why you can't explain qcd

[@tidenly]

"Angela Collier is my favourite KZbin science communicator" - Albert Einstein

[@BrianFedirko]

this quiote, I trust is from Uncle Albert, because it's true. Gr8! Peace ☮💜Love

[@andressigalat602]

"i was going to do that joke, but you got ahead of me." - Albert Einstein's first cousin once removed

[@GSBarlev]

​@@andressigalat602in other words, "A Einstein?"

[@dsracoon]

"Angela told me Feynman was a dumbass" Albert Einstein. Am I doing this right?

[@pinocleen]

"QCD on the lettuce" - A.E.

[@jameslloyd2540]

I'm really glad that this professional science communicator was able to ensure I understood that I do not understand QCD.

[@powernade]

"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.

[@aidanwarren4980]

Being delivered from the womb straight into Physics 101

[@DamienPalmer]

@@aidanwarren4980 Get that fetus into AP classes pronto!

[@bartroberts1514]

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.

[@scarlettjoehandsome6130]

​@@aidanwarren4980I knew that guy

[@shApYT]

@@bartroberts1514 8 years + 1 day

[@kylehill]

I take notes on your videos. Let's start a podcast.

[@marko1395]

10/10 would watch.

[@billyalarie929]

PLEASE I NEED THIS

[@byrnemeister2008]

I hope this conversation is happening off line!!

[@Marina_DU]

Uuuhh two of my KZbinr nerds interacting 🙊

[@drxyd]

Would. Watch, would watch.

[@KMO325]

“Albert Einstein catching strays from Dr. Collier is one of my favorite things about this channel.” - Mark Twain

[@rudyj8948]

Damn, many illustrious thinkers on here watching A Collier, i had no idea

[@savage5757]

1:10 you can't believe everything that is written on the Internet © Einstein, 1990 🤣

[@andyk2181]

"Something about that smells so bad it's not even pong" - Wolfgang Pauli

[@dannydetonator]

"I hear the voices of vegetables" - A. Jones

[@MarcusStenberg]

"Actually it was Samuel Clemens who said that" - Eldrick Tont

[@johngregor6743]

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.

[@Zeroisoneandeipi]

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.

[@scolton]

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.

[@idontwantahandlethough]

SUCCESS!!

[@thomasrivard9772]

You spend nearly 40 minutes in the shower?

[@scolton]

@@thomasrivard9772 no, but I do spend about 25. shaving takes a while 🤷‍♂️

[@mallninja9805]

@@thomasrivard9772 You don't??

[@anguskeesbury7278]

Glad i am not the only one who watches these in the shower

[@jeanf6295]

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.

[@billyalarie929]

“Subnuclear zoo” is one of the wildest phrases I’ve ever heard

[@carolynr570]

“W boson?? More like L bozo”- my attempt at a joke

[@MM-vs2et]

L elementary particle

[@jaspershepherdsmith9047]

It's a good bit, congratulations.

[@douggschmiddy9950]

Your attempt at a joke? more like your success at a joke. - my success at a joke

[@user-en5vj6vr2u]

“What the fuck is a W boson” -Albert Einstein

[@janmelantu7490]

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.”

[@umbraemilitos]

Math is a language, though. The reasons for doing the math, and the connection to experiment, can absolutely be written in English.

[@schok51]

​@@umbraemilitosyeah but quantum theory is known to be hard to make sense of through natural language. "Shut up and do the math" is usually what professors end up saying to students trying to grok quantum theory in their existing world model.

[@umbraemilitos]

@@schok51 The blackbox properties of quantum mechanics are up for debate and philosophical discussions, which can be done in English. However the mathematics and experiments are much easier to do in English. There is a flow of probability for quantum states, and the expectations and transitions of those states are not so abstract that we can't discuss or describe them.

[@schok51]

@@umbraemilitos I'm not saying it can't be talked about, I'm saying natural language is not an appropriate encoding for all knowledge, there's not a 1:1 equivalence between all math and english language such that any mathematically sound notion can be as clearly explained in English without ambiguity and overloading words such that understanding the math itself is a prerequisite. Language is not evolved around that kind of need. Anyway I'm not a quantum physicist or philosopher. If you are and think you can resolve any ambiguity or apparent unintuitiveness in quantum theory by explaining everything in natural language, i encourage you to do so and provide links to what you consider good attempts.

[@umbraemilitos]

@@schok51 All mathematics is taught in "natural language." All mathematics was developed by human curiosity, and was described and dreamed about in those terms. The symbols of mathematics are little more than a shorthand for language. They are not a replacement for it.

[@anotheral]

I would like to propose that "Quantum Gastrodynamics" is a way better term for weak force flavor interactions.

[@thenonsequitur]

That would legit be a better name.

[@dashoc9430]

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"!

[@mal2ksc]

@@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.

[@dashoc9430]

@@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 :)

[@GlennElert]

"Gastro" (γαστρο) is Greek for stomach, not flavor. Quantumstomachdynamics?

[@TanyaLairdCivil]

"Doesn't that suck for Einstein?...People just make stuff up and they say Einstein said it." -Albert Einstein

[@analoghabits9217]

always refer to yourself in the third person - AE

[@Flesh_Wizard]

"my balls exploded" - Albert Einstein

[@mosubekore78]

He died already, he doesn't care

[@JRV9113]

"These videos are just her what grinds my gears rants." -Albert Einstein

[@Matt_The_Hugenot]

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.

[@iansanford6544]

The pain on your face as you got out the "they're called gluons because... they stick... things together... like glue" xD

[@sjorgen9122]

Watching at 2x speed so I can not understand QCD in less than 20 mins

[@xponen]

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.

[@thomasj.treder7971]

@@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!

[@TheDemethar]

you forgot to give it to the next person

[@freddan6fly]

Take a big drink on next party and explain it to someone not nerding physics. They will really understand it.

[@SimonBuchanNz]

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.

[@stephanieparker1250]

“ I’m saying words but math math math.” I think I need a T-shirt that says this.

[@mallninja9805]

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...

[@ypey1]

Einstein said that

[@stephanieparker1250]

@@ypey1 I knew it!

[@stephanieparker1250]

@@mallninja9805 good luck on the exam! 🙌

[@werdwerdus]

please ❤ but a tank top haha

[@nicovaldes3850]

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!

[@aperiodicwalk3009]

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 😆

[@timothyclancy6919]

One could make a great debate between Lincoln and Einstein with all the things they never said.

[@KitagumaIgen]

You're quoting Socrates, right?

[@FPSIreland2]

@@KitagumaIgennah that’s Plato

[@GSBarlev]

What frustrates me about comments like this is that quotes wrongly attributed to Lincoln and Einstein are, in fact, wrongly attributed to Mark Twain! 😉

[@zamplify]

Lincoln had a secretary named Einstein. Einstein had a secretary named Lincoln.

[@chrisl6546]

With Yogi Berra as moderator

[@zorgus2002]

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!

[@Zappbrannigan83]

QCD is the most complex, sciency sounding name I've ever heard. Even more than the mathematics of quantum neutrino fields --Albert Einstein

[@AstarionGrle000]

😂

[@Rockyzach88]

Now start mixing different cool sounding sciency professions together. How about Quantum Computational linguistic Chromo Dynamics.

[@Zappbrannigan83]

@@Rockyzach88 you've embiggened science with your cromulent vocabulary. 🫵🫡🍻

[@ohno5559]

Mathematics of wonton burrito meals. Got it.

[@Zappbrannigan83]

@@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?

[@graemefenwick6925]

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.

[@craiggersify]

“Quantum Flavor Dynamics” sounds like the motto of a New Age Guy Fieri

[@dekumarademosater2762]

"Quantum Flavour Dynamics" needs a t shirt. A lickable t shirt.

[@clvr51]

I instantly thought it'd be a sick name for a math rock band lol

[@SkorjOlafsen]

"I never said half the things I said." - Yogi Berra

[@smoceany9478]

"i never said half the things i said" - babe ruth

[@GSBarlev]

"First time?" -Mark Twain

[@misterjaxon2559]

I wonder if he really said that.

[@Sam_on_YouTube]

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.

[@ad3larde]

I think that quote was mine - Ghandi

[@m.streicher8286]

I love being taught enough to know how much I don't know

[@odinson8761]

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.

[@freddy4603]

I wish this comment was the most liked one

[@Michael-kp4bd]

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.

[@5naxalotl]

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

[@Michael-kp4bd]

@@5naxalotl great elaboration. Of note though is that Einstein did not say that quote. Is there a different one you’re referring to?

[@meesalikeu]

@@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.

[@TheDMFW62]

Really loved this video. One of those occasions where KZbin 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.

[@andressigalat602]

"Don't go around grabbing five year olds" - Angela Collier (but I'm pretty sure Albert Einstein said it first)

[@astroalpha91]

This is one of the best and most genuine “explanations” of the standard model I’ve come across on KZbin. And I’ve spent the last three years doing my phd at CERN on explaining particle physics.

[@Stirdix]

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."

[@r3lativ]

That's a great point.

[@dinobotpwnz]

Exactly. The main reason is the sign of the beta function and that was missing from the video.

[@modolief]

Very informative, thanks!

[@pierrecurie]

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.

[@frederf3227]

QCD is the 1+2+3+4+... = -1/12 of physics?

[@MattMcIrvin]

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.

[@Lolleka]

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.

[@MattMcIrvin]

@@Lolleka oh yeah, and then Heinz Pagels died falling off a mountain

[@DavidvanDeijk]

Thanks, hope this is true because then i learned something

[@MattMcIrvin]

@@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.

[@jaybingham3711]

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."

[@BentArrowni]

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

[@GoldenMinotaur]

"I'm gonna explain why I can't explain it" My favorite kind of video

[@giovannironchi5332]

I mean, which 6-Years old cannot understand irreducible representations of SU(3)?

[@3zdayz]

Still prefer R3. A simple sphere and no tangrnts

[@steffenbendel6031]

A 6 year old in a woke school.

[@bridgetown1966]

this gotdamn american school system... when i was a kid, it was the three R's: readin', ritin', irreducibl' representations of SU(3)

[@rynabuns]

@@steffenbendel6031Can you explain "irreducible representations of SU(3)" to a 6 year old or are you "woke" as well?

[@edwinrollins142]

​@@steffenbendel6031what is a woke school and why is that a bad thing?

[@DKonigsbach]

General Relativity and the Equivalence Principle - extremely complex. Einstein's "happiest thought": "A man in a falling elevator does not feel his own weight." - pretty intuitive. At the core of most complicated things is a core concept. It doesn't provide the essential details, but it is the concept that all of the details hang off of. I believe Einstein was expressing that If you are so caught up in the details that you don't recognize the core concepts, then you don't truly understand the topic. The true test is whether you can explain the core concepts clearly and simply.

[@SpaveFrostKing]

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.

[@electro_fisher]

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

[@manfredfursich6779]

Dear Angela, I saw your KZbin video about quantum chromo dynamics and I was very impressed how you were able to explain this difficult issue in an understandable way - at least for an audience with some scientific background. Another interesting topic is quantum gravity. There are several approaches to this task but none of them is currently regarded as broadly accepted standard theory. I like the asymptotic safety quantum gravity approach, because it is similar to the QED and QCD approach. But as a layman I cannot express a profound opinion. I want to encourage you to produce another video about quantum gravity where you also mention which theory you like best. Best regards, Manfred Fuersich

[@badhombre4942]

They obviously meant explaining it to a 6 yr old Einstein.

[@BertrandLeRoy]

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.

[@Buttons841]

In this video, I learned that without gluons my Elmer's glue wouldn't work.

[@AdrianColley]

I mean yes.

[@xponen]

Elmer's glue using photon (QED), while atomic nucleus using gluon (QCD).

[@yarondavidson6434]

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.

[@Risu0chan]

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.

[@Wick9876]

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.

[@NeostormXLMAX]

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.”

[@Aeon135]

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.

[@Hyraethian]

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.

[@rossthebesiegebuilder3563]

If they're going to go with a term as silly-sounding as "flavors," they might as well lean into it and give the flavors names like "buffalo," "cool ranch," and "dark chocolate."

[@johnclawed]

If Feynman could have watched Angela's videos, he would have had the biggest grin from start to finish.

[@petergerdes1094]

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.

[@NotreDanish]

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

[@GSBarlev]

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]

We should describe it differently wrong ways instead. Like: "Matter and antimatter both go forward in time, but antimatter does it walking backwards."

[@Sturzfaktor2]

@@3X3NTR1K I now imagine a little positron constantly looking over its shoulder in order not to stumble into a nearby electron while walking backwards.

[@Sam27182]

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!

[@johnclawed]

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.

[@raevn11]

Kind of crazy, but i found your channel due to the algorithm tracking my interest in shows and their breakdowns and critiques. Just finished your 3+hr breakdown of Picard (awesome) and coincidentally, was doing research on QCD and QED this morning (was using Bing, so...) and upon clicking through your channel, found this little gem. Hilariously educational and supplemental, thank you.

[@thylacoleonkennedy7]

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.

[@GSBarlev]

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)!

[@shelterit]

You claim not to be a professional science communicator? I can tell your that you're the fucking BEST one!!!!! Holy crap, I've struggled with this analytical Vs. numerical parts of math my whole life, and never understood why all the big names couldn't make sense of QM for me. I thought I was just thick, only suited to philosophy. And here you are, finally!!! just talking through it with charm and a lovely human touch, and I get it! I get it now! I mean, not QCD, I don't get the details of how it works, but I now finally get the relations and complexities involved. You have no idea just how happy and grateful I feel right now, thank you! ❤ You've not only explained QED Vs. QCD, but how relativity fits in, Feynman diagrams (and the dimensionality limitations of them), prediction in math and its relation to projection Vs. reality ... I mean, gosh, this was nothing short of THE BEST VIDEO ON THE INTERNET!!!!!!!

[@jloiben12]

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…

[@capnmnemo]

Well, maybe Mileva was busy and couldn't do the work or him.

[@DanGRV]

"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

[@GingerWithEnvy]

I remember taking group theory and think "god this is tricky and weird, but i think I get whats going on kinda" and it helped me kinda understand what was going on in my QED lectures, then at the end of the group theory module they were like "okay, so if you wanted to try to apply this to QCD, youd also need to be keeping track of colour and flavour" and that wasnt to describe the interactions that was just to understand the math objects youd have to use before you look at interactions, and i remeber thinking "oh god please no" and fortunately the lecturer then informed us we didnt need to care about that because that wasnt on our course.

[@sleethmitchell]

'understanding' something is perhaps the biggest myth of physics.

[@brianarodriguez2090]

This comment goes so hard

[@zyansheep]

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!

[@conodigrom]

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.

[@kindlin]

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.

[@davidkeller6334]

It's an excellent introduction to an overlooked section of physics.

[@TheNeonParadox]

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.

[@DJRonnieG]

😆

[@ChristopherSadlowski]

Go to bed. 👉 Go to bed right now and think about what you said... 😊

[@TheNeonParadox]

@@ChristopherSadlowski 🤣🤣

[@dominicellis1867]

Why did the quark fall off my school project? Because I forgot to put the glue on.

[@Larr1954]

I didn’t mean that sarcastically. That explanation is honest and give one a feel for what QCD is like. Bravo!

[@bryandraughn9830]

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!

[@robertarmstrong3024]

A 71 yr old thanks you. I finally understand QCD.

[@n20games52]

If a 6-year old can't explain something to me, can I understand it?

[@GrantWaller.-hf6jn]

A good way to find out what they know.

[@n20games52]

@@GrantWaller.-hf6jn Ha! Yes!

[@3tp]

Why do we fall down, Master Bruce? To learn to pick ourselves back up. -Albert Eyestine

[@OliviaSNava]

I feel like I don't understand QCD, but I understand why I'd have to learn a lot more to understand QCD.

[@michaelprozonic]

"if you hold a proton in your hand it will just chill” proton beer cozy

[@АндрейДенькевич]

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.

[@michaelprozonic]

@@АндрейДенькевич but how does that keep my beer cold on a hot summer day?

[@АндрейДенькевич]

​@@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)

[@NullHand]

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!"

[@michaelprozonic]

@@АндрейДенькевич 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?

[@ABC_Guest]

34:19 ""QED, which is a mathematically rigorous proven thing" - this is a funny quote because that's what "quod erat demonstrandum" basically stands for

[@idontwantahandlethough]

1. cool glasses 2. great video yo 3. "Be the change you wish to see in the world" -- 50 Cent

[@ictogon]

Thank you 50 Cent

[@Googahgee]

As a layperson whose highest formal education in mathematics and physics are undergrad Calculus 2/Linear Algebra and AP physics, this was a wonderfully interesting explanation that helped me appreciate (a little bit better) the intricacies of more complex forms of physics. I have immense curiosity for all these sorts of things and this was a really interesting watch despite not knowing any specific details of the mathematics necessary to do these problems and to fully grasp the concepts. Generally I feel it was very well presented, and I now have a solid understanding of at least what these theories and models aim to explain. Thanks for the video!

[@d3line]

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!

[@trolleymanV]

Love this comment, I completely agree (probably also because I'm a programmer)

[@jell0goeswiggle]

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.)

[@Larr1954]

Now I don’t have to take QED and QCD to get an idea of what’s it’s like. I’m a retired pharmacist with a 6 years post high school used to love my physics and math classes, now I have time to explore educational paths I didn’t take like Brilliant provides. Thank-you for your explanation and opinions. Bravo!

[@fudgecicle2905]

I have only taken one semester of QFT, so honestly this was a really nice overview of QCD for me even if you didn't get super technical.

[@Palozon]

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.

[@tylerm.8684]

-Albert Einstein

[@merlinthegray]

In the beginning I was like "Can QCD really be so complex that I can't even get a basic grasp of the interactions without all the math?" The answer was unsurprisingly yes. Yes it can be. Thank you... Favorite science communicator I've found in a long time.

[@bethlong7115]

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?

[@hayuseen6683]

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

[@paulperkins1615]

For some unknown reason I want to build up a kind of map of how all the different kinds of physics fit together, where QCD is a little piece of the quantum area and so on, and this seemed to help with that, and was also just entertaining enough. So thanks.

[@arctic_haze]

"I was too stupid to come upon such a brilliant idea as the string theory" -- Albert Einstein according to string theorists

[@justintroyka8855]

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.

[@dustinking2965]

Let's crack open the proton. (Insert gif where Donald Glover walks into the apartment and everything is on fire.)

[@Wrynwynn]

I always interpretted the phrase to mean that the act of soothing and cartoonizing a notion til it could be explained to literally anybody was a great way of engaging your own brain on its broad essential aspects

[@OrbitalCookie]

Knowing how much you don't know is a superpower. Therefore the communication you do is very important. Too many people believe in cartoons and cartoon version of experts and severely underrate the work they do. This video shows the depth of the problems without getting boring, which is an actual achievement.

[@HarryNicNicholas]

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.

[@mateostenberg]

"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

[@benjaminwilson9007]

I have thought about "what if EM waves interacted with each other". And thanks for making this video. Because, there will be people who experience this and leave, convinced of their comprehension. But, for people who are inspired and devoted, they'll use your tone and emphasis on the challenge to keep their morale high.

[@mrguysnailz4907]

Me two minutes in: "wait, colours move?"

[@Darthsiroftardis]

Can’t wait for this video to age like a proton

[@rickandrygel913]

"Angela Collier has once again proven me wrong." -Albert Einstein

[@stevenspencer306]

I think that quote was from someone whose child kept asking "Why?" Not that you literally have to make the child understand, but that you have to keep going deeper and deeper into truly understanding the topic.

[@stevenspencer306]

Angela: "QCD is a bunch of nonsolvable math that we use computer programs to simulate and it's incredibly successful at predicting experiments." Child: "Why?"

[@joehartman87]

I finally understand how the recoiling of electrons are mediated by photons. The detailed explanation of a photon being emitted and the electron recoiling via the momentum and other electron absorbing the photon also recoiling from the momentum was worth the price of admission. Thank you.

[@narfwhals7843]

Now, how does attraction work?

[@joehartman87]

​@@narfwhals7843baby steps

[@ColonelFredPuntridge]

I would say the opposite: if you think that you _can_ explain something to a six-year-old, _then_ you probably don't really understand it.

[@chaotickreg7024]

First grade teachers understand nothing, then?

[@ColonelFredPuntridge]

@@chaotickreg7024 Would you hire one to teach physics?

[@hedgehog3180]

@@chaotickreg7024 I don't think First Grade teachers believe they know everything about linguistics and math when they teach the kids the alphabet and how to add and subtract numbers. That's why the saying “lies to children” exists.

[@chaotickreg7024]

@@ColonelFredPuntridge That's not what you said.

[@hayuseen6683]

Thinking you can and doing so are two different things. It's not saying the opposite - there is an apple would be opposite to there is no apple. This is saying liking the way an apple tastes is opposite to saying there is no apple. The quote can mean any number of things depending on interpretation, but the explainer's perspective of their capability isn't one I see in it.

[@IAmNotARobotPinkySwear]

As a 6 year old child, I now understand QCD. Also I want milk and cookies please

[@brendanh8193]

Ah, what I learned from this video: Quantum Chromodynamics is the salsa of the physics world - it's full of colours and flavours, little bits and forbidden feels that no one will admit to knowing.

[@zdzislawmeglicki2262]

The theory of relativistic Hamiltonian strings explains some aspects of QCD quite well even to the point of making accurate predictions of meson mass spectra. But in general, QCD is quite complicated, what with the three "colours," that represent QCD "charges," three generations of quarks, self-interacting gluons, asymptotic freedom, and nature's colour-blindness. It is astounding that we succeeded in understanding so much of it.

[@nuckyducky]

I was diagnosed with EDS 8 months ago. I wanted to be a physicist. I'm not giving up but rather I am now 100% confident in the future, even if I don't. If people like you are teaching the next generation of students to be critical and scientific, I have no doubts for our future. You talk about QED like its effortless, you illuminate the problems like its nothing, I hope a publisher bought your book. It's been a few hours for me but *checks notes* 3 years for you lol.

[@ericvilas]

God, there's nothing more satisfying than watching another physicist gush about the beauty of QED. Truly the most beautiful theory we have.

[@LazloHo]

Do I understand QCD now? Well, as you promised, no, no I don't. What I have is, by way of analogy, just enough of a quasi-idea that I can now go on the internet and stretch the analogy in ways it was not intended to be used in order to speculate on the impossible. I have just enough knowledge to weaponize my ignorance. But that's okay; that's what enthusiast, armchair physics is. Here's an example: While watching, and understanding well enough at the level you were teaching, I imagined the following philosophical question - If we had bigger brains, that could do trillions of complicated computations while understanding and storing the results... do you think there is a way to understand QED non-probabilistically? Do we simplify the problem and perturb it, and rely on estimates and probabilities, because we're just not smart enough to understand/do the math that would allow us to accurately predict precisely where the electron will be? Whether the photon will be absorbed or reflected? And then, of course, by extension to QCD, precisely when the neutron will turn into a proton. In these videos, where you and other physicists try to give us laymen a little bit of understanding, we are always taught that these things are, fundamentally, probabilistic. We hand-wave our way over to Heisenberg and we always come back to the copious experimental data that backs it up to several decimal points. In your video, here, what I thought I heard you say was, "actually, there is math, we even know it, but it's just so stupidly complicated and effectively infinite (really infinite or just effectively? that was unclear) in nature that we have to work with estimates to get anything done." Is reality fundamentally probabilistic or are we just too stupid to do it with an exactness? That's my weaponized ignorance. If you don't answer my question, I could easily make up the answer I like the most and use my superficial, analogized understanding to explain/justify my interpretation. This is how crackpots happen.

[@sturrum5250]

Note that perturbation theory has nothing to do with being probabilistic. Even if you could find exact mathematical solutions to interacting quantum field theories such as QED and QCD they would still be just as probabilistic, because the thing that makes them probabilistic in the first place (being quantum mechanics) is a feature of both exact and perturbative theories. It should also be stressed that quantum mechanics does not *necessarily* need to be interpreted as probabilistic. The Many Worlds interpretation is entirely deterministic, but states we only measure a very small part of reality. De Brogle-Bohm theory allows for completely predictable particle trajectories, but these can't actually be measured, so you'd be asserting the accuracy of new mathematics with no experimental backing. Some assert that any theory and especially quantum mechanics can only describe our knowledge of reality, but not reality itself. Most layman-level descriptions of quantum mechanics treat it as 'fundamentally probabilistic' is because it's simple and most in line with the practical reality of doing quantum mechanics and bringing up all the different interpretations of quantum mechanics is usually a waste of time.

[@hedgehog3180]

Something being hard to calculate isn't what makes it probabalistic. Tons of things are so hard to calculate that we have no analytic solution for them and need to rely on nummerical solutions or simulations. Some examples would be fluid dynamics, how will air or water flow around a certain object, anything involving the orbits of celestial objects, double jointed pendulums. All of these systems follow deterministic rules, like there's no % on where Mars will be in exactly 5 billion years, but they're so interdependent, complex and reliant on initial conditions that we cannot solve them analytically and have to rely on sorta ugly solutions where we just need to run it through a computer a ton of times to get a good idea of what will happen. And we might use randomness as a tool in these models to account for the inaccuracies in our measurements or just add the sort of random noise we'd expect in the real world but that still doesn't make the system itself random, because the underlying rules remain deterministic.

[@LazloHo]

@@sturrum5250 @roachybill @hedgehog3180 So I was right! I didn't understand it at all :) I appreciate all of you for your replies. I'm sure I'm still full of misunderstandings but that doesn't make it any less interesting.

[@reinerwilhelms-tricarico344]

When I was a geeky teenager in the late 60-ties I studied a book on Physics for young people. I really believed I then that I understood quarks and gluons and the basics of chromodynamics, which was then figured out as cutting edge science. I was probably delusional then. But I later studied physics and math and got a PhD in physics - but not in theoretical physics - too hard. Now I’m 71 and still trying sometimes to understand chromodynamics. I understand way more math now than when I was a kid but I still don’t really get chromodynamics. It’s all crazy Lie group stuff and too abstract. But I believe I’ll figure it out once I really understand geometric calculus - Clifford algebra and the Hestenes cult 😊.

[@glowinggrenade]

I'm imagining this works like the interactions in a game where each object has the specific interactions with every other object that it creates a wave function collapse (like how game worlds are rendered) except with math that is continuous and not absolute numbers or states. And so understanding it in a predictive manner is impossible and advanced.

[@sillygoofygoofball]

I love visual proofs in math, so feynman diagrams are particularly appealing to me. You definitely don’t need them to do calculations, besides checking your work. But they’re indispensable tor communicating the ideas

[@woodstock5nathan]

I did group theory and began to get the idea of how it would apply. But then dived into electron transport... I would like to pick up where i left off. Another great vid! Thank you!

[@1cynicalsaint]

As a lay person I watched the entire video and my takeaway is that you have the exact same Saturn V stuffie as my kid, so that's pretty cool!