How Electron Spin Makes Matter Possible

Sign Up on Patreon to get access to the Space Time Discord!
/ pbsspacetime
Today I’m going to explain why you’re not falling through your chair right now using one simple fact, and one object. The fact is that all electrons are the same as each other, and the object is a structurally critical item of my clothing. There’s a chance this episode could get very weird.
Electrons DO NOT Spin
• Electrons DO NOT Spin
Spin Renderings by the Incredible Jason Hise
entropygames.net/
Check out the Space Time Merch Store
www.pbsspacetime.com/shop
Sign up for the mailing list to get episode notifications and hear special announcements!
mailchi.mp/1a6eb8f2717d/space...
Hosted by Matt O'Dowd
Written by Graeme Gossel & Matt O'Dowd
Graphics by Leonardo Scholzer, Yago Ballarini, Pedro Osinski, Adriano Leal & Stephanie Faria
GFX Visualizations: Ajay Manuel
Directed by Andrew Kornhaber
Assistant Producer: Setare Gholipour
Executive Producers: Eric Brown & Andrew Kornhaber
End Credits Music by J.R.S. Schattenberg: / multidroideka
Special Thanks to Our Patreon Supporters
Big Bang Supporters
Peter Barrett
Nils Anderson
David Neumann
Ari Paul
Kyle Bulloch
Charlie
Mrs. Tiffany Poindexter
Leo Koguan
Sandy Wu
Matthew Miller
Ahmad Jodeh
Alexander Tamas
Morgan Hough
Juan Benet
Vinnie Falco
Fabrice Eap
Mark Rosenthal
David Nicklas
Quasar Supporter
Michael Schneider
Ethan Cohen
Stephen Wilcox
Christina Oegren
Mark Heising
Hank S
Hypernova Supporters
william bryan
drollere
Joe Moreira
Marc Armstrong
Elizabeth Smith
Scott Gorlick
Nick Berard
Paul Stehr-Green
MuON Marketing
Russell Pope
Ben Delo
Nicholas Newlin
Scott Gray
Антон Кочков
John R. Slavik
Mathew
Danton Spivey
Donal Botkin
John Pollock
Edmund Fokschaner
Joseph Salomone
Matthew O'Connor
chuck zegar
Jordan Young
m0nk
John Hofmann
Daniel Muzquiz
Timothy McCulloch
Gamma Ray Burst Supporters
Wrymouth
Andre Stechert
Ross Bohner
Farhan Wali
Paul Wood
Kent Durham
jim bartosh
Nubble
Chris Navrides
Scott R Calkins
Carl Scaggs
G Mack
The Mad Mechanic
Ellis Hall
John H. Austin, Jr.
Diana S
Ben Campbell
Lawrence Tholl, DVM
Faraz Khan
Almog Cohen
Alex Edwards
Ádám Kettinger
MD3
Endre Pech
Daniel Jennings
Cameron Sampson
Pratik Mukherjee
Geoffrey Clarion
Nate
Adrian Posor
Darren Duncan
Russ Creech
Jeremy Reed
Eric Webster
Steven Sartore
David Johnston
J. King
Michael Barton
Christopher Barron
James Ramsey
Justin Jermyn
Mr T
Andrew Mann
Peter Mertz
Isaac Suttell
Devon Rosenthal
Oliver Flanagan
Bleys Goodson
Robert Walter
Bruce B
Ismael Montecel
Simon Oliphant
Mirik Gogri
Mark Daniel Cohen
Brandon Lattin
Nickolas Andrew Freeman
Protius Protius
Shane Calimlim
Tybie Fitzhugh
Robert Ilardi
Eric Kiebler
Craig Stonaha
Martin Skans
Michael Conroy
Graydon Goss
Frederic Simon
Tonyface
John Robinson
A G
Kevin Lee
Adrian Hatch
Yurii Konovaliuk
John Funai
Cass Costello
Tristan Deloche
Bradley Jenkins
Kyle Hofer
Daniel Stříbrný
Luaan
AlecZero
Vlad Shipulin
Cody
Malte Ubl
King Zeckendorff
Nick Virtue
Scott Gossett
Dan Warren
Patrick Sutton
John Griffith
Daniel Lyons
DFaulk
GrowingViolet
Kevin Warne
Andreas Nautsch
Brandon labonte

[@Elzilcho87]

This makes me feel like I've accidentally sat in on the wrong lecture, but I'm now too interested to leave. Thanks for the mental stimulation.

[@ScumfuckMcDoucheface]

right? that's a really great description man... way over my head but incredibly interesting and stimulating. =)

[@dialect64]

That was a hobby of mine for a while actually, lol! I would go to my GF's college (which had a more in depth psychology and social science curriculum than mine) and go to all the open access lectures on the topic (was my minor, top of my class, but was focused on audio engineering)! Haha, even ended up in discussions with the speakers more than the students, since half them took it as an elective!😂

[@nathanpeterson1783]

We've all wandered in and then just kept coming back!

[@spracketskooch]

I'm tired, and I read "mental stimulation" as "menstrual stimulation". I'll be on my way now.

[@thetalantonx]

@@ScumfuckMcDoucheface @Jetpack Rorschach... I can't get over your amazing names. :D Thanks for the minstrel simulation.

[@karozans]

"If you don't spin, you don't matter." --Aggressive Electron

[@arthurharris9428]

Hahahahaha all spins matter 😛

[@mugwump7049]

Boson Lives Matter

[@Arashmickey]

We can spin if we want to We can leave your friends behind 'Cause your friends don't spin And if they don't spin Well, they're no fermions of mine

[@TheMixxon2]

xdddddddddDDDDDDDDD alfons por favor xdddddddddd

[@justsomedude7800]

😂

[@nickpiovesan4361]

"Of course before you want to watch this you should familiarize yourself with the subjects we touched upon in the previous 30 episodes of Space Time..." Love this channel.

[@ManyHeavens42]

Excuse me what did you say I was eating Hahaha

[@robertahrens5906]

I'd be getting smarter if I just had any notion of wtf he just said

[@Kawalajin]

PBS hustle game is wild.

[@flirtwithdanger_les]

I didn't understand this at all - maybe I should watch those 30 vids

[@bardsamok9221]

​@@flirtwithdanger_lesDo it, Ming!

[@w6wdh]

Great explanation! Richard Feynman said that if he really understood some aspect of physics, he could explain it to a freshman. But the Spin Statistics Theorem stumped him. He was unable to come up with a simple explanation, which you have done. Bravo!

[@erawanpencil]

This stuff really only makes sense if you throw out any conception whatsoever that 'electrons' 'photons' 'fermions, bosons, etc' are entities doing stuff lol. They're not really particles, they're apparently mathematical square roots temporarily hidden in the complex plane, sometimes not, and everything and some things are connected by 720 degrees or whatever. If you square them, you're rewarded with the knowledge of the probability that they 'might' have a physical property haha. It's cool that something so mathematical turns into semi-coherent physical observations, but it all feels a little disingenuous to represent all this as physics and not a Frankenstein math-physics demon child.

[@psychopompous489]

@@erawanpencil I might be dumb, but isn't that all of physics? You make a series of mathematical models that attempt to describe reality, derive implications, and then use experiments to see which implications are most aligned with reality. It just so happens that in this case the experiment is "can electrons of low spin energy dogpile an atom" to which the answer is no. Also they're not really particles; they're waves most of the time (described by mathematical square roots temporarily hidden in the [...]), and only really become particles for collisions. The idea that their wave functions cancel each other out is a real threat, and seeing as how that would constitute a loss of energy in the universe, violating conservation of energy, the aversion is fairly understandable.

[@williamlavallee8916]

No that's what theoretic physics has hoisted onto real deterministic-observational-philosophical Physics. No theory should be publishable without an experimental test along with it (ala String Theory, etc, etc, etc). @@psychopompous489

[@Morilore]

Matt: "don't worry, it's just addition and subtraction" Also Matt: *literally derives Slater determinants on-screen*

[@EduardoLauandeTeixeiradeSouza]

You are damn right. I suffered to study this at Chemistry course. And you put this very interestingly

[@kennarajora6532]

ironically, did it in a way that I actually understood it this time.

[@juandavidgilwiedman3490]

@@kennarajora6532 Well, Matt is a great storyteller, this is in part what makes a great teacher.

[@Mp57navy]

@@juandavidgilwiedman3490 If my physics or math teachers would have been 1% as enthusiastic about their job as Matt is...

[@Mastakilla91]

This just goes to prove that it's not math being to complicated to learn but our applied learning methods not being compatible with our brains method of learning.

[@Baconlessness]

I've been confused for years about what "half integer spin" meant, and here Matt clarifies it in a few words.

[@Robert_McGarry_Poems]

The Mobius belt, to the rescue!

[@camerondale6529]

Why educators are invaluable to society.

[@voidisyinyangvoidisyinyang885]

Has he done a vid on the Stern-Gerlach experiment? that's an even better explanation but this vid compliements that experiment also. The point being that the 1/2 spin is also nonlocal as noncommutative phase (i.e. asymmetric)

[@LetoJaxa]

Some people will just regurgitate what they've learned. A particle has half integer spin because it is what it is. While those that truly understand it, will be able to logically step through the reasoning and come up with analogies for regular people to understand. In other words, it's not magic and here's why.

[@nickhowatson4745]

@@LetoJaxa it is what is is due to an observer bias. life will always find itself in a universe whose properties and values can support it which gives the illusion of Fine Tuning.

[@shashikantrivankar3551]

Most textbooks or online lectures gloss over the deep meaning of the spin leaving one unsatisfied with the description. This is the first time i have seen someone explain the concept in a way makes it more satisfying an explanation. Kudos to Dr Matt O'Dowd for possessing such an ability!

[@ManyHeavens42]

Indubitably hahaha

[@ManyHeavens42]

Like I Like Smart people or Something Hahaha

[@SolidSiren]

Well lecturers dont typically have computer graphics. that is where at least half of the understanding on YT physics channels comes from, Id argue

[@ManyHeavens42]

@@SolidSiren yes they do what planet are you living on

[@SolidSiren]

@@ManyHeavens42 no, lecturers do not typically use the graphics used in a channel like this.

[@johnedwards2119]

Notice that around the ten minute mark Matt begins to pronounce "square" like an American, that is, with an R at the end, and, only moments later, he pronounces the same word as a Brit, so we are seeing a superposition of pronunciation states transitioning from the ground state, Brit, to the excited state, 'Mercan and yet in this case both states are clearly distinguishable.

[@magisimon4873]

Hahaha

[@ichigo_nyanko]

where is he from?

[@-_James_-]

@@ichigo_nyanko He's Australian.

[@SolidSiren]

Thats called rhotic vs nonrhotic.

[@raleighwalter4250]

Yes, he’s definitely Antipodean and most certainly not British

[@TimRrstrm]

Does any of this explain why USB plugs need to be turned 540° to return to the correct orientation?

[@mrsmiastef]

Hahahaha!!

[@samsungtelevision695]

If you don’t write this paper I will. It’s precisely the phenomenon

[@pbsspacetime]

Yes. It's well known in physics that USB plugs have 3/4ths Spin.

[@renerpho]

This has to be the final comment in the next comment response video.

[@eloniusz]

Does this mean USB type C is made of gravitons?

[@SolaceEasy]

In this video series there is a direct relationship between the incomprehensibility of a topic and the amount of gesticulation that Matt does.

[@Robert_McGarry_Poems]

Abstract concepts deserve a proportional amount of gesticulating for the level of abstractness that they portray. Incomprehensibly is relative to the amount of gesticulating that seems misplaced. It's a function.

[@ScumfuckMcDoucheface]

gesticulation - easily one of the best words ever created, of all time, in any language. =)

[@SolaceEasy]

@@ScumfuckMcDoucheface Luv me 'dem words

[@SolaceEasy]

@@Robert_McGarry_Poems I posit relationship; you state direct function. Who has overstated?

[@SolaceEasy]

🤞 I can safely say 👍 Matt's presentation style is 👏 hands down 👊 effective. 👌

[@timwatz2330]

I find it fascinating, how you can break extremely complicated topics down so far, that most highschool grads can understand them. Thank you so much, because nobody taught me this, even in college.

[@everythingisalllies2141]

except that all the fancy talk about electrons, fermions quarks, anything smaller than an atom, is pure guesswork, speculation, as none of those things can be demonstrated to exist in any experiment. They are all imaginary, based on assumptions. We can't even fully explain how electricity or light works without diving into the land of pure speculation. The real process may be totally different.

[@timwatz2330]

@@everythingisalllies2141 What kind of answer is that, so anyway I like Thorium too.

[@everythingisalllies2141]

It wasn't an answer, it was a statement of fact. Modern Physics is full of wild goose chases, deceptions and false assumptions and crap theories.

[@fruity4820]

​@@everythingisalllies2141 "no model in physics is accurate, some of them are useful"

[@everythingisalllies2141]

@@fruity4820 its the ones that are downright purposefully deceptive and wrong that I have issue with.

[@LMProduction]

I love that you guys always happen to make content that relates directly to the courses I’m doing. Good timing

[@Erik-pu4mj]

It took some years to get on my feet, but I started learning about wavefunctions formally this week. Thank you, PBS Space Time, for being my informal learning--up until now and inevitably moving forward. The heuristic understanding of a broad range of physics topics you've given me has done more than aid my education; you've fostered and kept alive an interest I hope to take to graduate school research and beyond. PBS Space Time is science communication at its finest.

[@renderproductions1032]

You should try Issac Arthur as well!

[@max-fj7np]

Best of luck to you! Not exactly the easiest field of study to get into but Im sure you got some rock solid foundations built from this channel!

[@paulmichaelfreedman8334]

@@renderproductions1032 Smart as he may be, I would strongly suggest to him to hire a narrator. No offense to him, but his speech impediment makes it fairly difficult for me to understand. And thus I don't watch his videos.

[@paulmichaelfreedman8334]

@@hyperduality2838 + - , yin yang, positive negative, and so on, and so forth...

[@paulmichaelfreedman8334]

@@hyperduality2838 How about this one: Our universe is dual to the other one in which all antimatter went...solves multiple problems with current theories. Oh and a moebius strip cut in half gives two rings that are interlocked.

[@dominikbeitat4450]

Next episode: Matt explains electron spin again, but this time with jumper cables, because you didn't pay attention.

[@Fres-no]

JUMPER CABLES...... BWAAAAAAAA!

[@nickllama5296]

I did pay attention, but the entry fee was attention x 1.5

[@arthurharris9428]

Hahahahaha

[@SoleaGalilei]

I understood that reference!

[@valjean76]

this channel is getting weird now.

[@crowlsyong]

It's inspiring and beautiful, the universe and your descriptions of it. Thank you so much Matt, the animators, and the PBS team that brings this to us for free. Thank you.

[@parthbartakke7988]

So true❤

[@MasonDixonLine1]

And just like that, after a year of trying to figure out what spin 1/2 actually means, he explains it so clearly.

[@rainmanj9978]

Right but since they don't spin it still doesn't make sense physically. The waves make sense but how do they create waves? 360 degrees is back to zero but the wave is traveling up stroke 720 degrees is back to where you started started on a wave but yeah still not sure.

[@EternalBooda]

Matt almost showed us the mystery of his intrinsic mass.

[@_redmenace1917]

LMAO

[@GearForTheYear]

wtf?

[@scottief8616]

Jail!

[@seanbrown2386]

*bonk*

[@user-wo5dm8ci1g]

PBS Space Time doing humor about privates was a fun new thing for me too.

[@soasertsus]

Wait this actually makes sense, I think I finally get now why they have half spins and why the Pauli exclusion principle is even a thing. This is the only channel that helps me understand the why of all the weird quantum phenomena without dumbing it down so much that it ends up just being "they just can't have the same quantum state, it's a fundamental law trust me."

[@ExpensiveGun]

@@hyperduality2838 Damn bro, skip your meds?

[@AboveEmAllProduction]

Haha yes the pauli exception. Indeed. Mathematics.

[@ManyHeavens42]

That's not the half of it the smaller you get you get to unravel everything, and Rebuild Don't tell them .

[@itsiwhatitsi]

@@hyperduality2838 matter and energy, body and soul

[@tetronym4549]

@@hyperduality2838 Disregarding most of the actual content of your comment, I wouldn't use the word "duality" like that, in a video about quantum physics. In physics, the word "duality" has a specific meaning -- Particles are not "dual" to antiparticles, because that implies opposites. In physics, "duality" means that they are ways of describing the SAME thing, with particles being "dual" to waves. There is only one thing between the two of them, particles and waves being the same thing. Some of your dualities you listed, however, are correct using the physics term, such as "Space is dual to time". Albert Einstein's theory of relativity is all about space and time being the same thing, "spacetime".

[@klauskervin2586]

This is one of the best episodes of Space Time yet. Thank you for the great content!

[@Jason-ip6li]

I feel like "literally just addition and subtraction" means something different to Matt than it does to me...

[@originalph00tbag]

Exponentiation is just a *lot* of adding.

[@Jason-ip6li]

@@originalph00tbag This information is as technically true as it is unhelpful.

[@princeofcupspoc9073]

Algebra would have been more accurate.

[@SolidSiren]

Oh come on. The symbols dont matter, dont let them intimidate you. Im sure you understand that 1 plus negative 1 is zero and so forth. and algebra.

[@Jadder88z]

I've never studied quantum physics, and only briefly covered the standard model for A-levels in 2007. I understood almost everything in this video on first pass; that's the sign of a really great teacher. Your ability to explain these principles so simply is testament to your understanding. Thank you for sharing your knowledge and making understanding the quantum world so accessible.

[@bhaskararaogondela3805]

Does electron really spins like this 🤔 can you explain that

[@jojausa4399]

@@bhaskararaogondela3805 no they dont, the cake is a lie

[@StefSubZero270]

Wait you never studied introductive quantum mechanics but covered an introduction to the Stanard Model? How is this even possible wtf

[@jamescollins4500]

"nonoverlapability", I'm never going to forget that word.

[@3hallaman]

i feel like where I live, unoverlapableness would be more linguistically productive

[@0xf7c8]

@@3hallaman 'Unoverlapableness'. Now, that's a nice word.

[@alistairlacaille]

I'm gonna need some hyphens in here please. The amount of extra brain power needed to parse these 'words' without them is asking too much.

[@alistairlacaille]

@Ranjit Tyagi ?

[@alistairlacaille]

@@innerfield5481 Waves interfere and overlap, not particles. Part of the weirdness of particle/wave duality.

[@pdelong42]

Thanks for the belt analogy, I never knew about that! I've long tried to find a good way to explain SU(2) symmetry to people (where "people" includes myself) in an intuitive way. This example is a good one to add to my bag of tricks.

[@antoniomaglione4101]

Compliments for the clarity and precision of your explanation of Fermions and Boson, and the Pauli principle. Thank youi...

[@runonwards9290]

Love this, the Pauli exclusion principle is assumed to be fundamental. I'd love to see more vids about the most fundamental principles

[@HermanVonPetri]

I'd like more explanation as to why the assumption is made that two electrons would resist entering the same state rather than simply annihilating each other as the math would seem to suggest. I know that that this is demonstrated experimentally, but how does the math indicate a preference for one outcome rather than the other?

[@nickhowatson4745]

@@HermanVonPetri particles with 1/2 integer spin cannot occupy the same state. its the Pauli Exclusion Principle.

[@ScumfuckMcDoucheface]

@@nickhowatson4745 YOU'RE the pauli exclusion principle!!! =|

[@spudmcdougal369]

I asked the same thing over on science asylum.

[@nickhowatson4745]

@@ScumfuckMcDoucheface its just the way it is. we just happen to be in a universe where these values and property's allow for life. so of course the values are what they are its an observer bias.

[@mikotagayuna8494]

This man just risked getting his pants down for us to understand all these complicated concepts.That is commitment, folks.

[@magisimon4873]

LoL

[@AboveEmAllProduction]

My pant are down do you want ip adress for webcam

[@burpie3258]

Reminds me of that one Nathan For You bit...

[@stringjazz2937]

Never before have I ever heard a most clear and beautiful Electron Spin before. Thank you very much.

[@yotigoti11]

Matt, you made it so clear! I feel I finally understood that stuff. All my gratitude to you. :)

[@terryboyer1342]

Matt: There's a chance this episode may get a little weird. Me: I couldn't possibly get any more confused than I already am.

[@greenshadow622]

Matt: Hold my beer.

[@LKRaider]

Me: I was worng D:

[@Haannibal777]

I agree. I did not expect him to take off his belt! I would advise not to get even weirder. Certain things are better left to the imagination.

[@DolphinSMG]

Right? 😂 It was as if I was listening to someone speak a foreign language and they stopped for a moment to tell me, in english, that I wouldn't understand the next part

[@AlephOneHalf]

Matt: Hold my spinor.

[@theopantamis9184]

The missing piece I was searching for so long was an intuition of why spin rotation properties imply particules swaping introduces a minus sign. I have it now, I can die in peace x)

[@Tinker1950]

Try again - that word salad was meaningless

[@Robert_McGarry_Poems]

Right... Mobius strips are even cooler now!

[@Robert_McGarry_Poems]

@@Tinker1950 Except the part where he used spin 1/2 meaning. It totally works out.

[@theopantamis9184]

@@Tinker1950 You know what you could do ? Asking question if you don't understand or helping instead of being mean :) You should try it, it makes you look less ugly actually !

[@Tinker1950]

@@theopantamis9184 It's still meaningless. Even after pointing it out, all you do is whinge like a 10 year old instead of looking at your comment and re-writing it.

[@googoogjoobgoogoogjoob]

It's weird, but not as weird as his trousers not falling down.

[@pxpl5538]

Wow, great explanation of quantum spin! Loved the Belt analogy. Thank you for this simple illustration of a complex idea.

[@lordofchaosinc.261]

The moment I read the title I knew that's an episode I wouldn't fully comprehend.

[@beepboop204]

for me, it is retaining it after i understand what he is saying. maybe that has to do with this potent cannabis im smoking.....

[@TheoEvian]

The Parth guy does this same explanation and also Eugene Khutoryansky and his explanation I like the most, since it has pictures. The idea is always the same - if electrons are indistinguishable it means they can't be in the same place because their wave functions would interfere in a bad way.

[@pecan4434]

This one's really well written even for the already high quality level of this show. It could've easily been incomprehensible but it was somehow really clear.

[@pedromoreira1836]

That's amazing! I've just gone through a scientific initiation (undergrad research) in math, as a physics student, in which I studied differential forms and its applications, and the possible combinations of a pair of fermions seems like a wedge product of two 1-forms. Physics is simply amazing.

[@kaiezon5655]

“…and there would be no such thing as chemistry..” Go on. I’m listening

[@EebstertheGreat]

I still remember a math lesson in middle school covering the precise mathematical meanings of common words like sum, product, factor, by, term, less, more, at least, at most, etc. In one of the problems assigned for homework, it asked us what was wrong with a store advertising a sale as "all items up to 20% off or more!"

[@Robert_McGarry_Poems]

No commas. Shame... Could have saved grandma too. Let's eat grandma!

[@alwaysdisputin9930]

Such a store should speak with better error bars in the future.

[@pierreabbat6157]

Another phrase that irks me is "one of the only" followed by a plural noun and no number. If you don't know the number, say "one of the few".

[@doctorkropotkin6710]

I remember an advert for a chocolate bar that claimed it was "up to 80% fat free". Sounds good 'til you think it through.

[@kashu7691]

@@doctorkropotkin6710 a chocolate bar of 80% pure fat is a terrifying thought

[@4fmagnet]

Woah, there! You have said/depicted something at 13:04 that could be very misleading without proper explanation! You have depicted the states as 'ground' and 'excited', implying these are energy states. Good so far. You have depicted the electrons as blobs with no assigned spin, and I understand this was done to get your point across. BUT, the electrons do have some intrinsic spin (+1/2 or -1/2; alpha or beta, however you want to call it--in the lab frame with respect to some axis that would align or anti-align with a magnetic field). What you have described (or implied) is the triplet state (both electrons are "spin up"--parallel), in which the "spin" portion is the wave function is symmetric and the "spatial" portion of the wavefunction is antisymmetric (for a total antisymmetric wavefunction). In this case, everything you said is correct. However, especially important in chemistry, is the single state (one electron spin up, the other spin down--antiparallel), in which the spin component of the wavefunction is antisymmetric and the spatial component symmetric. In this case, two electrons CAN both be in the ground energy state, as long as they have opposite spins. Of course this is a distinct quantum state, as you said, but not a distinct energy state. I just don't want anyone to be confused or walk away with the wrong impression.

[@davidhand9721]

You're right; that raised an eyebrow for me, too. Without that context, his explanation doesn't really have a link between spin and the exclusion principle at all. It sort of describes spin in the usual Copenhagen way, then separately describes anti-symmetric wavefunctions, but with some really weird simplifications. _f_ and _g_ are normally two wavefunctions, psi1 and psi2, not usually two different energy levels. Then there's _A_ and _B_ which are usually two positions, and that's even more confusing because it makes it look like we are talking about swapping particle identities or energy levels, not positions. The important bit, of course, is to show that the two wavefunctions can't be the same if they have the same state, and Matt gets there, but the extra bits about multiple energy levels and ambiguity about what kind of parameters are going into the combined wavefunction are just distracting from the point that opposite spin is what makes the particles pair up in the same state. And then he doesn't really explain how the effect is related to contact forces at all, he just states that they are one and the same. Overall, not the best episode of... SpaceTime. Unrelated note: go read the first two papers you find when you Google "Ohanian Dirac field". I can't recommend them enough for understanding spin without all the belts and ribbons and teacups and general insanity surrounding spin. They really are spinning after all, just on the outside, with charge density flowing twice as fast as mass/energy/probability density, no superluminal flow required. Much, much easier to wrap your head around, though I don't know how exactly that fits in the spin statistics theorem.

[@michaelcollier5219]

@@davidhand9721 I agree that Matt should have done better at explaining how the Pauli exclusion principle connects to solids and molecules and chemistry, but he still explained the details of the principle better than did all the quantum professors and textbooks I ever had. Had he spent just 1 minute more on that part of the explanation, he would have nailed the topic 100% perfectly. And I strongly disagree with you that "all the belts and ribbons and teacups" were unnecessary for understanding spin; those visual analogies were immensely helpful for my understanding, and I'm grateful that he used them.

[@CATinBOOTS81]

Well... you're right.

[@tantamounted]

Thank you. This, combined with the video above, just explained a bit more about electron shells around atoms, and why they layer the way they do.

[@davidhand9721]

@@michaelcollier5219 The reason you needed those visual analogies is that you have not yet read that paper by Ohanian, titled "What is spin?". The Dirac field really is spinning, or more accurately flowing circularly. Spin is spin. The visual analogy you need is... a thing spinning.

[@user-gd8xd4ws3x]

Thank you for going deeper and explaining the Pauli exclusion principle. Was very interesting to watch.

[@MargoMB19]

I love the intros on Space Time videos, they are always perfecting intriguing and kind of quirky.

[@ryansears4387]

This makes more sense than my quantum mechanics lectures in college lol I still did well in the class, but didn't really understand where the math came from.

[@TheGanamaster]

I guess this is where the "meth" jokes had started.

[@DrWhom]

you still don't

[@olehoiii]

The best thing I know is when I open my laptop and see PBS Space Time posted a video 5min ago! Thank you!

[@curiodyssey3867]

Phrasing

[@wleizero]

I wish this video had been available when I was at Uni. Spin was the stumbling block and made me stop trying to understand, and just "shut up and calculate". Really awesome video!!!

[@AshenZu]

There just aren't the correct words for how much I love these episodes. Particularly in one like this where I have a eureka moment. As opposed to the point running away like a child on sugar playing hide and seek.

[@johntavarez6605]

I honestly can't express how happy I am that I found this channel who knows how long ago Thank y'all for all the great educational content!

[@robertmroczek4994]

This is one brilliantly explained concept. One of your best videos yet in my humble opinion!

[@40watt53]

I love how this channel doesn't just go "Yeah accept this wacky thing as true. 'Why?' because quantum stuff I don't know man." but is like the first one to actually explain the concepts.

[@tnb178]

This guy never stops looking into the camera while doing the whole belt trick. Real pro KZbinr.

[@Roystonsmum101]

Does…… does Matt call his dong ‘Mysteries’? Another great episode that I think I understood a tiny bit more than half of, keep them coming!

[@ChemEDan]

The mystery machine

[@dionh70]

"Mystery", singular

[@umber6937]

Hmm, the implications of that may be worrying

[@paulmichaelfreedman8334]

Well i surprised myself by predicting the superposition as soon as Matt was talking about psi and psi squared, and that psi itself cannot be directly measured - it has to be squared first to remove any negatives (distribution probability cannot be negative). By taking the square root of psi squared there are two possible answers - a positive and a negative one, but which is which? -> superposition.

[@inkasaraswati7625]

@@paulmichaelfreedman8334 Oooh I didn't get the connection to superposition. I was too busy thinking that even though math was never intended to describe these things (it was probably first invented to count apples or something), millenias and a multitude of complexities later, it still is able to describe our physical world perfectly.

[@mandelbraught2728]

This one totally rocked my world. I freaking love this channel! Thank you. I'm so appreciative that you don't treat us normal schlumps out here like idiots. You really make an effort to explain the principles. It's great. Please don't stop. Dr. Matt, does that mean your belt has integer spin? Are those cg pants?

[@renerpho]

What gives Matt mass is the same thing as what holds up his pants. Now that's some hypothesis there.

[@sheepwshotguns42]

pretty sure ive seen about 80% of all of pbs space times videos, and this remains the best one to this day!

[@johnclark8359]

I think that just may be the best episode yet. Thanks a lot

[@camerondale6529]

I think a lot of confusion around spin is the fact that people think it has to do with the physical property itself, when in reality spin describes a mathematical property which relates to the behavior of particles within a particular frame. Think of it as spin = math of particle, not movement of particle.

[@tim40gabby25]

Spot on.

[@davidhand9721]

Read Ohanian's paper titled "What is spin?". You're welcome.

[@davidhand9721]

@@hyperduality2838 define "dual to" before you copy-pasta this again.

[@davidhand9721]

@@hyperduality2838 can you explain how duality makes any testable predictions?

[@davidhand9721]

@@hyperduality2838 sorry man, this sounds like a lot of confetti and no tool to me.

[@Sam_on_YouTube]

I used the Pauli Exclusion Principle in my metaphysics papers back in college. I used it to disprove the concept of "identical but numerically distinct." If two things are truly completely identical, then they cannot be well described with any distinction, they are inherently too entangled to make such a distinction. That causes many confusing problems in the philosophy of material composition (also called "mereology") to simply resolve themselves.

[@jrobinson1215]

Chairs, chairs everywhere!

[@anywallsocket]

it's really pretty obvious in retrospect: if two things are identical, who's to say they aren't actually one thing? i believe the pauli exclusion principle falls out of the conservation of information, not the other way around.

[@Sam_on_YouTube]

@@jrobinson1215 A typical setup for a philosophy thought experiment here would be "suppose you are cloned so there is an identical copy of yourself, but in a different place." To which I reply "that violates the laws of physics." Now that isn't ALWAYS a problem, but in many of these cases, the way it violates the laws of physics simply destroys the whole motivation for the question and leads to an obvious answer.

[@Sam_on_YouTube]

@@anywallsocket If I remember correctly (which I might not) that's how I learned it in Quantum I.

[@viktordominguez]

You explained this so well, I love these videos 😃

[@1.4142]

Wow, you've really got this stuff under your belt!

[@Joso997]

Honestly I love this show and this guy.

[@samsungtelevision695]

Amen. Gives me good memories of college back in the 00s

[@tzaidi2349]

I think I speak for my fellow Spacetimers when I say that I love that I have to watch it a few times to get it. Always pushing the limit of my understanding. I also think were all looking forward to future explainations where Matt takes off his shirt to explain entanglement. #physicsbod

[@cwojomusic556]

Will need to listen to this more than once. Ill be back.

[@TomAtkinson]

Thanks Matt and also Jason Hise that animation is inspirational. Thanks for going into that extra detail I think you read my mind. Diractastic.

[@MegaBrokenstar]

It takes someone like you, equally obsessed with astrophysics (and therefore GR) and quantum mechanics to become the sort of master-of-all physicist and communicator that you are. I consider you to be one of the leading overall scientists of our time.

[@chrisfrolik4014]

"We can't observe Psy" *Gangnam Style plays somewhere off in the distance*

[@Epistemonto]

Here I was thinking Hikaru No Go's Sai, but yeah...

[@LuisSierra42]

They are in a state of superposition

[@markdanielpatureau2925]

After watching this episode for the 3rd time, each viewing more interesting than the previous, I am beginning to grasp spinor theory. Thank you for enlightening me Matt!

[@Ebruskaya]

Thank you very much for these videos on spin. I am finally enlightened. It was quite hard to visualize.

[@navinsingh1730]

I love how Matt simplified math to feel like a child's play. He can teach a horse to drink water in a glass!

[@richp6716]

Why is the horse in a glass?

[@cam4636]

@@richp6716 He didn't use the anti-symmetric wave function

[@navinsingh1730]

@@richp6716 Due to quantum uncertainty!

[@hektor6766]

@@richp6716 Ba-dam-tsss!

[@whatfireflies]

Oh, I see! If their wavefunctions are anti-symmetric, any configurations where two fermions occupy the same state have zero amplitude and therefore zero probability of measurement. Nice.

[@Brandon_Tyr]

Well they would have zero wave function. But instead the Pauli Exclusion Principle swoops in like some magic voodoo and prevents it from happening.

[@alwaysdisputin9930]

@@Brandon_Tyr Why is voodoo necessary? Doesn't the zero probability of measurement mean you can't get ever find 2 electrons crammed on top of each other (i.e. with the same 4 quantum numbers)? I didn't understand the video & I don't know why whatfireflies said if their wavefunction are anti-symmetric then 2 fermions occupying the same state have 0 amplitude

[@alwaysdisputin9930]

@whatfireflies Why do you say: 2 anti-symmetric wavefunctions = 2 fermions occupying the same state have 0 amplitude?

[@enterprisesoftwarearchitect]

BETTER EXPLANATION than the whole video! I hate when they say Pauli Exclusion Principle and then don’t explain it.

[@enterprisesoftwarearchitect]

@@hyperduality2838 watch Alex Flournoy- he’ll set you right about dual vector representations in particle physics my friend. Get it straight- you are almost there.

[@benr3799]

14:40 man it was just yesterday I was watching Cyberchase on PBS on my cathode ray tube tv. Now I have Matt dropping trou’ while explaining spinnors. Thank you PBS. And to viewers like you, thank you.

[@cantubloodaxe768]

I kind of forgot what we were trying to prove till you reminded me at the end. It all makes sense now!

[@binkaboi5865]

That ending revelation on Matt's preference for QM over astrophysics 😆 too good.

[@hektor6766]

He'd make a great dad.

[@princeofcupspoc9073]

You can't have one without the other, as least not according to the standard model.

[@Danledz]

"You spin me right round baby right round"- Electrons, maybe

[@vblaas246]

"Molecular Shape of you" - Ed Sheeran parody

[@hektor6766]

"... right round, round--and stop!"

[@fredrickhinojosa4568]

You are a great teacher ! And quantum is getting closer to normal, thanks to your clear explanations of the latest facts . Matt O"Dowd you are a credit to your profession. Thank you

[@davidcarroll2911]

All of these space times are great, but this one was a cut above. Very nice job!

[@Sam_on_YouTube]

I studied philosophy of physics because once I got past sophmore year, the math required for a physics major just got hopelessly out of reach for me. But I still really wanted to learn the concepts in Quantum II to apply to my philosophy. I convinced the professor to let me audit the class, pass/fail and instead of the final, to write a philosophy paper about the subject matter. I explored whether a helium nucleus was one boson or four fermions. Ultimately, I concluded that the correct answer depends on the perspective set based on the context of the question. If you are exploring the macroscopic behavior of liquid helium, it is a boson. Explaining it as 4 fermions is simply not a useful answer to the question being asked. It is an answer to a different, more fundamental question and therefore, simply the incorrect response.

[@tomf3150]

Congrats, you have reached metaphysic. Litterally.

[@jimgraham6722]

Good

[@kenlogsdon7095]

@Sam Sorry but you've lost me. How does the quantum status of the helium nucleus affect the behavior of helium atoms in their liquid form?

[@shazide5358]

The helium nucleus is a boson formed by 4 fermions. I don't see whats the problem with this answer.

[@kenlogsdon7095]

@@shazide5358 The problem is that the nucleus of an atom doesn't directly interact with the nuclei of all the other atoms around it, it's the electron shells that do. Or am I somehow mistaken on that point?

[@waynethomas1726]

Wow, even though my brain really hurt by the time you were done...I actually understood what you were saying, I comprehended it for the most part. Quantum Physics has always struck me as nonsense because nothing seems to behave the way it does in "reality". In "reality" the laws of physics explain what we see. In the quantum world you need explanations just to understand the laws. At least that's how it seems to me. I could never pass any classes involving Quantum Physics. But the way you describe things I can kind of at least be in the same places as what you're describing, even if I don't fully comprehend any of it. Today, I actually comprehended most of it too! Total win! LOL Thank you!

[@KhalilEstell]

I'm certain someone has already said this, but the limit to the number of bosons that can overlap would be the amount needed to create a "kugelblitz" (although theoretical)

[@user-yu6dh7vf5b]

Guys... AMAZING JOB OF EXPLAINING EVERYTHING! Thank you for that so much! I don't have any physics background and yet I understood everything! Just the way how you moved from simple to more complicated and explaining the complicated with examples worked so good for me! It would be really nice to keep the same structure of explaining so people withe less brain like me can learn more about our universe! :)

[@ChrisWalshZX]

"... for you, here, on spacetime" - that's a bit of a cop out! It's a reference to the channel, not to spacetime itself! Excellent video. Absolutely amazing explanation of half-spin fermions and why the obey Pauli. Thanks.

[@AlienScientist]

This gives me great hopes for our upcoming Alzofon experiments...

[@cowlinator]

What is this?

[@MrRoguetech]

@@cowlinator Anti-gravity idea that Alzofon's own experiments proved wrong 30 years ago.

[@MrRoguetech]

@Science Revolution You seriously don't understand how tides work??

[@nevs0917]

Great video! Really helped clarify some of my QM lectures!

[@fpvwing]

A really enjoyable video Matt, thank you.

[@debyton]

The trouble with reverse engineering from a fixed perspective in nature, as we are often forced to do, even with accurate data, is we are forced to draw conclusions that fit the data, and yet, those conclusions are not guaranteed nor even likely to land anywhere near the true description of reality. For example, the earth-centric universe. The correctly observed, and measured motions of the planets didn't reveal in an obvious manner the underlying flawed perspective. Flawed descriptions and supporting mathematics and postulates can provide frequently accurate results even to 10 decimal places because they describe the symptoms and not the cause. One can measure and describe everything about a cool breeze as it passes over you and yet reveal nothing about whether it is the last gasp of a distant dying hurricane, or from a nearby wind turbine, or is a direct well-traveled atmospheric perturbation of our parent sun's energy. Absent the correct description of the underlying structure of any natural implementation, refinements to observed phenomena and their representative mathematics and symbology will continue to be flawed. Upon the realization of the actual defining structure, all of the previous notions are often deprecated for a new description.

[@TheRealInscrutable]

I'm looking forward to when we can make stellar observations "simultaneously" from many tens of light years apart. The debate over the non-privileged position from which we now view the universe can be settled. Sadly it'd be much more fun if it turned out we had a privileged position. Oh well.

[@harbingerdawn]

"The correctly observed, and measured motions of the planets didn't reveal in an obvious manner the underlying flawed perspective." On the contrary, it was precise and accurate measurements of the motions of the planets that allowed Kepler to discover the elliptical shape of planetary orbits, and thus construct a simple and elegant heliocentric description of the solar system that matched observed reality far more closely than the more complex geocentric model accepted at the time. The point you're making is a valid one though.

[@chewyjello1]

Considering that the literal only thing we can ever have direct access to is just patterns caused by the electrical impulses of neurons...I'd say we are doing pretty well. A direct, intuitive understanding of reality is probably too big an ask. But we can continue to refine the tools that allow us to play with reality (if there is such a thing as a single objective reality) even while trapped within our dark, windowless skulls.

[@sessival3030]

@@chewyjello1 Yeah, the only thing we really have access to IS measurements and data. This dives into philosophy of knowledge territory and epistemology. All we can do is make our conclusions on better and more data.

[@MylesKillis]

@@chewyjello1 perception eats rationality for breakfast

[@EvenTheDogAgrees]

Man, anyone remember when this channel required nothing but a keen intellect to be able to follow along?

[@Aurinkohirvi]

Nope. I must have found the channel later.

[@budo4]

What fascinates me even more is that a small but significant portion of the human species completely understands the non simplified version of this explanation on matter. Why is it so foreign to the majority of us but so easy to digest for these few.

[@xHellsProdigyx]

@Steve Bogucki, I agree, PBS SpaceTime has been my godsend. It has opened my eyes so far beyond what I thought was a love for astrophysics.

[@Cronos804]

Physics is all that matters but math is all that counts.

[@baremetaltechtv]

"All electrons are exactly the same. You can swap any two electrons etc..." I think the guy who thought it was turtles all the way down must have made a mistake.

[@janneaalto3956]

I remember when I realized, as a little kid, how little there is to solid matter. Soon after the realization, I got sick and a high fever. A couple times during that fever I imagined the world as it really is, with solid matter less concrete than mist, and then I'd get horrible vertigo with cold sweats as I grabbed the sides of my bed and imagined the twelve thousand kilometer abyss of super hot intangibility beneath me.

[@DFPercush]

On the bright side, at least you don't have to worry about the sun not rising in the morning like some ancient peoples...

[@sleeplessforawhile]

That 720 "rotation" makes me think on additional dimensions... Seems like the electrons and fermions in general, has to complete a "trip" on those additional dimensions to reach what we see as a complete simetric "trip" before it returns to original state. Thanks Matt. Your videos are a beautiful gift for me.

[@ChrisBrown-pw2lb]

I've never watched one of the vids without hitting the like icon. I don't understand all the math but I still know enough to enjoy these vids. Thank You Guys.

[@Factnomenal]

Another great video from the legend himself! 👏

[@SoulDelSol]

I didnt know he was a legend. He is pretty smart so I'm not surprised

[@erickrueger447]

Half integer spin is like an object on a circular Moebius path; once around just gets you to the same place in space but the 'other side' of the path.

[@deeponjitbose8188]

Best explanation of spinors and Spin-statistics Theorem

[@wayneyadams]

This is why the periodic table looks like it does. Each electron in an atom is assigned a set of four quantum numbers. One is the energy level, two are moments (angular and magnetic), and the third is spin. The spin can either be +1/2 or -1/2. The levels, or shells as they are called, are numbered much like the floors in a building. The levels can be divided into sublevels. The number of sublevels correspond to the number of the shell. The first shell has one, or effectively no sublevels. The second has two, the third has three and so on. These sublevels are further divided by a magnetic component into what we call orbitals. This was probably a bad choice of words because it misleads people into thinking that the electrons orbit like planets around the Sun. Each of the orbitals is formed by a maximum of two electrons, one with +1/2 spin and the other with -1/2 spin. Notice I said formed and not filled. Orbitals are not little empty containers waiting to be filled, they are formed by the electron, i.e., no electron, no orbital. More accurately, they are the volumes of space where the probability of finding the electrons are very high. The first energy level has one orbital and thus holds two electrons of opposite spin. It is a spherical orbital which we call s. The second energy level has two sublevels, with an s orbital in the lower energy sublevel, and three orbitals, each holding two electrons in the higher energy sublevel. We call these orbitals p. So this level can have 8 electrons, 2 in the s orbital, and 6 in the p orbitals. The third level gets more complicated. It has the two s orbitals, three p orbitals and an additional five orbitals, each holding two electrons, we call it d. So this energy level can hold 2 + 6 + 10 = 18 electrons The next energy level has an additional 7 orbitals called f, holding two electrons each for a total of 14. Find a picture of the Periodic Table and notice how it is arranged. The first row is the first energy level, the second is the second and so on. On the left are two columns corresponding to elements that have their outermost electrons in the s orbitals. The first column has one, the second has two. Over to the right you will see six columns, for elements with their outermost electrons in the p orbitals. Tucked in between a little lower in the table you will see a section with ten columns corresponding to the d orbitals. Finally at the bottom there are two rows of elements of 14 columns corresponding to the f orbitals. The critical point is that each electron is assigned a set of four quantum numbers, and no two electrons can have identical quantum numbers. The result is that each orbital can be occupied (formed) by two electrons of opposite spin, +1/2 and -1/2. -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- This section is for serious chemistry students. The first quantum number is n and it corresponds to the energy level. The second quantum number, the angular moment, is l. It has values from 0 to one less than n. For instance: n = 1, l = 0 n = 2, l = 0, 1 n = 3, l = 0, 1, 2 The third quantum number, the magnetic moment has values from -l to +l, including zero. n = 1, l = 0, m = 0 (the s orbital) n = 2, l = 0, m = 0 (the s orbital) l = +1, m = +1, 0, -1 (the three p orbitals) n = 3, l = 0, m = 0 (the s orbital) l =+1, m = +1, 0, -1 (the three p orbitals) l = +2, m = +2, +1, 0, -1, -2 (the five d orbitals) The fourth quantum number, is s, the electron spin (remember electrons do not actually spin) has values of +1/2 and -1/2. So each of those orbitals could have two electrons of opposite spin. For example two electrons occupying a p orbital in the second energy level might have numbers: n = 2, l = +1, m = 0, s = +1/2 n = 2, l = +1, m = 0, s = -1/2 -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- As Dr. Don Lincoln says at the end of his FermiLab videos, "Physics is everything," to which I am going to add, "we would not be here without Chemistry." Wayne Y. Adams B.S. Chemistry M.S. Physics

[@SolidSiren]

That's not for serious chem students. I took chemistry 1 and it included all of that. Plenty of kids in there were NOT chemistry students, or even science degrees actually for some reason. Im doing biophysics, so I have taken bio, chemistry AND physics every year so far.

[@SolidSiren]

I see you did chemistry and physics. Thats great, Im sure the chemistry helped!

[@wayneyadams]

@@SolidSiren It actually worked the other way. I had planned to do a double major as an undergraduate, but because of some red tape, I had to use all my physics credits to satisfy the university's silly 3rd science requirement. Even so, the physics made the chemistry much more understandable.

[@wayneyadams]

@@SolidSiren I'm talking about the people who watch KZbin videos, not chemistry students.

[@yoink6830]

Really love the episodes that shows some of the actual math behind the physics to show how it works.

[@samiaario8291]

This channel is excellent at bridging the gap between pop science and a deeper understanding of physics, and this particular episode is a shining example of that.

[@SinisterBlackShadow]

Absolutely awesome and clear explanation of the Pauli Exclusion Principle. I took a fair bit of time out of my younger days trying to get a grasp on this, whilst this video would've helped me in minutes. Years later, I have lost some of that knowledge but with the help of this video, I can now also remember in minutes. This video reminds me of another interesting point...I believe particles (bosons or fermions) tend to decay to lower energy (mass)...so it seems we have proof that nothing is less massive than an electron, with the same properties. In other words, it is stable because nothing else exists. Now I could be wrong here so don't take my word for it.

[@renato360a]

For a laymen like me, the whole argument seems to be based on the fact that "you can't just vanish electrons" (12:55). But I don't know about that.

[@Jerom_]

If both electrons are in the same state, the wave function would be zero. That means that the squared wavefunction, which represents the probability of finding the two particle system in that state, becomes zero. In other words: the chance of both electrons being in the same quantum state is zero. Another way to make that same statement is to say that two electrons cant occupy the same quantum state. Hope that clears things up.

[@ZetaFuzzMachine]

You're right, that phrasing was unfortunate. The thing is that, if two electrons share the same state, then the wavefunction (psi) of the swapped pair would be the same as minus the wavefunction (-psi). And when you have the equation x = - x the answer is x = 0 When psi = 0, it means that there are no electrons there. (Because the wavefunction is a statistical tool that represents probability. When the wavefunction is null, then probability of existence is null)

[@scotthammond3230]

Exactly.. psi = -psi, 0=0.. ok thats bad, you cant disappear electrons! The math works, but it doesnt explain why electrons dont overlap and disintegrate each other.

[@seanathans103]

@@scotthammond3230 lepton number and charge would not be conserved

[@twistedtachyon5877]

@@seanathans103 now we're getting somewhere! Next step on this rabbit hole: particles annihilate each other all the time. Do all such annihilations have balanced charges? All the cases I know of do, now that I think about it. Does that mean that, in a sense, "we can have nice things" because, while electrons would all like to vanish into oblivion, they can't manage it because they all have something about themselves they can't let go of? I guess the overly simplistic explanation about charge holding things apart is better than I thought. (It's optimistic nihilism ark the way down...)

[@christopherdurham1999]

Episode might get "quantum-weird"... I mean, isn't that what we're here for?

[@billlarson2382]

Makes my head spin...and I love it. Thanks!

[@vajrapromise8967]

This actually makes sense and doesn't seem too complicated, I wonder why it has been presented before as such a mystery. Must be that many others don't really know what they are describing, this is the best description I've ever come across though and look forward to learning more-Thanks!

[@pretzelboi64]

Some people just like to impress and appear intelligent when explaining things instead of focusing on actually getting the person to understand. It's the biggest driver in the failure to learn things for most people imo