space-time. And then you turn it on its head and say that gauge symmetry is what *determines* electromagnetism--you start with the relativistic QM of matter particles, then add gauge symmetry and the potentials have to come in, then you somehow breathe life into those and treat them as aspects of a physical field and you've got QED. Then you say, well, the gauge symmetry involved a mathematical object called a Lie group, and for QED the group is the simplest nontrivial one you can use, "U(1)", which is actually the same as a circle (messing with phases of the wave function, which go in a circle). Then you go from "messing with the phase" to "messing with some multidimensional space of color charges", which is a different Lie group, and QCD falls out, and then you mess with other quantities (the "flavordynamics" stuff Angela was talking about) and a big chunk of the Standard Model falls out. And whether the force carrying field has charge has to do with whether the group operations are commutative. But the class has this big mountain climb to even get to that point and it's very abstract. How do you even do that in an elementary context? I haven't quite figured it out. I recall Heinz Pagels trying in his book "The Cosmic Code", but it was a stretch.
@@DavidvanDeijk This is how all the forces in the Standard Model are constructed--it's all gauge theory. The part I left out is that if you do this you get force-carrying particles that have no mass, but the W and Z particles that carry the weak force are very massive, and that's where the Higgs field comes in. Even general relativity is a different kind of gauge theory, where the gauge transformations are on space-time.
Maybe the elementary context can be fortified informally. YT has numerous high-quality videos that can serve as executive summaries much like what you went over here. Check out Highly Entropic Mind's episode "The math of how atomic nuclei stay together is surprisingly beautiful."
There is a reason for QCD : the subnuclear zoo. In the late 60s the number of particles discovered using particles accelerators numbered in the hundreds. QCD brought that mess down to a handful.
I don't know if you have ever tried to explain something to a 6 year old, but they will ask you why about a thousand times while you are explaining something. To me, this is the root of the quote. It is not about being able to get the 6 year old to understand or have them be able to explain in the future. It is about being able to answer all of their why questions. If you can accurately answer all of their questions then you fully understand the subject.
i want to give you half marks for this. i feel like the skill einstein is talking about is the ability to conceive of a useful model that can be built out of simple chunks in a recursive process where each step can be stamped as an image in a small mind. consider one of those dog dancing competitions, for example, where the trainer has trained the dog in an inordinate number of little elements, including the stitches that link them into sequences. dumb dog, complex result. however, i also know exactly what you're talking about and i think it's an admirable skill to be able to answer a child's but-why questions until the child is exhausted before the adult. this is a different but similar process of being able to package concepts for a small mind, and requires a really secure sense of philosophy to understand all things in terms of well defined components. the difference though is that in one process the adult is controlling the structure because they can see what the end point is and how to get there, and in the other process the child is allowed to drive. i realise it can be a fine distinction
@@5naxalotlyou never let a child start on that path without pressing them to tell you what they think or to give you a guess why first - that tends to slow the why why why’s down.
I'm procrastinating when I should be studying for my differential equations final exam tomorrow, and I saw this comment just as she said it. I feel this sentence in my soul...
Thank you. Fun explanation. When I got my Ph.D in physics, we were searching for quarks. I heard Feynman, Gell-Mann and others speak on Unified Field Theory at an APS meeting in D.C. I gave my first paper as a grad student and went down stairs after the talk. There was a standing room only crowd in the Ball Room. I wiggled in and found a place to stand and not block others. After the intro, Feynman spoke. Feynman had long hair light brown hair down to his shoulders. He was young and spoke with the accent of a Brooklyn truck driver. He opened with a pretty bold statement that was close to "I don't know what you know because I never read the literature". Someone gave his talk (Gell-Mann?) writing on an opaque projector with a black marker blocking 50% of the image (equations) on the screen with his head. We have still trying to do Unified Field Theory. Fun video.
Hi Angela! First of all, I loved the video! But I wanted to add on to what you said at the end -- that QCD can only be evaluated numerically (via lattice QCD). I just wanted to say that absolutely not! Most experimentally-relevant calculations of QCD are done completely analytically. It's literally what I did for my PhD and the ATLAS collaboration was even able to measure and compare to our analytical predictions. I know this isn't well-known in the community, so here's a bit of background: The idea that QCD can't be computed perturbatively ("knowing which Feynman diagrams matter") is because the strong coupling alpha_s is very large (0.118 at 91.2GeV, compared to 0.007 of QED). However, since alpha_s runs, it gets smaller as you go to higher energies (asymptotic freedom, as you mentioned in the outro). By the time that you get to experimentally-relevant energies (i.e. 13.6 TeV at the LHC), alpha_s is again small enough to be able to treat the theory as being perturbative. In fact, at experimental energies QCD is basically just fancy QED. So, recap: At small energies you need lattice QCD to say anything tangible, but at high energies QCD is just a regular perturbative theory. There is one additional complication however: The fact that colliders collide protons, which are low-energy QCD objects, and not quarks, which can be treated perturbatively. It turns out that this wrinkle gets handled by something called a "parton distribution function", which essentially connects quark/gluon cross-sections with proton cross-sections. In fact, because of this, your typical QCD experimental prediction pipeline looks as follows: 1) Experimentalists measure these parton distribution functions at other experiments, 2) A theorist computed the cross-section for some QCD process completely perturbatively/analytically, 3) They multiply their result with a parton distribution function. And voila, you've got yourself a phenomenological prediction for a proton-proton QCD experiment!
This is valid. In programming it is known as "rubber duck debugging" which is used for solving problems, at which you get into an answer while you are trying to describing the problem to someone else. To exploit this phenomenon, instead of bothering a friend to listen to you, they place a rubber duck and explain their hurdles and where they are stuck until you get an insight while you are bitcjing about it.
@@xantiommy work just had an outing and we ended the night at Dave & Busters, where one of my coworkers used all her credits on the rubber duck claw machine (honestly best value, cuz your credit doesn’t get used until you get a duck). Anyway, she gave them out and now I have an actual rubber duck to rubber-duck with as I develop. My coworkers didn’t know the term, and I showed them the wiki article, and the article’s main picture shows the same lil’ guy I got! Anyway, my troubleshooting ability is about to skyrocket
What frustrates me about comments like this is that quotes wrongly attributed to Lincoln and Einstein are, in fact, wrongly attributed to Mark Twain! 😉
At CalTech in 1970 (and probably in his books later) Feynman described trying to tell his father, an intelligent layperson, about what he did. I remember Feynman telling how, when his father asked “when the neutron becomes an electron and a proton, was the electron always there ‘inside’ the neutron?” “And I couldn’t explain it to him.”
But he did explain it to him. via his son talking about the “word bag” in his stomach that ran out of words. 😂. But maybe he got that analogy post 1970, yet it was a problem solved.
I remember someone asking if there was an electron inside the nucleus during beta decay. This derailed the lecture, and the question never was really answered.
Appreciate the space between "8" and your exclamation mark when counting the number of gluon types in your table. Not leaving any ammunition for these factorial jokers 😆
I love relearning all this stuff. When I studied it 40+ years ago unitary symmetry was the model and quarks were still somewhat controversial. Now everything's changed and I'm learning from people half my age.
@@ohno5559 in ur proposal, are u going to dynamically cram wontons into the burrito? With a glueon layer of cheese? Or will the burritos be inside the wontons?
When I was 6 years old I would get into trouble for mixing the colors of my Play-Doh. Imagine my horror if someone had tried to teach me that it was ok for quarks.
Angela just explained to me that QCD is a videogame where you have to train for years to get the basic controls down and the computer does all the playing but you recover the loot after tons of missions
I think the important thing is you successfully taught me that I don't need to know any more about QCD. I've tried before, but now I am happy to stop worrying about it. Thanks for the video Angela!
36:22 This went very well. I now understand why I don't understand QCD. That said, I feel I have a better understanding of what is in the forest, and why I should stay out of the forest. Thanks for taking the time to make this.
I am studying chemistry. The moment you said "field theory" i was like: "Nope. I have no clue what those are, and if i find out i'll be stuck modeling molecules for the rest of my life. Byeeeee!!"
that really is a feeling when learning about stuff in your field of study. You don't want to learn too much about something or you'll get hired to work with/study it! In urban planning, I've ignored some friends warnings against studying GIS.
My explanation of why QCD is hard (for physicists to do, which is kind of a different matter from why it's difficult to explain) is to show Feynman diagrams and explain roughly what they mean, then say: "you can always draw more and more complicated diagrams. With QED, these diagrams get less and less important, so you can often get away with ignoring them past a point, and get a pretty good answer by only computing the simple ones. With QCD, the complicated diagrams get *more* important, so you can't get away with that kind of trick."
Even ignoring the Landau pole, the # of diagrams grows too fast. It's an asymptotic series. The QED coupling constant is small enough that a reasonable # of diagrams leads to a "good enough" answer.
"I am not a professional science communicator" says PhD with 150k+ subscribers on a CZcams channel where she mostly communicates science. Jokes aside, love your content. Looking forward to finding out why my understanding of QCD is wrong. It's the one I thought I knew pretty well! Although I'm sitting here now wondering if anti-red and cyan are the same thing, so maybe not. Update: I'm not sure what I understand anymore, except this: to the chagrin of pure mathematians everywhere, Monte Carlo wins again.
Wow, you really give me hope! I’m a 66 year old retired woman and that you understand all this so well makes me happy. Thank goodness there is someone who understands this so well. Thank you.
I think you did a great job of explaining most of the stuff and got close to describing what's hard about QCD, but didn't quite get to the punchline. The hardest part about QCD isn't that the Feynman diagrams are more complicated, or that there's so many gluons and flavors - that's an annoying thing for sure, but people can still compute diagrams up to a couple of loops (especially using Mathematica packages). The hard and beautiful thing about QCD is that if you wanna describe the inside of a proton, it just doesn't make sense to compute Feynman diagrams because what's going on inside is nonperturbative. Feynman diagrams wouldn't give a meaningful answer in any way to the problem, even if you could compute and sum all of them! That's why we need to do the path integrals with lattice QCD. You got close to mentioning this when you talked about perturbing QED, but I think it's worth pointing out as another pitfall of Feynman diagrams. Not only are they a cartoon for the math, they are sometimes cartoons for math that we shouldn't be doing in the first place for certain physical questions. (I know that the main point of the video wasn't to explain why QCD is hard, just hard to explain. But I guess my point is that it's hard to explain if you start from Feynman diagrams, precisely because they don't work in the theory. But explaining it with just path integrals might be "easier"?) Cheers and thanks for all the fun the content!
If your average 5yo child is already familiar with advanced linear algebra, complex matrix calculus, Lagrangian mechanics, Dirac's quantum field equations, non-abelian Lie groups and the Yang-Mills gauge theory, yes, I think you can explain QCD to them.
As someone who doesn't have a physics degree and sucks at advanced math, this video taught me basically everything I'd actually want to know about qcd.
My best understanding of that "Einstein" quote is that giving a satisfying simplified explanation of something requires a much better understanding than what you need to just feel satisfied by your own understanding.
Quite the opposite. Without gluons there won't be even a single material that your Elmer's glue (in the theoretical case you could get any) would fail to work on.
The word "understanding" is kinda just a disguised query for a bunch of different things that are expected of people who "understand" a concept to be able to do with the concept, i.e. explain it, apply it, draw parallels to other concepts... like for many (most) words the true underlying reality is messy and complicated, the word just represents a pattern our brains abstract that reality into for convenience. Now _thats_ the real myth!
Except Feynman spent most of his time warning us that if understand something on paper because you're not smart enough or you've not spend enough time on it or you're not seeing it in the proper way and end up thinking like "come on, it is really complex, who can REALLY understand this? but i can manage the equations and say the right words, therefore it's ok" akin to a philosophical zombie, you're only fooling yourself.
Understanding buoyancy is easy, do you sink or float? Do you weight more or less than the water you can displace? It's a problem any child has asked and anybody after a couple years of school should be able to solve, assuming the boat is a rectangle or you just know the displacement. But there is so much more you could know: how the forces balance, hydrostatics, what is the force of the water made of, what is the force of gravity, what if you vary any or all of these in either space or time? Once you start asking these questions, you are now beginning to truly understand that topic.
You definitely did reminded me of the book called «Thinking physics». It's not for 6 yo, it's for middle schoolers, but it starts with integrals and ends with quantum theory, and all of that with actual physics problems explained in a way middle schooler would be able to do them. The book is wonderful introduction to physics for younger teens, you could learn it in your 5th year of school.
Really loved this video. One of those occasions where CZcams throws up a spot on recommendation as weirdly I'd just spent my Saturday lunch time reading an article about QCD in Scientific American, possibly to the bemusement of the staff at Wagamamas but certainly to my own bemusement. Whilst I definitely didn't understand it, I did get the impression it is an exciting time for QCD theorists who seem to have solved long standing problems evaluating the strength of the strong force against distance in the limit and at low energies. Then to have this video pop up within a few hours was perfect. I'm never going to understand QCD but I feel I don't understand it on a deeper level now 🙂 - You have a new subscriber.
I left school when I was 14 and even then I wasn’t great at math or science. I didn’t understand almost any of this. I still watch all your videos the whole way - there’s something so enjoyable about someone talking about a very specific topic they have mastery over.
What really impressed me when I learned Feynman diagrams is that they’re not cartoons, but notations. How expressive they are while maintaining a 1:1 relationship with complex equations was mind blowing to me.
I want to thank you from the bottom of my heart for what you have told me in your previous videos. I am very interested in physics and I am able to learn things pretty well. I have been reading books and for the most part I felt like I understood the English explanation of what happens in physics. I knew that I would have to understand the math in order to add to the knowledge of humanity in this field. I taught myself calculus 20 years after taking it in college and getting an A- but not really getting it. I understand what I taught myself. Thinking I could get a little into the math I was hit with reality quickly. So I procrastinated and I kept using words to learn physics. THEN YOU SAID THAT IF A PERSON DOESN'T DO THE MATH THEY ARE NOT DOING PHYSICS. I hate being patronized and people worrying about my feelings instead of being blunt So thank you for being your kinda snarky self. Oh I found free MIT classes or at least the lectures online linear algebra differential integral calculus more linear algebra matrices introduction to quantum physics weave and electric physics etc. I am still in the beginning but understanding and have an opportunity to actually succeed thank you
There may be a lot of made up quotes of Einstein, but he is a very good frame of reference a range of things. Like how it took Einstein 4 years after getting his PhD to finally get a professorship gig. And what’s even more crazy is that it took him four years after his miracle year, after producing four seminal pieces of research that also includes his Nobel-winning work, to get a job as a professor. If it took a Nobel laureate 4 years after he did his Nobel-winning work to get the job he wanted…
This video reminds me of that time I brought a proton and a gluon to my favorite bar. We had a strong bonding experience. What a positive interaction it was.
He'd probably just try to sleep with her. Sorry, all the Feynman worship grates on me. I remember talking to the old physicists at Caltech when I went there and they all kinda seemed to think he was a bit of a narcissistic asshole -- a brilliant one sure but also kinda a narcissistic asshole.
Perhaps it's my background as a programmer, but I really don't see the problem here. For me it's kinda backward, most of the time I don't have an elegant mathematical model, or even an algorithm for a particular problem, so for me "let's just brute force (if feasible) or simulate" is the first kind of solution I go for. Finding or creating a neat algorithm that runs fast and produces the exact solution is a nice cherry on top, you use it if you already know it or if your code *must* run fast. Having a closed-form mathematical solution, a formula that just spits out an answer is like having a surprise birthday present. For me, the thought that reality doesn't fit into a math model is just a base assumption. I'm very happy to be proven wrong, but the closer you get to reality, the more factors your program must consider - the rearer such happy accidents occur. Like, generating _the_ optimal schedule for a school that considers a basic set of restrictions (no double-booking of instructors, classrooms, and students, balanced loads on students and faculty, no excessive movement across the building, etc.) is already computationally intractable. And that's all in the macroscopic world, so no wonder that we can't have exact probabilistic models for the QCD. It's kinda amazing that we can solve a hydrogen atom!
In addition to the NP problems, simulating natural phenomena is messy on its own. The two tests are: "is it fast (enough)" and "does it look plausible (enough)". Obviously how those are weighted varies on what you're trying to do (1 second of simulation per day is acceptable for like, Pixar, but certainly not for Nintendo). Even in the macroscopic here, there are tons of things that get commonly ignored because they play so small a part in the classical physics. (E.g. approximating friction as a simple coefficient, ignoring aerodynamics, etc. intra-molecular interactions in liquids, etc. depending on the ~~field~~ domain.)
23:31 I think you make a really good point about the Feynman diagrams giving people a false sense of understanding, and especially about the whole “antimatter does not go backwards in time” thing
She covered this in depth in another video, and while I was initially pretty... defensive? about the interpretation, because-hey, the math works-her larger point about "unphysical" solutions to equations (like Dirac Holes) has ultimately won me over and disabused me of much of my juvenile Feynman Fanboism.
@@3X3NTR1K I now imagine a little positron constantly looking over its shoulder in order not to stumble into a nearby electron while walking backwards.
Until the 1800's, the popular perception was that bishops were highly educated, so all common aphorisms were attributed to one bishop or another. Then they were mostly given to Einstein. In the 1990's people who had just discovered email began attributing complete articles and speeches to either Bill Gates or Jay Leno, alternately. I always thought it was strange that they both had the same writing style.
The quote isn't meant to be taken literally. Kinda like how the subreddit ELI5 isn't meant to be taken literally, it just means people are looking for simplified answers.
I wanted to know where this quote originated (expecting some 19th century romantic) and was wildly disappointed that the original is attributed to *Hank Green.* But then I dug further and found that, in keeping with the theme of the opener, it's a misattribution (he _popularized_ it but didn't originate it)!
I'm so embarrassed. I used to think I understood some of this stuff. Frank Wilczeck wrote a book titled "Longing for the Harmonies" and I read it over and over and over until I was able to grasp his explanations. Now I realize he was explaining only the most basic notions of his field. He's a really good explainer. I'm just not a very good understander. Love the video!
Actually the channel «All Angles» gives quite good introduction of QCD with algebra and group theory, and the group theory is so simple, kindergartener would be able to understand it. Simple symmetries and basic counting and arithmetics under 10.
This channel is a gift to the world. I have more than once thought about transcribing these videos, adding visual explainers to the pages, and printing them out as accessible pamphlets! (I haven't, though... copyright's a bitch!)
The main obstacles to these sorts of ideas are our procrastination and the excuses we make for ourselves. Copyright, shmopyright! Jokes aside, I can see how copyright is a genuine obstacle, but if you're really determined, try something short and simple. You can fit a lot of info in a tri-fold brochure (double-sided).
@@DJRonnieG I did make an A3 horizontal scientific poster for the "Why aliens won't be made of Silicon" video! And I mostly 'scripted' one other pamphlet of this sort too. I just wouldn't actually distribute/sell these. They're more like pet projects for myself.
@tomasroque3338 I hear you, I've done my own fair share of pet projects in various forms of printed material. There's something rewarding about creating something nice in print that you can hold in your hand. It's long overdue for me to make a "turtle care pamphlet". So many people adopt Red-eared sliders with precious little information about their needs. 🐢 In any case good luck and if you ever want to share any finished project, feel free to drop me a comment.
@@DJRonnieG Wow, I love that! I've laid out plans for a custom chess board where each piece is a different type of turtle (the movements and playstyle being analogous to each turtle's behavior and traits). But it would cost some to built it, and that's the kind of thing I'd have to pay someone else to do.
Thank you for explaining why I don't understand QCD except in a vague, limited, fragmented, intuitive way. I appreciate the jargon tossed in at the end. All in all I've learned something, had a few laughs, and at least have enough information to keep asking questions.
Proton, unlike magnet, has degree of freedom in 4d, therefore repulsion between 2 protons changes in attraction. like with magnets: if to hold 2 magnets in 2 hands (dof=1) then repulsion wins, but if drop them (dof>1) then attraction wins.
@@michaelprozonicit's easy. protons starts to attract each other and make 1d lines (like with magnets if throw them on table) so one degree of freedom disappears. in that 1d line they became motionless (temperature=0)
Dang, you Fizzicists are so much more laid back. Whenever I went around with too many protons in my hand I was usually told "Get that $*':$@ back in the fume hood you idiot!"
@@user-ys3ev5sh3w ok, working on that now. how do i fit my beer can into a 1d line though and how many protons do I need for each 12oz can? Can you tell me which aisle at Home Depot has the protons?
After almost a decade of having a rough idea of what gluons are and what they are doing, I just now realised that gluons are called gluons because some physicist thought "hey these things are pretty strongly held together, its like these force mediators are the glue!" And now I am angry. Edit: I paused the video and posted this comment at the point literally 5 seconds before Angela articulated and then shared in my pain
Only Angela Collier would claim it's impossible to explain something and then proceed to explain it beautifully. Of course she didn't explain how to actually do QCD, but this video gave me a rough sense of what QCD is trying to do, what methods it uses to achieve that, and what the main obstacles are.
One thing that bothers me just a bit, Feynman diagrams are not only used in the path integral formulation - like, you use Feynman rules all the time even if you are exclusively doing canonical quantization
As an undergrad physics student, I thought this explanation was great for me. It gives a very good window into what I might be learning eventually. As usual, amazing video!
I think we over-emphasize the empirical aspect of particle theory, where we can't find when beta decay will happen, etc. and not that it's a probability distribution. Yes those mean the same thing, but it's a nitpick. I feel its more sufficient to my brain to say "we know that there's a 10% chance of an electron being 30 angstroms away from a point" than "we cannot actually find this electron"
This feels like, in molecular biology, going from understanding how certain proteins interact with other proteins or genes to developmental biology where you suddenly have 20,000-25,000 (ish for a eukaryote) points that all can be modified in many ways and exist in specific places at specific times. You can't really have an analytical explanation of multicellular development for now and im glad other stem people have similar struggles lol
It is possible to know what something is at one level without understanding how it works. We don't understand how most things work, so this is very common.
I want to get it, but I am irresistably distracted by that glorious neon-chromo Starfleet sculpture in the background. Well played, Doctor. Well played.
Why is it that we’re always taught that Feynman diagrams should have time going upwards but when we actually use Feynman diagrams time is always going across?
I think it's so cool that there are some types of expertise it's impossible to "dabble" in. You have to devote yourself to it, to even take the first steps. I suspect that's always been true, even in prehistory.
i've been a carer for schizophrenia for around ten years, i don't have any formal qualification other than a certificate that says i've done a carers course, but one thing i learned even before the course is that when someone is hallucinating saying "you're imagining things" results in a very bad day. anyway. i treat all people as if they are mentally ill, i find that most people have hard time understanding how to tie shoelaces, never mind einstein. so in order to get your point across and have it actually register in someone else's brain, you have to put things in the simplest terms - that, say, a six year old can grasp. cos most people are six year olds, mentally. including me.
"I treat all people as if they are mentally ill" if most people had a hard time trying their shoes, maybe your point of reference for mental illness is skewed? I get hyperbole but it's just kind of a weird thing to say
There is a very good quote from peter watt’s echopraxia “But people have an unfortunate habit of assuming they understand the reality just because they understood the analogy. You dumb down brain surgery enough for a preschooler to think he understands it, the little tyke's liable to grab a microwave scalpel and start cutting when no one's looking.”
"Angela Collier is my favourite CZcams science communicator"
- Albert Einstein
this quiote, I trust is from Uncle Albert, because it's true. Gr8! Peace ☮💜Love
"i was going to do that joke, but you got ahead of me."
- Albert Einstein's first cousin once removed
@@andressigalat602in other words, "A Einstein?"
"Angela told me Feynman was a dumbass" Albert Einstein. Am I doing this right?
"QCD on the lettuce" - A.E.
The video really delivers on its promise, at the beginning of my shower I didn't understand QCD and at the end of my shower I still do not understand QCD.
SUCCESS!!
You spend nearly 40 minutes in the shower?
@@thomasrivard9772 no, but I do spend about 25. shaving takes a while 🤷♂️
@@thomasrivard9772 You don't??
Glad i am not the only one who watches these in the shower
"Those are cartoons. They're not math." Angela shoving a category theorist into his locker.
shoving mathematicians into lockers? well... that's what physicists do on a daily basis because the mathematicians keeps bickering about rigorousness or something
I laughed so hard a frictionless spherical cow shot out my nose, keeping in mind that I only say that to simplify the math.
Sad Oliver Lugg noices
@@penttierareika4837 Oliver Lugg can define the set of all things that make you feel pain
_•said monadic noises•_
I would like to propose that "Quantum Gastrodynamics" is a way better term for weak force flavor interactions.
That would legit be a better name.
Oh, the flatulence jokes just waiting to be told… :P Just in case it satisfies anyone's curiosity, if we were to be strict with our Greek roots, I believe the topic would be called "quantum geumodynamics" - "gastro-" more precisely comes back to "stomach"!
@@dashoc9430 But cooking is known as "gastronomy" when attempting to sound important. I say they're trying to incite chaos along the lines of cosmologist/cosmetologist. About the only thing those two professions have in common is that they both need proficiency in Photoshop.
@@mal2ksc I don’t know exactly what the OP’s intentions were, but I took their comment to be humorous (and found it funny myself). My comment isn’t meant to negate it, but to complement it. Like the neutron to the OP’s proton, or the side to the their main :)
"Gastro" (γαστρο) is Greek for stomach, not flavor. Quantumstomachdynamics?
"You can't explain it to a six year old because it takes 4 years of undergrad and 4 years of grad school-"
Ok, so they must be at LEAST 8 years old. Got it.
Being delivered from the womb straight into Physics 101
@@aidanwarren4980 Get that fetus into AP classes pronto!
Takes about sixteen hours to teach all of the coding needed for simulation, though.
PDEs, if you cut out the timewasting geometry, accounting math, and trains leaving Chicago, another three months.
The real issue is all of QM is just models, and what's behind the models is only vaguely represented by all of QED and QCD, so possibly a six year old, undistracted by all the noise adults have in their heads might be Mozart, and all of us Salieri.
@@aidanwarren4980I knew that guy
@@bartroberts1514 8 years + 1 day
“Albert Einstein catching strays from Dr. Collier is one of my favorite things about this channel.” - Mark Twain
Damn, many illustrious thinkers on here watching A Collier, i had no idea
1:10 you can't believe everything that is written on the Internet © Einstein, 1990 🤣
"Something about that smells so bad it's not even pong" - Wolfgang Pauli
"I hear the voices of vegetables"
- A. Jones
"Actually it was Samuel Clemens who said that" - Eldrick Tont
I like Feynman's opposite quote: "If I could explain it simply, it wouldn't be worth a Nobel Prize."
Einstein once said: "I have predicted many things in my life. My theory can predict Mercury's precession. My theory predicts black holes. But the prediction I am most proud off is that 12 year olds will incorrectly attribute quotes to me on the internet."
> sign up for a qcd lecture
> Ask the professor if it's really about qcd or if it's just qed
> They don't understand
> Prepare a half hour CZcams video about the difference between qcd and qed
> They laugh "it's a qcd lecture"
> Attend
> It's all qed
The last 10 seconds is the professor saying QCD is beyond the scope of this QCD lecture.
Watching at 2x speed so I can not understand QCD in less than 20 mins
By watching at higher speed, it actually enhances understanding because all points are presented temporally closely together, this mitigates issue like 1) low memory retention (memory fading before all points are presented) and 2) ADHD by focusing all attention at shorter time frame.
@@xponen Thanks! I'd been steadying myself to rip through at 4x -- *or more!* -- so I could not understand QCD even faster than my peers. Now that I know it won't work, I can get ignorant about something else instead. Saved my afternoon!
you forgot to give it to the next person
Take a big drink on next party and explain it to someone not nerding physics. They will really understand it.
I'm really glad that this professional science communicator was able to ensure I understood that I do not understand QCD.
I take notes on your videos. Let's start a podcast.
10/10 would watch.
PLEASE I NEED THIS
I hope this conversation is happening off line!!
I’d watch a @kylehill collab with @acollierastro!
"Doesn't that suck for Einstein?...People just make stuff up and they say Einstein said it."
-Albert Einstein
always refer to yourself in the third person - AE
"my balls exploded"
- Albert Einstein
He died already, he doesn't care
"These videos are just her what grinds my gears rants."
-Albert Einstein
“W boson?? More like L bozo”- my attempt at a joke
L elementary particle
It's a good bit, congratulations.
Your attempt at a joke? more like your success at a joke. - my success at a joke
“What the fuck is a W boson”
-Albert Einstein
My favorite quote about quantum mechanics is from CGPGrey: “look, ‘spin’ and ‘whirl around’ don’t mean what you think they mean. In the quantum world, words mean NOTHING, there is only MATH.”
Math is a language, though. The reasons for doing the math, and the connection to experiment, can absolutely be written in English.
My mental model of the relative complexity:
QED: watching 2 or 3 billiard balls run into each other on a nice smooth pool table.
QCD: watching a writhing ball of spaghetti the size of the solar system and oh yeah, the spaghetti is moving at nearly the speed of light and is made up of super-powerful magnets.
I think I can summerize QCD. It is a game where a lot of 6 year old quarks spin on thier hands or feet or jump up and down. They wear red, green or blue T-Shirts, some of them are a bit strange but others are charming. Then there are other players which can use glue to catch the quark players. The rules who can catch whom are complicated, you have to consider the color of the shirts, how they are spinning, relativistic effects and the probability of sun shine during the game. The rules are so complicated that there is no way to calculate the exact outcome of the game you can only do some computer simulations.
And I forgot to mention that the best players can play as bosons which makes everything more complicated.
"you don't think the 5 year old understood machine learning, do you?"
not even that far into the video and i'm already cracking up
"Don't go around grabbing five year olds." -Angela Collier, science communicator
"Explain machine learning, CHILD!" 😂
Yea she is really funny.
The more I listen to Dr Collier, the more I realize I don't know shit about fuck but also the more I enjoy realizing this about myself. Dr Collier is a superhero. Her power is knowledge. Her secret weapon is an anti-crackpot-Dunning-Krueger-syndrome-theorists mischievous smile.
Thank you so much.
Dude this is pure gold.
I agree with every single word and laughed my ass off from start to finish.
Hats off to you my friend.
@@clvr51 Me too.
you were able to finally put into words how I've been thinking about her, perfection
Yup. That.
She easily destroys the false veneer of youtube/online-aquired science knowledge that so many have. Idk I watched a lot of pbs space time and though I at least knew a bit about quantum mechanics, but after watching her stuff I quickly realised that I don't know shit...
One of the problems is that the approach that makes the leap from QED to QCD seem simple and natural is a really mathematically abstract one, where you take *gauge symmetry* as the most important thing that determines the whole theory. Usually when you study electromagnetism in a quantum mechanics class, gauge symmetry comes in kind of late as an advanced topic. If you express electromagnetism as potentials, you can do things to the potentials and simultaneously do something to the phases of the matter wave functions, and it's unchanged even if you do it differently at every point in space-time. And then you turn it on its head and say that gauge symmetry is what *determines* electromagnetism--you start with the relativistic QM of matter particles, then add gauge symmetry and the potentials have to come in, then you somehow breathe life into those and treat them as aspects of a physical field and you've got QED.
Then you say, well, the gauge symmetry involved a mathematical object called a Lie group, and for QED the group is the simplest nontrivial one you can use, "U(1)", which is actually the same as a circle (messing with phases of the wave function, which go in a circle).
Then you go from "messing with the phase" to "messing with some multidimensional space of color charges", which is a different Lie group, and QCD falls out, and then you mess with other quantities (the "flavordynamics" stuff Angela was talking about) and a big chunk of the Standard Model falls out. And whether the force carrying field has charge has to do with whether the group operations are commutative.
But the class has this big mountain climb to even get to that point and it's very abstract. How do you even do that in an elementary context? I haven't quite figured it out. I recall Heinz Pagels trying in his book "The Cosmic Code", but it was a stretch.
You don't. You just don't ask anyone that hasn't already climbed lots of mountains to follow you on a tour of the Seven Summits.
@@Lolleka oh yeah, and then Heinz Pagels died falling off a mountain
Thanks, hope this is true because then i learned something
@@DavidvanDeijk This is how all the forces in the Standard Model are constructed--it's all gauge theory. The part I left out is that if you do this you get force-carrying particles that have no mass, but the W and Z particles that carry the weak force are very massive, and that's where the Higgs field comes in.
Even general relativity is a different kind of gauge theory, where the gauge transformations are on space-time.
Maybe the elementary context can be fortified informally. YT has numerous high-quality videos that can serve as executive summaries much like what you went over here. Check out Highly Entropic Mind's episode "The math of how atomic nuclei stay together is surprisingly beautiful."
There is a reason for QCD : the subnuclear zoo.
In the late 60s the number of particles discovered using particles accelerators numbered in the hundreds. QCD brought that mess down to a handful.
“Subnuclear zoo” is one of the wildest phrases I’ve ever heard
I don't know if you have ever tried to explain something to a 6 year old, but they will ask you why about a thousand times while you are explaining something. To me, this is the root of the quote. It is not about being able to get the 6 year old to understand or have them be able to explain in the future. It is about being able to answer all of their why questions. If you can accurately answer all of their questions then you fully understand the subject.
I wish this comment was the most liked one
And chances are that you do not _fully_ understand any topic, and this is one of the most effective ways to recognize the things you don’t.
i want to give you half marks for this. i feel like the skill einstein is talking about is the ability to conceive of a useful model that can be built out of simple chunks in a recursive process where each step can be stamped as an image in a small mind. consider one of those dog dancing competitions, for example, where the trainer has trained the dog in an inordinate number of little elements, including the stitches that link them into sequences. dumb dog, complex result. however, i also know exactly what you're talking about and i think it's an admirable skill to be able to answer a child's but-why questions until the child is exhausted before the adult. this is a different but similar process of being able to package concepts for a small mind, and requires a really secure sense of philosophy to understand all things in terms of well defined components. the difference though is that in one process the adult is controlling the structure because they can see what the end point is and how to get there, and in the other process the child is allowed to drive. i realise it can be a fine distinction
@@5naxalotl great elaboration. Of note though is that Einstein did not say that quote. Is there a different one you’re referring to?
@@5naxalotlyou never let a child start on that path without pressing them to tell you what they think or to give you a guess why first - that tends to slow the why why why’s down.
“ I’m saying words but math math math.” I think I need a T-shirt that says this.
I'm procrastinating when I should be studying for my differential equations final exam tomorrow, and I saw this comment just as she said it. I feel this sentence in my soul...
Einstein said that
@@ypey1 I knew it!
@@mallninja9805 good luck on the exam! 🙌
please ❤ but a tank top haha
Thank you. Fun explanation. When I got my Ph.D in physics, we were searching for quarks. I heard Feynman, Gell-Mann and others speak on Unified Field Theory at an APS meeting in D.C. I gave my first paper as a grad student and went down stairs after the talk. There was a standing room only crowd in the Ball Room. I wiggled in and found a place to stand and not block others. After the intro, Feynman spoke. Feynman had long hair light brown hair down to his shoulders. He was young and spoke with the accent of a Brooklyn truck driver. He opened with a pretty bold statement that was close to "I don't know what you know because I never read the literature". Someone gave his talk (Gell-Mann?) writing on an opaque projector with a black marker blocking 50% of the image (equations) on the screen with his head. We have still trying to do Unified Field Theory. Fun video.
Hi Angela! First of all, I loved the video! But I wanted to add on to what you said at the end -- that QCD can only be evaluated numerically (via lattice QCD). I just wanted to say that absolutely not! Most experimentally-relevant calculations of QCD are done completely analytically. It's literally what I did for my PhD and the ATLAS collaboration was even able to measure and compare to our analytical predictions.
I know this isn't well-known in the community, so here's a bit of background: The idea that QCD can't be computed perturbatively ("knowing which Feynman diagrams matter") is because the strong coupling alpha_s is very large (0.118 at 91.2GeV, compared to 0.007 of QED). However, since alpha_s runs, it gets smaller as you go to higher energies (asymptotic freedom, as you mentioned in the outro). By the time that you get to experimentally-relevant energies (i.e. 13.6 TeV at the LHC), alpha_s is again small enough to be able to treat the theory as being perturbative. In fact, at experimental energies QCD is basically just fancy QED. So, recap: At small energies you need lattice QCD to say anything tangible, but at high energies QCD is just a regular perturbative theory.
There is one additional complication however: The fact that colliders collide protons, which are low-energy QCD objects, and not quarks, which can be treated perturbatively. It turns out that this wrinkle gets handled by something called a "parton distribution function", which essentially connects quark/gluon cross-sections with proton cross-sections. In fact, because of this, your typical QCD experimental prediction pipeline looks as follows: 1) Experimentalists measure these parton distribution functions at other experiments, 2) A theorist computed the cross-section for some QCD process completely perturbatively/analytically, 3) They multiply their result with a parton distribution function. And voila, you've got yourself a phenomenological prediction for a proton-proton QCD experiment!
thank you for saying this, that really bothered me
Nice!
Do you think this would reach general undergrad level education anytime soon? Obviously not its most verbose form!
I used to have an abstract algebra professor who told us that you don't understand a proof until you can explain it to your teddy bear.
If the teddy bear understands your explanation, you have an entirely different problem on your hands.
This is valid. In programming it is known as "rubber duck debugging" which is used for solving problems, at which you get into an answer while you are trying to describing the problem to someone else.
To exploit this phenomenon, instead of bothering a friend to listen to you, they place a rubber duck and explain their hurdles and where they are stuck until you get an insight while you are bitcjing about it.
@@xantiommy work just had an outing and we ended the night at Dave & Busters, where one of my coworkers used all her credits on the rubber duck claw machine (honestly best value, cuz your credit doesn’t get used until you get a duck).
Anyway, she gave them out and now I have an actual rubber duck to rubber-duck with as I develop. My coworkers didn’t know the term, and I showed them the wiki article, and the article’s main picture shows the same lil’ guy I got!
Anyway, my troubleshooting ability is about to skyrocket
This makes way more sense than the saying it's a spoof on.
"I never said half the things I said." - Yogi Berra
"i never said half the things i said" - babe ruth
"First time?" -Mark Twain
I wonder if he really said that.
Berra actually said a LOT of really funny things that are well documented. There's a bunch he didn't say, but I think that one is real.
I think that quote was mine - Ghandi
I'm extremely grateful to this video for showing me that a Saturn V plushy not only exists but is now also in my online shopping cart.
Plushy? I thought it was one of those wobbly AI generated things.
"wait, this video has nothing to do with war. why am i here?"
- Sun Tzu
"Shut up dude, it's quantum" - Richard Feynman
One could make a great debate between Lincoln and Einstein with all the things they never said.
You're quoting Socrates, right?
@@KitagumaIgennah that’s Plato
What frustrates me about comments like this is that quotes wrongly attributed to Lincoln and Einstein are, in fact, wrongly attributed to Mark Twain!
😉
Lincoln had a secretary named Einstein. Einstein had a secretary named Lincoln.
With Yogi Berra as moderator
At CalTech in 1970 (and probably in his books later) Feynman described trying to tell his father, an intelligent layperson, about what he did. I remember Feynman telling how, when his father asked “when the neutron becomes an electron and a proton, was the electron always there ‘inside’ the neutron?” “And I couldn’t explain it to him.”
Hell, if I could explain it to the average person, it wouldn't have been worth the Nobel Prize."-Richard Feynman.
But he did explain it to him. via his son talking about the “word bag” in his stomach that ran out of words. 😂. But maybe he got that analogy post 1970, yet it was a problem solved.
I remember someone asking if there was an electron inside the nucleus during beta decay. This derailed the lecture, and the question never was really answered.
Does anyone have a source for this? Would really like to read/watch the full speech/lecture.
I can explain that! I'd just say "no".
(that's close enough to being the right answer)
Appreciate the space between "8" and your exclamation mark when counting the number of gluon types in your table. Not leaving any ammunition for these factorial jokers 😆
I love relearning all this stuff. When I studied it 40+ years ago unitary symmetry was the model and quarks were still somewhat controversial. Now everything's changed and I'm learning from people half my age.
QCD is the most complex, sciency sounding name I've ever heard. Even more than the mathematics of quantum neutrino fields --Albert Einstein
😂
Now start mixing different cool sounding sciency professions together. How about Quantum Computational linguistic Chromo Dynamics.
@@Rockyzach88 you've embiggened science with your cromulent vocabulary. 🫵🫡🍻
Mathematics of wonton burrito meals. Got it.
@@ohno5559 in ur proposal, are u going to dynamically cram wontons into the burrito? With a glueon layer of cheese? Or will the burritos be inside the wontons?
When I was 6 years old I would get into trouble for mixing the colors of my Play-Doh. Imagine my horror if someone had tried to teach me that it was ok for quarks.
Physics parents: "No! You don't have the same quantity of red, green and blue! That's illegal!"
You should read about how your brain perceives colors. You’ll probably be so traumatized that you’ll gouge your eyes out.
@@AdrianBoyko So... you *shouldn't*.
@@DamienPalmer I already did 😵
Hold on... I really think we need to go back to the maths here so you can more fully grasp how everything you know about Play-Doh is wrong.
Angela just explained to me that QCD is a videogame where you have to train for years to get the basic controls down and the computer does all the playing but you recover the loot after tons of missions
I think the important thing is you successfully taught me that I don't need to know any more about QCD. I've tried before, but now I am happy to stop worrying about it. Thanks for the video Angela!
"you really think someone would do that, go on the internet and tell lies?" -Aberham Lincoln
Aberham Linkin
@@jocabulous Aberham Linkin Park
@@lbgstzockt8493Abracadabrahamilton LinkedIn
-shinzo abe lincoln
I think this is misattributed, didn't Einstein say this?
“Quantum Flavor Dynamics” sounds like the motto of a New Age Guy Fieri
"Quantum Flavour Dynamics" needs a t shirt. A lickable t shirt.
I instantly thought it'd be a sick name for a math rock band lol
36:22 This went very well. I now understand why I don't understand QCD.
That said, I feel I have a better understanding of what is in the forest, and why I should stay out of the forest.
Thanks for taking the time to make this.
I am studying chemistry. The moment you said "field theory" i was like: "Nope. I have no clue what those are, and if i find out i'll be stuck modeling molecules for the rest of my life. Byeeeee!!"
that really is a feeling when learning about stuff in your field of study. You don't want to learn too much about something or you'll get hired to work with/study it! In urban planning, I've ignored some friends warnings against studying GIS.
"Don't go around grabbing five year olds"
- Angela Collier (but I'm pretty sure Albert Einstein said it first)
My explanation of why QCD is hard (for physicists to do, which is kind of a different matter from why it's difficult to explain) is to show Feynman diagrams and explain roughly what they mean, then say: "you can always draw more and more complicated diagrams. With QED, these diagrams get less and less important, so you can often get away with ignoring them past a point, and get a pretty good answer by only computing the simple ones. With QCD, the complicated diagrams get *more* important, so you can't get away with that kind of trick."
That's a great point.
Exactly. The main reason is the sign of the beta function and that was missing from the video.
Very informative, thanks!
Even ignoring the Landau pole, the # of diagrams grows too fast. It's an asymptotic series. The QED coupling constant is small enough that a reasonable # of diagrams leads to a "good enough" answer.
QCD is the 1+2+3+4+... = -1/12 of physics?
You definitely can explain QCD to a six year old, it's just the explanation takes usually about two decades.
Then you explained QCD to a 26 year old
@@roger5059 would it be more accurate to say you explained it to a 16-year-old? That's the average age at least
"I am not a professional science communicator" says PhD with 150k+ subscribers on a CZcams channel where she mostly communicates science.
Jokes aside, love your content. Looking forward to finding out why my understanding of QCD is wrong. It's the one I thought I knew pretty well! Although I'm sitting here now wondering if anti-red and cyan are the same thing, so maybe not.
Update: I'm not sure what I understand anymore, except this: to the chagrin of pure mathematians everywhere, Monte Carlo wins again.
I mean, which 6-Years old cannot understand irreducible representations of SU(3)?
Still prefer R3. A simple sphere and no tangrnts
A 6 year old in a woke school.
this gotdamn american school system... when i was a kid, it was the three R's: readin', ritin', irreducibl' representations of SU(3)
@@steffenbendel6031Can you explain "irreducible representations of SU(3)" to a 6 year old or are you "woke" as well?
@@steffenbendel6031what is a woke school and why is that a bad thing?
They obviously meant explaining it to a 6 yr old Einstein.
Wow, you really give me hope! I’m a 66 year old retired woman and that you understand all this so well makes me happy. Thank goodness there is someone who understands this so well. Thank you.
I think you did a great job of explaining most of the stuff and got close to describing what's hard about QCD, but didn't quite get to the punchline. The hardest part about QCD isn't that the Feynman diagrams are more complicated, or that there's so many gluons and flavors - that's an annoying thing for sure, but people can still compute diagrams up to a couple of loops (especially using Mathematica packages).
The hard and beautiful thing about QCD is that if you wanna describe the inside of a proton, it just doesn't make sense to compute Feynman diagrams because what's going on inside is nonperturbative. Feynman diagrams wouldn't give a meaningful answer in any way to the problem, even if you could compute and sum all of them! That's why we need to do the path integrals with lattice QCD. You got close to mentioning this when you talked about perturbing QED, but I think it's worth pointing out as another pitfall of Feynman diagrams. Not only are they a cartoon for the math, they are sometimes cartoons for math that we shouldn't be doing in the first place for certain physical questions.
(I know that the main point of the video wasn't to explain why QCD is hard, just hard to explain. But I guess my point is that it's hard to explain if you start from Feynman diagrams, precisely because they don't work in the theory. But explaining it with just path integrals might be "easier"?)
Cheers and thanks for all the fun the content!
If your average 5yo child is already familiar with advanced linear algebra, complex matrix calculus, Lagrangian mechanics, Dirac's quantum field equations, non-abelian Lie groups and the Yang-Mills gauge theory, yes, I think you can explain QCD to them.
Think of how stupid the average 5yo is, and realize half of them are stupider than that. They may not have even mastered their Dirac.
As someone who doesn't have a physics degree and sucks at advanced math, this video taught me basically everything I'd actually want to know about qcd.
The pain on your face as you got out the "they're called gluons because... they stick... things together... like glue" xD
My best understanding of that "Einstein" quote is that giving a satisfying simplified explanation of something requires a much better understanding than what you need to just feel satisfied by your own understanding.
In this video, I learned that without gluons my Elmer's glue wouldn't work.
I mean yes.
Elmer's glue using photon (QED), while atomic nucleus using gluon (QCD).
Quite the opposite. Without gluons there won't be even a single material that your Elmer's glue (in the theoretical case you could get any) would fail to work on.
'understanding' something is perhaps the biggest myth of physics.
This comment goes so hard
The word "understanding" is kinda just a disguised query for a bunch of different things that are expected of people who "understand" a concept to be able to do with the concept, i.e. explain it, apply it, draw parallels to other concepts... like for many (most) words the true underlying reality is messy and complicated, the word just represents a pattern our brains abstract that reality into for convenience. Now _thats_ the real myth!
Except Feynman spent most of his time warning us that if understand something on paper because you're not smart enough or you've not spend enough time on it or you're not seeing it in the proper way and end up thinking like "come on, it is really complex, who can REALLY understand this? but i can manage the equations and say the right words, therefore it's ok" akin to a philosophical zombie, you're only fooling yourself.
Understanding buoyancy is easy, do you sink or float? Do you weight more or less than the water you can displace? It's a problem any child has asked and anybody after a couple years of school should be able to solve, assuming the boat is a rectangle or you just know the displacement. But there is so much more you could know: how the forces balance, hydrostatics, what is the force of the water made of, what is the force of gravity, what if you vary any or all of these in either space or time? Once you start asking these questions, you are now beginning to truly understand that topic.
"I'm gonna explain why I can't explain it"
My favorite kind of video
You definitely did reminded me of the book called «Thinking physics». It's not for 6 yo, it's for middle schoolers, but it starts with integrals and ends with quantum theory, and all of that with actual physics problems explained in a way middle schooler would be able to do them. The book is wonderful introduction to physics for younger teens, you could learn it in your 5th year of school.
Thanks! I now have a full understanding of QCD from this 30m CZcams video
That’s exactly what Einstein said!
Float like a butterfly, sting like a bee.
-Allen Einstein
"I don't fear the man that solved a thousand different equations,
I fear the man that solved the same equation a thousand times."
- Albert Eistein
Sexy, almost evil,
talkin' bout butterflies in my head
-Shifty Shellshock
I have been trawling various wikipedia articles every so often for years trying to understand the "but why" of QCD, so this is great for me
Really loved this video. One of those occasions where CZcams throws up a spot on recommendation as weirdly I'd just spent my Saturday lunch time reading an article about QCD in Scientific American, possibly to the bemusement of the staff at Wagamamas but certainly to my own bemusement. Whilst I definitely didn't understand it, I did get the impression it is an exciting time for QCD theorists who seem to have solved long standing problems evaluating the strength of the strong force against distance in the limit and at low energies. Then to have this video pop up within a few hours was perfect. I'm never going to understand QCD but I feel I don't understand it on a deeper level now 🙂 - You have a new subscriber.
I left school when I was 14 and even then I wasn’t great at math or science. I didn’t understand almost any of this. I still watch all your videos the whole way - there’s something so enjoyable about someone talking about a very specific topic they have mastery over.
If a 6-year old can't explain something to me, can I understand it?
A good way to find out what they know.
@@GrantWaller.-hf6jn Ha! Yes!
What really impressed me when I learned Feynman diagrams is that they’re not cartoons, but notations. How expressive they are while maintaining a 1:1 relationship with complex equations was mind blowing to me.
I want to thank you from the bottom of my heart for what you have told me in your previous videos. I am very interested in physics and I am able to learn things pretty well. I have been reading books and for the most part I felt like I understood the English explanation of what happens in physics. I knew that I would have to understand the math in order to add to the knowledge of humanity in this field.
I taught myself calculus 20 years after taking it in college and getting an A- but not really getting it. I understand what I taught myself.
Thinking I could get a little into the math I was hit with reality quickly.
So I procrastinated and I kept using words to learn physics.
THEN YOU SAID THAT IF A PERSON DOESN'T DO THE MATH THEY ARE NOT DOING PHYSICS.
I hate being patronized and people worrying about my feelings instead of being blunt
So thank you for being your kinda snarky self.
Oh I found free MIT classes or at least the lectures online linear algebra differential integral calculus more linear algebra matrices introduction to quantum physics weave and electric physics etc.
I am still in the beginning but understanding and have an opportunity to actually succeed thank you
There may be a lot of made up quotes of Einstein, but he is a very good frame of reference a range of things.
Like how it took Einstein 4 years after getting his PhD to finally get a professorship gig. And what’s even more crazy is that it took him four years after his miracle year, after producing four seminal pieces of research that also includes his Nobel-winning work, to get a job as a professor.
If it took a Nobel laureate 4 years after he did his Nobel-winning work to get the job he wanted…
Well, maybe Mileva was busy and couldn't do the work or him.
"There may be a lot of made up quotes of Einstein, but he is a very good frame of reference a range of things."
-Albert Einstein
This video reminds me of that time I brought a proton and a gluon to my favorite bar. We had a strong bonding experience. What a positive interaction it was.
😆
Go to bed. 👉 Go to bed right now and think about what you said...
😊
@@ChristopherSadlowski 🤣🤣
Why did the quark fall off my school project? Because I forgot to put the glue on.
If Feynman could have watched Angela's videos, he would have had the biggest grin from start to finish.
He'd probably just try to sleep with her.
Sorry, all the Feynman worship grates on me. I remember talking to the old physicists at Caltech when I went there and they all kinda seemed to think he was a bit of a narcissistic asshole -- a brilliant one sure but also kinda a narcissistic asshole.
the steady pace and enthusiasm with which you present a really cool topic (at the pointy end of science) makes for a great video
Perhaps it's my background as a programmer, but I really don't see the problem here. For me it's kinda backward, most of the time I don't have an elegant mathematical model, or even an algorithm for a particular problem, so for me "let's just brute force (if feasible) or simulate" is the first kind of solution I go for.
Finding or creating a neat algorithm that runs fast and produces the exact solution is a nice cherry on top, you use it if you already know it or if your code *must* run fast.
Having a closed-form mathematical solution, a formula that just spits out an answer is like having a surprise birthday present.
For me, the thought that reality doesn't fit into a math model is just a base assumption. I'm very happy to be proven wrong, but the closer you get to reality, the more factors your program must consider - the rearer such happy accidents occur.
Like, generating _the_ optimal schedule for a school that considers a basic set of restrictions (no double-booking of instructors, classrooms, and students, balanced loads on students and faculty, no excessive movement across the building, etc.) is already computationally intractable. And that's all in the macroscopic world, so no wonder that we can't have exact probabilistic models for the QCD. It's kinda amazing that we can solve a hydrogen atom!
Love this comment, I completely agree (probably also because I'm a programmer)
In addition to the NP problems, simulating natural phenomena is messy on its own. The two tests are: "is it fast (enough)" and "does it look plausible (enough)". Obviously how those are weighted varies on what you're trying to do (1 second of simulation per day is acceptable for like, Pixar, but certainly not for Nintendo).
Even in the macroscopic here, there are tons of things that get commonly ignored because they play so small a part in the classical physics. (E.g. approximating friction as a simple coefficient, ignoring aerodynamics, etc. intra-molecular interactions in liquids, etc. depending on the ~~field~~ domain.)
23:31 I think you make a really good point about the Feynman diagrams giving people a false sense of understanding, and especially about the whole “antimatter does not go backwards in time” thing
She covered this in depth in another video, and while I was initially pretty... defensive? about the interpretation, because-hey, the math works-her larger point about "unphysical" solutions to equations (like Dirac Holes) has ultimately won me over and disabused me of much of my juvenile Feynman Fanboism.
We should describe it differently wrong ways instead. Like:
"Matter and antimatter both go forward in time, but antimatter does it walking backwards."
@@3X3NTR1K I now imagine a little positron constantly looking over its shoulder in order not to stumble into a nearby electron while walking backwards.
Until the 1800's, the popular perception was that bishops were highly educated, so all common aphorisms were attributed to one bishop or another. Then they were mostly given to Einstein. In the 1990's people who had just discovered email began attributing complete articles and speeches to either Bill Gates or Jay Leno, alternately. I always thought it was strange that they both had the same writing style.
The quote isn't meant to be taken literally. Kinda like how the subreddit ELI5 isn't meant to be taken literally, it just means people are looking for simplified answers.
13:26 "Behold! The field in which I grow my equations. Lay thine eyes upon it and thou shalt see that it is -incredibly complicated- barren.
I wanted to know where this quote originated (expecting some 19th century romantic) and was wildly disappointed that the original is attributed to *Hank Green.*
But then I dug further and found that, in keeping with the theme of the opener, it's a misattribution (he _popularized_ it but didn't originate it)!
I'm so embarrassed.
I used to think I understood some of this stuff.
Frank Wilczeck wrote a book titled "Longing for the Harmonies" and I read it over and over and over until I was able to grasp his explanations.
Now I realize he was explaining only the most basic notions of his field.
He's a really good explainer.
I'm just not a very good understander.
Love the video!
Ironically I did learn more from this 37 minute video about QCD/the strong interaction than I did in my grad particle physics course.
Actually the channel «All Angles» gives quite good introduction of QCD with algebra and group theory, and the group theory is so simple, kindergartener would be able to understand it. Simple symmetries and basic counting and arithmetics under 10.
This channel is a gift to the world.
I have more than once thought about transcribing these videos, adding visual explainers to the pages, and printing them out as accessible pamphlets!
(I haven't, though... copyright's a bitch!)
The main obstacles to these sorts of ideas are our procrastination and the excuses we make for ourselves. Copyright, shmopyright! Jokes aside, I can see how copyright is a genuine obstacle, but if you're really determined, try something short and simple. You can fit a lot of info in a tri-fold brochure (double-sided).
@@DJRonnieG I did make an A3 horizontal scientific poster for the "Why aliens won't be made of Silicon" video! And I mostly 'scripted' one other pamphlet of this sort too. I just wouldn't actually distribute/sell these. They're more like pet projects for myself.
@tomasroque3338 I hear you, I've done my own fair share of pet projects in various forms of printed material. There's something rewarding about creating something nice in print that you can hold in your hand.
It's long overdue for me to make a "turtle care pamphlet". So many people adopt Red-eared sliders with precious little information about their needs. 🐢
In any case good luck and if you ever want to share any finished project, feel free to drop me a comment.
@@DJRonnieG Wow, I love that! I've laid out plans for a custom chess board where each piece is a different type of turtle (the movements and playstyle being analogous to each turtle's behavior and traits). But it would cost some to built it, and that's the kind of thing I'd have to pay someone else to do.
You know we're the worst when we all come down here immediately to make up a bullshit quote only to see a million people have beat us to it.
-Albert Einstein
Thank you for explaining why I don't understand QCD except in a vague, limited, fragmented, intuitive way. I appreciate the jargon tossed in at the end. All in all I've learned something, had a few laughs, and at least have enough information to keep asking questions.
"She right, I withdraw my statement and offer my congratulations." - Einstein
"if you hold a proton in your hand it will just chill”
proton beer cozy
Proton, unlike magnet, has degree of freedom in 4d, therefore repulsion between 2 protons changes in attraction.
like with magnets: if to hold 2 magnets in 2 hands (dof=1) then repulsion wins, but if drop them (dof>1) then attraction wins.
@@user-ys3ev5sh3w but how does that keep my beer cold on a hot summer day?
@@michaelprozonicit's easy. protons starts to attract each other and make 1d lines (like with magnets if throw them on table) so one degree of freedom disappears.
in that 1d line they became motionless (temperature=0)
Dang, you Fizzicists are so much more laid back.
Whenever I went around with too many protons in my hand I was usually told "Get that $*':$@ back in the fume hood you idiot!"
@@user-ys3ev5sh3w ok, working on that now. how do i fit my beer can into a 1d line though and how many protons do I need for each 12oz can? Can you tell me which aisle at Home Depot has the protons?
16:37 "Every single thing you know and touch and love can be described with qed"
Put that on a T-Shirt and sell it please.
But I love gravity - that keeps me grounded.
Yes! Also "it's all electrons babe"
I'm going to show up with my “The cool stuff is actually all organic chemistry” t-shirt and start an argument.
There's also caesium-133 but it doesn't meet the "love" criterion.
Also... _is mostly described with_
After almost a decade of having a rough idea of what gluons are and what they are doing, I just now realised that gluons are called gluons because some physicist thought "hey these things are pretty strongly held together, its like these force mediators are the glue!" And now I am angry.
Edit: I paused the video and posted this comment at the point literally 5 seconds before Angela articulated and then shared in my pain
Only Angela Collier would claim it's impossible to explain something and then proceed to explain it beautifully. Of course she didn't explain how to actually do QCD, but this video gave me a rough sense of what QCD is trying to do, what methods it uses to achieve that, and what the main obstacles are.
One thing that bothers me just a bit, Feynman diagrams are not only used in the path integral formulation - like, you use Feynman rules all the time even if you are exclusively doing canonical quantization
1. cool glasses
2. great video yo
3. "Be the change you wish to see in the world" -- 50 Cent
Thank you 50 Cent
The deadpan humour is awesome. Thank you for your contribution of good content on CZcams :D
As an undergrad physics student, I thought this explanation was great for me. It gives a very good window into what I might be learning eventually. As usual, amazing video!
I think we over-emphasize the empirical aspect of particle theory, where we can't find when beta decay will happen, etc. and not that it's a probability distribution. Yes those mean the same thing, but it's a nitpick. I feel its more sufficient to my brain to say "we know that there's a 10% chance of an electron being 30 angstroms away from a point" than "we cannot actually find this electron"
I like that clarification, thank you :)
This feels like, in molecular biology, going from understanding how certain proteins interact with other proteins or genes to developmental biology where you suddenly have 20,000-25,000 (ish for a eukaryote) points that all can be modified in many ways and exist in specific places at specific times. You can't really have an analytical explanation of multicellular development for now and im glad other stem people have similar struggles lol
It is possible to know what something is at one level without understanding how it works. We don't understand how most things work, so this is very common.
I want to get it, but I am irresistably distracted by that glorious neon-chromo Starfleet sculpture in the background. Well played, Doctor. Well played.
Why is it that we’re always taught that Feynman diagrams should have time going upwards but when we actually use Feynman diagrams time is always going across?
Maybe because we don't read or write bottom to top, so we turn it to the side to make a linear sense of progression of the statements
Why do we fall down, Master Bruce? To learn to pick ourselves back up.
-Albert Eyestine
A 71 yr old thanks you. I finally understand QCD.
I think it's so cool that there are some types of expertise it's impossible to "dabble" in. You have to devote yourself to it, to even take the first steps. I suspect that's always been true, even in prehistory.
Grug likes to dabble in Clovis points but Grug cannot do that newfangled bronze smithing.
"I was too stupid to come upon such a brilliant idea as the string theory" -- Albert Einstein according to string theorists
i've been a carer for schizophrenia for around ten years, i don't have any formal qualification other than a certificate that says i've done a carers course, but one thing i learned even before the course is that when someone is hallucinating saying "you're imagining things" results in a very bad day.
anyway.
i treat all people as if they are mentally ill, i find that most people have hard time understanding how to tie shoelaces, never mind einstein. so in order to get your point across and have it actually register in someone else's brain, you have to put things in the simplest terms - that, say, a six year old can grasp. cos most people are six year olds, mentally. including me.
"I treat all people as if they are mentally ill" if most people had a hard time trying their shoes, maybe your point of reference for mental illness is skewed? I get hyperbole but it's just kind of a weird thing to say
I love being taught enough to know how much I don't know
There is a very good quote from peter watt’s echopraxia
“But people have an unfortunate habit of assuming they understand the reality just because they understood the analogy. You dumb down brain surgery enough for a preschooler to think he understands it, the little tyke's liable to grab a microwave scalpel and start cutting when no one's looking.”