How to turn a circle inside out (Visual Calculus and the Tractrix)

  Рет қаралды 91,614

Physics for the Birds

Physics for the Birds

Күн бұрын

The shape that a dog walks in when pulled by its owner shows up in more places than you might think. This video explores a curve called the tractrix and introduces visual calculus, a method for calculating integrals without any calculations.
Become a Patreon member: / physicsforthebirds
0:00 Dog on a leash, intro
1:23 Deriving the tractrix
3:17 Visual calculus
6:01 Area between bike tracks
8:04 Conclusion
Yo-yo on the ISS: • International Toys in ...
Proof of Tractrix Equation: proofwiki.org/wiki/Equation_o...
Mamikon's Visual Calculus: www.its.caltech.edu/~mamikon/...
Gaussian curvature of the pseudosphere: Manfredo P. do Carmo, "Differential Geometry of Curves and Surfaces", p.168-169
Great video on bike tracks: • A Curious Track, or Wh...

Пікірлер: 148
@lexinwonderland5741
@lexinwonderland5741 Жыл бұрын
your presentation is absolutely adorable, your explanation is satisfying but accessible, please please please keep making content!!
@physicsforthebirds
@physicsforthebirds Жыл бұрын
Will do!
@mihailmilev9909
@mihailmilev9909 Жыл бұрын
Thought the same thing
@Brunoenribeiro
@Brunoenribeiro Жыл бұрын
If you like it that much, it means... you're a bird! 😝 (jk I love it too)
@not_David
@not_David Жыл бұрын
I'm floored by how good your videos are, please keep making more!
@yumnuska
@yumnuska Жыл бұрын
I’m just flabbergasted at how good your videos are. Please keep going. First, your casual style really minimizes completely in a beautiful way. It’s just so simple!! Meaning that you introduce complexity in such a natural way that it doesn’t feel complex at all. Second, and following from the first, I just feel so happily, jubilantly surprised when you use a simple example to describe a complex result. The bike path metaphor leading to 2pi just shocked me in the best way. I love it. As a casual math geek, I just love how you present complex ideas without getting too deep in the details. I don’t care about the details, I care about the joy of the relationships, and you do that just so wonderfully.
@mihailmilev9909
@mihailmilev9909 Жыл бұрын
Exactlyyyyy
@mihailmilev9909
@mihailmilev9909 Жыл бұрын
Although I do like details, i think it shows the relationships even more clearly
@46evenlessreal
@46evenlessreal Жыл бұрын
same as mihail
@iamstickfigure
@iamstickfigure Жыл бұрын
The factoid about area traced out while riding a bike is delightful. And your illustrations to support the idea were perfect! It really made it click for me, and I think the idea will stick with me every time I ride a bike
@cougar2013
@cougar2013 Жыл бұрын
I have a physics PhD and I never heard of the tractrix. I’m glad you made this video because I learned something. Very well done and please keep it up!
@josephblattert6311
@josephblattert6311 Жыл бұрын
This channel better blow up soon. You deserve to be so much bigger with this kind of quality.
@mihailmilev9909
@mihailmilev9909 Жыл бұрын
Frrrrr
@katarixy
@katarixy Жыл бұрын
This was beautifully done. As a math teacher myself I cannot help but thank you for the brilliant perspective and detailed presentation.
@physicsforthebirds
@physicsforthebirds Жыл бұрын
I'm glad you liked it! I think visual calculus fits well in a classroom since it's so hands on.
@katarixy
@katarixy Жыл бұрын
@@physicsforthebirds Do you use a wacom tablet or iPad to make the animations?
@physicsforthebirds
@physicsforthebirds Жыл бұрын
@@katarixy I make the animations on iPad with Procreate
@AJMansfield1
@AJMansfield1 Жыл бұрын
That trick with the area between a bicycle's tracks is also (with some coordinate substitutions) the way a planimeter works.
@andrewpappas7198
@andrewpappas7198 Жыл бұрын
Well done. I was enthralled through the entire presentation. Please, continue to make videos.
@mihailmilev9909
@mihailmilev9909 Жыл бұрын
Yup yup
@sulfurx777
@sulfurx777 Жыл бұрын
I didn’t realise this channel only had 9k subs until a couple videos in. With this level of quality you’ll definitely have a bunch more in no time.
@drkirka
@drkirka Жыл бұрын
I'm in SHOCK that you don't have as much subscribers as i thought you would. Your visuals, audio, script and overall production quality are incredible. Keep up the work!!!! Love it. 💕
@bhavin_ch
@bhavin_ch Жыл бұрын
Isn't this an Irodov problem? This feels like an Irodov problem! This is like bringing back some massive nostalgia from my college entrance prep days ❤
@nenben8759
@nenben8759 Жыл бұрын
When you first posed the question, I imagined the dog making a perfect circular orbit around the owner
@fable4315
@fable4315 Жыл бұрын
Love your videos, so entertaining and still super informative. Hopefully you get a bit more attention in the future!
@physicsforthebirds
@physicsforthebirds Жыл бұрын
Me too, Fable, me too...
@derpaderp9824
@derpaderp9824 Жыл бұрын
Top tier content. This is genuinely enjoyable.
@mcloudyoutube
@mcloudyoutube Жыл бұрын
I’ve been slowly going through your videos this past week, and I absolutely love all of them. Please keep up your content, I love how you focus on explaining through the theoretical/contextual lens rather than force feeding all of the practical information and hard numbers
@BreadSauce4
@BreadSauce4 Жыл бұрын
This is an amazing video. Keep up the great work!
@micahsilverman5284
@micahsilverman5284 Жыл бұрын
You are my new favorite KZfaq channel! I feel lucky that KZfaq reccomended you!
@twelvethousandths1698
@twelvethousandths1698 Жыл бұрын
You are one of the best math youtubers out there! Shame that you are so underappreciated!
@charlychatelain8795
@charlychatelain8795 Жыл бұрын
already my new favorite youtuber :))
@RED-jg6mt
@RED-jg6mt Жыл бұрын
UNBELIEVABLY UNDERRATED. Thank you so much for this video, so interesting!
@jpeglucy
@jpeglucy Жыл бұрын
this video is incredibly easy to follow even though its describing more advanced mathmatical concepts, and its fun to look at! definitely dererves more subs
@osmanosman6206
@osmanosman6206 10 ай бұрын
Thank you very much for these very nice explanations and demonstration.
@jhemilae
@jhemilae Жыл бұрын
Give this man more subscribers.
@mr_rede_de_stone916
@mr_rede_de_stone916 Жыл бұрын
Love it! You'd think after years of roaming around the maths youtube you wouldn't find any more thingy that's both simple and full of secrets but here we are... And oh such a lovely explanation too, congrats!
@congruentcrib
@congruentcrib Жыл бұрын
The whole analogy with the bike is actually used in safety measures in cars. We always suggest you have your best tires in the back; even if you have a front wheel drive car. The reason is if you hydroplane in the read, but not the front, the rear tires new angle (total toe/ thrust angle) will dictate where you go. On the other hand if your front tires hydroplane your steer ahead will change and this is much easier to recover. Along with that, if you step on the brakes and your rear tires hydroplane, your rear end will be pushed forward making your thrust angle exponentially greater. If your front tires hydroplane and you brake, the front end will pull on the vehicle which will not put you into a uncontrolled drift of over 45 degrees. A 45 degree spin out is much easier than a 360 spin out. These both are extremes, but we’ve seen you guys drive… I’m amazed anyone is alive to be honest. If you want more details, I’d love to share them. I’m alignment certified by Hunter Engineering, and that’s why I may use fancy terms like “total toe, steer ahead, thrust angle, etc.” and if you need me to explain, I’m happy to. I just will say that it’s easier to show than it is to tell. After all, it is geometry… and physics. Stuff is hard to explain with visuals, but is much harder using only words.
@kenshininoue7648
@kenshininoue7648 Жыл бұрын
loved the video. i used to watch a lot of cliff stoll's lecture on topology back in my freshman. it reminded me of that.
@potato_cm
@potato_cm Жыл бұрын
You are awesome your videos are so much fun!
@EdwardChan.999
@EdwardChan.999 Жыл бұрын
I'm leaving a comment here to let you know that I am shocked by how well you transitioned between seemingly irrelevant yet logically relevant concepts across applications in different fields... you've beaten SciShow as my favourite science channel 👍🏻
@imsleepy620
@imsleepy620 Жыл бұрын
bro this is incredible
@RyanLynch1
@RyanLynch1 Жыл бұрын
great video! hope to see more from this channel
@RuleOfThrees
@RuleOfThrees Жыл бұрын
This is really excellent! I am amazed and learned something cool!
@jojoanggono3229
@jojoanggono3229 Жыл бұрын
I love Calculus. Dog will be infinitely close to owner path but never touches. Your visual method of explaining is very appealing, I imagine it would be interesting for young audience.
@TheLogotero
@TheLogotero Жыл бұрын
I just love this videos
@moonface3665
@moonface3665 Жыл бұрын
Don't know if I needed to know this but I am highly intrigued, will be staying around for a while
@ipeaceful6
@ipeaceful6 Жыл бұрын
great video! thanks!!
@mikefischbein3230
@mikefischbein3230 Жыл бұрын
Superb video!!
@taliaturner9926
@taliaturner9926 Жыл бұрын
What if you leash another dog to the first one? Is that just another tractrix, or do you get a super-tractrix?
@physicsforthebirds
@physicsforthebirds Жыл бұрын
Wow, that's a question! Since the first dog isn't moving in a straight line, the second one can't be moving in a tractrix. The angle of the second leash would lag behind the first, so the super-tractrix must be steeper than the original. Whatever the case, the area between the two dogs must be the same as the tractrix. But now I want to know what happens as you approach many dogs with infinitesimal leashes!
@Awerewolf101
@Awerewolf101 Жыл бұрын
@@physicsforthebirds you should probably know that dogs do not do a tractrix they go where they want whether it's nearby, ahead of you or even using the leash to make a tangled mess
@howdy832
@howdy832 Жыл бұрын
This is fantastic!
@thementosII
@thementosII Жыл бұрын
This was brilliant
@Friek555
@Friek555 Жыл бұрын
The area between bike tire tracks is easily the best fun math fact I learned in years!
@donchaput8278
@donchaput8278 Жыл бұрын
Great Content!
@ifroad33
@ifroad33 11 ай бұрын
I can totally see Matt Parker calculating Pi from the trails of a bicycle for his next Pi-day video. Interesting video, and very nice visual explanations!
@nymX_X
@nymX_X Жыл бұрын
i love this channel, somehow you explain physics in a way that’s kinda similar to computer science
@XxdaleforlifexX
@XxdaleforlifexX Жыл бұрын
careful you're pinching it infinitely tight
@kidredglow2060
@kidredglow2060 22 күн бұрын
Wrong dimension buddy
@EPMTUNES
@EPMTUNES Жыл бұрын
Awesome video!
@KumaBones
@KumaBones Жыл бұрын
This was really insightful and interesting to listen to, after just taking trig and going into calc1 lol
@humanperson8418
@humanperson8418 Жыл бұрын
You Sir Bird have earnt yourself a sub for a great video.
@Thejosiphas
@Thejosiphas Жыл бұрын
so fire dude
@Kids_Scissors
@Kids_Scissors Жыл бұрын
I usually go home and watch KZfaq to get away from geometry (haven't learned claculus yet) but damn this is mad interesting
Жыл бұрын
Broh, just found out your channel. I just fucking love it. Please, keep doing videos like this!
@beansprugget2505
@beansprugget2505 Жыл бұрын
Good video
@lunaponta594
@lunaponta594 Жыл бұрын
"so next time you're riding your bike or walking your dog, you can tell your friend all about the tractrix" GODDAMNIT i already have too much to talk about! thanks tho
@flamshiz
@flamshiz Жыл бұрын
this feels like an April fool's day prank
@jojnokirk8035
@jojnokirk8035 Жыл бұрын
my favorite fun fact about spheres and pseudospheres is the right angles in a "square." on a plain (surface with constant 0 curvature) a square is shape made entire of right angles and it has 4 sides. on a sphere, a shape made of only right angles would be 3 sides (equator, up to north pole, turn, back down to equator, turn, back to where you started), but on a hypersphere, an only-right-angled shape would have 5 sides! pretty cool
@physicsforthebirds
@physicsforthebirds Жыл бұрын
Pretty sweet! That's how I was able to make the 5-sided and 3-sided origami paper for my non-Euclidean cranes
@Nosewrecky
@Nosewrecky Жыл бұрын
thanks!
@robloggia
@robloggia Жыл бұрын
I really wish you had been my Algorithms teacher back in college.
@rizalardiansyah4486
@rizalardiansyah4486 Жыл бұрын
Just stumbled upon this channel in my feed. Really like the way you explain stuff! Another example I found it useful about this tractrix curve is on CNC drag knife. It works just like the bike example! One question though, when you mention that differential equation (DE), I don't think that is a DE? It looks like an ordinary integration problem because from what I know it has to have a "y" Variable in the equation for it to be DE. I hope someone can confirm or tell why if it is otherwise. I'm kinda new to DE stuff... Thanks!
@superparadox
@superparadox Жыл бұрын
this is cool
@QuartzChrysalis
@QuartzChrysalis Жыл бұрын
Making these shapes with string, nails and a board when i was a kid might be part of why i like maths.
@aappaapp6627
@aappaapp6627 Жыл бұрын
Cool!
@bourgeoibee
@bourgeoibee Жыл бұрын
4:35 is a perfect visual for integration by substitution
@aidenboudreau
@aidenboudreau Жыл бұрын
Let it be known I was your 484th subscriber once your famous. Great job!
@xbox70333
@xbox70333 Жыл бұрын
We can view any closed shape polygon is just a special form of a circle, a circle which has edge length > 0, thus made of finite number of line segments, unlike a circle which can be thought of being made of infinite line segments, thus the smooth shape. Once you realise this, all paths that end up at the start, traced by a bike, are just forming concentric circles in the end. Just special forms of circles.
@sydney5585
@sydney5585 Жыл бұрын
Love it
@johnnicholson8811
@johnnicholson8811 Жыл бұрын
As I watch this, I thought of another tractrix. An 18 wheeler truck.
@physicsforthebirds
@physicsforthebirds Жыл бұрын
That's actually a very relevant example; some of this same bike track math has applications in parking control systems for autonomous vehicles with trailers.
@tsunamio7750
@tsunamio7750 Жыл бұрын
4:39 Oh my god this example of your is painfullll! xD But yes, I accept that, keep going, don't stop now! :)
@damie9412
@damie9412 Жыл бұрын
Nice
@SpaceSoups
@SpaceSoups Жыл бұрын
I can see this outro jingle being as culturally significant as the Vsauce one in a few years.
@user-hs9ul3yi9g
@user-hs9ul3yi9g 18 күн бұрын
The rule to get area between tracks only applies to Euclidean geometry or if the plane of the paths is flat. If you make a trip on a bicycle around the Earth wiggling around the equator - the area is positive but you made no turns cause you end up in the beginning in the same orientation
@DarkAngelEU
@DarkAngelEU Жыл бұрын
Can you make a video on how to turn a sphere inside out?
@mallardmax3127
@mallardmax3127 Жыл бұрын
What are the intro/outro songs. They are really good!
@davisremmenga4906
@davisremmenga4906 Жыл бұрын
I have that same Yoda backpack
@JTCF
@JTCF Жыл бұрын
I remember that old youtube video about turning a sphere inside out... IIRC it said that turning a 2d circle inside out is not possible. Well, well, well...
@Fire_Axus
@Fire_Axus Жыл бұрын
Why are the comments on this video so kind?
@mehdimabed4125
@mehdimabed4125 Жыл бұрын
Hey !Really cool video ! y the way, what is the veeery cool music in the background at 8:04 ? Really nice music !
@physicsforthebirds
@physicsforthebirds Жыл бұрын
The music is my own, made for the video. I'm glad you like it!
@redstone8513
@redstone8513 Жыл бұрын
@@physicsforthebirds Please release it!
@plootyluvsturtle9843
@plootyluvsturtle9843 Жыл бұрын
dog drawing is underrated
@pal181
@pal181 Жыл бұрын
I can't imagine how these triangles make up the circle or it's quarter.
@luciuscaeciliuslucundus3647
@luciuscaeciliuslucundus3647 Жыл бұрын
Your videos are absolutely incredible! Just watched the jazz one and now this! I do have but one question however: if the bike changes direction, i.e starts turning left then turns right, does the area kind of cancel itself out a but like being above or below the x axis in an integral, in which case the degree it turns through doesn't represent the area? I'm not sure if this is right but if anybody knows I would appreciate it! Keep up the absolutely perfect videos!!
@physicsforthebirds
@physicsforthebirds Жыл бұрын
That's exactly how it works! As long as you keep track of the angles that went in the other direction the area will still be proportional to the total angle. At 4:11 the red triangles are ones that went the other way, so you can see how I subtracted them instead of added.
@luciuscaeciliuslucundus3647
@luciuscaeciliuslucundus3647 Жыл бұрын
@@physicsforthebirds awesome! Thank you so much for letting me know - very very cool! Keep it up!
@psylonmusic5264
@psylonmusic5264 Жыл бұрын
It's Appa ! =D
@legoworks-cg5hk
@legoworks-cg5hk 11 ай бұрын
It's similar to when slices of fruit lean on each other and make a curve on top
@RilianSharp
@RilianSharp Жыл бұрын
i wanted to know what shape you would walk in if you're walking at the same speed as another person who is walking in a straight line and you're always walking towards them, and i think this is the same problem, so yea!
@kamehamehey22615
@kamehamehey22615 Жыл бұрын
Imagine if they made a bike called the Tractrix
@TheLetterB123
@TheLetterB123 Жыл бұрын
3:45 aperture science refrence lol
@richardnavas2610
@richardnavas2610 Жыл бұрын
Isn't that also the shape of gabriel's horn? The one with finite volume but infinite area
@RussellSubedi
@RussellSubedi Жыл бұрын
Quick question: is that race happening in San Fierro?
@physicsforthebirds
@physicsforthebirds Жыл бұрын
It's a map of San Francisco, which I guess San Fierro is based on 🤣 ...wasn't meant as a reference!
@dimitrisivak738
@dimitrisivak738 Жыл бұрын
so a sphere in 3d creates a funnel in 4d...?
@theorixlux2605
@theorixlux2605 Жыл бұрын
Okay. Maybe you're right, and I hear you, 100%. But how do you turn a circle happy?
@hella_cool1312
@hella_cool1312 Жыл бұрын
Visual Calculus [Challenging: Success]
@Fire_Axus
@Fire_Axus Жыл бұрын
Where do you turn the církve inside out?
@Fire_Axus
@Fire_Axus Жыл бұрын
sorry autocorrect
@ruroruro
@ruroruro Жыл бұрын
The author has an unfortunate habit of lying in their video titles. They made another video the title of which claimed that the universe has negative curvature, but the video actually concluded that the universe is flat.
@cejkisondrej1113
@cejkisondrej1113 Жыл бұрын
Wow
@Isaac-ph5co
@Isaac-ph5co Жыл бұрын
Is it the braquistochrome curve?
@appa609
@appa609 Жыл бұрын
It does depend on *some* physics. If you did this experiment in zero g vacuum the dog will end up rotating around you. This is obvious if you view the problem from the human's (inertial) frame
@DissonantSynth
@DissonantSynth Жыл бұрын
This was a phenomenal video, but if I may make a suggestion, please try to filter out the wet sounds from your mouth when you're talking
@RilianSharp
@RilianSharp Жыл бұрын
7:32 what is happening here, is the bike moving backwards
@physicsforthebirds
@physicsforthebirds Жыл бұрын
Yeah, if the front tire turns around in a small enough radius then the back tire will make a sharp stop and then start moving backwards. At 7:34, the back tire (green) was moving backwards between those two sharp points and the front tire was always moving forwards.
@lordofthe6string
@lordofthe6string Жыл бұрын
In the original question it doesn't state the dog needs to be facing the owner, so couldn't the dog just walk to the right at the same pace as the human and draw a straight line? lol
@Quadr44t
@Quadr44t Жыл бұрын
Hmm, isn't this the shape that makes balls roll down the fastest? Why are these curves connected? I feel like there should be an underlying logic here.
@physicsforthebirds
@physicsforthebirds Жыл бұрын
The brachistochrone is a cycloid, a curve drawn by a point on the edge of a rolling circle. The tractrix can be drawn as the curve that always perpendicularly intersects a rolling circle, so they're somewhat related!
@existing666
@existing666 Жыл бұрын
Dogs are the best
@reecec626
@reecec626 Жыл бұрын
Isn't that called a brachistochrone?
@physicsforthebirds
@physicsforthebirds Жыл бұрын
The brachistochrone is drawn by a point on the edge of a rolling circle, but the tractrix can be drawn as the curve that always perpendicularly intersects a rolling circle, so they're somewhat related!
@dadutchboy2
@dadutchboy2 Жыл бұрын
Bro used Roblox to visualize falling 💀
@physicsforthebirds
@physicsforthebirds Жыл бұрын
You caught me... it's a pretty fast and cheap way to make simulations
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