> analyse > objets > π-6

Why is pi here? And why is it squared? A geometric answer to the Basel problem

3Blue1Brown - 2018-03-02

A most beautiful proof of the Basel problem, using light.
Home page: https://www.3blue1brown.com/
Brought to you by you: http://3b1b.co/basel-thanks
And by Brilliant: https://brilliant.org/3b1b

Brilliant's principles list that I referenced:
https://brilliant.org/principles/

Get early access and more through Patreon:
https://www.patreon.com/3blue1brown

The content here was based on a paper by Johan Wästlund
http://www.math.chalmers.se/~wastlund/Cosmic.pdf

Check out Mathologer's video on the many cousins of the Pythagorean theorem:
https://youtu.be/p-0SOWbzUYI

On the topic of Mathologer, he also has a nice video about the Basel problem:
https://youtu.be/yPl64xi_ZZA

A simple Geogebra to play around with the Inverse Pythagorean Theorem argument shown here.
https://ggbm.at/yPExUf7b

Some of you may be concerned about the final step here where we said the circle approaches a line.  What about all the lighthouses on the far end?  Well, a more careful calculation will show that the contributions from those lights become more negligible.  In fact, the contributions from almost all lights become negligible.  For the ambitious among you, see this paper for full details.

If you want to contribute translated subtitles or to help review those that have already been made by others and need approval, you can click the gear icon in the video and go to subtitles/cc, then "add subtitles/cc".  I really appreciate those who do this, as it helps make the lessons accessible to more people.

Music by Vincent Rubinetti: 
https://vincerubinetti.bandcamp.com/album/the-music-of-3blue1brown

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If you are new to this channel and want to see more, a good place to start is this playlist: http://3b1b.co/recommended

Various social media stuffs:
Website: https://www.3blue1brown.com
Twitter: https://twitter.com/3Blue1Brown
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Kexmonster - 2019-11-11

"In honor of Basel" or rather "We had to find something other to name it than 'Euler'"

Tri Kỷ - 2019-12-15

Too many Euler mathematical things 😂

Miguel! I Draw! - 2020-02-25

@Tri Kỷ Euler's little theorem ( ͡° ͜ʖ ͡°)

Ayman Jameel - 2020-03-04

Euler number = e = 2.718281828 ..........

mr.1n5an_e - 2020-03-07

Haha, thats probably what happened, that legend had his name all over mathematics😂

Ornithocowian King - 2019-02-02

Other mathematicians: QED
3Blue1Brown: Badaboom badabing

Vinay VardhanYT - 2019-10-07

@Kings Cross 😂😂😂

Ultimantis - 2019-10-21

I wonder if he got that from Beakman's World

Davi Gabriel - 2019-11-19

C.Q.D.

Adarsh Tiwari - 2019-12-12

@Kings Cross 😂😂😂

Mohammed Mesum Hussain - 2020-01-10

@Kings Cross because he was passing time watching π creatures videos on YouTube!!😂😂

Sherin Funmes - 2019-10-15

Pi is like an uninvited guest who shows up at every party where he isn't supposed to be

AdelaeR - 2019-12-28

Except ... he actually IS supposed to be there, he was simply uninvited.

James Perrin - 2019-12-29

pi is the party host.

Venom 64 - 2020-02-02

😂

Ozymandias - 2020-02-05

Don't forget e

Omkar Ghanekar - 2020-03-03

Alon Amit explains why. They are related by another function you all have seen before.
https://qr.ae/p8EQu9

Maria Cecília - 2018-12-15

"I'm so tired of studying, guess I'll just watch some funny videos on youtube"
Me 30 seconds later:

Moomin - 2019-11-10

Maria Cecília This is fun

Davi Gabriel - 2019-11-19

Yeah, this is really fun if you know enough to understand :)

Shahnawaz Ansari - 2019-12-29

Maria Cecília you’re not tired of studying. You’re just tired studying the conventional stuff the conventional way

Lzz7 - 2020-03-04

exactly definition jajajajaja

plane Dagorlad - 2019-05-05

why these subjects are so interesting only when i'm preparing midterm exam

facite non victimarum - 2019-06-12

what term is at its mid point in May? just curious.

Tech Made Easy - 2019-06-29

@facite non victimarum seems China stuff

facite non victimarum - 2019-06-30

@Tech Made Easy
Thank you.

Jacqueline Liu - 2019-07-20

Tech Made Easy
No, because
a) the Chinese Spring term goes from Feb to Jun
b) the OP's name is Korean

Justin Zhang - 2019-08-07

Lol

R S - 2019-06-17

I want to nominate 3Blue1Brown the noble peace prize for year 2020. Thanks.

Абдаллах Муслим - 2019-06-20

because of his wife having cheated on him it can not be))))

Gaster Blaster Master - 2019-08-25

It's nobel prize not noble just a correction

Neelesh Bansal - 2019-12-13

but for mathematics FIELDS MEDAL

FiXioN - 2019-12-21

Абдаллах Муслим wow im ruski look Im making cringy jokes using bad English))))))) so funny right?))))

bolec - 2019-08-08

15:11 "the number line is kind of like a limit of ever growing circles" - i've been thinking of a number line like this since forever, i thought i was insane, but it makes sense now

Ibrahim Mahmoud - 2020-02-11

DUDE SAME this video blew my mind with that statement

krakow - 2019-06-02

12:57 that circular right angle kills me to this day

Nacho López - 2019-11-28

@Divas verma I live in Europe and I see "circular" right angles all the time

Julie Křížková - 2019-12-04

Yeah i live in Europe and we use only circular right angle with dot

andriworld - 2020-01-19

Pac-Man

alonamaloh - 2020-01-26

In this particular step that angle is 90 degrees, but the analogous angle in subsequent steps it will be smaller. I think it makes more sense to keep it circular.

Isaac Deutsch - 2020-02-28

omg same

Elliott Sampson - 2019-06-21

0:40 challenge posed in 1644 first 4 digits of awnser 1.644 coincidence I think not!

tanki zoltan - 2019-06-22

Just wow.

Divyansh Maurya - 2020-02-26

Nice observation man

Macion 0123 - 2020-02-26

Next digit is 9 (for 90 years when problem was unsolved) and 34 (for 1734, year before Euler solve this problem). It can't be coincidence

Ian Rui - 2020-03-05

1.644*9* so actually yeah

Y.C. Lin - 2018-09-29

Now I understand how wizards draw a magic circle: MATH!

EpicMapper - 2020-02-27

Mathic thircle

Megablademe - 2019-04-09

I am still in high school but love watching these videos,even tough I didn’t understand 95% of what he was saying.

Rupa Prasad - 2019-11-12

I am still 1 and I don't even understand the words but still i love these

TomDance - 2019-11-29

I am at high school too at seven grade in colombia

Zartaf Raza - 2019-12-02

@Virat Kohli Galat channel pe aa gye bhai

PRATEEKsirji - 2020-02-07

I am doing my masters and still didn't understand this

D4RKPIX3L - 2020-02-23

I am 2 years old and I still goo goo ga ga

Tonio DND - 2019-01-16

0:00 "okay I'm not English so i hope it won't be so so hard to understand c:"






Rip my poor brain, i loved u

Romaji - 2019-12-26

Did the captions help?

Nithun Sridhar - 2019-01-14

"What is pi doing here?" Can be said to be the greatest question is math!

Youssef Wassef - 2019-01-04

This is beautiful man!!
I wish the whole world can see and appreciate how amazing your explanations and representations in your videos are.
You're showing the true beauty of maths

Jay M - 2018-09-13

takes one look at tumbnail
Riemann Zeta, my old nemesis, we meet again!

sini harshan - 2020-01-18

ζ(3)=?

Pavit - 2019-03-11

Wonderfull!!!!!!!
Marvelous!!!!!!!!!!
Excellent!!!!!!!!!!
Brilliant(Not The org Though)!!!!!!!
I Don't have more Adjectives So....................
Great Video.

Pi - 2019-06-23

I found some more:
Superb
Magnificent

Sharda Bishnoi - 2019-12-23

@Pi What is pi doing here?

Nani gopal Saha - 2020-02-06

@Sharda Bishnoi This needs more likes

D4RKPIX3L - 2020-02-23

@Sharda Bishnoi Sen-pi

Fenil Kamdar - 2019-09-09

After every amination
Me: Wowww!!!

Chad Muse - 2019-05-29

I've been wondering how this equation related to Geometry for more than 20 years since I first saw it in college. THANK YOU!

Jonathan Bryant - 2019-07-12

11:30 what kind of math witchcraft is this?!

Apratim Ghosh - 2018-03-21

There are already so many mathematical results named after "Euler", that if they had called this "Euler's Problem" or something, it would start getting confusing...

Tommy Cetee - 2019-07-31

Go get a reuler

Flash-Flire - 2019-10-11

Theorems mathematics have to be named after the second person who discover them, otherwise they'd all just be called "Euler's theorem".

Trystan Govender - 2019-10-20

It is said that every maths problem should be named after the 2nd person who solves since Euler probably already solved it 1st

Paweł Buczyński - 2019-11-11

Euler had too many problems

sini harshan - 2020-01-18

@Aleph Null 1. i love ur username mr. א
2. wtf why is there a wiki page on things named after euler

Redkillahh - 2019-03-23

I just submitted my final year paper on the Basel Problem, I kinda wish I'd seen this video a few weeks ago!

marwan aljohary - 2019-10-11

That was the most exciting math lesson I've ever been to.
Thank you for making math so fun.

Davi Gabriel - 2019-11-19

That's the Magic of Mathematics. A non-sense idea of LightHouses solving a weird problem like that.

Peter Klopfenstein - 2019-03-18

13:53 instantaneous cardioid!

Ani Jose - 2019-08-07

Explaining lighthouse placements 11:28
Accidentally draws a pentagram
A wild morningstar appears

Ser glian - 2019-10-04

the luc in lucifer DOES mean light..

Feng Han - 2019-08-07

Amazing, this is how math works with physics. The video, of course, fantastic!!!

Vidyanand Wagh - 2018-09-01

At the beginning you said, "You've never had the experience of your heart rate increasing in excitement, while you were imagining an infinitely large lake with lighthouses around it. Well, if you feel anything like I do about math, That is gonna change by the end of this video." And that does. I literally had goosebumps at the end!

Dave Grox - 2020-03-04

did anyone hav those "aha" (more like holy sh*t) moment when watching 3B1B videos?
Mine is at 10:00 for this one

La Tortue PGM - 2018-03-02

it's fascinating and frustrating at the same time to see how super-abstract concepts can be linked to some weird geometrical ones, like honestly wtf ?!

Tang Dexian - 2018-03-11

they are just numbers, and we human find a way to map number to 2d and 3d plane, and thus the geometry, they're not that fundamentally different.

A Dog - 2018-03-15

The most frustrating thing in it is I am not intelligent enough to figure out the concepts myself. I clearly see it just requires way higher IQ than I have. And it seems like nothing that could be learned anyhow. Either you brain sees and processes such relations between super-abstract concepts, or it doesn't. You can learn about the relations, you can even barely understand what happens here, but... I don't really believe that problem solving skill can be learned, at least not by an adult person. Well, not by me anyway.

Anton Quirgst - 2018-03-28

äähhhmm ... yeah - i mean math is ofc not restricted to eucledian space but like physics and math are still different things: like math can deliver the geometric framework wherein the physics happen... (for example how in general relativity the gravitational field would have an effect on spacetime itself and therefore change its metric continuesly (which remains a big problem still to quantifiy as far as I understand it).... (so 1 meter would at a given distance from a center of mass would not equal one meter at another distance from the same center of mass in relation to a refernce fram of meters that does not underly the effects of the gravitational field)... and so on... so yeah 1+1 would still be 2 but since thered be a dimension added to each "1" like 1meter for example at given at a certain distance from the center of mass and added another meter at a different distance from that center it would add up to two meters with a different lenght in relation to a reference frame than two meters lenght for example starting at a different distance from said center of mass... like I think thats what he ment.. (lets say physicall geometry is "weighed) by its dimensions and than in general relativtiy compared to a reference frame where spacetime is not affected by physical effects!

Sandil Adhikari - 2019-04-01

I thought that was only me who felt that way.

Arriaga Two - 2019-12-30

Not sure if Euler came to his answer using this method at all or just is for pedagogic porpouses only... It's fascinating that things that seem have not relation between them at all actually have it. Notice that there are some basic concepts involved: right angle in a circle and other more obscures: inverse Pythagorean theorem, and especially the property of those "bacons' light". The most frustrating thing must to be that there are many other hidden relationships out there but not many are able to see them.

RA - 12CJ - Central Peel SS (2522) - 2019-11-02

This is absolutely amazing. How do you even change your perspective and think of that!

GA Narayanan - 2018-12-31

Watched during 2018-2019 (10 pm to 1 am) until I understood it. Thanks for new years gift

Osmium - 2018-06-20

When you first mentioned light sources I was like "ok, where's he going with this?" Then you them along a number line and immediately realized "holy crap, that's the inverse square law!" I needed the rest of the video to get the things with triangles and pi, but I was pleased when I was able to figure out for myself where the squared part of the summation was coming from before you explained it.

Brek Martin - 2019-03-10

I ain’t never seen no lighthouse emit no light from its base before.

Shahar S - 2018-03-02

Wow! This proof is so beautiful and not that complex.
I was worried the channel will go down hill when I heard more people were going to join. But now I have no doubt in my mind that it's going to be GREAT!

Good job Ben for the awesome video!

Alpha Eta - 2018-03-03

michael einhorn sadly,I believe sum of any other higher powers is impossible for a human to compute,since the extension would need higher dimensions than 3,which we are unable to properly imagine,on our own

Awk Werp - 2018-03-03

jayasri ganesh Currently we can do some really cool maths in the 4th spacial dimension, even if its near-impossible to visualize. So while Im not sure if it will work, I wouldn't rule it out

The Last Lion Turtle - 2018-03-03

I have seen sums for up to a 6th degree p series, and only evens

http://www.math.drexel.edu/~tolya/p_series.pdf

Alpha Eta - 2018-03-03

Awk Werp nvm,it may be possible, (An relation equivalent to the inverse Pythagoras theorm may exist in higher dimensions,which enables us to distribute some quantity in the order of required sum), however ,I believe the computation would be Cumbersome (Note:Although it may be impossible to solve through this method ,we can find the power sums through other methods, so a solution exists,although it may not be enlightening)

S H - 2018-04-01

still going downhill. But underground now...

DavidGP - 2019-10-11

Mindblowing stuff, presented by the most soothing voice imaginable. Awesome

NicosoftNT - 2020-02-25

6:02 RIGHT >:(

Jan Lewandowski - 2018-09-16

This is one of the best YouTube videos I've ever seen so far and I've seen much <3 It makes you think about life, my reaction is just "wow"

coryj1990 - 2018-09-11

8:58 I wasn't buckled up.

Sophia Campana - 2018-03-16

15:11 "The number line is kind of like a limit of ever-growing circles"
MY MIND IS BLOWN

Gaurav Singh - 2019-06-19

My mind exploded so hard that my round skull became straight

Federal Bureau of Investigation - FBI - 2019-09-11

संख्या रेखा एक प्रकार की सीमा है जो कभी बढ़ते हुए वृत्तों की सीमा होती है

Dongsheng Han - 2020-01-23

Me: oh I totally understand
Brain: no u don’t

MrMylord - 2020-03-08

Hi! I am struggling to understand how you connect the amount of brightness to 1/a^2 + 1/b^2 ? It is clear that 1/a^2 + 1/b^2 equals 1/h^2 and that those angles correspond to each other when you scale down and transform the big rectangle into a smaller one. But 1) how do you prove that each of those angles covered by each of the lighthouses A and B equal to the original brightness from a lighthouse at the distance h and 2) where do you use the fact the all 3 lighthouses emit the same amount of light?

Akhil Ramidi - 2019-03-12

Why am I here? And why is this in my recommendations?




Whatever the reason, I’m glad it was
This was amazing

It's Hollow - 2018-07-27

this is awesome my dad is clapping with joy nobody can make him clap so much : ) : 3

Dellon Collins - 2018-03-03

this channel's quality is unmatched

Information Paradox - 2019-10-30

This visualisation couldn't be so beautiful without BADABOOM BADABING!

Albert Newton - 2019-04-09

Wow this has blown my mind. Seriously

Daniel Knudsen - 2018-10-29

I love that moment where it just clicks

Lochlan Smith - 2019-10-22

11:31 he almost summoned satan for a moment there.

Johan Wästlund - 2018-03-04

This is wonderful! As I said in my paper, it's based on proofs by Yaglom & Yaglom, Hofbauer, and others, and I added some of my own ideas. I thought of the light sources as stars revolving around a common center of gravity, but light-houses are arguably easier to move around! :) I hope the "light-house proof" now becomes folklore, and I'm happy to have contributed to that!

the therorist - 2019-04-08

you can have double the usual percentage off the top.....20 percent@josematias2010

the therorist - 2019-04-08

we can have our attorneys hash out the future intellectual rights and patents on software and applicability ....lol....is that easy enough for you and your fantasy youtube conversation?@josematias2010

josematias2010 - 2019-04-08

@the therorist 3 million sounds good, you did not specified the currency, I took the liberty to define it as Zimbabwe dollars, we should meet. Hope I can bring your knowledge to the crypto community, I am excited

josematias2010 - 2019-04-08

Don't go all Grigori Perelman on me!

the therorist - 2019-04-09

he didn't accept the money...........@josematias2010