Euclid's Big Problem - Numberphile

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  • Опубліковано 19 січ 2025

КОМЕНТАРІ • 1,5 тис.

  • @numberphile
    @numberphile  10 років тому +1491

    Message from Zsuzsanna (in the video)
    Hello Everyone,
    Everett Sass and Fenrakk101 (possibly others as well) posted correct
    solutions on constructing a segment of length square root 3.
    [Spoiler Alert! If you read them, you can discover that the idea behind
    both is the same: to construct a right triangle with hypotenuse 2 and one
    leg of length 1, so the other leg will be length sqrt(3).]
    This solves the puzzle of "tripling a square", that is, you can now
    construct a square of area 3. As some of you point out, this is not the
    same as doubling the cube, which comes down to constructing a segment of
    length cube root of 2, which is impossible by Euclidean means.
    Some of you mention the idea of trisecting an angle by constructing an
    isosceles triangle and trisecting the base. This does not work: if you
    look closely, the middle part will be a bigger angle than the two side
    parts. In other words, the three thin triangles are not congruent. As one
    person points out, what you'd need to do is trisect a circle arc, not the
    base of the triangle, and that is impossible by straight edge and compass.
    Of course you can trisect _some_ angles, like a right angle or a 45 degree
    angle, but there is no general procedure using straight edge and compass
    that will trisect any arbitrary angle.
    Sorry about staining that nice straight edge with the marker! I felt bad.

    • @nsfpeace3442
      @nsfpeace3442 10 років тому +13

      Hello! I was wondering if you could maybe talk a little bit about The Martingale System and The Elliot Waves Theory.
      Kindest regardings,
      Orionar Johnattan.

    • @learningsimplyvideos
      @learningsimplyvideos 10 років тому +12

      Hey guys so it's pretty difficult to get noticed on youtube but I was really hoping that you would give my channel a shot. I make educational videos in hopes that it will help students with their classes. You don't even have to subscribe if you don't want to but it would mean a lot to me if you took a look! Thanks so much in advance!

    • @WhiteKestrell
      @WhiteKestrell 10 років тому +3

      So I cannot trisect most angles with these 2 things, except for a 45 or 90 degree triangle? Has this been proven impossible to do, and what do I win if I trisect it? Also Numberphile what happened to that guy with the Richard Hammond accent?

    • @James92453
      @James92453 10 років тому +6

      Numberphile I think I'm missing something.
      You can trisect a line, but not an angle using only a compass and a straight line.
      So... Why can't you take your angle, measure points at equal distance from the intersection of the angle, then draw a line between those two points (forming an isosceles triangle).
      Now all you need to do is trisect that line as per the previous example and connect the points to the angle and bingo, one trisected angle of any size using just a straight line and a compass.
      You say this is impossible, so I'm gonna verge on the side that I'm missing something here rather than I've solved an impossible problem!

    • @xaostek
      @xaostek 10 років тому +15

      James92453 that is already addressed in the comment; the three new angles that you derive from that process will not be equal, the middle angle will be larger.
      if you use the new unit you derived from constructing and trisecting your new line and extended it to infinity, and connected all of your new points to the one point at the angle, you'll find that the angles you are constructing will start approaching 0. in other words, dividing an angle into more than 2 equal parts is impossible with this method.

  • @Lutranereis
    @Lutranereis 10 років тому +127

    I had a professor who insisted on taking a few weeks to teach us all of this, and I really didn't get why it was such a big deal until we continued on throughout the semester. Turns out, using a straight edge and compass is a great way to not only understand geometry, but to also to become aware of just how many assumptions we never knew we were making about mathematics when we are taught it.

    • @IDontKnow-dl3lq
      @IDontKnow-dl3lq 2 роки тому +2

      same but my teacher looks like walter white

    • @mlokosss
      @mlokosss Рік тому +2

      @@IDontKnow-dl3lq cookin math

  • @joseapar
    @joseapar 3 роки тому +62

    exactly 7 years later and this video still bangs. What a fantastic bit of teaching

    • @PC_Simo
      @PC_Simo 2 роки тому +2

      Sorry, I ruined your 7 likes 🫢.

  • @TreuloseTomate
    @TreuloseTomate 10 років тому +720

    Revolutionize math.
    Turn 19.
    Die in a duel.
    What a life story.

    • @Blastgun1
      @Blastgun1 5 років тому +32

      His life is pretty sad honestly.
      He was a great mind that wasn’t recognized by authorities of the time and he died very early.

    • @Blastgun1
      @Blastgun1 4 роки тому +20

      Quentin Styger History disagrees.

    • @shweatypalms4423
      @shweatypalms4423 4 роки тому +15

      @Quentin Styger Yeah they were the dominate land power in Europe for around 1000 years

    • @sillysausage4549
      @sillysausage4549 4 роки тому +17

      Revolutionise. Maths. Please stop destroying English, America.

    • @sillysausage4549
      @sillysausage4549 4 роки тому

      @@shweatypalms4423 lol

  • @kiprs
    @kiprs 10 років тому +133

    Ths one is really great. She explained points very well, she created tension in the storytelling ("before I tell you the answer" and goes onto another segment) and generally was clear and fun.

  • @GreenMachine415
    @GreenMachine415 Рік тому +8

    12:58 Brady not only cracks this classic dad joke but then actively chooses to include it in the edit. Decisions like these are key to the channel’s success

  • @TheIslandwaters
    @TheIslandwaters 10 років тому +19

    I really enjoined this video; with my limited knowledge of math, this is one of the few videos I can fully understand without a single question. She had shown many examples and clear, understood proof. I really enjoined her!

  • @secularmonk5176
    @secularmonk5176 10 років тому +114

    Euclidean geometry uses a straight edge and compass in two dimensions.
    Origami does not allow drawing of circles within the paper (within those two dimensions) ... but ...
    Folding is equivalent to the use of a compass, in a third dimension!
    And utilizing three dimensions allows third roots. Marvelous!

    • @robkim55
      @robkim55 10 років тому

      *****
      how do you 'fold' in N dimensions.

    • @secularmonk5176
      @secularmonk5176 8 років тому +6

      robkim55
      You have to use mathematics to "simulate" physical folding in higher dimensions, but that's merely *our* limitation as three-dimensional beings.
      The principle of geometric calculation by straight edge and compass is an expression of the ultimately *physical* nature of all phenomena.

    • @JonWilsonPhysics
      @JonWilsonPhysics 5 років тому +2

      Except that Einstein demonstrated to us in 1915 that we live in a non-Euclidean world.

    • @roelin360
      @roelin360 2 роки тому

      @@JonWilsonPhysics we do?

    • @roelin360
      @roelin360 2 роки тому +1

      @@ntf5211 but it's relatively flat besides the effects of gravity, as far as we are aware

  • @xmachina1
    @xmachina1 10 років тому +46

    "...and then people thought about it for 2000 years..." : my favorite line of the video.

  • @gnosomai
    @gnosomai 10 років тому +7

    Good video. I was spellbound by the simple complexity and complex simplicity underlying the ruler-and-compass-constructions. Brady's questions are always to the point and he says insightful and poetic things like "so the cube root is the point you can't reach".

  • @Jarretman
    @Jarretman 10 років тому +272

    Her voice is absolutely mesmerizing.

    • @UmlautBanana
      @UmlautBanana 7 років тому +30

      More like mASMRizing

    • @DeathBringer769
      @DeathBringer769 6 років тому +6

      Lots of vocal fry going on (not an insult, just an observation.)

    • @PrinceEWS
      @PrinceEWS 6 років тому +6

      kom-pahhhs

    • @c.darwin9259
      @c.darwin9259 5 років тому +15

      It’s sexy.

    • @spaceman4935
      @spaceman4935 5 років тому +16

      Vodkacannon that is the stupidest thing I’ve ever heard

  • @amielmatt
    @amielmatt 4 роки тому +14

    There is something so beautiful about these simple geometric ideas. Love this content!

  • @fearofdark77
    @fearofdark77 9 років тому +203

    I always had his question.
    Lets say you are the first to prove something in math. What do you do after? Do you contact someone? :/

    • @EGarrett01
      @EGarrett01 9 років тому +90

      Tap Studios
      Check it. Check it. Check it, and then check it. And if you truly find that it's right, put it on the Arxiv.

    • @liltunwin
      @liltunwin 9 років тому +126

      +Tap Studios Put it on Reddit. Duh.

    • @shivshankarpe
      @shivshankarpe 9 років тому +40

      lol. you try to publish before anyone else.

    • @chessengineer837
      @chessengineer837 8 років тому +23

      +TAP. Studios lol, the obvious one is don't email that to professors, since tons of cranks do that often, it's vexing.

    • @v3le
      @v3le 7 років тому +4

      show it to you high school teacher

  • @joeldick6871
    @joeldick6871 2 роки тому +3

    When lines and circles come together and intersects, points are born.

  • @12345DJay
    @12345DJay 9 років тому +46

    it sounds like galois was a legend. revolutionising a fundamental part of mathematics before he turned 19 and then fighting a duel. i feel so useless right now

    • @karldavis7392
      @karldavis7392 9 років тому +2

      +12345DJay I can't believe he joined that duel. I don't know how the same person can be such a genius and such an idiot. Well, I know, but I just can't believe it.

    • @hillwalker8741
      @hillwalker8741 9 років тому +4

      +12345DJay We have got to re-establish dueling to solve this cubed root business

    • @johnvonhorn2942
      @johnvonhorn2942 9 років тому

      +Trail Guy Challenge extended, challenge accepted.

    • @daxiomus
      @daxiomus 7 років тому

      yes, a major branch of algebra is named after him. (maybe because they couldn't come up with a better name. for example we don't call set theory "cantor theory" :D )

  • @jmasterX
    @jmasterX 10 років тому +144

    This video was awesome!

  • @electricdreamer
    @electricdreamer 8 років тому +205

    Everything Euclid couldn't. People thought about it for 2000 years.

    • @readingRoom100
      @readingRoom100 4 роки тому +1

      No one thought about it for 2000 years

    • @nihilisticalbino
      @nihilisticalbino 4 роки тому +5

      @@readingRoom100 I thought about it for 1000 years owned

    • @m_uz1244
      @m_uz1244 3 роки тому

      Yeah I watched the video too

    • @andrewhooper7603
      @andrewhooper7603 3 роки тому +2

      @@readingRoom100 Imagine it's 536 and some dork is like "can you trisect an angle?" and you're like, "sir, I'm a farmer and the harvest has failed."

    • @leif1075
      @leif1075 3 роки тому

      What do you mean wjat couldn't Euclid do??

  • @daledude66
    @daledude66 10 років тому +786

    Trisection of angles? It is certainly possible. I have discovered a truly marvelous proof of this, which this comment box allows too few characters to contain.

    • @PaperGlazed
      @PaperGlazed 10 років тому +67

      Fermat..?

    • @AifosViruset
      @AifosViruset 10 років тому +161

      Fermat was either a genius or a troll... I'd like to think he was both.

    • @stalfithrildi
      @stalfithrildi 9 років тому +47

      Validifyed is that Thermat's Last Feorem?

    • @Userkuko123
      @Userkuko123 9 років тому +2

      Validifyed ujuik

    • @Blox117
      @Blox117 9 років тому +17

      Dale S actually google changed the comment box, so I think you can post it :)

  • @bluefandango
    @bluefandango 3 роки тому +5

    what an interesting subject and such a soft spoken guest.
    thank you for this vid.

  • @SendyTheEndless
    @SendyTheEndless 8 років тому +325

    I can unisect an angle.

  • @mouradfrh368
    @mouradfrh368 7 років тому +10

    well! that smile trisected my heart

    • @official-obama
      @official-obama 3 роки тому

      Huh? Show me a sharp angle of your heart.

  • @shannonmann7536
    @shannonmann7536 5 років тому +1

    Trisecting any angle is actually possible. Based on work I did 30 years ago, and a snippet I got from this video, I finally figured a way. I plan on completing the proof and submitting it for publication in the new year. Happy Holidays..

    • @MikeRosoftJH
      @MikeRosoftJH 5 років тому

      Trisecting an angle has been proven to be impossible with a straightedge and a compass. The precise rules are: start with a unit line segment (points [0,1] and [0,0]). Then as a step, add a circle centered on one of the existing points and going through another, or add a line going through two existing points, and then add points where the new line/circle intersects the existing lines and circles. A length is constructible, if it can be obtained by taking finitely many steps of this kind. (Before you ask: allowing an additional operation: taking a distance between two points and making a circle of that radius centered on a third point does not make the construction any stronger - any point which can be constructed with a "non-collapsing" compass can also be constructed with a "collapsing" compass.)
      It has been proven that constructible lengths are precisely such numbers which can be expressed as a formula with integer coefficients using addition, multiplication, division, subtraction, and square roots. Trisecting an arbitrary angle requires taking a cube root, which can't be done with a straightedge and a compass. It can be done using other tools, like origami, or by making marks on the straightedge (this can be formalized as a "neusis" construction).

  • @guilemaigre14
    @guilemaigre14 10 років тому +11

    This video is odly calming and relaxing, probably from the way and rate she speaks with. And most of all, it was intresting.

  • @Schenkel101
    @Schenkel101 8 років тому +98

    You can say Pierre got to the... root of the problem.

    • @djimms5644
      @djimms5644 7 років тому +10

      Prophet
      i recommend you tri a different angle

    • @VideoNOLA
      @VideoNOLA 7 років тому +3

      A radical assertion, indeed!

    • @legionxiii8055
      @legionxiii8055 6 років тому +5

      This whole thing is irrational.

    • @elr1833
      @elr1833 6 років тому +3

      It's funny in Portuguese "Pierre" is pronounced exactly as "πR", and you can really "square πR"

    • @ezekielbrockmann114
      @ezekielbrockmann114 6 років тому

      Is This a joke about Gregor Mendel?

  • @Roxas99Yami
    @Roxas99Yami 9 років тому +436

    He died at 19 in a duel LOL ... manliest mathematician ever

    • @2CSST2
      @2CSST2 8 років тому +103

      +Roxas99Yami true but he could be manlier if he'd won it...

    • @inferno7181
      @inferno7181 8 років тому +35

      +2CSST2 just participating in a duel makes you manly.

    • @Adiaf8oros
      @Adiaf8oros 8 років тому +8

      Source? Because I call bs

    • @gatoradeee
      @gatoradeee 8 років тому +56

      Roxas99Yami Confusing Euclid with Galois?

    • @ulture
      @ulture 7 років тому +11

      Watch the video, they talk about Galois

  • @faramund9865
    @faramund9865 Рік тому +1

    It is UNBELIEVABLE we don't learn this in school where I live. THIS is the foundation.

  • @Hakusan75
    @Hakusan75 9 років тому +22

    Amazing video. And I love Zsuzsanna's accent!

  • @yanntal954
    @yanntal954 Рік тому +1

    10:41 Engineers would be like "wait what!?" because if you can bisect any angle, then you can get arbitrarily close to trisecting it by repeatedly bisecting appropriately which as every engineer knows, approximations are the exact values!

  • @necromanticer621
    @necromanticer621 10 років тому +13

    That seemed like a lot of extra steps to construct a square with length root 2.
    Once you have the perpendicular lines, all you need to do is draw a circle with radius 1 around the intersection of the perpendicular lines and those 4 points are your vertices for a square with side length root 2.
    It works because the distance between the points on the same line is going to be the diameter of the circle: 2. this is going to be the diagonal of the new square, so if you have a square with diagonal length 2, you necessarily have a square with side length root 2.

    • @VikeingBlade
      @VikeingBlade 5 років тому +1

      Or just draw a diagonal on your unit square and copy it

    • @thecarpet8831
      @thecarpet8831 4 роки тому

      Nah prolly not true

    • @professorsogol5824
      @professorsogol5824 3 роки тому

      @@VikeingBlade In the Socratic Dialogue "Meno," Socrates talks a slave boy through using this method. First they construct a unit square, they then construct three more unit square to form a larger square with area 4. Then they connect the corners of the unit squares that are at the midpoints of the larger square with area 4. We can see by inspection that the area of the inscribed square is exactly twice the area of the original unit square because the original unit square contains exactly two right isosceles triangle and the inscribed square contains four of these triangles.

  • @Muppajevel
    @Muppajevel 5 років тому +1

    I'm a completely halfwit when it comes to maths, yet i still do find these Numberphile videos so entertaining. I'm puzzled. But great to watch while recovering from knee surgery and way to much time indoor for the next couple of months.

  • @DavidRutten
    @DavidRutten 10 років тому +6

    Awesome video! Would have happily sat here and watched another 4 hours of this.

  • @Cleisthenes2
    @Cleisthenes2 2 роки тому +2

    This kind of thing is maybe why the Greek saw maths (which was for them mainly geometry) as so closely related to music and architecture.

  • @AirIUnderwater
    @AirIUnderwater 9 років тому +236

    I absolutely love her English. omg...

    • @Reydriel
      @Reydriel 9 років тому +46

      +AirIUnderwater
      It is so cute >_

    • @ZimZam131
      @ZimZam131 6 років тому

      you like mumbling?

    • @tamassimon5888
      @tamassimon5888 5 років тому +1

      Magyar akcentussal beszél, mert magyar

    • @843idfa
      @843idfa 5 років тому

      That how you get qualified into MIT.

    • @uszkaybalazs
      @uszkaybalazs 4 роки тому

      @@tamassimon5888 Hát valahogy úgy, de azért voltak akadozások

  • @ozdergekko
    @ozdergekko 9 років тому +1

    Zsuzsannas eyes shine so brightly when explaining. I had to smile through all of the video. Awsome girl!

  • @SteinGauslaaStrindhaug
    @SteinGauslaaStrindhaug 10 років тому +36

    0:25 Oh, just like in computer science where ideal Turing machines have infinite memory and time, and in Physics where we tie frictionless masses together with massless strings. Gotta love the world of the abstract! ;)

    • @NowhereManForever
      @NowhereManForever 10 років тому +9

      Infinite straightedges and compasses are only to generalize the theorems. You could easily say that they are finite in length, but then there would be nothing saying that anything you showed would still be true if someone went and grabbed a larger straightedge or compass. Basically, it could be reworded to say an arbitrarily large straightedge and compass and would still hold true.

    • @zelda12346
      @zelda12346 10 років тому +3

      "Infinite" generally has two different meanings. The one we generally know and love, actual infinity, is aleph0, which is the cardinality of N. The infinities in your examples and the videos just mean, "no matter how long a straight edge we need, we could eventually construct one." Those are potential infinities, things that have no bound to how great a distance from 0 they can get.

    • @Markus9705
      @Markus9705 10 років тому +2

      NowhereManForever Nope. In Euclidean geometry a line is per definition infinite long.

    • @NowhereManForever
      @NowhereManForever 10 років тому +2

      Menea6587 This has nothing to do with his comment or the video.

    • @zelda12346
      @zelda12346 10 років тому +2

      NowhereManForever
      "Infinite memory and time"
      "Massless string and frictionless surface"

  • @Xev729
    @Xev729 Рік тому +1

    We learned these constructions in technical drawing class without knowing where they came from.....it was quite magical

  • @sanath8483
    @sanath8483 8 років тому +30

    There is a game called euclidea with stuff just like this

  • @parlormusic1885
    @parlormusic1885 10 років тому +2

    Wow. I've always had a piecemeal understanding of the relation between algebra and geometry. You've presented that relationship completely and elegantly. Thank you!

  • @ElGringoCastellano
    @ElGringoCastellano 8 років тому +24

    I think the secret to Brady's success is the paper. Lots of mathematicians in different Numberphile videos have asked if they could have more of the "wonderful paper".
    This video brings back nostalgic memories of doing geometry in primary school, with compasses and straight edges and protractors, long before I took high school geometry and learned about postulates and theorems and etc. The Greeks were really on to something when they thought everything boiled down to geometry, that geometry was pure and everything else revolved around it. The Fundamental Theorem of Algebra video showed how algebra is connected to geometry.

  • @ricardoortiz1746
    @ricardoortiz1746 3 роки тому +1

    Drawing right now a heart only with a ruler and a compass to Zsuzsanna!

  • @brendanward2991
    @brendanward2991 8 років тому +3

    Euclid's compass was a collapsing compass. You can not use it to transfer a distance from one starting point in the plain to another. As soon as you lift the compass from the plain, it collapses! If you want to construct a 20 cm line from a given 1 cm line you must use Book I Proposition 2 of Euclid's Elements.

    • @brendanward2991
      @brendanward2991 8 років тому +1

      Plane! D'oh!

    • @vincenzomontecalvo9311
      @vincenzomontecalvo9311 8 років тому

      i dont get it...

    • @NoriMori1992
      @NoriMori1992 8 років тому

      +Brendan Ward Compass equivalence theorem.
      Also, you could always just place the compass on a line and then keep constructing half-circles down the line without lifting it from the plane. :D

  • @losthor1zon
    @losthor1zon 9 років тому +2

    I remember an old Mathematical Games article by Martin Gardner where he described a device for trisecting angles. It was something like a compass, with two more legs between the outer ones. As you expanded the outer legs to a specific angle, the two inside legs always maintained a division of 1/3 - 1/3 - 1/3 of the distance (or angle, actually) between the outer legs.

    • @ffggddss
      @ffggddss 9 років тому

      +losthor1zon
      Yes, I remember something of that - I seem to recall another kind of instrument, passive, rather than the 'active' one you're describing - that was formed with some kind of special curve as its edge. I can't recall how it was used to do the trisection.

  • @zubirhusein
    @zubirhusein 10 років тому +6

    I miss geometry class, drawing all these angles and circles and stuff was so fun

  • @molnarcsaba85
    @molnarcsaba85 10 років тому +1

    Nice to see a hungarian mathematician on Numberphile. She speaks english like everyone else here in Hungary. Funny to hear the hungarian accent your video.
    Amúgy ha olvasod ezt Zsuzsa grat hogy kijutottál Amerikába és most ott kutatsz! Pacsi!

  • @mackexr
    @mackexr 10 років тому +154

    poor ruler at 2:57 hurts to watch

    • @MBogdos96
      @MBogdos96 10 років тому +15

      I thought I was the only one that got upset about that

    • @jimmyhashat
      @jimmyhashat 10 років тому +33

      just a ruler? *just* a ruler?!?! honestly how can you say somthing so obtuse? that isnt *just* a ruler... that... no your right its just a ruler. funny note: my phone auto corrected a misspelled "ruler" as "euler" HA math jokes

    • @jdgrahamo
      @jdgrahamo 10 років тому +7

      In my day it was called a 'rule' not a ruler, which is more, er, regal. To 'rule it out' was to take your rule and draw a line through the words you didn't want. To this day, the expression 'rule it in' makes me wince.

    • @jimwidenroth8816
      @jimwidenroth8816 9 років тому

      mackexr
      Indeed..

    • @adizmal
      @adizmal 7 років тому

      Lol man some peoples OCD is off-the-charts obscure, rofl.

  • @stevefrandsen7897
    @stevefrandsen7897 10 років тому +1

    Thank you Zsuzsanna for some refresher examples.

  • @TacoSt8
    @TacoSt8 9 років тому +70

    the most thing that i like in Numberphile is that almost every matematician its from a different country

    • @NoriMori1992
      @NoriMori1992 8 років тому

      +Omar St Same!

    • @krashd
      @krashd 7 років тому +7

      Universities are like sports teams you try to get the best regardless of where they are from, and then you hope another university doesn't get their hooks in to them and entice them away.

  • @chrisdiboll2256
    @chrisdiboll2256 4 роки тому +2

    I don’t know why, but geometry has always been the ‘prettiest’ branch of maths to me. I like a formula or some interesting arithmetic, but there’s something so satisfying and aesthetic about things like this video

  • @GabrielConstantinides
    @GabrielConstantinides 10 років тому +18

    Another great video! I am loving these, is anyone else too?

    • @robkim55
      @robkim55 10 років тому

      i too am loving it

  • @greg55666
    @greg55666 10 років тому +1

    This is the best episode I've ever seen. At the very end I was even, for the first time, to begin to glimpse the relationship between Galois and these questions. What he's looking at when he's extending Fields. Good!

  • @katiekawaii
    @katiekawaii 10 років тому +20

    She is great! Super understandable. I we get to see more of her in future videos. ^_^

  • @PestOnYT
    @PestOnYT 6 років тому +2

    As for trisecting the angle... If you draw a circle with the centre at the meeting point of both lines. Then you draw a line through both points where the circle intersects with the lines of the angle. Next you trisect this line. Now you have the two points you are looking for to trisect the angle.

  • @Qbe_Root
    @Qbe_Root 10 років тому +29

    14:34 But… I didn’t mean to cause you trouble… _sobs and leaves_

  • @felynecomrade
    @felynecomrade 10 років тому +2

    What a beautiful and relaxing video. A young woman with a lovely accent reciting ancient questions and answers.

  • @NoriMori1992
    @NoriMori1992 8 років тому +5

    I was reading about classical constructions the other day, and there's something I don't understand. One of the restrictions of compass-and-straightedge constructions is that the compass is assumed to collapse when lifted from the plane, making it impossible to directly transfer lengths. But the compass equivalence theorem means that this is ultimately an immaterial restriction, since lengths can still be transferred indirectly (albeit in a complicated fashion). So what I don't get is, why does that restriction even exist if it doesn't make any practical difference?

    • @zeeanemone6482
      @zeeanemone6482 8 років тому

      Do you mean theoretical difference? It makes a practical one. It is a practical problem. You mean. .. Why not build better compasses?

    • @NoriMori1992
      @NoriMori1992 8 років тому +4

      +zee anemone No. I mean exactly what I said.

    • @johnbray8384
      @johnbray8384 6 років тому

      NoriMori, you are essentially correct. A compass should be used to construct a circle through one known point with its centre at another known point. And it does make a difference. There is a construction to trisect the angle with a
      marked straight-edge and compass. If one can directly transfer lengths off the paper with a compass, one can effectively have a marked straight-edge. (Note that a marked straight-edge is forbidden; a straight-edge joins two
      known points by an infinitely long straight line.)

  • @myuu22
    @myuu22 10 років тому +2

    This video made me nostalgic because half of the things done in this video were things that I learned how to do when getting my certificate in mechanical/architectural engineering: bisecting and abritrary angle, finding the perpendicular bisector of an arbitrary line segment, finding parallel lines, trisecting an arbitrary line segment.
    However, I never was taught that you could double an arbitrary square. And one thing that was not talked about in the video was finding the center of an arbitrary triangle.
    Boy, I used the word "arbitrary" a lot in this comment.

  • @NoriMori1992
    @NoriMori1992 8 років тому +6

    YOU DEFILED THAT STRAIGHTEDGE WITH A MARKER.
    Edit: I now see from +Numberphile's comment that Zsuzsanna apologized for this. XD

  • @cheezelz100
    @cheezelz100 10 років тому +2

    As a big fan of geometry, this is one of my favourite numberphile videos!

    • @adderiv149
      @adderiv149 9 років тому

      ***** geoetry won't get you anywhere else. nice to understand though. but makes no sense to put it in a high pedestal. maybe, for historical purposes.

    • @cheezelz100
      @cheezelz100 9 років тому +7

      Ad Deriv I don't take geometry as something I need in life, I just like it. You don't have to take something as a career choice to enjoy it.

  • @fossilfighters101
    @fossilfighters101 7 років тому +3

    This was a very relaxing video to watch.

  • @ingGS
    @ingGS 4 роки тому +2

    This was lovely 😍. I find myself exploring videos of classic Math that can be relevant today, and this is one of them.

  • @hasch5756
    @hasch5756 10 років тому +8

    1:10 Wait a second! So now we're talking about modern compasses instead of Euklidian compasses?

  • @zaclaplant3001
    @zaclaplant3001 4 роки тому

    As for trisecting an angle, I'm not sure if this is allowed, but it's mathematically valid...
    - Use the compass to draw an arc connecting the two lines.
    - Move and rotate a markable edge (straight edge, piece of paper, etc) from one end of the arc to the other, marking it's arc length as a straight line (this can be interpreted as 1 unit, if it makes you any happier).
    - Trisect the straight line that is the arc length.
    - Retrace the arc length with your trisected line, marking 3 equal arc segments.
    - Connect the vertex to the marks on the arc.
    The problem, of course, is knowing how precise the measurement and retrace of the arc length and segments are. If it were a free body as opposed to a drawing, you could just roll the arc over a straight line and measure that way.

  • @EvanTse
    @EvanTse 9 років тому +15

    Well if you were in a 4D world and had a 3D surface to mess about on cube roots should be possible right?

    • @Adam-rt2ir
      @Adam-rt2ir 8 років тому +3

      why would we need 4D if we can access 3D from 3D

    • @EvanTse
      @EvanTse 8 років тому +7

      Because it'd quite difficult to draw in 3D accurately without a computer and if you had a computer why bother using geometry to do cube roots

    • @andobando4873
      @andobando4873 6 років тому +1

      No. Even in arbitrarily many dimensions the distance norm is still in terms of squares.

    • @elr1833
      @elr1833 6 років тому

      I really would like to write on 3D paper

  • @ukguy
    @ukguy 9 років тому +1

    I was just about to say you were wrong as I had learnt how to trisect an angle using Origami, then I watched the last part and saw that you had beaten me to it lol. Interesting video thank you.

  • @jeremyj.5687
    @jeremyj.5687 10 років тому +10

    At around 3:10, shouldn´t it have said "perpEndicular"? I´m really unsure now.

    • @RochesterOliveira
      @RochesterOliveira 10 років тому +3

      Didn't she? I'm not sure what you heard there

    • @NintendoGamer2011
      @NintendoGamer2011 10 років тому +3

      You're right, it should have. Just a simple spelling mistake though, the maths is sound.

    • @MrPartylala
      @MrPartylala 10 років тому +2

      Rochester Oliveira it wasn't what you heard, it was the caption on the diagram :)

    • @account5223
      @account5223 Рік тому

      per- + _pend_ + -icular

  • @bazoo513
    @bazoo513 5 років тому

    Not that is matters much, but of all your engaging, informative, funny mathematicians, Zsuzsanna is the sweetest by far. :o)

  • @franklinjuarez100
    @franklinjuarez100 8 років тому +3

    Beautiful talk. Beautiful teacher,Thank you very much

  • @RalphDratman
    @RalphDratman 10 років тому +2

    This is great! Zsuzsanna. Dancso is a wonderful teacher.

  • @xriskava2151
    @xriskava2151 8 років тому +8

    12:13 impossible in Greek is: αδύνατον, not άδυνατον. In ancient Greek it would be: ἀδύνατον. I'm just correcting something that I saw it's s wrong. Generally I really liked this video a lot.

    • @ItzCrisonFTW
      @ItzCrisonFTW 7 років тому +1

      είναι πνεύμα ψιλή απο τα αρχαία ελληνικά και όχι τόνος του μονοτονικού συστήματος που έχουμε σήμερα οπότε δεν είναι λάθος. Το μόνο λάθος είναι οτι δεν έχει μπεί η οξεία στο υ.

    • @Rsharlan3
      @Rsharlan3 6 років тому +1

      @@ItzCrisonFTWWoohoo! I'm patting myself on the back for reading this comment just from having taught myself Κοινή in college-I never took Modern and I only had to look up λάθος (a little embarrasing since it comes straight from the aorist stem of λανθάνω via a little sliding of the meaning).

  • @nomitio3709
    @nomitio3709 5 років тому +2

    Finally someone else who writes their 1’s like that!

  • @LordSatoh
    @LordSatoh 10 років тому +3

    but....
    if it's possible to divide a line segment in 3, couldn't this be done to trisect an angle: cut the 2 lines from the angle in same length; close an isosceles triagle; divide this new segment in 3; connect the dividing points to the original corner... ?

    • @slartibartfast336
      @slartibartfast336 10 років тому +5

      The resulting angles aren't all equal... the center one will be different than the order ones.

    • @slartibartfast336
      @slartibartfast336 10 років тому +3

      "older" should be "outer"

    • @LordSatoh
      @LordSatoh 10 років тому +1

      Slarti Bartfast yeah... it's true... :/

    • @MountainBlade100
      @MountainBlade100 10 років тому

      Slarti Bartfast
      What would happen if we would divide the line infinetley , we could by knowing how much we divide know what each point is worth , so if we would to add all of the points to find out where the spots are equally different .
      I think it wouldn't be possible to infinitley pinpoint but idk ...
      (If it were i would think the angles would be equal !)
      This would mean that the inability to pinpoint it would make the angles different by just a slight .
      But then again we can pinpoint a line in it's 1/3 so i guess this theory would stand .
      Btw +LordSatoh , i thought the exactly same thing ...
      P.S. i think you meant to 4-sect the line .
      This could be a proof that you can't cut a line in 3 equal sections ...

    • @bunnysnack
      @bunnysnack 10 років тому +2

      Slarti Bartfast I thought the same thing as LordSatoh, but had my doubts that such a simple, intuitive solution could have gone so long without being figured out. Thanks for pointing out the error in our intuition :)

  • @JKrollling
    @JKrollling 10 років тому

    doing a bit of oscillation, and mid way through, had an epiphany, on how to triple the square! love this difficulty of question for the viewer to do! Feed me more problems

  • @Fenrakk101
    @Fenrakk101 10 років тому +3

    Isn't it entirely possible to make a root-3 segment from a triangle? Take your unit length, double it, use the new line as the base of an equilateral triangle. If you draw a line from an angle to a side (bisecting that side) the length of that line would be root 3.

    • @ThrowFence
      @ThrowFence 10 років тому

      That seems to make sense, I can't see why that wouldn't work, actually. That's weird, we need someone smarter to explain this.

    • @LordDragon1965
      @LordDragon1965 10 років тому +16

      (Square) Root three segments, yes. Third root segments, no.

    • @guroux
      @guroux 10 років тому

      i was thinking the same thing. it looks like it works, can't figure out a flaw in it.

    • @spaldar
      @spaldar 10 років тому +10

      Root three is completely different to a cube root.

    • @LordDragon1965
      @LordDragon1965 10 років тому +1

      Constructing a Cube with sides of the square root of 3 does not create a cube with volume of 2. The sides of that cube have an area of 3 so the volume of the cube is about 5.2. The cube root of 2 which would be the side length for a cube with volume 2 is about 1.26.

  • @ricochet188
    @ricochet188 7 років тому

    I don't know what it is, but this woman's eyes and demeanour make me melt

  • @theskoomacat7849
    @theskoomacat7849 10 років тому +7

    Yeeey a fellow Hungarian :D She has the same family name as one of the most famous comdeian in Hungary :D

  • @calciferfelix
    @calciferfelix 10 років тому +1

    Sorry that my comment is irrelevant but her voice so calming and has one of the best accents I've ever heard. I think I'm gonna go to sleep listening her.

  • @KeZkinOG
    @KeZkinOG 10 років тому +4

    men i nschool , this is what they also should have shown us.... might be really usefull for CAD programs

    • @trespire
      @trespire 10 років тому +2

      You've hit on a very good point. When we learned draftsmanship at highschool, the school was just starting to transitioning from paper to CAD (1986). We learned all these classic techniques for geometric construction using compass and straight ruler. For any one working in the engineering or technical field, this knowledge is very practical.

  • @Astro319
    @Astro319 3 роки тому

    ASMR: The comfort of listening to someone's voice even if you have ABSOLUTELY NO F'N IDEA WHAT THEY ARE TALKING ABOUT

  • @hassanhan9124
    @hassanhan9124 5 років тому +12

    Sweet, pretty, nice and mathematician..what a combination..!

  • @JamieDenAdel
    @JamieDenAdel 10 років тому

    This is the most interesting Numberphile video in quite a while.

  • @sandreid87
    @sandreid87 8 років тому +5

    Is that really called "a compas" in english? It's really strange, because I think of "a compass" every time I hear that word. In Danish, they are called (If translated directly) "a school-follower". It's a really strange name, but I guess it's because it helps you follow school? Or something? o.O

    • @sandreid87
      @sandreid87 8 років тому +1

      ***** Oh okay. Thanks for the info :)
      Well, I guess school-follower is a bit weird, because it's not about following the actual school building itself, but about making sure you don't fall behind with homework and such. That you listen in class etc. It's that kind of "following". Can't for the life of me think of a better term in english, at this moment, lol.
      Edit: I actually just looked it up, and apparently the danish word for it, which is "Passer" comes from (old) german. A word identical to it, which meant to measure or adjust. It might also be related to the French word "compas".
      TL:DR Danish is weird! lol

    • @Robi2009
      @Robi2009 8 років тому +2

      In Poland "kompas" means a device used to show north in field. The circle-creating compass is called "cyrkiel" (sounds almost exactly like circle)

    • @SKyrim190
      @SKyrim190 8 років тому

      I have the opposite problem in Portuguese, because the device to make a circle is called "um compasso", while the device that points to north is called "uma bússola". So every time I pick up a compass in a Zelda game, the first thing that comes to mind is this stuff! lol

    • @Gunbudder
      @Gunbudder 8 років тому +1

      It really is called a compass. Just to make it even more confusing, a compass is also a device that indicates north. I'm not sure why these two things have the exact same name, but its probably because you can use them both for navigation. We also have something called a sextant, but that is specifically for navigation, and you wouldn't be drawing circles for fun with it.

    • @zastaphs
      @zastaphs 8 років тому +1

      In Slovakia, we call that "kružidlo" which would translate roughly into something like "circler" - maker of circles :-)

  • @scowell
    @scowell 10 років тому +1

    If you are given a unit cube, you are also given root 2 as the diagonal. You can just pull that from the cube with the compass and save some time. Continuing the process gives a quadruple cube, so the tripled cube is missed.

  • @mattwatt3006
    @mattwatt3006 8 років тому +2

    PLEASE HELP!! I don't understand why this is difficult...! Can't you just
    - Draw a circle at angle A, making points B and C equidistant from A;
    - Connect BC, trisecting the new line at D and E
    - Connect AD and AE, and then you're done??
    I mean, I understand from a recent video that all triangles can be represented as an Equilateral triangle viewed in 3d space

    • @natekunnen7021
      @natekunnen7021 6 років тому +1

      Nobody here is smart enough t answer you apparently, but the basis of mathematics and science says keep going until you’ve been proven wrong or you can prove it correct

  • @giusepperesponte8077
    @giusepperesponte8077 10 років тому

    My favorite numberphile video. Mind boggling for sure

  • @TheJaredtheJaredlong
    @TheJaredtheJaredlong 8 років тому +8

    That seems so wrong being unable to trisect an angle with Euclidian tools. It just seems too benign to be impossible. I'm going to waste so much time now trying to get it to work even though I was just told it's been proven impossible.

    • @NarikGaming
      @NarikGaming 8 років тому +1

      How is that going for you?

    • @TheJaredtheJaredlong
      @TheJaredtheJaredlong 8 років тому +3

      K463178 Can confirm, it cannot be done.

    • @NarikGaming
      @NarikGaming 8 років тому +1

      TheJaredtheJaredlong I think i may have found a way to do it

    • @TheJaredtheJaredlong
      @TheJaredtheJaredlong 8 років тому +1

      K463178 I found a way that worked for acute angles, but I couldn't get it to work on obtuse angles. I think my method for the acute angles was also technically wrong, and the error is so small it _looks_ right, but when I tried it on some obtuse angles it was very clearly wrong.

    • @AlessandroFenuTower02
      @AlessandroFenuTower02 8 років тому +2

      TheJaredtheJaredlong bisect an angle, create a perpendicular line, and divide that line in 3 equal parts, obtaining so 2 points. Connect then the points to the origin of the angle, and erase the bisect line and the perpendicular line.. why not?

  • @philindeblanc
    @philindeblanc 3 роки тому +1

    This geometry makes sense. Numbers are a human construct of measure, so the Eucilean seams more of a anchoring reality in how we understand our surrounding. This is rather amazing, and I am shocked I never learned this basic method to geometry....sure some overlap, but not based in. This should be in schools from perhaps 2nd or 3rd grade on and into the complexity in high school and university.

  • @NavsangeetSingh
    @NavsangeetSingh 8 років тому +3

    So you have to go one dimension up to crack cube roots. What about fourth roots? O_o; Do we go up one more dimension? :P

    • @H0A0B123
      @H0A0B123 8 років тому +11

      fourth root is square root of square root, which isn't a problem

  • @ryanprov
    @ryanprov 7 років тому

    If people are interested in straightedge and compass constructions, there is an app called Euclidea that basically poses these construction problems as puzzles. If you like thinking about this stuff you will love the app, it can be really tricky and fun to find the most efficient solutions.
    For example, an especially tough one: given a circle and a point on that circle, can you construct a tangent line through that point using only 3 lines/circles?

  • @DLTA64
    @DLTA64 10 років тому +21

    She's Hungarian!!!

    • @trespire
      @trespire 10 років тому +12

      I had two Hungarian teachers, they were very well educated, nice people and good teachers.

  • @shruggzdastr8-facedclown
    @shruggzdastr8-facedclown 6 років тому

    You can use a cube to construct a square whose area is three times the area of the square that defines one of the six faces of that cube: Just as the hypotenuse of a right triangle whose sides are equal in length to one another is equal to the sqrt-2 times the length of either side, the diagonal within a cube that connects the two most-remote vertexes (four such paired vertexes exist on a given cube -- all equal in length to one another) is of a length which measures exactly sqrt-3 times the side of the square that defines one of the faces of the cube.

  • @bluebeachdog12
    @bluebeachdog12 10 років тому +6

    Even a slaveboy could figure out how to double a square!
    -Socrates
    haha....Plato reference.

    • @professorsogol5824
      @professorsogol5824 3 роки тому

      I believe Socrates claimed that the slave boy was not "figuring out how to double a square" but only "recollecting" what his immortal soul already knew. (Meno)

  • @MentalVideographer
    @MentalVideographer 9 років тому +2

    For doubling the square, you can also just double the diagonal, and construct the square around it.

    • @PhilosophyVajda
      @PhilosophyVajda Рік тому

      ​'double the diagonal' just means double the hypotenuse not one of the other sides.

  • @JackassBauer1
    @JackassBauer1 8 років тому +3

    Adidas = Trisector :0

  • @spindoctor6385
    @spindoctor6385 3 роки тому +1

    I must be missing something, If you can trisect a line segment then surely you can trisect an angle.
    Measure out the same distance on each arm of the angle. Create a new line segment between those points, trisect that line segment and draw a line to each new point from the origin of the angle....
    What did I miss?

    • @anweshdas6510
      @anweshdas6510 3 роки тому +2

      Your idea is grt but I see a problem with it..
      When u talk about trisecting an angle we need to trisect the circular section between the two points and not the straight line as both will not be the same...Atleast that's what I think..I can be wrong... We can see this making the circle very large and visualise...Trisecting the circular section is what stood to be the problem for Euclid

    • @spindoctor6385
      @spindoctor6385 3 роки тому +1

      @@anweshdas6510 I do not see how they would be different, to simplify if you were to bisect the angle anywhere and extend that to any size circle then it would still be bisected. I am not seeing why the same does not apply to trisecting. I do not know if I understand exactly what you are saying either. Obviously better minds than mine have worked on this, but there is no logical error in my method. I am assuming I am missing something. I just do not see what it is, please explain more if you are sure you are right, I know it is hard without diagrams.

    • @anweshdas6510
      @anweshdas6510 3 роки тому +2

      @@spindoctor6385 I just sketched up an arbitrary angle and trisected it like u said....guess what... It works...I am no expert( not even close...just a high school student) but I think u r right...And also rather than measuring out the lengths initially.. We can just take a length using the compass and cut it both ends and then join to make the line segment..(Yours is absolutely fine too)..I don't know what else to say but Congratulations..

    • @anweshdas6510
      @anweshdas6510 3 роки тому +2

      @@spindoctor6385 If u want to see the diagrams just contact.. I am a bit busy but I will try to proof this Conjecture in my free time

  • @daftbence
    @daftbence 8 років тому +26

    Hungarians unite!

    •  8 років тому

      userful1 persze angolul írd le xd

    • @daftbence
      @daftbence 8 років тому

      Legalább más is megérti

    • @sha99yBee
      @sha99yBee 7 років тому +1

      van bojler elado!

    • @arnold7432
      @arnold7432 7 років тому

      bojler eladó

    • @cesteres
      @cesteres 6 років тому

      Christobanistan No

  • @faramund9865
    @faramund9865 Рік тому

    Was wondering if you could construct a right angle with only a compass.
    Thanks for showing it so I don't have to go through the Elements to find it. :)
    Also I think I'm in love with this approach to maths, it's so practical and 'simple'. Straightforward.

  • @GuiltyGearRockYou
    @GuiltyGearRockYou 10 років тому +3

    >>> HEY BRADY!!

  • @rkpetry
    @rkpetry 7 років тому +1

    For trisecting an angle, there was a 'clever' construction decades ago that drew a circle around the vertex of the angle and taped the compass to the straight edge and slid that through an intercept while resting its far point on the diagonal extending the other side of the angle-'til the near point touched the circle... (a non Euclidean geometry solution)....

  • @samyakvaidya9001
    @samyakvaidya9001 8 років тому +15

    all this is 10th grade

    • @sloaiza81
      @sloaiza81 8 років тому +8

      not in my country

    • @Zzzip13Strike
      @Zzzip13Strike 8 років тому +9

      Samyak Vaidya no this is like 6th grade

    • @Omcsesz
      @Omcsesz 7 років тому +1

      In deed.

    • @gctscott
      @gctscott 6 років тому +1

      My daughter is learning this in 4th grade.

  • @ximecreature
    @ximecreature 10 років тому +1

    Great video, as always.
    Galois, the amazing mathematician who died at 19, died after a duel. But do you know what the duel was about? In some of his notes, he talks about « l'infâme coquette », I don't know how to translate it perfectly, but basically it was a girl he used to date. The uncle and the fiance asked a "legitimate" duel (back then) which he couldn't refuse :)