The Bizarre Behavior of Rotating Bodies

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Spinning objects have strange instabilities known as The Dzhanibekov Effect or Tennis Racket Theorem - this video offers an intuitive explanation.
Part of this video was sponsored by LastPass, click here to find out more: ve42.co/LP
References:
Prof. Terry Tao's Math Overflow Explanation: ve42.co/Tao
The Twisting Tennis Racket
Ashbaugh, M.S., Chicone, C.C. & Cushman, R.H. J Dyn Diff Equat (1991) 3: 67. doi.org/10.1007/BF01049489
Janibekov’s effect and the laws of mechanics
Petrov, A.G. & Volodin, S.E. Dokl. Phys. (2013) 58: 349. doi.org/10.1134/S102833581308...
Tumbling Asteroids
Prave et al. doi.org/10.1016/j.icarus.2004...
The Exact Computation of the Free Rigid Body Motion and Its Use in Splitting Methods
SIAM J. Sci. Comput., 30(4), 2084-2112
E. Celledoni, F. Fassò, N. Säfström, and A. Zanna
doi.org/10.1137/070704393
Animations by Ivy Tello and Isaac Frame
Special thanks to people who discussed this video with me:
Astronaut Don Pettit
Henry Reich of MinutePhysics
Grant Sanderson of 3blue1brown
Vert Dider (Russian JPvid channel)
Below is a further discussion by Henry Reich that I think helps summarize why axes 1 and 3 are generally stable while axis 2 is not:
In general, you might imagine that because the object can rotate in a bunch of different directions, the components of energy and momentum could be free to change while keeping the total momentum constant.
However, in the case of axis 1, the kinetic energy is the highest possible for a given angular momentum, and in the case of axis 3, the kinetic energy is the lowest possible for a given angular momentum (which can be easily shown from conservation of energy and momentum equations, and is also fairly intuitive from the fact that kinetic energy is proportional to velocity squared, while momentum is proportional to velocity - so in the case of axis 1, the smaller masses will have to be spinning faster for a given momentum, and will thus have more energy, and vice versa for axis 3 where all the masses are spinning: the energy will be lowest). In fact, this is a strict inequality - if the energy is highest possible, there are no other possible combinations of momenta other than L2=L3=0, and vice versa for if the energy is the lowest possible.
Because of this, in the case of axis 1 the energy is so high that there simply aren't any other possible combinations of angular momentum components L1, L2 and L3 - the object would have to lose energy in order to spin differently. And in the case of axis 3, the energy is so low that there likewise is no way for the object to be rotating other than purely around axis 3 - it would have to gain energy. However, there's no such constraint for axis 2, since the energy is somewhere in between the min and max possible. This, together with the centrifugal effects, means that the components of momentum DO change.

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2019/09/18

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コメント数 : 19 417

qfmarsh64 年前

As a kid, I would frequently watch my dad flipping the TV remote control in his hand and studying the inevitable half-turn in its flight pattern. He concluded that his wrist was subtly imparting spin. If he were alive today, his mind would probably be blown watching this video.

ılılıᴘᴀʟᴇʙʟᴜᴇᴅᴏᴛɢᴜʏılılı 年前

aww that's so cool

Elgoog 9 ヶ月前

"He concluded that his wrist was subtly imparting spin." Well, as we've learned in your video, your dad was right

Michael Roast 9 ヶ月前

Cannot tell you how many hours I have done this with a TV remote too, trying to get a straight flip. Futile all along.

Siggy Retburns 8 ヶ月前

This physics trick puzzled me years ago when I was flipping a claw hammer. No matter what I did or how I flipped it it would not just flip with the claw on the right and the hammerhead on the left. It would end up that way but half way through the flip, the claw and hammer would switch sides. From what I understood of physics at the time, I assumed it was because either the claw or the hammer weighed more than the other and gravity interrupted the momentum. But this video proves me wrong. One thing I dont understand is that if its perfectly balanced, it shouldn't happen. I still think that Earths rotation has something to do with it.

Elgoog 8 ヶ月前

@Siggy Retburns Yes that is correct, if it were perfectly balanced, it would not happen. But there is no such thing as "perfect" in practice.

Shawn 年前

I always assumed this happened because I was adding spin without realizing it. The theory of a rotating object trying to minimize its kinetic energy actually makes a lot of sense.

Luke Ernst 年前

I mean, you are adding spin without realizing it. In the point mass simulation even the intermediate axis is stable until there was a tiny deviation from exactly straight spinning. Whether it’s you unknowingly rotating it along an axis slightly different than the true intermediate axis, or air later misaligning it, it’s almost impossible to not see this effect in practice

ayoosh iyer 年前

@Luke Ernst if air is causing this misalignment why do we still see this effect in space ?

Vishal Singh 11 ヶ月前

@ayoosh iyer If the intermediate axis is pulled into a spin by the larger axis then this intermediate spin can only end once the larger axis has spun itself 180 degrees. By this deduction alone the outer intermediate masses must be switched hence the flip.

Hellencita 8 ヶ月前

@ayoosh iyer cause there is air on that cabin, remember that they are still breathing... i think if they left it in space without air we cant see this phenomenon.

RareBeeph 6 ヶ月前

@Hellencita the air has nothing to do with it. as derek (veritasium) said, in the reference frame of the initial rotation of the disk, the centrifugal force inherent to the rotation is what causes the disk to flip, with a frequency dependent on how much deviation the smaller masses are initially given from the axis of rotation. that's why the wingnut spins for so long between each flip, while most other things flip much sooner: the wingnut was given very nearly axis aligned rotation when it was spun off of its screw, so the centrifugal turning forces are very small for a rather long time.

Inscrutable Mungus 4 ヶ月前

The biggest lesson I've learned from getting a PhD in physics is the following: Landau and Lifshitz has *everything* . I was reviewing a paper on plasma physics once where the authors claimed that a certain analytical solution didn't exist -- sure enough L&L had an expression for the exact problem that paper was citing.

Dear Green Places 3 ヶ月前

Came to comment the same thing. It was such a red flag when I read that quote I had to pause the video and make a note to check myself.

Inscrutable Mungus 3 ヶ月前

@Dear Green Places My advisor in grad school used to have a flat rule for the group -- we're not allowed to claim that a certain problem doesn't have an analytical solution till we've meticulously gone through L&L and Jackson. I wouldn't be surprised if each of the millennium problems is not buried somewhere as a short example or 'left as an exercise to the reader' in one of the two.

Rahul Sharma 3 ヶ月前

Can you let me know what books you guys are talking about??

Inscrutable Mungus 3 ヶ月前

@Rahul Sharma Look up 'Course of Theoretical Physics' by Landau and Lifschitz (it's a set of 10 books); and 'Classical Electrodynamics' by Jackson. Fair warning: Both are fairly intense reads, but well worth it if you've got the required background.

Rahul Sharma 3 ヶ月前

@Inscrutable Mungus Thanks I had looked up and I am already on it, Vol 1 Mechanics -Maulertuis Principle. I had already solved Russian physics problem books Irodov and Krotov before. L&L has a similar feel so far and apparently a more comprehensive coverage in all volumes. Thanks 🙏for recommendation.

Tony Fourpaws 2 ヶ月前

I got in trouble at work today because I was tossing various objects and watching the flip. I tried to explain it to the boss but he wasn't having it. He fired me. Now I have more time to watch your videos!

HyperVectra 17 日前

You must not have explained it well. Sometimes people need to experience it themselves to truly understand the concept. If you cut his brake lines, his car should spin around the maximum angle of inertia.

Koutentogiwrghs 11 ヶ月前

A colleague pointed me to this great video! I was fascinated to find that it also contained two additional facts about the great condensed matter physicists of the past century. 1) If you claim that any physical concept is not in the Landau-Lifshitz books, most probably you have not looked for it as carefully as you should. 2) It is really tough to beat Feynman's physical intuition on anything, even if he thought about it for less than half a minute.

Teatro Grottesco 3 ヶ月前

Watching a mathematician do something physical and coordinated is almost as interesting as the great info provided.

Joe Daly 3 年前

As a carpenter for over fifty years I've recognized this behavior with flipping of a hammer because I early on decided to teach myself to juggle hammers. I tried to prevent the twist-flip with absolutely no success. It became clear there was more stability in working with the flip instead of against it. This explanation is such a relief! I thought it was a personal curse. Now I realize hammers are the perfect object to demonstrate this motion because they, unlike tennis rackets, have no symmetry about any axis!

John Possum 2 年前

You just got defective hammers.🤣

Joe Daly 2 年前

@John Possum additional evidence: rip claw configuration in hammers produce more consistent axial twisting.

Paul McGee 2 年前

Once again ball pein better than claw hammer. 😀 😉

Al Steiner 2 年前

@Joe Daly that has been my experience flipping a straight claw for years--it never rotated about the intermediate axis. Very east to flip

JamesPP Pyacek 2 年前

Yeah. Same here. Carpenter. Hammer. Flipping.

Michael Rush 年前

I greatly appreciate all your time and efforts to explain things in a way that make it exciting. I believe I may have an idea. I’m currently attempting to create the idea. It’s a smash up of a lot of things combined to one sir. Thank ya for your time again.

Jackson Starky 年前

This was two and a half years ago, and the Riemann Hypothesis is still unsolved. What else could Terry Tao have possibly been working on that was more important than this??? Edit: I just realized... it was the Collatz Conjecture, wasn't it? 😄

Evan Harsh 11 ヶ月前

I had always wondered why a tennis racket could never flip straight, finally get an explanation! Thank you lol

Rosalina Pickstone 年前

Have you ever heard of anyone turning one gyroscope inside another, rotating in the opposite direction. So that, when both gyroscopes are in action, the inner one appears to be stationary. Would these counter rotating gyroscopes negate the gyroscopic effect?

Professional Tiresome 3 ヶ月前

It becomes more difficult to travel further in any one axis. Accelerating in one direction of rotation meets this criteria. The wingnut flips because the continuing rotation acts like an acceleration yet with an easy way to change axes from 0 g. The limit as a rational value goes to infinity becomes irrational in the same axis, every time. Nice video!

ılılıᴘᴀʟᴇʙʟᴜᴇᴅᴏᴛɢᴜʏılılı 2 年前

This explaination is beautiful when you're actually learning this stuff in school... keeps me wanting to know more. Thanks Veritasium!!!

attic Slabs 2 年前

Never been a more deserving like to a comment on a video!

ılılıᴘᴀʟᴇʙʟᴜᴇᴅᴏᴛɢᴜʏılılı 2 年前

@attic Slabs :)

Mapk 46 2 年前

I watch this as a break from stupid school work.

James Smith 2 年前

@ılılıᴘᴀʟᴇʙʟᴜᴇᴅᴏᴛɢᴜʏılılı %ï

Rita Maru 2 年前

@Mapk 46 Good

Drake Withers 年前

This was an incredibly clear and concise overview. Brilliantly done.

stainlesssteelfox1 6 ヶ月前

Thank you! This is an amazing explanation and I can finally see in my head how it works. I've never been able to follow the maths involved.

Gautam Vashi 9 ヶ月前

This guy solves my problems, that I never had. He's simply awesome. 😍 I always learn alot from his every video ❤

Cosens-Prior 年前

Fascinating and the maximum moment of inertia appears to apply to your consistent delivery of this long and very clear explanation. It didn't look like you were reading off an autocue either! Anyhow my brain hurts after all that! Maybe the phenomenon should be re-named the wibbly wobbly effect ie the instability of energy transfer. Or why figure skaters don't always fall over when they're spinning.

John Papiewski 3 ヶ月前

This reminds me a lot of the Wilberforce Pendulum, in which a bouncing up and down motion shifts to a rotating motion and back again, the KE phasing back and forth between the 2 modes. And there's a swinging mode also I think.

Alexander Saavedra 3 年前

There is also a skateboard trick called the impossible flip because of this. They counter it by leading the front foot trough the flip to keep it from flipping on the other axis.

Commie 3 年前

yeah thats exactly what i was thinking and i was like-wait are they defying this theory?

Tooba 3 年前

I saw the physics girl video about that.. but I understood that here..

FerousFolly 3 年前

this effect is also what makes the 360 flip (tre flip) work the way it does.

Jon Bowman 3 年前

yes! this took forever to learn. btw using the front foot to balance the board is a "front foot impossible." An impossible uses the back foot.

Yumidori Iro 8 ヶ月前

The earth flipping over at some point does sound like a frightening scenario

Dave Strider 19 日前

I’m trying to replicate this with the iPad I’m watching on and I can’t figure out why the centrifugal forces act in the z direction (they seem like they should be limited to the x). But physics is physics and I can feel myself adding the unstable twist in. It’s a wonky feeling like my hands are being forced in a certain way.

James R 年前

My physics professor described this effect using a hammer. With a little practice I discovered I could put just the right amount of torque on the hammer when I flipped it to prevent this effect.

chris fitzsimmons 年前

ive known about this effect since i was a kid. I didn't know what it was called, but I would do this with my tv remote. it fascinated me how it was doing a half twist in the air. i started tossing the remote higher so it would spend more time in the air to get the full twist or even 1.5

Giardi Asis 8 ヶ月前

The smaller pair of cubes, if you were to trace their outlines, appear to create a pair of identical, yet mirrored, Morlet wavelets.

Mark P 2 年前

I was a dynamicist in the aerospace industry for 43 years, and THAT is the BEST plain text explanation of this behavior I have ever seen! Fantastic!

Greg Smith 2 年前

Wow! You have sold me! I'll watch it again!

Xccgh Vb no 2 年前

Then you're probably the person to ask what are the odds that the plates shifting around could in fact change the Earth's moment of inertia to where it could possibly effect the crust in a dramatic way? Just curious not every day one has a chance to ask a question to an expert who's possibly even thought about the same But actually with the educational background to get through the weeds of the problem and Come up with a Realistic hypothesis even if it is just A rough mental outline

Daniel Hope 2 年前

Was I watching this correctly to assume that if the frozen poles had enough elevated weight and then melted lowering that weights and even some of the water dissipating towards the equator, this could shift the moment of inertia ?

Xccgh Vb no 2 年前

@Daniel Hope very good point. Time For me to go research exactly how much ice is estimated to be Frozen.Thanks for the input

Karl-Konrad Klotzkopf 2 年前

@Daniel Hope The poles are where the least mass is, on the spinning axis. So if their mass would be distributet all over spinning system, the spin should become even more stable, because the mass around the equator would become even more significant.

Tapis T 8 ヶ月前

I've noticed that spinning racket phenomenon when I was little, but I convinced myself that it was due to air friction and didn't think further.

Harry Mattah 3 ヶ月前

Reminds me of the inertial roll coupling experienced by some aircrafts (F100, F102). This was theorized by Philips in 1948, and experienced some years later..

Special EDy 4 ヶ月前

I've always done this with a hammer, or large crescent wrenches, and wondered why it would flip around the handle axis.

Ed Stent 年前

As I was watching this video I realized these were the forces that cause a tire to need to be dynamically balanced because it's masses are out along its rotational axis.

Stan Weaver 7 ヶ月前

That was interesting and really intuitively explained. Thanks!

Andrew Chapman 3 年前

Video: contains the phrase "prove Feynman wrong" Also video: doesn't use this phrase as clickbait. I salute you.

Leonardo de Abreu 3 年前

One could still argue that it is clickbait. Because an intuitive explanation is relative to the person receiving the explanation. And Feynman probably knew his students wouldn't be able to understand this explanation. Hence it being hard for him to intuitively explain it to his students.

Bryant 3 年前

Living Legend I concur. Derek in this case used 3d animation to explain this phenomenon while Feynman would’ve been limited to making some drawings and mental pictures. The explanation subjectively intuitive but intuitive nonetheless, at least more so than math equations.

TheLaXandro 3 年前

He could make a "3d model" out of a plate and a pencil to mark the axis out, and demonstrate it in a largely similar way.

Volker Siegel 3 年前

"prove Feynman wrong" is not working clickbait - it's so obviously spam that nobody would click it. And then... he actually did what?

mvmlego1212 3 年前

Of course, it's not "bait" if he actually does it (which, in my opinion, he did). I still appreciate that he gave it an informative and non-confrontational title, though.

Julian 4 ヶ月前

Why isn't the explanation for the intermediate (y)-axis in 8:28 not equally valid for the x-axis. A small inclination from it should give the same periodically movement in my view, the only difference is that now the mass ratio between the main rotating mass and the tilted is different... Any ideas about that? I would appreciate it :D

Brian Bordenkircher 年前

Woah. Yep. I’m wondering what would happen if the earth flipped. Or heck, the sun. Lol :-o Still, even if it isn’t supposed to flip, aren’t the magnetic poles still slowly moving though? Will that affect us? Curious if you could make a video on that. I’d watch that too. Love your videos!

Agitprop Psyop 6 ヶ月前

I almost didn’t watch this one but then I remembered that it’s impossible for veritasium to have bad content

bsrcat1 7 ヶ月前

I used to do this with knives when I was a chef back in 1995. My favorite was the 4 lb meat cleaver. Of course I would do this behind my back and catch it with the other hand but I noticed it right off mainly because you concentrate really hard when you're tossing a blade. I would flip a wide tooth pocket comb and it would do the same thing. Leave it to the Soviets think that they figured out something revolutionary 🤣.

Steve C 年前

I've been doing this with ball peen hammers for 30 years. When you flip the handle around the side profile of the head (like the tennis racket) it changes direction.

Aviatordude 年前

I thought the reason the Russians kept this a secret was going to be so their female gymnasts would always win gold!

Kim Vang – Video Marketer – Bangkok, Thailand 年前

Hah! Underrated comment

Narrator 年前

Agreed

Icerecruit 年前

I mean their olympic athletes were at an advantage anyways for other reasons

Aozzya 15 年前

@Icerecruit What advantage? I don't really keep up with Olympic stuff sorry.

Icerecruit 年前

@Aozzya 15 the Russians aren’t allowed to compete as “Russia” anymore because they used steroids lmao

Jerry 年前

That was a great explanation. when I was a kid I always wondered why flipping a hammer when you caught it was always facing the other way. I once seen a conspiracy theory that was saying the Earth would flip. As man builds large cities we are moving large amounts of rock and steal from spread through out the world to large masses which is changing the balance of the Earth as it spins.

kbf ヶ月前

Asking a mathematician to explain something intuitively be like: “Imagine a massless disc with heavy point masses on it”

G80 GZT 年前

If you're spinning it front-ways, it wants to spin side-spinning-wheel way, but it tilts from one side of front to the other.

Dossip 年前

So going back to Tao’s explanation, what happens if Y axis is not tilted, what if we are able to flip it from a perfect level position?

Forgie Dusker 11 ヶ月前

I think i commented about this one a long while ago, i first noticed the phenomenon while flipping a TV remote just like the tennis racket. Great to get some closure :)

Ismael Abufon 3 年前

Spent all my teenage years playing with the tv remote, flipping it on the air and noticing the flip. I never asked why I couldn't flip it vertically without it turning. The trick for me was to throw it higher, so it would turn 2 times, so I would catch it how I threw it. Similar with phones when they came around. Then, older I became a bartender for a while and while flipping bottles and stuff (flair bartending) I sometimes noticed the same thing as I would try to get the label to face "forward" when the bottle landed on my hand. You just solved a mini life-long question that I had hahahaha.... kudos! (I was getting a bit judgemental when you mentioned proving Feynman wrong -- "this guy is cocky" hahaha... but then you brought Tao into play and it was all good 🤷🏻‍♂️😂 -- and anyways, is still a bit cheating as Feynman didn't have all the 3D bells and whistles we have today)

KHP's physics & mathematics 3 年前

Hmm u r R8 actually feyman thought on this only for 15 second thats not fair.

Joe Brown 3 年前

I noticed this too in my teenage years with the remote. I asked everyone I could think of if they knew why. Parents, science teachers, etc. Nobody could provide an answer.

Dus-DB 3 年前

Also me haha !! - noticed the flip since school days with my ruler and since then always tried with rectangle shaped things

NateStorm12 3 年前

Flipping TV remotes is incredibly entertaining

craigfenson 3 年前

or it could also be that feynman perfectly understood the phenomenon, but since he was asked about an 'intuitive' explanation whilst knowing the difficulty of getting it across in a simple manner, he just said no.

Gokul G 年前

I've always tried flipping my badminton and Tabletennis racket this way and got flustered everytime because i couldn't rotate it along a single axis, Now this video explained everything... My sincere Thanks to the random dude in instagram who introduced this video to me.

Luuki puuk 年前

I always throw my phone in this way and it always flips over. So cool to have an explanation

Enas 年前

the tennis racket axis reminds so much how quantum particles can have different angular momentums.

Santiago Ricoy 年前

Okay but imagine being the author of the paper and getting called out on a paper you wrote 30+ years ago by Veritasium.

MTV Gamer 24 ヶ月前

I love explaining all this every time I throw my racquet in the air for style.

EconomiVision 3 年前

I've never been so educated, filled with a learned horror and then so suddenly and gratefully relieved in a single video. You deserve an award for creating the most educational drama in human history.

Patrick McLeod 3 年前

Well, at least we now know that the Earth has 3 potential axis spin directions........... you know, because it's flat....... Darn, why couldn't God have made the Earth round!!?? Lol 😂

Andy Clark 3 年前

Wont it have infinite axe's of rotation due to it being a ball??? (Not taking the piss or being sarcastic or trying to sound clever)

Smash To Bits 3 年前

@Andy Clark it is sphere-ish. But it is heavier in areas like the gravity image of Mars he showed

decidiousrex 3 年前

Watch his other videos. He has some seriously cool plot twists involving nothing but science

Bob Rolander 3 年前

Isn't this just a special case of the butterfly effect?

Carole SM 年前

Really professionally put together video. Excellent.

birnenaugust birnenaugust 4 ヶ月前

It might be an attempt to explain the two sides of the same coin and how they cross and turn at a single point. Let's start with this zero point, starting point, origin, singularity, aniilization of opposites... the rabbit hole... In space, after a few turns, a screw tends to rotate 180°. Every time you throw a tennis racquet in the air, after one rotation around one axis, it also makes a half rotation around another axis, so you always see the other side of the racquet. If you imagine a coin that is positive on one side and negative on the opposite side, you need to be aware that on the other side you have a mirror image of that side in front of you. So what is positive on the side facing you is negative on the other side. Positive attracts negative and repels positive. Now it happens that positive turns negative in cycles, but does it really turn negative? No... it just rotates the other side towards the viewer's view. So it's just an illusion of polarity reversal, but in reality it's just moving backwards to be seen from the other side. That's how magnetism works. The point of strongest attraction is just inside the magnet at the center of the mass. What does that have to do with religion? Religions are unaware of this scientific fact and demonize science. Good and Evil rotate in cycles because they are an "object" and attract their reflection, causing this rotation in that zero point, which happens to be the ideal symmetry. You can't see it all at once, but we're perfectly capable of understanding it... the observer effect. The equinoxes are the zero point of time when day equals night. Then we can observe the greatest mystery of our reality. It is the time of perfect symmetry (achiral). Summer or winter solstices are the times of highest asymmetry (chiral). Right in the middle of the swastika, where the North Pole is, happens the turning point. This is the illusion of time, but not the reason for our existence. The cause of our existence is the recovery of the Cross, which is perfect symmetry...no opposites. All equal, monopoly, neutral, balance... and the cross meets right in the middle of two sticks with a north pole in the middle. An interesting fact is also the expansion of the universe. It could be due to earth movements. The north pole shift describes an ever-expanding spiral. A fixed north would always show a single point that never grows and never expands.

Steben Elle 年前

Even as an experienced mechanical engineer, I am amazed at what I don't know. Thanks for this,

xwatchid 年前

Thanks for the explanation, the most intuitive part for me is the animation starting around the 9:30, where I am following the wobble of a single smaller pointmass.

Jay G.A 年前

I remember years ago, there was a commercial for I believe it was, the Red Cross and being prepared for any emergency. It had a disaster, where the whole earth turned upsidedown and the family walked out of the house and we're then standing on the roof that was now the floor. It had me seriously thinking they were warning us to prepare for something.

KozmykJ 2 年前

I first observed this phonomenon 54 years ago when I was juggling books, as one does, especially at age 10. I asked again and again over the years what caused it. My parents, teachers, anyone who'd listen, No one ever had a answer. Most had never noticed it happening at all. I'm sure knife throwers must have figured how to predict it even if they didn't know the cause . Well. thanks to Veritasium, if finally got my answer last year, in 2019. 🖖

Kurt Reber 2 年前

I too flipped books and now that you mention it, I HAVE noticed this turn during flip. I just assumed I wasn't balancing the book very well to start.

wondering albatros 2 年前

@Kurt Reber Ditto. I'm high IQ, ADD as f$%k and embarrassed to admit I didn't question a single thing.

Christopher Conner 2 年前

I saw it happen as a child, saw that there was no " explanation " shrugged my shoulders and continued to twist flip things to see it's center of gravity so I could educate my self without books and others telling me their point of view. Lol

KozmykJ 2 年前

@wondering albatros I'm only 95th percentile ... a bit thick really 😜

Glen Apfelstadt 2 年前

Ya know, some read books and others realize physical phenomena as the books fly through the air.

Gary Riley 11 ヶ月前

Nice video! You should consider doing a video dedicated to why we have or think we have magnetic pole shifts on the earth

Man with No name 年前

As a skateboarder who flips things daily, this is very interesting!

William Allen 8 ヶ月前

What about plate tectonics? As the crust is dragged under, and redistributed is there a chance that the maximum moment of inertia of the could be changed by this redistribution?

Peter Marreck 年前

I just realized that bowling balls designed with density-lopsided interiors that change the center of mass (and thus cause really bizarre, but desirable, ball behavior at certain points down the lane) are probably tapping into this effect

CoyoteFeral 8 ヶ月前

Man, these animations are always top notch.

David King 3 年前

I've been flipping tennis rackets for years and never been able to get my head around this effect. Incredible.

FXM 3 年前

I always figured I was just giving it some spin around the long axis unintentionally, because I didn't have enough dexterity to do otherwise. Now I know better.

Nathan Lang 3 年前

I always assumed it had to due with imbalanced rotation compounded by air resistance. Which I guess was half right.

Tim Beaton 3 年前

Was this a Head, tennis racquet by any chance? 😎

Thiago Dias 3 年前

I've also been flipping tennis rackets for years, but never been able to get my head away from its path on its way down... ;(

LArry RIch 3 年前

David King I always thought it was my skill that caused the flip I didn't know it was doing it on its own 😕

Xenkuru 11 ヶ月前

When I saw it I thought: It would be incredibly difficult to spin something perfectly on one axis

Shubhranshu 年前

Totally fascinating. I believe the Oumuamua was also flipping over longitudinally.

Rohan 2 ヶ月前

I have a feeling that when Feynman replied "No" to the question, it was because he considered even this "intuitive" explanation, not that intuitive for most non-physicists/engineers.

Richard Mansur 11 ヶ月前

@Veritasium. This was very enlightening. As an Electrical Engineer, I spend my time understanding the intangible. I’d really love to have a discussion about this topic and the history of Earth and global warming solely focused on the potentials of this science.

Carnifex 4 ヶ月前

Interesting. I guess that's why in skateboarding we call similar trick "Impossible". But of course it's possible cuz with the help of your feet you wrap around the skateboard so you prevent it from flipping.

Hakkapeele 年前

My question after watching this, though, is "How much mass would we need to dump at the poles to make the earth flip 90 degrees?"

Mike Mondano 年前

The questions asked show just how deeply deluded people are who say they understood the video.

awfuldynne 年前

@Mike Mondano Going by the abstract "disk with point masses on it" example, we'd need some parts of the equator to have a different mass than other parts for Earth to be in danger of flipping 180°, right? (e.g. the two quadrants centered at 0°W and 180°E are more massive than the other two centered at 90°E and 90°W) But that's a 180° flip. Hakkapeele asked about a 90° flip which would put the current poles on the new equator and the new poles somewhere on the old equator. edit: posted before finishing the video. The poles would need to have a mass between that of the light equatorial quadrants and the heavy ones to make Earth's rotation about its intermediate axis rather than the one with the greatest moment of inertia. Also, I've been using "mass" where I should be using "moment of inertia".

Mike Beam 年前

no, the question is - how much mass(ice) has to disappear before we flip?

Asag 年前

@Mike Beam Well, if you reduce the ice, water from that ice, would move to equator. Witch, would simply slow down the spinning. But if you would reduce the amount of water on equator, and transfer it to the ice and put it on the poles, than there is a possibility of flip. But even if you melt, or froze water. The mass of the planet is still the same. So its not really possible. You just change where the mass is. But if you could add more Ice/Water on the planet or transfer out of the planet, than you can change its rotation.

Mike Beam 年前

@Asag Let me ask you this, remembering that, as a planet we go through periodic ice ages - which weighs more ice or water? If ice weighs more, then, as the polar ice caps re-freeze, which we can easily assume is true, weight(water) will move from the equatorial regions freezing and condensing at the poles. Correct? Leading to the flip.

Marcos Alonzo 年前

Growing up I’ve always wondered why a hammer did a half twist when thrown up as well as knives

Josh Partridge 年前

Could a tectonic shift, albeit likely through a long period of time but ultimately happening in a moment, alter the mass of the earth enough to change the intermediary vector and cause a total rotation?

Victor Camara 10 ヶ月前

This video actually helped my tremendously in my physics class on angular momentum and torque lol

Wessel Joubert 5 ヶ月前

Is it possible to spin a sphere on all 3 axis at the same time with the same amount of rotation? if so, what would be the path of a single point on the surface of the sphere through space?

Thomas Fraser 年前

Your video brings to mind Golf. Our hands and wrists have three axis as does all golf clubs. When it comes to swinging a club our rotating body is the centrifuge that swings the club on it centripetal path All golf clubs are designed to swing on an intermediate axis as they reaches the bottom of their arc at the ball. So if golfers were to permit all this to happen they all would be much happier. At age 75 I finally learned to simply fold my trail arm and swing my club and wow the difference it made in my game. Cheers

Kody Cook 3 年前

I'm a carpenter and I'm constantly flipping my hammer while I'm not busy. I've wondered for the past 10 years (I became a carpenter in 2010) why is it the head and claws of my hammer flip flop when I flip my hammer head over handle. I thank you for this video!! I suffer from ADD/ADHD and I find myself pondering this very often (driving myself nuts over it). Thanks again for the answers!!!!

alberto Serrano 3 年前

anxious minds made modern world possible

Mellow Guy 3 年前

First thing that occurred to me too. Been a carpenter for many years. Hammers will do that every time you flip them.

Pseudo Gamer 3 年前

Yeah.....I understand ur struggle for all this year's I mean u could have done nothing about it..... If someone from MIT got this idea he would have derived it in few days because of their technology and advancements in maths n physics ..... I've gone through the same thing many times .....it takes time to solve problems .....unless i meet some expert on that topic and gain complete idea .....then i can solve it xd

Carlos Byrd 3 年前

Alexandre BrunetI hope so

SquareRootOf2 3 年前

Compliment Thief Stop thieving.

F M 3 ヶ月前

If SpaceX made a large Mars transport vehicle that looked like a long cylinder with a rotating ring at one end of the vehicle and rocket engines at the other end, would the craft experience The Dzhanibekov Effect while flying to Mars? If yes, would a second ring spinning the opposite way that was nearby to the first ring cancel out the effect?

Jack Harrington 8 ヶ月前

Wow, I've always noticed this and while I wasn't confused with how it happens or why or anything, it just confused me whenever I tossed something in the air and caught it the other way.

Kaldrin 5 ヶ月前

So this is what happens whenever I flip the remote and it does a half spin

random 5 ヶ月前

Yeah 😆

Ray Miller 3 ヶ月前

I didn't understand why it did it every time playing around with a tennis racket waiting for an open court in the seventies. I showed the other guys we were playing with, and they took no interest in it. I tried to spin it later to try to stop the behavior but was unsuccessful. Never thought of it again till 2022 when I saw the video. Well now I can move on with my life.

Robert Stone 年前

Really nice Mechanics 'lecture'! Would Earth's rotation be affected somewhat by continents shifting as a result of plate tectonics?

Machtyn 2 年前

The crazy thing is, skateboarders, specifically, Rodney Mullen, intuitively knew this when he developed the "Impossible" skateboard trick back in the 1980s.

Yoda 2 年前

The best one. Ever.

D L 2 年前

No. They attributed it to air resistance.

Mister M 2 年前

No.

French20cent 2 年前

You also watch Physics girl don't you :)

Machtyn 2 年前

@French20cent On occasion. Actually landed on the Mullen - Physics Girl episode on a Tony Hawk youtube bender.

Julien Cooper 2 ヶ月前

Do you see the optical illusion happening in some of your animated graphics? At about 727 into the video, the disk on y axis suddenly flipped. Instantly. Even as the arrows appeared and lengthened. Then I was able to back to that to try to see it both ways with concentration, not even sure which way it is supposed to be going. I let the video go on and saw that in later parts, where they transitioned but still with them going and transitioning this way or that way. When I first saw this at 727, I thought that was without it transitioning to another rotation or axis with that detail about to be added and explained. But this is the diagrams seen either way. Check it, let me know what you think.

Andrew D Mackay 8 ヶ月前

What about this? Some weeks ago I discovered if you suspend a sphere - or apple - on a string - it will start wobbling and then begin to spin quite fast for as long as it can before the suspension string twists up on itself and causes an opposite torque. I need to find a frictionless coupling which would prevent the string from twisting up and see if the sphere continues to rotate indefinitely. Perpetual motion?!

Zanthum 3 ヶ月前

I love the explanation at the end that the earth won't flip because of the molten (fluid) mantle; question: what about the solid body inside that fluid body ie, the core. Could that solid core within the larger fluid filled body not flip independently of the outer layers?

Paul L 年前

Anyone who held and tossed a TV remote control into the air has probably experienced this before.

Epic Tales 11 ヶ月前

I had seen a video on this subject awhile back and today I heard something about it and it turned on the lightbulb. I searched for a video of this happening and wrote in the comments: "I know why they do this, and it is a lot more simple than it looks!! To figure it out, all you have to do it watch the ending half of this when the handle spins slowly enough that you can play in slow motion and see the moment of change. It is a balance issue from material being removed to add in a set screw location for the handle. That small imbalance is enough to cause the flip every few rotations due to build up of imbalance. The handle part of the T handle doesn't play a role in inducing the "dancing" effect." Then realized it wasn't even a science channel and wanted to put this somewhere that others would read it instead of readers just being awe struck with the video alone and ignoring the how and what is going on.

NLTops 3 年前

Someone should tell the Flat Earthers of the Dzhanibekov Effect. They'll freak out and think that sooner or later their precious disc world will flip and they'll all fall off.

I Am Psychology 3 年前

Not necessarily, but this effect does correctly explain why the stars rotate in the opposite direction in the so-called southern hemisphere.

NLTops 3 年前

@I Am Psychology There's a new update out for your sense of humour, don't forget to download it.

WonderFurret 3 年前

@I Am Psychology Flat Earther Physicist: So you're saying that the direction of spin on these stars depends on where you observe them? This is some serious quantum physics...

Robert Rudd 3 年前

NLTops Hmm? It appears that quite flatly you have to acquire the correct perspective, which revolves around the “Absolute!”

NLTops 3 年前

@Robert Rudd What are you trying to say? I don't follow.

Dan Daniels 3 ヶ月前

I remember when I was 10yrs old I discovered this effect with my own experiments and observations. Conducting fail-safe test that proved to myself that it didn't occur by the influence of my own actions. Fascinated by my unexplained discovery the thought of how the earth's rotation was effecting it I assumed it would flip in the opposite direction depending on which hemisphere you did it in? I still haven't conducted this experiment and was wondering if anyone has? Thanks. Dan from the land down under 🇦🇺

Vladimir Lenkov 年前

@veritasium One very interesting question was not answered - why flips occurs regularly? And what’s the force, that disturbs balance and force to flip object by intermediate axis?

kaleb Gonzales 年前

I was dancing to 80s music a while ago and I have done a few spin moves and then I thought of something philosophically unconventional but, I thought that Rotational Motion was sacred and I was a bit surprised to even think about it. Then I started to think about car engines for some reason after. Now I’m watching this haha.

Fox Salinas 年前

I use this property of rotation in fire dance and never once thought about why it works. So cool!

That Old Bob 10 ヶ月前

I was not aware of this though I have the same ring on my little finger as you have. Regarding the “centrifugal force indicated by arrows” may miss lead some. I always refer to tangent directional arrows as the “ manifestation” of the centrifugal force, as we all know that there are no centrifugal force, only the force which is retaining object in a circular path. I love your shows, very educational though I loose you in math pretty soon. I am very old but this is no excuse. Keep it up, something among the few it worse while to watch.

Kenneth McComb 年前

I noticed this years ago flipping a hammer in the air. Each time the head points a different direction. It's cool to have it explained.

Michael M. 年前

Me too !!!

SW6 年前

And me, used to think it was the way I flipped it.

GrimResolve 年前

Same, but with a pair of scissors (not recommended).

mnf12345 年前

Where and how the force used to turn the object at which point it releases this contact impacts how the force will react. Use less twist and the flipping motion weakens. Applying more and less force at alternative points while flipping corrects this.

William R Buchanan 年前

Think it’s about a wing nut in space,nil gravity.. That wing nut spin in space,comes off the thread spinning with its extra inertia.nothing to stop its spin or guide or draw it off its line of original traverse. Not restrained by the thread it has an inbuilt signal of its initial power supply. Having in air on Earth in first use, now it has a atmosphere of the space station. Resistance to the onboard air. Pressure. It gets a build up of resistance and reverses to balance of air resistance. But can’t overcome the power of the thread spinning to remove. Which was excess to requirement for its removal. It is weightless and obey its kinetic energy until it is used by some means of being attracted. It then turned to what ever mass was attracting it as it slowed. The equipment within the space station. Mass attracts weaker mass, if it has freedom to follow the attraction. Snooker ball hit too hard will bounce back and forward in the pocket jaws on Earth and not go into the pocket the rebound resistance has changed its path of drop . It has to lose it kinetic energy at its intended terminal, the pocket.

Fredrik 4 ヶ月前

Thanks this is super interesting. It brings to mind the recent discoveries of the massive blobs of higher density that's been found inside the earth. Its thought that these have higher density than other parts and if you look at some 3d maps you'll see that they support these rotation theories as the blobs are centered along earths 'mid riff' so could possibly be the factor deciding earths orientation.

LawDog 4 ヶ月前

Like the stability-bar on top of the top rotor of an RC helicopter.

Денис Михайлов 3 ヶ月前

that was intense ! it's been more than a year probably when I watched the video by the first time and I did not understand much. I'm glad that today I understand more. Thank yo so much for what you do. You are awesome !

cole poston 年前

I watched Rodney mullen doing a Ted talk about the physics of the "impossible" skateboard trick and it's basically this principal here it's cool he's so interested in the physics of his hobby/career

Awesome Wolf 年前

I've always wondered why my phone flipped with a half turn when I toss it. Thanks Verit

Paul Halicki 年前

When I took physics in the 1980s this one of the demonstrations. The lecturer did it with a book. Rotate it about an axis parallel to the cover or to the shortest edge of the book and it rotates in a sable fashion. Rotate it about the other axis and it flips around in multiple axes. (In your video as soon as you said it was a new phenomenon I thought BS right away.) EDIT: And there it is at 11:10 although I'm disappointed you didn't show the other axis.

Paulo Manuel Sendim Aires Pereira 年前

Mechanical Engineers found out many years ago that the best approach for dealing with real problems intuitively is to consider inertial forces. Otherwise, you get lost in a massive amount of equations.

Rohit Chachlani 7 ヶ月前

enter flywheel effect

mpederson1316 年前

About 25+ years ago when I was a kid I remember the same kind of twisting with a claw hammer. Hold it by the handle and flip it the head will twist to the other side.

c alex 3 ヶ月前

Makes you wonder if this explains wave/particle duality with light as it relates to Venn’s paradox with the polarized lenses bc it then would explain the missing photons maybe. Also the Adam and Eve story from Chan Thomas saying that the earth has made 90degree shifts (like Hudson Bay being the North Pole for awhile before current orientation). If this is the case then the inner core slowing down may be ominous.

Pranav P 年前

So, can I assume that Earth in its really really early days was spinning about its intermediate axis, and then switched to the axis with maximum moment of inertia?

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