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Grant Sanderson: 3Blue1Brown and the Beauty of Mathematics

第2020-01-07期2020-01-07English

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§01Transcript · 00:00–07:29

00:00The following is a conversation with Grant Sanderson.

00:03He's a math educator and creator of 3Blue1Brown,

00:06a popular YouTube channel

00:08that uses programmatically animated visualizations

00:11to explain concepts in linear algebra, calculus,

00:14and other fields of mathematics.

00:17This is the Artificial Intelligence Podcast.

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00:28at Lex Friedman, spelled F-R-I-D-M-A-N.

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01:51And now, here's my conversation with Grant Sanderson.

01:56If there's intelligent life out there in the universe,

01:59do you think their mathematics is different than ours?

02:02(Grant laughs)

02:03- Jumping right in.

02:04I think it's probably very different.

02:08There's an obvious sense the notation is different, right?

02:11I think notation can guide what the math itself is.

02:13I think it has everything to do

02:16with the form of their existence, right?

02:19- Do you think they have basic arithmetics?

02:20Sorry to interrupt.

02:21- Yeah, so I think they count, right?

02:23I think notions like one, two, three, the natural numbers,

02:25that's extremely, well, natural.

02:27That's almost why we put that name to it.

02:30As soon as you can count,

02:31you have a notion of repetition, right?

02:33'Cause you can count by two, two times or three times.

02:37And so you have this notion of repeating

02:39the idea of counting,

02:40which brings you addition and multiplication.

02:43I think the way that we extend to the real numbers,

02:47there's a little bit of choice in that.

02:49So there's this funny number system

02:50called the surreal numbers

02:52that it captures the idea of continuity.

02:55It's a distinct mathematical object.

02:57You could very well model the universe

03:00and motion of planets with that

03:01as the back end of your math, right?

03:04And you still have kind of the same interface

03:06with the front end of what physical laws you're trying to,

03:10or what physical phenomena

03:12you're trying to describe with math.

03:13And I wonder if the little glimpses that we have

03:15of what choices you can make along the way

03:17based on what different mathematicians

03:19have brought to the table

03:20is just scratching the surface

03:22of what the different possibilities are

03:24if you have a completely different mode of thought, right?

03:27Or a mode of interacting with the universe.

03:29- And you think notation is a key part of the journey

03:32that we've taken through math.

03:33- I think that's the most salient part

03:35that you'd notice at first.

03:36I think the mode of thought is gonna influence things

03:38more than like the notation itself.

03:40But notation actually carries a lot of weight

03:42when it comes to how we think about things,

03:44more so than we usually give it credit for,

03:47I would be comfortable saying.

03:48- Do you have a favorite or least favorite piece of notation

03:52in terms of its effectiveness?

03:53- Yeah, yeah, well, so least favorite,

03:54one that I've been thinking a lot about

03:56that will be a video, I don't know when, but we'll see.

03:58The number e.

04:00We write the function e to the x,

04:02this general exponential function

04:04with the notation e to the x.

04:06That implies you should think about a particular number,

04:08this constant of nature,

04:09and you repeatedly multiply it by itself.

04:11And then you say, oh, what's e to the square root of two?

04:14And you're like, oh, well,

04:14we've extended the idea of repeated multiplication.

04:17That's all nice, that's all nice and well.

04:19But very famously, you have like e to the pi i,

04:22and you're like, well,

04:23we're extending the idea of repeated multiplication

04:25into the complex numbers.

04:27Yeah, you can think about it that way.

04:28In reality, I think that it's just the wrong way

04:31of notationally representing this function,

04:34the exponential function,

04:36which itself could be represented

04:37a number of different ways.

04:38You can think about it in terms of the problem it solves,

04:41a certain very simple differential equation,

04:43which often yields way more insight

04:45than trying to twist the idea of repeated multiplication,

04:48like take its arm and put it behind its back

04:50and throw it on the desk and be like,

04:51you will apply to complex numbers, right?

04:53That's not, I don't think that's pedagogically helpful.

04:56- So the repeated multiplication

04:58is actually missing the main point,

05:00the power of e to the x.

05:02- I mean, what it addresses is things where the rate

05:05at which something changes depends on its own value,

05:10but more specifically, it depends on it linearly.

05:12So for example, if you have like a population

05:15that's growing and the rate at which it grows

05:16depends on how many members of the population

05:18are already there,

05:19it looks like this nice exponential curve.

05:21It makes sense to talk about repeated multiplication

05:23'cause you say how much is there after one year,

05:25two years, three years, you're multiplying by something.

05:27The relationship can be a little bit different sometimes

05:29where let's say you've got a ball on a string,

05:33like a game of tetherball going around a rope, right?

05:37And you say its velocity

05:39is always perpendicular to its position.

05:42That's another way of describing its rate of change

05:44as being related to where it is,

05:47but it's a different operation.

05:48You're not scaling it.

05:49It's a rotation.

05:49It's this 90 degree rotation.

05:51That's what the whole idea of like complex exponentiation

05:54is trying to capture,

05:55but it's obfuscated in the notation

05:57when what it's actually saying,

05:59like if you really parse something like e to the pi i,

06:01what it's saying is choose an origin,

06:03always move perpendicular to the vector

06:06from that origin to you, okay?

06:08Then when you walk pi times that radius,

06:12you'll be halfway around.

06:14Like that's what it's saying.

06:15It's kind of the, you turn 90 degrees and you walk,

06:18you'll be going in a circle.

06:19That's the phenomenon that it's describing,

06:22but trying to twist the idea

06:24of repeatedly multiplying a constant into that.

06:26Like I can't even think of the number of human hours

06:30of like intelligent human hours that have been wasted

06:33trying to parse that to their own liking and desire

06:36among like scientists or electrical engineers

06:39or students everywhere,

06:40which if the notation were a little different

06:42or the way that this whole function

06:44was introduced from the get-go were framed differently,

06:47I think could have been avoided, right?

06:49- And you're talking about

06:51the most beautiful equation in mathematics,

06:53but it's still pretty mysterious, isn't it?

06:55Like you're making it seem like it's a notation.

06:57- It's not mysterious.

06:59I think the notation makes it mysterious.

07:01I don't think it's,

07:02I think the fact that it represents, it's pretty.

07:05It's not like the most beautiful thing in the world,

07:06but it's quite pretty.

07:07The idea that if you take the linear operation

07:10of a 90 degree rotation

07:12and then you do this general exponentiation thing to it,

07:15that what you get are all the other kinds of rotation,

07:18which is basically to say,

07:20if your velocity vector is perpendicular

07:22to your position vector, you walk in a circle, that's pretty.

07:26It's not the most beautiful thing in the world,

07:27but it's quite pretty.

07:28- The beauty of it, I think,

07:29comes from perhaps the awkwardness of the notation

§02Transcript · 07:33–15:07

07:33somehow still nevertheless coming together nicely.

07:35'Cause you have like several disciplines coming together

07:38in a single equation.

07:40- Well, I think-- - In a sense,

07:42historically speaking.

07:43- That's true.

07:44So like the number E is significant.

07:45It shows up in probability all the time.

07:47It shows up in calculus all the time.

07:49It is significant.

07:50You're seeing it sort of mated with pi,

07:52this geometric constant,

07:53and I, like the imaginary number and such.

07:55I think what's really happening there

07:57is the way that E shows up

08:00is when you have things like exponential growth and decay.

08:03It's when this relation

08:04that something's rate of change has to itself

08:07is a simple scaling, right?

08:08A similar law also describes circular motion.

08:14Because we have bad notation,

08:16we use the residue of how it shows up

08:19in the context of self-reinforcing growth,

08:21like a population growing or compound interest.

08:23The constant associated with that

08:25is awkwardly placed into the context

08:27of how rotation comes about

08:29because they both come from pretty similar equations.

08:32And so what we see is the E and the pi juxtaposed

08:34a little bit closer than they would be

08:38with a purely natural representation, I would think.

08:40Here's how I would describe the relation between the two.

08:43You've got a very important function we might call exp

08:45that's like the exponential function.

08:47When you plug in one,

08:49you get this nice constant called E

08:50that shows up in like probability and calculus.

08:53If you try to move in the imaginary direction,

08:55it's periodic and the period is tau.

08:58So those are these two constants

08:59associated with the same central function.

09:02But for kind of unrelated reasons, right?

09:04And not unrelated, but like orthogonal reasons.

09:07One of them is what happens

09:08when you're moving in the real direction.

09:09One's what happens when you move in the imaginary direction.

09:12And like, yeah, those are related.

09:14They're not as related as the famous equation

09:17seems to think it is.

09:18It's sort of putting all of the children in one bed

09:20and they'd kind of like to sleep in separate beds

09:22if they had the choice.

09:23But you see them all there and, you know,

09:25there is a family resemblance, but it's not that close.

09:29- So actually thinking of it as a function

09:31is the better idea.

09:34And that's a notational idea.

09:36- And yeah, and like, here's the thing.

09:38The constant E sort of stands

09:41as this numerical representative of calculus, right?

09:43- Yeah.

09:44- Calculus is the like study of change.

09:47So at the very least,

09:48there's a little cognitive dissonance

09:49using a constant to represent the science of change.

09:53- Never thought of it that way.

09:54Yeah.

09:55(laughs)

09:55- Right?

09:56- Yeah.

09:57- It makes sense why the notation came about that way.

09:59- Yes.

10:00- It's the first way that we saw it

10:02in the context of things like population growth

10:03or compound interest.

10:04It is nicer to think about as repeated multiplication.

10:07That's definitely nicer,

10:08but it's more that that's the first application

10:11of what turned out to be a much more general function

10:13that maybe the intelligent life,

10:15your initial question asked about,

10:17would have come to recognize

10:18as being much more significant than the single use case,

10:21which lends itself to repeated multiplication notation.

10:24- Let me jump back for a second to aliens

10:28and the nature of our universe.

10:30Okay.

10:30Do you think math is discovered or invented?

10:35So we're talking about the different kind of mathematics

10:37that could be developed by the alien species.

10:40The implied question is,

10:42yeah, is math discovered or invented?

10:46Is, you know, is fundamentally everybody going to discover

10:49the same principles of mathematics?

10:53- So the way I think about it,

10:54and everyone thinks about it differently,

10:55but here's my take.

10:56I think there's a cycle at play

10:57where you discover things about the universe

11:00that tell you what math will be useful.

11:03And that math itself is invented in a sense,

11:08but of all the possible maths that you could have invented,

11:11it's discoveries about the world

11:12that tell you which ones are.

11:14So like a good example here is the Pythagorean theorem.

11:17When you look at this,

11:18do you think of that as a definition

11:19or do you think of that as a discovery?

11:21- From the historical perspective, right,

11:23it's a discovery because they were,

11:25but that's probably because they were using physical object

11:29to build their intuition.

11:31And from that intuition came the mathematics.

11:34So the mathematics was in some abstract world

11:37detached from the physics.

11:39But I think more and more math has become detached from,

11:43you know, when you even look at modern physics,

11:46from string theory to even general relativity,

11:49I mean, all math behind the 20th and 21st century physics

11:53kind of takes a brisk walk outside

11:57of what our mind can actually even comprehend.

12:00In multiple dimensions, for example,

12:02anything beyond three dimensions, maybe four dimensions.

12:05- No, no, no, higher dimensions

12:07can be highly, highly applicable.

12:08I think this is a common misinterpretation

12:11that if you're asking questions

12:13about like a five-dimensional manifold,

12:15that the only way that that's connected

12:16to the physical world is if the physical world

12:19is itself a five-dimensional manifold or includes them.

12:22- Well, wait, wait, wait a minute, wait a minute.

12:25You're telling me you can imagine

12:27a five-dimensional manifold?

12:31- No, no, that's not what I said.

12:33I would make the claim that it is useful

12:34to a three-dimensional physical universe

12:37despite itself not being three-dimensional.

12:39- So it's useful, meaning to even understand

12:41a three-dimensional world, it'd be useful

12:43to have five-dimensional manifolds.

12:44- Yes, absolutely, because of state spaces.

12:47- But you're saying in some deep way for us humans,

12:50it does always come back to that three-dimensional world

12:54for the usefulness of the three-dimensional world.

12:56And therefore it starts with a discovery,

12:59but then we invent the mathematics

13:02that helps us make sense of the discovery in a sense.

13:06- Yes, I mean, just to jump off

13:07of the Pythagorean theorem example,

13:09it feels like a discovery.

13:11You've got these beautiful geometric proofs

13:12where you've got squares and you're modifying the areas.

13:14It feels like a discovery.

13:16If you look at how we formalize the idea of 2D space

13:19as being R2, all pairs of real numbers,

13:23and how we define a metric on it and define distance,

13:25you're like, "Hang on a second, we've defined distance

13:28"so that the Pythagorean theorem is true,

13:30"so that suddenly it doesn't feel that great."

13:32But I think what's going on is the thing that informed us

13:35what metric to put on R2,

13:38to put on our abstract representation of 2D space

13:41came from physical observations.

13:43And the thing is there's other metrics

13:44you could have put on it.

13:45We could have consistent math

13:47with other notions of distance.

13:49It's just that those pieces of math

13:50wouldn't be applicable to the physical world that we study

13:53'cause they're not the ones

13:54where the Pythagorean theorem holds.

13:56So we have a discovery, a genuine bona fide discovery

13:59that informed the invention,

14:00the invention of an abstract representation of 2D space

14:03that we call R2 and things like that.

14:06And then from there, you just study R2 as an abstract thing

14:09that brings about more ideas and inventions and mysteries,

14:12which themselves might yield discoveries.

14:14Those discoveries might give you insight

14:17as to what else would be useful to invent.

14:19And it kind of feeds on itself that way.

14:20That's how I think about it.

14:22So it's not an either or.

14:24It's not that math is one of these or it's one of the others.

14:26At different times, it's playing a different role.

14:29- So then let me ask the Richard Feynman question

14:33then along that thread.

14:36Is what do you think is the difference

14:37between physics and math?

14:40There's a giant overlap.

14:42There's a kind of intuition

14:45that physicists have about the world

14:46that's perhaps outside of mathematics.

14:49It's this mysterious art that they seem to possess,

14:52we humans generally possess.

14:54And then there's the beautiful rigor of mathematics

14:58that allows you to, I mean, just like as we were saying,

15:01invent frameworks of understanding our physical world.

15:07So what do you think is the difference there

§03Transcript · 15:10–23:31

15:10and how big is it?

15:11- Well, I think of math as being the study

15:13of like abstractions over patterns

15:15and pure patterns in logic.

15:17And then physics is obviously grounded

15:19in a desire to understand the world that we live in.

15:22I think you're gonna get very different answers

15:24when you talk to different mathematicians

15:25'cause there's a wide diversity in types of mathematicians.

15:28There are some who are motivated very much by pure puzzles.

15:31They might be turned on by things like combinatorics.

15:34And they just love the idea of building up a set

15:36of problem solving tools, applying to pure patterns.

15:40There are some who are very physically motivated,

15:43who try to invent new math or discover math in veins

15:48that they know will have applications to physics

15:50or sometimes computer science.

15:52And that's what drives them.

15:53Like chaos theory is a good example of something

15:55that's pure math, that's purely mathematical,

15:57a lot of the statements being made.

15:59But it's heavily motivated by specific applications

16:02to largely physics.

16:05And then you have a type of mathematician

16:06who just loves abstraction.

16:08They just love pulling into the more and more abstract

16:10things, the things that feel powerful.

16:12These are the ones that initially invented topology

16:15and then later on get really into category theory

16:17and go on about infinite categories and whatnot.

16:20These are the ones that love to have a system

16:23that can describe truths about as many things as possible.

16:27People from those three different veins of motivation

16:31into math are gonna give you very different answers

16:32about what the relation at play here is.

16:34'Cause someone like Vladimir Arnold,

16:37who has written a lot of great books,

16:40many about like differential equations and such,

16:42he would say, "Math is a branch of physics."

16:45That's how he would think about it.

16:47And of course he was studying like differential equations

16:49related things, because that is the motivator

16:51behind the study of PDEs and things like that.

16:53But you'll have others who,

16:56like especially the category theorists,

16:58who aren't really thinking about physics necessarily.

17:01It's all about abstraction and the power of generality.

17:04And it's more of a happy coincidence

17:06that that ends up being useful

17:08for understanding the world we live in.

17:10And then you can get into like, why is that the case?

17:12It's sort of surprising that that which is

17:16about pure puzzles and abstraction

17:17also happens to describe the very fundamentals

17:21of quarks and everything else.

17:23- So why do you think the fundamentals of quarks

17:27and the nature of reality is so compressible

17:33into clean, beautiful equations

17:35that are for the most part simple, relatively speaking?

17:39A lot simpler than they could be.

17:41So you have, we mentioned somebody like Stephen Wolfram

17:45who thinks that sort of there's incredibly simple rules

17:50underlying our reality,

17:51but it can create arbitrary complexity.

17:54But there is simple equations.

17:56I'm asking a million questions

17:59that nobody knows the answer to.

18:00- Yeah, I have no idea.

18:02(laughing)

18:03Why is it simple?

18:04- It could be the case that

18:07there's like a filtration at play.

18:08The only things that physicists find interesting

18:10are the ones that are simple enough

18:11they could describe it mathematically.

18:13But as soon as it's a sufficiently complex system,

18:15like, oh, that's outside the realm of physics.

18:16That's biology or whatever have you.

18:19And of course-- - That's true.

18:21- Maybe there's something where it's like,

18:22of course there will always be some thing that is simple

18:26when you wash away the non-important parts

18:31of whatever it is that you're studying.

18:33Just from like an information theory standpoint,

18:35there might be some like,

18:36you get to the lowest information component of it.

18:39But I don't know.

18:40Maybe I'm just having a really hard time conceiving

18:41of what it would even mean for the fundamental laws

18:45to be intrinsically complicated.

18:47Like some set of equations

18:50that you can't decouple from each other.

18:52- Well, no, it could be that sort of we take for granted

18:56that the laws of physics, for example,

18:59are for the most part the same everywhere.

19:03Or something like that, right?

19:05As opposed to the sort of an alternative could be

19:10that the rules under which the world operates

19:15is different everywhere.

19:17It's like a deeply distributed system

19:20where just everything is just chaos.

19:22Like not in a strict definition of chaos,

19:25but meaning like just it's impossible

19:28for equations to capture,

19:31to explicitly model the world

19:34as cleanly as the physical does.

19:36I mean, we almost take it for granted

19:38that we can describe,

19:39we can have an equation for gravity,

19:41for action at a distance.

19:42We can have equations for some of these basic ways

19:45the planets move and just the low level

19:50at the atomic scale, how the materials operate,

19:54at the high scale, how black holes operate.

19:56But it doesn't, it seems like it could be,

19:59there's infinite other possibilities

20:01where none of it could be compressible into such equations.

20:05It just seems beautiful.

20:06It's also weird, probably to the point you were making,

20:10that it's very pleasant that this is true for our minds.

20:15So it might be that our minds are biased

20:17to just be looking at the parts of the universe

20:19that are compressible.

20:21And then we can publish papers on

20:23and have nice E equals mt squared equations.

20:26- Right.

20:27I wonder, would such a world with uncompressible laws

20:31allow for the kind of beings that can think about

20:35the kind of questions that you're asking?

20:37- That's true.

20:38- Right, like an anthropic principle coming into play

20:40in some weird way here?

20:42I don't know, I don't know what I'm talking about at all.

20:44- Or maybe the universe is actually not so compressible,

20:48but the way our brain evolved,

20:52we're only able to perceive the compressible parts.

20:55I mean, we are, so this is a sort of Chomsky argument.

20:58We are just descendants of apes.

20:59We're like really limited biological systems.

21:03So it totally makes sense that we're really limited

21:06little computers, calculators,

21:08that are able to perceive certain kinds of things.

21:10And the actual world is much more complicated.

21:13- Well, but we can do pretty awesome things, right?

21:16Like we can fly spaceships.

21:18And we have to have some connection of reality

21:21to be able to take our potentially oversimplified models

21:25of the world, but then actually twist the world

21:27to our will based on it.

21:29So we have certain reality checks

21:30that physics isn't too far afield,

21:33simply based on what we can do.

21:35- Yeah, the fact that we can fly is pretty good.

21:37- It's great, yeah.

21:38It's a pretty good proof of concept

21:40that the laws we're working with are working well.

21:44- So I mentioned to the internet that I'm talking to you,

21:47and so the internet gave some questions.

21:50So I apologize for these.

21:51But do you think we're living in a simulation,

21:54that the universe is a computer,

21:56or the universe is a computation running on a computer?

22:00- It's conceivable.

22:02What I don't buy is, you know, you'll have the argument

22:05that, well, let's say that it was the case

22:07that you can have simulations,

22:09then the simulated world would itself eventually

22:13get to a point where it's running simulations.

22:15And then the second layer down would create

22:17a third layer down, and on and on and on.

22:19So probabilistically, you just throw a dart

22:21at one of those layers, we're probably

22:22in one of the simulated layers.

22:25I think if there's some sort of limitations

22:27on the information processing

22:28of whatever the physical world is,

22:31it quickly becomes the case that you have a limit

22:33to the layers that could exist there,

22:35because the resources necessary to simulate a universe

22:39like ours clearly is a lot,

22:41just in terms of the number of bits at play.

22:43And so then you can ask, well, what's more plausible?

22:46That there's an unbounded capacity of information processing

22:50in whatever the highest up level universe is,

22:53or that there's some bound to that capacity,

22:56which then limits the number of levels available.

22:58How do you place some kind of probability distribution

23:00on what the information capacity is?

23:02I have no idea.

23:03But I don't, like, people almost assume

23:06a certain uniform probability over all of those meta layers

23:10that could conceivably exist when,

23:12it's a little bit like a Pascal's wager,

23:15on like, you're not giving a low enough prior

23:17to the mere existence of that infinite set of layers.

23:20- Yeah, that's true.

23:21But it's also very difficult to contextualize the amount.

23:25So the amount of information processing power

23:28required to simulate like our universe

23:31seems like amazingly huge.

§04Transcript · 23:34–31:40

23:34- But you can always raise two to the power of that.

23:37- Yeah, exactly.

23:38- Yeah, like numbers get big.

23:40- And we're easily humbled

23:41by basically everything around us.

23:43So it's very difficult to kind of make sense of anything,

23:48actually, when you look up at the sky

23:51and look at the stars and the immensity of it all,

23:53to make sense of the smallness of us,

23:57the unlikeliness of everything that's on this earth

24:00coming to be.

24:02Then you could basically, anything could be,

24:05all laws of probability go out the window to me.

24:09Because I guess, because the amount of information

24:14under which we're operating is very low.

24:17We basically know nothing about the world around us,

24:22relatively speaking.

24:23And so when I think about the simulation hypothesis,

24:26I think it's just fun to think about it.

24:29But it's also, I think there is a thought experiment

24:31kind of interesting to think of the power of computation,

24:35where there are the limits of a Turing machine.

24:38Sort of the limits of our current computers.

24:41When you start to think about artificial intelligence,

24:44how far can we get with computers?

24:45And that's kind of where the simulation hypothesis

24:50is useful to me as a thought experiment,

24:52is the universe just a computer?

24:55Is it just a computation?

24:58Is all of this just a computation?

25:00And sort of the same kind of tools

25:01we apply to analyzing algorithms, can that be applied?

25:04You know, if we scale further and further and further,

25:07will the arbitrary power of those systems

25:09start to create some interesting aspects

25:12that we see in our universe?

25:13Or is something fundamentally different

25:15needs to be created?

25:17- Well, it's interesting that in our universe,

25:20it's not arbitrarily large, the power,

25:22that you can place limits on, for example,

25:24how many bits of information can be stored per unit area.

25:27Right, like all of the physical laws,

25:30you've got general relativity and quantum coming together,

25:32to give you a certain limit on how many bits you can store

25:36within a given range before it collapses into a black hole.

25:40Like the idea that there even exists such a limit

25:42is at the very least thought provoking,

25:44when naively you might assume,

25:46oh, well, you know,

25:47technology could always get better and better,

25:49we could get cleverer and cleverer,

25:50and you could just cram as much information as you want

25:54into like a small unit of space.

25:56That makes me think it's at least plausible

26:02that whatever the highest level of existence is,

26:07doesn't admit too many simulations,

26:10or ones that are at the scale of complexity

26:12that we're looking at.

26:13Obviously, it's just as conceivable that they do,

26:15and that there are many,

26:16but I guess what I'm channeling is the surprise

26:20that I felt upon learning that fact,

26:22that there are, that information is physical in this way.

26:25- It's that there's a finiteness to it.

26:27Okay, let me just even go off on that,

26:29from a mathematics perspective,

26:31and a psychology perspective.

26:33How do you mix,

26:35are you psychologically comfortable

26:38with the concept of infinity?

26:39- I think so. - Are you okay with it?

26:42- I'm pretty okay, yeah.

26:43Are you okay?

26:44- No, not really, it doesn't make any sense to me.

26:47- I don't know, like how many words,

26:50how many possible words do you think could exist,

26:52that are just like strings of letters?

26:55- So that's a sort of mathematical statement

26:58that's beautiful,

26:59and we use infinity in basically everything we do,

27:02everything we do in science, math, and engineering, yes.

27:06But you said exist.

27:09The question is, you said letters or words?

27:13- I said words. - Words.

27:14To bring words into existence, to me,

27:18you have to start saying them,

27:19or writing them, or listing them.

27:22- That's an instantiation.

27:23Okay, how many abstract words exist?

27:25- Well, the idea of abstract.

27:28The idea of abstract notions and ideas.

27:31- I think we should be clear on terminology.

27:33I mean, you think about intelligence a lot,

27:35like artificial intelligence.

27:36Would you not say that what it's doing

27:39is a kind of abstraction?

27:40That like abstraction is key to conceptualizing the universe?

27:45You get this raw sensory data.

27:47I need something that every time

27:48you move your face a little bit,

27:50and they're not pixels, but like analog of pixels

27:52on my retina change entirely,

27:55that I can still have some coherent notion of,

27:57this is Lex, I'm talking to Lex, right?

27:59What that requires is you have a disparate set

28:01of possible images hitting me

28:03that are unified in a notion of Lex, right?

28:07That's a kind of abstraction.

28:08It's a thing that could apply

28:09to a lot of different images that I see,

28:12and it represents it in a much more compressed way,

28:15and one that's like much more resilient to that.

28:17I think in the same way,

28:18if I'm talking about infinity as an abstraction,

28:21I don't mean non-physical, woo-woo,

28:23like ineffable or something.

28:26What I mean is it's something that can apply

28:28to a multiplicity of situations

28:30that share a certain common attribute,

28:31in the same way that the images

28:32of like your face on my retina

28:34share enough common attributes

28:35that I can put this single notion to it.

28:37Like in that way, infinity is an abstraction,

28:40and it's very powerful,

28:41and it's only through such abstractions

28:44that we can actually understand

28:45like the world and logic and things.

28:47And in the case of infinity, the way I think about it,

28:49the key entity is the property

28:51of always being able to add one more.

28:54Like no matter how many words you can list,

28:56you just throw an A at the end of one,

28:57and you have another conceivable word.

28:59You don't have to think of all the words at once.

29:01It's that property, the oh, I could always add one more,

29:04that gives it this nature of infiniteness,

29:08in the same way that there's certain

29:09like properties of your face

29:10that give it the lexness, right?

29:12So like infinity should be no more worrying

29:16than the I can always add one more sentiment.

29:19- That's a really elegant,

29:21much more elegant way than I could put it,

29:23so thank you for doing that

29:24as yet another abstraction.

29:26And yes, indeed, that's what our brain does,

29:29that's what intelligent systems do,

29:30that's what programming does,

29:31that's what science does,

29:32is build abstraction on top of each other.

29:35And yet, there is at a certain point,

29:38abstractions that go into the quote, woo, right?

29:42(both laughing)

29:44Sort of, and because we're now,

29:47it's like we built this stack of,

29:51you know, the only thing that's true

29:53is the stuff that's on the ground,

29:54everything else is useful for interpreting this.

29:57And at a certain point,

29:58you might start floating into ideas

30:01that are surreal and difficult,

30:04and take us into areas that are disconnected

30:08from reality in a way that we could never get back.

30:11- What if instead of calling these abstract,

30:13how different would it be in your mind

30:14if we called them general?

30:15And the phenomenon that you're describing

30:17is overgeneralization.

30:19When you try to-- - Generalization, yeah.

30:20- Have a concept or an idea that's so general

30:23as to apply to nothing in particular in a useful way.

30:25Does that map to what you're thinking of

30:28when you think of-- - First of all,

30:29I'm playing a little just for the fun of it.

30:31- Yeah, I know. - I'm the devil's advocate.

30:32And I think our cognition, our mind,

30:36is unable to visualize.

30:39So you do some incredible work with visualization and video.

30:42I think infinity is very difficult to visualize

30:46for our mind.

30:48We can delude ourselves into thinking we can visualize it.

30:52But we can't.

30:54I don't, I mean, I would venture to say it's very difficult.

30:57And so there's some concepts in mathematics,

31:00like maybe multiple dimensions, we could sort of talk about,

31:03that are impossible for us to truly intuit.

31:06And it just feels dangerous to me to use these

31:13as part of our toolbox of abstractions.

31:15- On behalf of your listeners,

31:17I almost fear we're getting too philosophical.

31:19- No, heck no, heck no.

31:22I think to that point, for any particular idea like this,

31:26there's multiple angles of attack.

31:28I think when we do visualize infinity,

31:32what we're actually doing, you write dot, dot, dot.

31:34One, two, three, four, dot, dot, dot.

31:37Those are symbols on the page that are insinuating

31:40a certain infinity.

§05Transcript · 31:41–39:28

31:41What you're capturing with a little bit of design there

31:46is the I can always add one more property.

31:49I think I'm just as uncomfortable with you are

31:52if you try to concretize it so much

31:56that you have a bag of infinitely many things

31:59that I actually think of, no, not one, two, three, four,

32:00dot, dot, dot, one, two, three, four, five, six, seven,

32:03eight, I try to get them all in my head.

32:05And you realize, oh, your brain would literally collapse

32:08into a black hole, all of that.

32:10And I honestly feel this with a lot of math

32:12that I try to read, where I don't think of myself

32:15as like particularly good at math.

32:19In some ways, I get very confused often

32:21when I am going through some of these texts.

32:23And often what I'm feeling in my head is like,

32:25this is just so damn abstract.

32:27I just can't wrap my head around it.

32:29I just want to put something concrete to it

32:31that makes me understand.

32:32And I think a lot of the motivation for the channel

32:35is channeling that sentiment of, yeah,

32:38a lot of the things that you're trying to read out there,

32:40it's just so hard to connect to anything

32:43that you spend an hour banging your head

32:45against a couple of pages and you come out

32:47not really knowing anything more

32:49other than some definitions maybe

32:51and a certain sense of self-defeat.

32:54One of the reasons I focus so much on visualizations

32:58is that I'm a big believer in,

33:01I'm sorry, I'm just really hampering on

33:03this idea of abstraction,

33:04being clear about your layers of abstraction.

33:07It's always tempting to start an explanation

33:09from the top to the bottom.

33:11You give the definition of a new theorem.

33:14You're like, this is the definition of a vector space,

33:16for example, that's how we'll start a course.

33:18These are the properties of a vector space.

33:20First from these properties,

33:22we will derive what we need in order to do the math

33:24of linear algebra or whatever it might be.

33:27I don't think that's how understanding works at all.

33:29I think how understanding works

33:30is you start at the lowest level you can get at

33:33where rather than thinking about a vector space,

33:35you might think of concrete vectors

33:37that are just lists of numbers

33:38or picturing it as like an arrow that you draw,

33:41which is itself like even less abstract than numbers

33:45'cause you're looking at quantities,

33:46like the distance of the X coordinate,

33:48the distance of the Y coordinate.

33:49It's as concrete as you could possibly get.

33:51And it has to be if you're putting it in a visual.

33:53- It's an actual arrow.

33:56- It's an actual vector.

33:57You're not talking about like a quote unquote vector

34:00that could apply to any possible thing.

34:02You have to choose one if you're illustrating it.

34:04And I think this is the power of being in a medium

34:06like video, or if you're writing a textbook

34:09and you force yourself to put a lot of images,

34:11is with every image, you're making a choice.

34:14With each choice, you're showing a concrete example.

34:17With each concrete example,

34:18you're aiding someone's path to understanding.

34:20- Yeah, I'm sorry to interrupt you,

34:22but you just made me realize that that's exactly right.

34:25So the visualizations you're creating

34:27while you're sometimes talking about abstractions,

34:30the actual visualization is an explicit low-level example.

34:35- Yes.

34:36- So there's an actual, like in the code,

34:38you have to say what the vector is.

34:41What's the direction of the arrow?

34:43What's the magnitude?

34:44The, yeah, so that's, you're going,

34:47the visualization itself is actually going to the bottom.

34:51- And I think that's very important.

34:52I also think about this a lot in writing scripts,

34:54where even before you get to the visuals,

34:57the first instinct is to, I don't know why,

35:00I just always do, I say the abstract thing,

35:02I say the general definition, the powerful thing,

35:05and then I fill it in with examples later.

35:07Always, it will be more compelling and easier to understand

35:09when you flip that.

35:10And instead, you let someone's brain

35:13do the pattern recognition.

35:16You just show them a bunch of examples.

35:18The brain is going to feel a certain similarity between them.

35:21Then by the time you bring in the definition,

35:23or by the time you bring in the formula,

35:25it's articulating a thing that's already in the brain

35:28that was built off of looking at a bunch of examples

35:30with a certain kind of similarity.

35:32And what the formula does is articulate

35:34what that kind of similarity is,

35:36rather than being a high cognitive load set of symbols

35:41that needs to be populated with examples later on,

35:45assuming someone's still with you.

35:46- What is the most beautiful or awe-inspiring idea

35:51you've come across in mathematics?

35:53- I don't know, man.

35:55- Maybe it's an idea you've explored in your videos,

35:57maybe not.

35:58What just gave you pause?

36:01- What's the most beautiful idea?

36:03- Small or big.

36:04- So I think often the things that are most beautiful

36:07are the ones that you have a little bit of understanding of,

36:11but certainly not an entire understanding.

36:14It's a little bit of that mystery

36:15that is what makes it beautiful.

36:17- What was the moment of the discovery for you personally,

36:20almost just that leap of aha moment?

36:23- So something that really caught my eye,

36:25I remember when I was little, there were these,

36:27I think the series was called wooden books or something,

36:31these tiny little books that would have

36:33just a very short description of something on the left

36:35and then a picture on the right.

36:36I don't know who they're meant for,

36:37but maybe it's like loosely children or something like that,

36:40but it can't just be children

36:41'cause of some of the things it was describing.

36:43On the last page of one of them,

36:45somewhere tiny in there was this little formula

36:47that on the left hand had a sum

36:49over all of the natural numbers.

36:51You know, it's like one over one to the S

36:53plus one over two to the S plus one over three to the S

36:56on and on to infinity.

36:57Then on the other side had a product over all of the primes.

37:01And it was a certain thing, had to do with all the primes.

37:03And like any good young math enthusiast,

37:06I had properly been indoctrinated

37:07with how chaotic and confusing the primes are,

37:09which they are.

37:10And seeing this equation where on one side

37:14you have something that's as understandable

37:15as you could possibly get, the counting numbers.

37:18And on the other side is all the prime numbers.

37:20It was like this, whoa, they're related like this?

37:23There's a simple description that includes

37:26all the primes getting wrapped together like this.

37:28This is like the Euler product for the zeta function.

37:32As I like later found out, the equation itself

37:34essentially encodes the fundamental theorem of arithmetic

37:37that every number can be expressed

37:39as a unique set of primes.

37:42To me still, there's, I mean, I certainly don't understand

37:44this equation or this function all that well.

37:47The more I learn about it, the prettier it is.

37:50The idea that you can, this is sort of what gets you

37:53representations of primes, not in terms of primes themselves

37:57but in terms of another set of numbers

37:59that are like the non-trivial zeros of the zeta function.

38:01And again, I'm very kind of in over my head

38:04in a lot of ways as I like try to get to understand it.

38:06But the more I do, it always leaves enough mystery

38:09that it remains very beautiful to me.

38:11- So whenever there's a little bit of mystery

38:13just outside of the understanding that,

38:16and by the way, the process of learning more about it,

38:19how does that come about?

38:20Just your own thought or are you reading?

38:23- Reading, yeah.

38:24- Or is the process of visualization itself

38:26revealing more to you?

38:28- Visuals help.

38:28I mean, in one time when I was just trying to understand

38:31like analytic continuation and playing around

38:33with visualizing complex functions,

38:36this is what led to a video about this function.

38:39It's titled something like

38:40Visualizing the Riemann Zeta Function.

38:42It's one that came about because I was programming

38:45and tried to see what a certain thing looked like.

38:47And then I looked at it and I'm like,

38:48"Whoa, that's elucidating."

38:50And then I decided to make a video about it.

38:53But I mean, you try to get your hands

38:56on as much reading as you can.

38:58You, in this case, I think if anyone wants

39:01to start to understand it,

39:03if they have like a math background of some,

39:06like they studied some in college or something like that,

39:08like the Princeton Companion to Math

39:10has a really good article on analytic number theory.

39:13And that itself has a whole bunch of references

39:15and anything has more references

39:17and it gives you this like tree to start pawing through.

39:20And like, you try to understand,

39:22I try to understand things visually as I go.

39:24That's not always possible,

39:26but it's very helpful when it does.

39:28You recognize when there's common themes,

§06Transcript · 39:30–46:56

39:30like in this case, cousins of the Fourier transform

39:34that come into play and you realize,

39:35oh, it's probably pretty important

39:36to have deep intuitions of the Fourier transform,

39:39even if it's not explicitly mentioned in like these texts.

39:42And you try to get a sense of what the common players are.

39:45But I'll emphasize again, like I feel very in over my head

39:48when I try to understand the exact relation

39:52between like the zeros of the Riemann zeta function

39:54and how they relate to the distribution of primes.

39:56I definitely understand it better than I did a year ago.

39:59I definitely understand it 1/100 as well as the experts

40:02on the matter do, I assume.

40:04But the slow path towards getting there is,

40:08it's fun, it's charming.

40:09And like to your question, very beautiful.

40:12- And the beauty is in the, what,

40:14in the journey versus the destination?

40:17- Well, it's that each thing doesn't feel arbitrary.

40:19I think that's a big part,

40:20is that you have these unpredictable,

40:23not, yeah, these very unpredictable patterns

40:25or these intricate properties of like a certain function.

40:30But at the same time, it doesn't feel like humans

40:32ever made an arbitrary choice

40:33in studying this particular thing.

40:35So, it feels like you're speaking to patterns themselves

40:39or nature itself.

40:41That's a big part of it.

40:43I think things that are too arbitrary,

40:45it's just hard for those to feel beautiful

40:46because this is sort of what the word contrived

40:49is meant to apply to, right?

40:51- And when they're not arbitrary,

40:55it means it could be, you can have a clean abstraction

41:00and intuition that allows you to comprehend it.

41:04- Well, to one of your first questions,

41:06it makes you feel like if you came across

41:07another intelligent civilization,

41:09that they'd be studying the same thing.

41:12- Maybe with different notation.

41:13- Certainly, yeah.

41:14But yeah.

41:15Like, that's what I think,

41:16you talked to that other civilization,

41:18they're probably also studying the zeros

41:20of the Riemann zeta function.

41:21Or like some variant thereof that is like

41:25a clearly equivalent cousin or something like that.

41:28But that's probably on their docket.

41:31- Whenever somebody does a lot of something amazing,

41:35I'm gonna ask the question

41:37that you've already been asked a lot,

41:40and that you'll get more and more asked in your life.

41:43But what was your favorite video to create?

41:46- Oh, favorite to create.

41:49One of my favorites is,

41:51the title is "Who Cares About Topology?"

41:53- Do you want me to pull it up or no?

41:55- If you want, sure, yeah.

41:57It is about, well, it starts by describing

42:00an unsolved problem that's still unsolved in math

42:03called the inscribed square problem.

42:05You draw any loop, and then you ask,

42:06are there four points on that loop that make a square?

42:09Totally useless, right?

42:10This is not answering any physical questions.

42:12It's mostly interesting that we can't answer that question.

42:14And it seems like such a natural thing to ask.

42:17Now, if you weaken it a little bit and you ask,

42:21can you always find a rectangle?

42:22You choose four points on this curve.

42:24Can you find a rectangle?

42:25That's hard, but it's doable.

42:27And the path to it involves things like looking at a torus,

42:32this surface with a single hole in it, like a donut,

42:35or looking at a Mobius strip,

42:37in ways that feel so much less contrived

42:39to when I first, as like a little kid,

42:41learned about these surfaces and shapes,

42:43like a Mobius strip and a torus.

42:45Like what you learn is, oh, this Mobius strip,

42:47you take a piece of paper, put a twist, glue it together.

42:50And now you have a shape with one edge and just one side.

42:53And as a student, you should think, who cares, right?

42:58Like, how does that help me solve any problems?

43:00I thought math was about problem solving.

43:02So what I liked about the piece of math

43:05that this was describing that was in this paper

43:08by a mathematician named Vaughn

43:10was that it arises very naturally.

43:12It's clear what it represents.

43:14It's doing something.

43:15It's not just playing with construction paper.

43:17And the way that it solves the problem is really beautiful.

43:20So kind of putting all of that down

43:24and concretizing it, right?

43:25Like I was talking about how,

43:27when you have to put visuals to it,

43:29it demands that what's on screen

43:30is a very specific example of what you're describing.

43:33The construction here is very abstract in nature.

43:35You described this very abstract kind of surface

43:38in 3D space.

43:39So then when I was finding myself,

43:40in this case, I wasn't programming,

43:42I was using a grapher that's like built into OSX

43:44for the 3D stuff to draw that surface,

43:48you realize, oh man,

43:49the topology argument is very non-constructive.

43:52I have to make a lot of,

43:54you have to do a lot of extra work

43:55in order to make the surface show up.

43:57But then once you see it, it's quite pretty.

43:59And it's very satisfying to see a specific instance of it.

44:02And you also feel like, ah,

44:03I've actually added something

44:04on top of what the original paper was doing,

44:06that it shows something that's completely correct.

44:09That's a very beautiful argument,

44:10but you don't see what it looks like.

44:12And I found something satisfying

44:14in seeing what it looked like

44:16that could only ever have come about

44:17from the forcing function

44:19of getting some kind of image on the screen

44:21to describe the thing I was talking about.

44:22- So you almost weren't able to anticipate

44:24what it was gonna look like?

44:25- I had no idea.

44:26I had no idea.

44:26And it was wonderful.

44:28It was totally,

44:29it looks like a Sydney Opera House

44:30or some sort of Frank Gehry design.

44:31And it was,

44:33you knew it was gonna be something.

44:35And you can say various things about it,

44:36like, oh, it touches the curve itself.

44:39It has a boundary that's this curve on the 2D plane.

44:42It all sits above the plane.

44:43But before you actually draw it,

44:45it's very unclear what the thing will look like.

44:48And to see it, it's very,

44:49it's just pleasing, right?

44:50So that was fun to make,

44:51very fun to share.

44:53I hope that it has elucidated,

44:56for some people out there,

44:58where these constructs of topology come from,

45:00that it's not arbitrary play with construction paper.

45:03- So let's,

45:04I think this is a good sort of example

45:07to talk a little bit about your process.

45:09So you have a list of ideas.

45:12That's sort of the curse of having an active

45:17and brilliant mind,

45:18is I'm sure you have a list

45:19that's growing faster than you can utilize.

45:22- Yeah, I love the head.

45:23Absolutely.

45:24- But there's some sorting procedure,

45:26depending on mood and interest and so on.

45:29But, okay, so you pick an idea,

45:32then you have to try to write a narrative arc

45:36that's sort of, how do I elucidate,

45:38how do I make this idea beautiful and clear and explain it?

45:42And then there's a set of visualizations

45:44that will be attached to it.

45:46Sort of, you've talked about some of this before,

45:48but sort of writing the story,

45:50attaching the visualizations.

45:52Can you talk through interesting, painful,

45:56beautiful parts of that process?

45:58- Well, the most painful is

46:00if you've chosen a topic that you do want to do,

46:03but then it's hard to think of,

46:05I guess, how to structure the script.

46:07This is sort of where I have been on one

46:10for like the last two or three months.

46:12And I think that ultimately the right resolution

46:13is just like set it aside and instead do some other things

46:17where the script comes more naturally.

46:18'Cause you sort of don't want to overwork a narrative.

46:23The more you've thought about it,

46:24the less you can empathize with the student

46:26who doesn't yet understand the thing you're trying to teach.

46:28- Who is the judger in your head?

46:31Sort of the person, the creature,

46:35the essence that's saying this sucks or this is good.

46:38And you mentioned kind of the student

46:40you're thinking about.

46:42Can you, who is that?

46:44What is that thing?

46:45That's Chris, that says, the perfectionist

46:48that says this thing sucks,

46:49you need to work on that for another two, three months.

46:53- I don't know.

46:54I think it's my past self.

46:56I think that's the entity

§07Transcript · 46:57–54:34

46:57that I'm most trying to empathize with.

46:59Is like you take who I was,

47:00because that's kind of the only person I know.

47:02Like you don't really know anyone

47:03other than versions of yourself.

47:05So I start with the version of myself that I know

47:07who doesn't yet understand the thing, right?

47:10And then I just try to view it with fresh eyes,

47:15a particular visual or a particular script.

47:17Like, is this motivating?

47:18Does this make sense?

47:20Which has its downsides.

47:21'Cause sometimes I find myself speaking to motivations

47:25that only myself would be interested in.

47:28I don't know, like I did this project on quaternions.

47:30Where what I really wanted was to understand

47:33what are they doing in four dimensions?

47:34Can we see what they're doing in four dimensions, right?

47:37And I came up with a way of thinking about it

47:40that really answered the question in my head.

47:42That made me very satisfied

47:43in being able to think about concretely with a 3D visual,

47:46what are they doing to a 4D sphere?

47:48And so I'm like, great,

47:49this is exactly what my past self would have wanted, right?

47:51And I make a thing on it.

47:52And I'm sure it's what some other people wanted too.

47:55But in hindsight,

47:56I think most people who want to learn about quaternions

47:58are like robotics engineers or graphics programmers

48:01who want to understand how they're used

48:04to describe 3D rotations.

48:06And like their use case was actually a little bit different

48:08than my past self.

48:09And in that way, like,

48:10I wouldn't actually recommend that video

48:12to people who are coming at it from that angle

48:14of wanting to know, hey, I'm a robotics programmer.

48:17Like how do these quaternion things work

48:20to describe position in 3D space?

48:22I would say other great resources for that.

48:25If you ever find yourself wanting to say like,

48:27but hang on, in what sense are they acting in four dimensions

48:30then come back.

48:31But until then, that's a little different.

48:34- Yeah, it's interesting

48:35'cause you have incredible videos on neural networks,

48:38for example.

48:39And from my sort of perspective,

48:41'cause I've probably, I mean,

48:43I looked at the,

48:44it's sort of my field

48:46and I've also looked at the basic introduction

48:49of neural networks like a million times

48:51from different perspectives.

48:52And it made me realize

48:53that there's a lot of ways to present it.

48:55So you are sort of, you did an incredible job.

48:58I mean, sort of the,

49:00but you could also do it differently and also incredible.

49:04Like to create a beautiful presentation of a basic concept

49:09is, requires sort of creativity, requires genius and so on,

49:16but you can take it from a bunch of different perspectives.

49:18And that video on neural networks made me realize that.

49:21And just as you're saying,

49:22you're kind of have a certain mindset, a certain view,

49:26but from a, if you take a different view

49:28from a physics perspective,

49:30from a neuroscience perspective,

49:33talking about neural networks,

49:34or from a robotics perspective,

49:38or from, let's see,

49:40from a pure learning theory, - Statistics.

49:42- statistics perspective.

49:43So you can create totally different videos.

49:46And you've done that with a few actually concepts

49:48where you've have taken different cuts,

49:49like at the, at the, at the Euler equation, right?

49:54The, you've taken different views of that.

49:56- I think I've made three videos on it

49:58and I definitely will make at least one more.

50:00- Never enough.

50:03- Never enough.

50:04- So you don't think it's the most beautiful equation

50:06in mathematics?

50:07- Like I said, as we represent it,

50:10it's one of the most hideous.

50:11It involves a lot of the most hideous aspects

50:13of our notation.

50:14I talked about E, the fact that we use pi instead of tau,

50:16the fact that we call imaginary numbers imaginary,

50:20and then, hence,

50:22actually wonder if we use the I because of imaginary.

50:24I don't know if that's historically accurate,

50:26but at least a lot of people,

50:27they read the I and they think imaginary.

50:30Like all three of those facts,

50:31it's like, those are things that have added more confusion

50:33than they needed to,

50:34and we're wrapping them up in one equation.

50:35Like, boy, that's just very hideous, right?

50:39The ideas that it does tie together

50:40when you wash away the notation,

50:42like it's okay, it's pretty, it's nice,

50:44but it's not like, mind-blowing,

50:47greatest thing in the universe,

50:49which is maybe what I was thinking of when I said,

50:51like once you understand something,

50:53it doesn't have the same beauty.

50:55Like I feel like I understand Euler's formula,

50:58and I feel like I understand it enough to sort of see

51:02the version that just woke up,

51:04that hasn't really gotten itself dressed in the morning,

51:07that's a little bit groggy,

51:08and there's bags under its eyes.

51:10It's like it's the real-- - So you're past

51:11the dating stage, and you're now married.

51:13- I'm no longer dating, right?

51:15I'm still dating the zeta function,

51:16and like she's beautiful, and right,

51:18and like we have fun, and it's that high dopamine part,

51:22but like maybe at some point we'll settle

51:24into the more mundane nature of the relationship

51:26where I like see her for who she truly is,

51:28and she'll still be beautiful in her own way,

51:30but it won't have the same romantic pizzazz, right?

51:33- Well, that's the nice thing about mathematics.

51:35I think as long as you don't live forever,

51:38there'll always be enough mystery and fun

51:41with some of the equations.

51:42Even if you do, the rate at which questions comes up

51:45is much faster than the rate at which answers come up.

51:48- If you could live forever, would you?

51:50- I think so, yeah.

51:52- So you don't think mortality's the thing

51:54that makes life meaningful?

51:55- Would your life be four times as meaningful

51:58if you died at 25?

52:00- So this goes to infinity.

52:02I think you and I, that's really interesting.

52:04So what I said is infinite, not four times longer.

52:09I said infinite.

52:10So the actual existence of the finiteness,

52:15the existence of the end, no matter the length,

52:18is the thing that may sort of,

52:20from my comprehension of psychology,

52:22it's such a deeply human,

52:25it's such a fundamental part of the human condition,

52:28the fact that there is, that we're mortal,

52:31that the fact that things end,

52:34it seems to be a crucial part of what gives them meaning.

52:37- I don't think, at least for me,

52:39like it's a very small percentage of my time

52:43that mortality is salient,

52:45that I'm like aware of the end of my life.

52:47- What do you mean by me?

52:48I'm trolling.

52:51Is it the ego, is it the id, or is it the super ego?

52:54- The reflective self, the Wernicke's area

52:58that puts all this stuff into words.

52:59- Yeah, a small percentage of your mind

53:02that is actually aware of the true motivations

53:05that drive you.

53:06- But my point is that most of my life,

53:08I'm not thinking about death.

53:09But I still feel very motivated to make things

53:12and to interact with people,

53:13like experience love or things like that.

53:15I'm very motivated.

53:16And it's strange that that motivation comes

53:19while death is not in my mind at all.

53:21And this might just be because I'm young enough

53:23that it's not salient.

53:24- Or it's in your subconscious,

53:25or that you constructed an illusion

53:28that allows you to escape the fact of your mortality

53:31by enjoying the moment,

53:32sort of the existential approach to life.

53:34- Could be.

53:36Gun to my head, I don't think that's it.

53:38- Yeah, another sort of way to say gun to the head

53:40is the deep psychological introspection of what drives us.

53:44I mean, that's in some ways to me,

53:46I mean, when I look at math, when I look at science,

53:49is a kind of an escape from reality

53:51in a sense that it's so beautiful.

53:54It's such a beautiful journey of discovery

53:58that it allows you to actually,

54:00it sort of allows you to achieve a kind of immortality

54:04of explore ideas and sort of connect yourself

54:09to the thing that is seemingly infinite,

54:12like the universe, right?

54:13That allows you to escape the limited nature

54:18of our little, of our bodies, of our existence.

54:23- What else would give this podcast meaning?

54:25- That's right.

54:26- If not the fact that it will end.

54:28- This place closes in 40 minutes.

54:30- And it's so much more meaningful for it.

54:34How much more I love this room because we'll be kicked out.

§08Transcript · 54:37–1:02:28

54:37- So I understand just because you're trolling me

54:42doesn't mean I'm wrong.

54:43But I take your point, I take your point.

54:49- Boy, that would be a good Twitter bio.

54:51Just because you're trolling me doesn't mean I'm wrong.

54:54- Yeah, and sort of difference in backgrounds.

54:58I'm a bit Russian, so we're a bit melancholic

55:01and seem to maybe assign a little too much value

55:04to suffering and mortality and things like that.

55:07Makes for a better novel, I think.

55:09- Oh yeah, you need some sort of existential threat

55:13to drive a plot.

55:15- So when do you know when the video is done

55:18when you're working on it?

55:19- That's pretty easy, actually,

55:21because I'll write the script.

55:24I want there to be some kind of aha moment in there,

55:27and then hopefully the script can revolve around

55:28some kind of aha moment.

55:30And then from there, you're putting visuals

55:32to each sentence that exists,

55:34and then you narrate it, you edit it all together.

55:36So given that there's a script, the end becomes quite clear.

55:39And as I animate it, I often change

55:44certainly the specific words,

55:46but sometimes the structure itself.

55:49But it's a very deterministic process at that point.

55:53It makes it much easier to predict

55:54when something will be done.

55:55How do you know when a script is done?

55:57It's like, for problem-solving videos,

55:59that's quite simple.

56:00It's once you feel like someone

56:01who didn't understand the solution now could.

56:03For things like neural networks, that was a lot harder,

56:05because like you said, there's so many angles

56:07at which you could attack it.

56:09And there, it's just at some point you feel like

56:12this asks a meaningful question,

56:15and it answers that question.

56:17- What is the best way to learn math

56:20for people who might be at the beginning of that journey?

56:22I think that's a question that a lot of folks

56:24kind of ask and think about.

56:26And it doesn't, even for folks who are not really

56:28at the beginning of their journey,

56:29like they might be actually deep in their career,

56:33some type, they've taken college,

56:35they've taken calculus and so on,

56:36but still wanna sort of explore math.

56:39What would be your advice in sort of education at all ages?

56:42- Your temptation will be to spend more time

56:45watching lectures or reading.

56:48Try to force yourself to do more problems

56:50than you naturally would.

56:52That's a big one.

56:53Like the focus time that you're spending

56:56should be on solving specific problems

56:59and seek entities that have well curated lists of problems.

57:02- So go into like a textbook almost,

57:04and the problems in the back of a text,

57:06kind of thing, back of a chapter.

57:08- So if you can, take a little look through those questions

57:10at the end of the chapter before you read the chapter.

57:12A lot of them won't make sense.

57:13Some of them might, and those are the best ones

57:15to think about.

57:16A lot of them won't, but just take a quick look

57:18and then read a little bit of the chapter

57:20and then maybe take a look again and things like that.

57:22And don't consider yourself done with the chapter

57:25until you've actually worked through a couple exercises.

57:28And this is so hypocritical, right?

57:31'Cause I like put out videos that pretty much never

57:33have associated exercises.

57:35I just view myself as a different part of the ecosystem,

57:38which means I'm kind of admitting

57:40that you're not really learning,

57:42or at least this is only a partial part

57:44of the learning process if you're watching these videos.

57:47I think if someone's at the very beginning,

57:50like I do think Khan Academy does a good job.

57:52They have a pretty large set of questions

57:54you can work through.

57:55- Just the very basics, sort of just picking up,

57:58getting comfortable with the very basic linear algebra

58:01or calculus or something, Khan Academy.

58:04- Programming is actually, I think, a great,

58:05like learn to program and let the way that math

58:08is motivated from that angle push you through.

58:11I know a lot of people who didn't like math

58:14got into programming in some way,

58:15and that's what turned them on to math.

58:17Maybe I'm biased 'cause I live in the Bay Area,

58:19so I'm more likely to run into someone

58:21who has that phenotype, but I am willing to speculate

58:25that that is a more generalizable path.

58:28- So you yourself kind of in creating the videos

58:30are using programming to illuminate a concept,

58:32but for yourself as well.

58:35So would you recommend somebody try to make a,

58:37sort of almost like try to make videos?

58:40Like you do as a way to learn?

58:41- So one thing I've heard before,

58:43I don't know if this is based on any actual study.

58:44This might be like a total fictional anecdote of numbers,

58:47but it rings in the mind as being true.

58:49You remember about 10% of what you read.

58:51You remember about 20% of what you listen to.

58:54You remember about 70% of what you actively interact with

58:57in some way, and then about 90% of what you teach.

59:00This is a thing I heard again,

59:02those numbers might be meaningless,

59:03but they ring true, don't they?

59:05Right, I'm willing to say I learned nine times better

59:07if I'm teaching something than reading.

59:09That might even be a low ball, right?

59:11So doing something to teach or to like actively try

59:14to explain things is huge for consolidating the knowledge.

59:17- Outside of family and friends,

59:19is there a moment you can remember

59:22that you would like to relive

59:23because it made you truly happy

59:26or it was transformative in some fundamental way?

59:30- A moment that was transformative?

59:32- Or made you truly happy?

59:35- Yeah, I think there's times,

59:36like music used to be a much bigger part of my life

59:38than it is now.

59:39Like when I was a, let's say a teenager.

59:41And I can think of sometimes in like playing music,

59:45there was one, my brother and a friend of mine,

59:48so this slightly violates the family and friends,

59:50but there was a music that made me happy.

59:51They were just accompanying.

59:54We had like played a gig at a ski resort,

59:57such that you like take a gondola to the top

59:59and like did a thing.

60:00Then on the gondola ride down,

60:01we decided to just jam a little bit.

60:04And it was just like, I don't know,

60:06the gondola sort of over, came over a mountain

60:09and you saw the city lights

60:10and we're just like jamming, like playing some music.

60:13I wouldn't describe that as transformative.

60:16I don't know why, but that popped into my mind

60:18as a moment of, in a way that wasn't associated

60:21with people I love, but more with like a thing I was doing,

60:24something that was just, it was just happy.

60:26And it was just like a great moment.

60:28I don't think I can give you anything deeper

60:30than that though.

60:32- Well, as a musician myself, I'd love to see,

60:34as you mentioned before, music enter back into your work,

60:38back into your creative work.

60:40I'd love to see that.

60:41I'm certainly allowing it to enter back into mine

60:43and it's a beautiful thing for a mathematician,

60:47for a scientist to allow music to enter their work.

60:51I think only good things can happen.

60:53- All right, I'll try to promise you a music video by 2020.

60:57- By 2020? - By the end of 2020.

60:58- Okay, all right, good.

60:59- I'll give myself a longer window.

61:01- All right, maybe we can like collaborate

61:04on a band type situation.

61:05What instruments do you play?

61:07- The main instrument I play is violin,

61:08but I also love to dabble around on like guitar and piano.

61:11- Beautiful, me too, guitar and piano.

61:14So in "The Mathematician's Lament,"

61:17Paul Lockhart writes, "The first thing to understand

61:20"is that mathematics is an art.

61:22"The difference between math and the other arts,

61:24"such as music and painting,

61:26"is that our culture does not recognize it as such."

61:30So I think I speak for millions of people,

61:32myself included, in saying thank you

61:35for revealing to us the art of mathematics.

61:39So thank you for everything you do

61:40and thanks for talking today.

61:42- Wow, thanks for saying that

61:43and thanks for having me on.

61:45- Thanks for listening to this conversation

61:47with Grant Sanderson.

61:48And thank you to our presenting sponsor, Cash App.

61:51Download it, use code LEXPODCAST,

61:54you'll get $10 and $10 will go to FIRST,

61:57a STEM education nonprofit

61:59that inspires hundreds of thousands of young minds

62:01to become future leaders and innovators.

62:04If you enjoy this podcast, subscribe on YouTube,

62:07give it five stars on Apple Podcast,

62:09support it on Patreon, or connect with me on Twitter.

62:13And now, let me leave you with some words of wisdom

62:16from one of Grant's and my favorite people, Richard Feynman.

62:20"Nobody ever figures out what this life is all about,

62:24"and it doesn't matter.

62:26"Explore the world.

62:28"Nearly everything is really interesting

§09Transcript · 1:02:30–1:02:39

62:30"if you go into it deeply enough."

62:33Thank you for listening and hope to see you next time.

62:36(upbeat music)

62:39(upbeat music)

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