Does a Falling Slinky Defy Gravity?

[@AnnaCurser]

suddenly i feel that the loony toons were on point

[@elifdurmus8243]

EXACTLY what I was thinking. Remember when characters would glance into the camera to realise they were suspended mid-air, and only fall down afterwards?

[@nikilragav]

It's basically the opposite of looney tunes

[@OfficialGOD]

@@nikilragav no

[@sillierthangooberous]

@@elifdurmus8243 they where at the bottom of the slinky

[@luvpranay]

Best comment ever

[@invertedgames7993]

Don't worry, this physics glitch will be patched out in the next version of the universe.

[@SuperRockstar99999]

they already patched it on their other Universe.

[@Mandragara]

Sourav Das It sucks that we have the beta version, so many bugs. Just look at black holes, how was that not fixed in the alpha?!?!?

[@WholyMcLag]

XD this is not a video game

[@invertedgames7993]

Wholy McLag that's exactly what an NPC would think.

[@SuperRockstar99999]

There are some tests going on in our Test Universe(which uses the same engine as our universe), We haven't yet heard anything from the owner or admin of our universe yet. But the owners of other universe(different engine) have already fixed it. Hope we will hear something soon.

[@bradbradford8576]

Did he really just not mention that the slinky has stored energy from a spring function that matches gravity exactly? When the slinky is stretched out and the top is held, the bottom is being pulled up with a force equal to the gravity pulling it down. That's why it only stretches out so far. When the top is released, the bottom is still being pulled upward by the spring function until the slinky's stored energy is gone.

[@mightycahjo4906]

understandable, thanks

[@sheikhimtiaz5921]

Exactly!! I'm thinking why didn’t they mention this.

[@nickonashfermilan6673]

That explanation is better. The video, it is just so satisfying to see how a mass is seemingly defying gravity. Could have been much better if they suspended a ball at the bottom of the slinky.

[@ENetArch]

Hush .. stop spoiling the rumors and alternative facts w real facts 🤣🤣🤣

[@syafieqrazak8870]

thabks man

[@IgorRyltsev]

Looks to me like a spring force is trying to pull it together. However, the gravity wouldn't let it go back up. Instead the upper part of it is accelerating faster down and the bottom part remains constant and creates an illusion of defining gravity. Cool effect. 😎

[@dougmaitelli]

I came in the comments looking to say the same thing 😁 Thanks for doing a great job on the explanation.

[@BoundlessDrop]

I was thinking this too, but I didn’t have the words to describe it. Thanks!!

[@randomcontrol]

And the bottom stands still, because everything was pulled apart with exactly the force of gravity. Doesn’t he understand or is he just that bad at describing physics in an understandable way?

[@crude75]

yup, I was thinking the same thing

[@Templestone]

Right!

[@Tannestokkie]

My explanation: There is tension in the slinky - The top pulls the bottom up and the bottom pulls the top down. When the slinky is released, gravity has a downward force on both the top and the bottom, but the tension has an upward force on the bottom equal to gravitational pull, keeping it at rest. The opposite happens with the top - The force pulling it down is double gravitational force. At least this is my hypothesis - If someone can possibly determine the acceleration of the top part, it would prove/disprove this.

[@timl2k11]

That is what the computer animation is showing. The center of gravity is falling as you would expect, thus the slinky must be doing exactly as you describe. Nothing else is possible.

[@Skirk84]

This is how i would explain it also, and the reason the bottom of the slinky doesn't spring up towards the top, is because it's pull is equal to the gravity due to the slinky already being stretched out and the weight and spring already fighting against gravity to its maximum ability, therefore its static position remains true until the fighting force against gravity is released by the spring tension already being consumed in the fall.

[@joshuacantin514]

This is also how I would view this. Not that this is contradictory to the notion of information propagation, just a different perspective. Also, if one would look at the slinky in the accelerating frame, the slinky would just appear to be contracting from both ends, cf. the equivalence principle.

[@yatogami7393]

@@joshuacantin514 exactly the slinky carries a mass and exerts tension in the upward j direction , infact my professor did an experiment and made fbds that easily describe what's happening

[@Nudnik1]

My idea as well.

[@veritasium]

Thanks Mike, I'll put a link in the description.

[@baraskparas9559]

Hey Derek, see if you like my brief answer to the gravity defying slinky.

[@elmooth0]

@@baraskparas9559 You do realize this video is 8 years old right?

[@baraskparas9559]

@@elmooth0 Oh well. If Derek can mix Mike and Rory up I can be a late wierdo.

[@elmooth0]

@@baraskparas9559 LOL

[@HamedAdefuwa]

@@elmooth0 in our recommended now though lol KZbin algorithm is fudged

[@SgtLion]

So.. a slinky of infinite length.. could hover?

[@Mandragara]

SgtLion It would never start to fall at the top, as the gravitational field is 0 at infinity :P

[@FuzedBox]

***** Nope. The inherent tension will draw both ends together rapidly... forever.

[@Mandragara]

FuzedBox No it wouldn't, the slinky is too long for that information to propagate down even an infinitesimal fraction of it's length.

[@IssaMe]

I guess it would basically be like a train on trains, in a way. Dam I've always sucked at explaining things...

[@FuzedBox]

***** Ah. Good point, so my theory would probably be correct with the inverse; somewhere in the "middle" will snap from the tension and both parts will spring outward from each other... forever.

[@mikeegan]

Interesting demo but it is not because the information has not flowed to the bottom of the spring, that happens almost as soon as the spring is released. The bottom of the spring is moving up towards its centre of mass as it’s centre of mass is falling under gravity minus the residual tension of the upper part of the spring. I did these calculations while studying springs in engineering. It was flight of fancy stuff as we were looking at the action of large valve springs where effectively you can discount gravity but it is still an element in the formula. The same is true for a solid bar which stretches when suspended vertically and then contracts on release.

[@doomender3858]

Jeez

[@Salatiels]

I’ve never studied it deeply, but that’s exactly what my common sense says .

[@lachiemunro7]

Yeah the guy with glasses is so loopy

[@rushikeshbhor6069]

Yes this is correct. The guy in the video couldn’t even explain elementary physics where the spring force or tension is still balancing the bottommost element or part of the slinky.

[@ashleytaylor994]

Gravity causes the oceans to stick to the globe but a helium balloon floats up? Makes no sense

[@jennp94]

This is way more productive than studying for my physics final

[@oskarehrhardt7651]

How did it go?

[@royalmastergaming6065]

Yea mate, you got a job?

[@noobgamer-rel]

@@royalmastergaming6065 we will never know (until he answer)

[@GurrenPrime]

It's like reverse Loony Toons. There, their heads would always be the last part to fall down, and here it's the bottom that's the last part to fall down.

[@carsons.1757]

Hey... You're right!

[@cjsmith411yt]

OK, with only under grad knowledge of physics (core curriculum at that) I'm thinking this has more to do with gravity and spring torsion than "signaling." Basically, when you're holding the spring, gravity is pulling down on it, stretching it out as your hand is pulling up on it's top end. When you release the top, gravity and the reclamation of the torsion are in equilibrium until the spring fully compresses. The small amount of slacking toward the end is from imperfections in the experiment (including the inevitable loss of torsion every time a spring is flexed).

[@Shazzington]

I love this physicist. "This looks to me much more realistic." "Well, it is. That's why I did it." And then "A lot of people on the internet get uncomfortable with the term information" You can almost feel the urge to say "A lot of people on the internet are stupid."

[@veritasium]

Do you have a link for us? The computer simulation was not numerically solving the problem, it was just a way of visualising what was happening. Check out the link to the paper in the description to see the details.

[@candowe4926]

Hello from after 10 years

[@Adrianlesj]

​@@candowe4926hello from an extra 10 months

[@SMBBBBxx]

At 0:40 I thought Sherlock's theme song was going to play.

[@aMilling]

Haha same

[@a_r_m_a_a_n588]

Lmao me too

[@SIMKINETICS]

Note that these demonstrations start with the Slinky held stationary, so it is as a coil spring extended by gravity toward the bottom. In this mode, the spring starts in tension that's equal to the pull of gravity throughout the spring. When the Slinky is released, that tension is applied against the center of mass that falls only slightly slower than the collapsing top while maintaining equilibrium against gravity toward and at the bottom. The Slinky's contraction starts and is maintained from the top which is freed and collapsing under tension also against the center of mass (below it) while also falling with the force of gravity, accelerating at a rate near 2 G's. The resulting standing wave cannot propagate faster than the falling center of mass while the length of the released Slinky contracts when its bottom is maintained in equilibrium between gravity & contraction. A much stiffer and/or shorter spring wouldn't likely behave this way because the natural frequency of the spring would be too high for the C.G. to catch it in its descent. Rotation of the bottom coils results from the way all contracting extension springs are made in which a twist of the wire (around the *wire's* axis) is accompanied by helically coiling the spring so that it maintains a fully compressed form until extending forces are applied; the wire-twist stores and releases spring energy, twirling the coil around its helical axis in a screw-like manner and increasing the coil diameter slightly as it contracts in length.

[@jeevanix]

Bottom end also falling, but it's being dragged upward at the same speed of it's fall. Because , bottom is in equilibrium of gravity and spring's tension. Until both forces are nuetralized, the bottom portion doesn't move. More gravity more streching . If you want to see bottom's movement, drag the bottom end with hand and release both ends at the same time. If tension force is more , it moves upwards . and if gravity force is more than tension, it moves downward. Such as add wheight to bottom.

[@sasyuke5583]

In International physics olympiad 2019, we had to solve problem related with that effect

[@spacetime314]

So, the answer is?

[@MartinPradoGuerra]

@@spacetime314 You haven't even seen the question he was asked to solve. He said they gave him a related problem.

[@EdySmi]

The bottom bit not moving is straight up badass

[@HivonoviH_Jiji]

I feel the way he says it is misleading. The slinky doesnt wait for the info, it does wait any info at all... It simply reacts to forces. The centre of gravity of the slinky fall at 1g (like all object)(abstraction of air resistance) Because a slinky ''pulls'' to go back to initial state : - The bottom pulls the top 1g towards the ground + gravity (1g+1g = 2g) - The top pulls the bottom 1g toward the sky - gravity (1g-1g = 0g) Ok a bit more complicated i guess, but still, the math will add up.

[@cupido4amor]

When the slinky is held from the height it has tension on both the ends. On the top there is more tension than at the bottom end which is gravitational pull. When it is released, the top end cancels out the tension faster also acceralated by gravitational pull and the bottom is already at a neutral level. So the top end goes down first followed by the bottom.

[@hassanahmed8381]

Bla bla bla nobody cares bitch

[@shworn4487]

You need to think of this from an inertial frame. When we stand still on earth, we are not in an inertial frame (the earth is spinning, and revlolvinv around the sun, the sun revolves around the centre of the Milky Way, the Milky Way the great attractor). If gravity is pulling objects down, then that would mean it also has to push them in the direction the earth is spinning (so, not just pull down, but pushed from the left and right, too), aswell as push them to stay on the path of the earths orbit, and the path of the suns orbit around the centre of the Milky Way, etc. Gravity just isn’t what you think it is. Think about it, g is a measure of acceleration. Acceleration is a force, hence, gravity is just what happens when acceleration encounters other factors. Gravity is not a force, in itself What you are saying / believe, is that someone standing on earth is more “stationary” then an object floating in space (an inertial frame). When we measure from an inertial frame, we find gravity is the result of matter bending space time. The path an object falls to the earth on, can be seen as a straight line through space time that is being bent by the mass of the earth. An object floating in space is also following a straight line through space time, except it is not being bent by the earths mass. “Falling” is just travelling through space time in a straight line, or more simply, a person floating in space would not move at all in relation to a person that’s falling on earth, as both are in inertial frames. In other words, falling objects are not falling, they are staying in the same point in space, the earth is moving and rotating into them. And no, you don’t fall off if you’re on the other side of earth, and earth doesn’t need to travel in all directions at once neither, because of how mass bends spacetime (you’d need to be able to comprehend 4 dimensional space to picture it) And once the falling person reaches the earths surface, they must accelerate themselves upwards (away from the surface) by the same value that earths mass bends or deviates space time by (which is 1g), in order to stay in the present (which in space time, the present on earth is accelerating through space, not stationary). This is the mysterious “force” we experience we’ve called gravity, it’s more just a very complex process that can be expressed in simple and comprehendable terms (like the formula for gravity). The traditional view of gravity is just much more conventional and useful because we are in fact in the reference frame of earth.

[@shworn4487]

So, what you just said can only be observed on earth. If somebody on Pluto measured these forces your describing, they would get different answers, ones that are framed around Pluto’s speed, rotation, and Mass. If you measured the gravity of Pluto on Pluto, you would disagree with what people on earth say Pluto’s gravity is. However, an inertial frame (floating in space and not accelerating, or “falling” on earth) would get an answer that both Pluto and earth can agree on. This is the basis of special relativity, which states we should always measure and calculate based on inertial frames.

[@ASMRJapan]

Great to have met you in San Fran!

[@skuldug1250]

@Wisp Here's a peaceful little comment to your 2 year old comment that nobody cared to reply to

[@wh0isgeorgee270]

@@skuldug1250 here's a peaceful little comment to your 5 months old comment that nobody cared to reply to

[@bldjln3158]

@@wh0isgeorgee270 Here's a peaceful little comment to your 3 month old comment that nobody cared to reply to

[@Space_and_history]

Here’s a peaceful little comment on your 4 years old comment that no one cares

[@maxwellsequation4887]

@@Space_and_history here's a peaceful little reply to your 22 hour old comment that noone cared to comment on

[@imrustyokay]

Wow, I suddenly had a flashback to when I saw this in my recommended when I was 12....man

[@sathvikreddy4807]

Did you watch it back then?

[@electricradcliffe82]

Your... OLD

[@ethanrab4262]

Amazing, the very first anti-gravity device, and it costs 1$ for 2 at the dollar store...

[@ayushdeshmukh284]

Every object in existence does this

[@nickaddison385]

Ayush deshmukh humans

[@gregoryegan8624]

I'm not a physicist but isn't the reason for the bottom staying still due to the spring tension of the slinky and the gravity acting upon it such that when released, the spring tries to compress back to original shape but since there's gravity force plus the tension on top it speeds up the top while the bottom seems to stand still since it's already at a state where the tension equals to the force of gravity so it keeps that same position until the top reaches the bottom. Hope you can understand what I mean by that. Just my though on this. 👍

[@juld55]

Footage at the beginning was used in an episode of QI: Series J Episode 16.

[@Xaasrevile]

the top part of the slinky has more stored energy so when you let go the top part accelerates faster and pulls on the bottom half which keeps that half in place

[@MyBallzGotShocked]

Hey now, lets not make things easy to understand. Lets just call any force is a signal.

[@DreamGaming12]

No. All objects accelerate at at 9.81m/s unless they have a large surface area to mass ratio which the slinky does not

[@bregottmannen2706]

All y'all niggas be droppin straight doodoo

[@shworn4487]

You need to think of this from an inertial frame. When we stand still on earth, we are not in an inertial frame (the earth is spinning, and revlolvinv around the sun, the sun revolves around the centre of the Milky Way, the Milky Way the great attractor). If gravity is pulling objects down, then that would mean it also has to push them in the direction the earth is spinning (so, not just pull down, but pushed from the left and right, too), aswell as push them to stay on the path of the earths orbit, and the path of the suns orbit around the centre of the Milky Way, etc. Gravity just isn’t what you think it is. Think about it, g is a measure of acceleration. Acceleration is a force, hence, gravity is just what happens when acceleration encounters other factors. Gravity is not a force, in itself What you are saying / believe, is that someone standing on earth is more “stationary” then an object floating in space (an inertial frame). When we measure from an inertial frame, we find gravity is the result of matter bending space time. The path an object falls to the earth on, can be seen as a straight line through space time that is being bent by the mass of the earth. An object floating in space is also following a straight line through space time, except it is not being bent by the earths mass. “Falling” is just travelling through space time in a straight line, or more simply, a person floating in space would not move at all in relation to a person that’s falling on earth, as both are in inertial frames. In other words, falling objects are not falling, they are staying in the same point in space, the earth is moving and rotating into them. And no, you don’t fall off if you’re on the other side of earth, and earth doesn’t need to travel in all directions at once neither, because of how mass bends spacetime (you’d need to be able to comprehend 4 dimensional space to picture it) And once the falling person reaches the earths surface, they must accelerate themselves upwards (away from the surface) by the same value that earths mass bends or deviates space time by (which is 1g), in order to stay in the present (which in space time, the present on earth is accelerating through space, not stationary). This is the mysterious “force” we experience we’ve called gravity, it’s more just a very complex process that can be expressed in simple and comprehendable terms (like the formula for gravity). The traditional view of gravity is just much more conventional and useful because we are in fact in the reference frame of earth.

[@shworn4487]

@@MyBallzGotShocked the “signal” is just the part of the object moving through time (spacetime). Without these “signals” everything would travel instantly, and anything would make up everything. Think about this; the part of the slinky that is “falling” would be observed as perfectly still or not moving by somebody that was floating in space (said person would be in an inertial frame, where spacetime is not bent), to them, it would be the bottom of the slinky and the earth that’s moving to the top of the slinky. So, gravity as most people know it is only possible if we view the surface of earth as an inertial frame. That would mean that everything in earth (and earth) is stationary and that everything else in the universe is moving. Also, gravity pulling down / standard gravity formulas only exists / only work if measured or calculated in reference to earth, where as the measurements from an inertial frame will be the same as the measurements from ANY frame (so, measurements from a point floating in space, or “falling” on earth, will support measurements done from earth or Pluto, or any point in the universe, moving or not. But measurements from earth might suggest Pluto’s measurements are wrong and vice versa) Gravity does not mean the earth is pulling us down. It means that mass bends spacetime by accelerating through it, and said bending equally effects the acceleration, time dialation, etc. of objects that get caught in the bent line of spacetime.

[@madhurzawar9863]

And they say chemistry has exceptions

[@lunaponta594]

0:14 so satisfying the slinky falling on beat

[@oSlig]

I think there is some misconception in the comment section. While it is true that there are spring forces counteracting gravity at each point of the slinky when Derek holds it, this does not fully explain why the lower part completely floats as the upper part collapses. The “information” propagation is the important factor to consider. I would like to elaborate on that a bit. First, let’s see why the spring-force explanation alone does not explain the phenomenon. You understand it correctly that the tension completely negates the gravity leading to the stable equilibrium when Derek holds the slinky at the top. But it does not explain the dynamics after he releases it. In particular, it is not clear why the bottom still experiences the same gravity-negating spring tension while the top collapses. Shouldn’t the spring force gradually decrease as the slinky contracts back leading to the net force pointing downwards? In order to understand it, watch the video again and try to see which parts of the slinky do not move when Derek releases it. You will notice that not only the bottom floats but some segments above it too. You might also see the traveling longitudinal wave that sort of “activates” different parts of the slinky from top to bottom. This wave is what was referred to as “information” in the video. If you have studied solid states physics, you may realize that this is a phonon. Now, what about the rotation at the bottom? The slinky is stretched not just longitudinally but also torsionally (in a transverse direction). It appears that this second wave travels faster than the first one. As the result, the information about torsional stretching reaches the lower parts of the slinky sooner that the info about longitudinal stretching. The wave’s speed depends on several factors but rigidity is one of them. If you repeat the same experiment with a usual spring rather than a slinky, the floating time will decrease significantly. That is why this effect is usually demonstrated on slinkies.

[@shworn4487]

Crazy seeing how contrarian everyone was being. I really enjoyed reading your comment, especially the explanation of the wave. Are you familiar how gravity is just the bending of spacetime that large amounts of mass creates? (Sorry if that is apart of solid states physics) you know how if you graphed the path of a falling object, it will plot a straight time in space time? Well, I view each segment that makes up the wave of information as individual points in space time. Additionally, I found the video very cool to watch when you understand that (if the bottom of the slinky were at the same elevation as the camera) the bottom of the slinky only appears to be motionless because it is is accelerating in equilibrium with the earth and camera. Essentially, if you watch the video upside down and reverse it, the slinky acts exactly how you thought it should have (and that’s because falling objects / top of the slinky isnt falling, they are actually in inertial frames)

[@Taylor4073]

Agreed. The tension at the bottom of the slinky is equal to the force of gravity. Therefore, until the tension from the top of portions of the slinky are less than the force of gravity, the bottom portions appear to be suspended.

[@Timmyotoolify]

The slinky is actually collapsing together but the tension is equal to gravity (because it was set by gravity) so the bottom doesn't move. If you pulled on the bottom more than just gravity the bottom would actually move upwards until both sides meet which visualizes what is actually happening much clearer.

[@AtAGlimpse_UB]

this actually is a simply explanation.. But how is the tension set by gravity?

[@Timmyotoolify]

@@AtAGlimpse_UB It's hangin freely, so the only thing pulling on it is gravity. So the tension is set by gravity and hence equal to gravity.

[@AtAGlimpse_UB]

@@Timmyotoolify ahh got it! thanks!

[@globalcompliancesystem3303]

An interesting second experiment: drop a ball next to and simultaneously with the slinky. The following questions are left as exercise for the reader. Comparing the 'top end' speed to the ball, which would fall faster? Comparing 'center of mass of slinky' and ball, which would fall faster? At what point would the ball (if ever) would the ball pass the end of the slinky?

[@utube6656]

1.slinky would fall faster than ball. 2.both move with same speed. 3.it depends on the position of the center of mass of slinky compare to the ball .

[@matthewbell9119]

@@utube6656 Yes, and even more interesting is that the top end has constant velocity while falling!

[@thorny8013]

The slinky has a Spring constant, so basically when you release it, the energy stored in it by you also converts into kinetic energy, hence adding more speed to the slinky than if there was just Gravitational Potential Energy. So definitely V.slinky > V.ball

[@DANGJOS]

@@thorny8013 The spring force is internal. The center of mass wouldn't fall any faster.

[@MrCmon113]

I think the graphs with the center of mass are somewhat good for the understanding, however the talk of "information" likely isn't. I'd also point out that really any object acts the same when we hold it at the top and then let go. The effect is just not visible.

[@MoronicAcid1]

The speed of the "information" is just the speed of sound in the slinky.

[@hurktang]

Hey veritasium, try this one in slow mo, it could give great effect : You drop the slinky but catch back the top before it reach the bottom at the middle. If I understand correctly, the bottom should fall the same distance starting a split second later and then stop again.

[@petershen1984]

In reverse, if we lift a slinky it will stretch so much before the bottom loop lifts off the ground.

[@alans172]

Sure will!

[@ivanbalog3426]

The question to ask is what kind of a slinky do you need to have in order for the lower end to start going before the full collapse happens?

[@eddy26ish]

Ok so here is what I think. If i am wrong (witch probably) feel free to comment. The reason why the bottom doesn't touch the floor before the top is because the bottom is being pull by the top. Why? because is a spring, even if its coming down still have gravity or force to pull it up. I'm sure there is an equation somewhere for that. Now lets go a little far here, hover-boards, how do they work? or better question how do we think they work? So far the only hover-boards that we had made are with metal, magnetic and cooling system if i'm not mistaking. if the bottom of the spring by doing this action doesn't touch the floor, then is it the bottom hovering the floor? now imagine you can expand this Slinky for miles up, the bottom's not going to touch the floor till the top collapses or comes down right? maybe, here is the solution for hover-boards. Don't ask me to explain the science i'm not that smart.

[@corebore7o7]

You were pretty much on it in the beginning. When you hold one end of the slinky and let the bottom extend down you're seeing Hooke's Law which says the force to extend or compress a spring by some distance is proportional to that distance. The force in the case is the pull of gravity. So once the slinky extends down and stops, the force of gravity and the elasticity of the spring are equal. The top of the slinky has no elastic force pulling up and so it falls and it removes the elastic force from each section of the slinky as it reaches it. The fastest a propagation of force can travel through a medium is the speed of sound and that's why the bottom stays until the force wave reaches it.

[@JamesJohnson-lg1iz]

Or better yet just imagine the whole thing horizontally. It is easier to think of it as a rubber band rather than a slinky because it makes the horizontal action stronger. If you pull the rubber band from both ends and let go of them simultaneously, the band simply contracts toward the relative center, so each end moves inward an equal distance. In the case of the slinky, the distance of the movement of the bottom end toward the relative center naturally counteracts the rate at which gravity pulls the relative center down, so the bottom remains stationary until the contraction is complete, since it is the same amount of time and distance that the center has fallen. I would like to see them drop a contracted slinky at the same time, from the same height as the top end of the expanded one, it would help illustrate the fact that the expanded slinky is not just falling.

[@GBFallenDreamers]

You're correct, and what this video explains is that all things act in this way, it's just that a slinky is what we call elastic, and a metal bar is not. The molecules have almost no where to go before they are fully collapsed once you let go of the bar, so the compression phase is done (for all intents and purposes) immediately, and then it falls just like the slinky would in the simulation.

[@TheGreatFace]

the channel never gets old

[@thorny8013]

I THINK IT'S THIS T= Tension Mg = Force due to gravity/ weight K= Spring Constant X = Increase in length of spring Kx = The spring force The spring is streatched and the increase in length is Spring Constant × Increased Length(x) = [ Kx ] Now the spring has tension at both Ends, Which is equal to [ Kx ], but They act in opposite directions. One acts ⬆️ and one acts ⬇️ BUT, the force on the String is only due to Gravity, so I can say that [ Kx ] = [ mg ] (mass × acceleration) Hence, T = [ mg ] Now The tension Above acts in the direction Below, so the total force Will be T + Mg, but The Forces on the Lower Point of the Spring, T and MG are in opposite directions! T = Mg so they cancel each other out, and hence the net force is 0 on the lower part of the spring, hence no acceleration.

[@rmessenger]

I think the key difference between a slinky and a string in the spring constant. The springyness of a slinky is much larger then that of a string. I can't stress enough, the phenomenon shown here is universal. It occurs in ALL materials. The only difference is speed. It occurs in slinkys, string, and iron bars.

[@kikook222]

So I take it that gravity pulls it down but the equal tension upward keeps parts of it static?

[@beenz07]

Maybe but center of mass is involved.

[@Subparanon]

So when you stretch the slinky out with gravity and then let go, it's already in balance between spring tension to contract, and gravities pull right? Then when you let go of the top end the spring force pulling up equals the gravity force pulling down and that's why the bottom doesn't move?

[@georgiospaul1861]

+Subparanon That's what i think.

[@chillsweety]

+Subparanon The upward spring tension on the bottom is not reduced below g until the wave gets to the last section. It appears that each coil of the spring collapses locally. When the upward tension is reduced below g then that section collapses. That is why the bottom doesn't move downward until the very end, even though the "information" has clearly already propagated (as indicated by the wobble and then the spinning at the bottom of the slinky) before the bottom falls. The compression wave seems to give the sections a "push" and start them falling just before the full collapse of each section. imo

[@ledude114]

It is not a good way to see it (as it is wrong). The spring is in static equilibrium at the beginning (no velocity, mg = kx, where k is the spring constant and x is the ellongation, here the half length of the spring). But, as soon as it starts moving, x gets smaller, thus the spring is not in equilibrium, making your statement wrong as soon as it starts moving. Like gobble gobble said, it's the collapsing of each part of the spring (when F

[@MrCmon113]

+Subparanon Yes, the bottom parts still experience the upwards pull until the molecules right next to them also begin to fall. The same is really true for any object. When hold a hammer by the head and let it go, the head falls first and then the handle, but it's so close in time that we cannot notice it. Springs make the phenomenon visible.

[@aucklandbathroomsrenovatio6809]

That what I think so or better say believe as well?! not sure why the Prof. trying to put into people mind information is behind the time! even when they left slinky from above building first time shows top even take advance of the below that same answer cover that.

[@vincentleone4959]

I'd like to see the simulation for the system more sensitive to air friction.

[@shworn4487]

There is literally no point, other than to overcomplicate things. After figuring out all the calculations for the air friction, they’d be left with the same answer had they not added air molecules in the first place. It would just overcomplicate the results

[@srikrishna7883]

PLEASE POST AN ANOTHER VIDEO ON THIS TOPIC

[@magnetospin]

The center of mass if the first thing I think about. It seems so obvious.

[@SHAJ115]

"Awesome HD Slinky Slow-Mo."

[@timl2k11]

This is nothing new. Any medium (material) has a propagation speed related to its tension and density. It takes a certain amount of time for the information (slinky being released) to propagate to the bottom of the slinky. It takes a certain amount of time for a compression wave of air molecules (sound) to travel through air. The speed of light is telling that space has something analogous to tension and density.

[@gluino]

Can you explain why the information about being released must be transmitted via the spring bulk wave speed (relatively slow, according to slinky's spring constant and mass per unit length) rather than via sound-conduction speed through the material of the slinky (much faster than the former, either thru metal or plastic)?

[@greenarcangel]

yeap... one thin its the propagation of waves on a material (sound on air) (ligth on space) and other the information to gravity.

[@DARKSN0VV]

So in theory, if I strap two slinkies to my feet that reached higher than world trade center and I was hanging a few feet of the ground. I would float for a few seconds before slaming my face to the floor?

[@rumfordc]

lol the torque might break your ankles

[@finlan2190]

This is a complicated scenario, but I do believe you would levitate for a significant amount of time, given the right circumstances. If you apply Newtons laws of motion, where an object stays in the state it's in until affected by another force, it would imply that you would levitate. If you hung yourself close to the ground via slinky with the right amount of tension from the top of the building, you would stabilize your momentum. If you did this from the top of a house, it wouldn't work because the forces aren't equal. But a slinky so long would most likely have more density than you stretched out very high. The slinky would be so big that it wouldn't be as affected by you, because you might have a lesser force in all. Either way, your force on the slinky would be watered down. If the tension force is just weaker than the pull of gravity on you and the slinky itself, it would pull you up and would make you levitate due to the forces canceling out. Once the tension becomes increasingly weaker than the gravitational pull, you will start to drop. It had nothing to do with "signals". That guy is an idiot. Laws of nature are not conscious like we are. Put it this way: Compare dropping a regular slinky vs a permanently stretched out slinky. The fixed slinky is stabilized and has no force. It would immediately begin falling once you let go. If you were hung by it, you would fall with it. Now imagine this: You're hanging from the slinky. The slinky is stabilized. Then imagine the tension strength becomes stronger than the pull of gravity, you would be pulled up until the slinky fully retracts itself. Obviously, with two polar outcomes, there has to be a sweet spot in the middle where you would indeed levitate. It's very possible. It would be really cool to test out.

[@alexissuarez7571]

in? j

[@DianaAbouKhalil]

Alexis Suárez you tube

[@johntaki2704]

You wouldn't hover because you are pulling down on the slinky from the bottom than the top. There would be more force and weight at the bottom than top. I don't know if my theory is correct or not. You may float for a micro second but I'm not really sure.

[@koslanga]

Thanks for all the comments back everyone cleared that one up for me!! :)

[@katyry5095]

I am so glad I went to look at your old videos to find this masterpiece (also nice choice of music)

[@RaveNNNN]

I saw this video featured in an episode of QI

[@EDentzo]

Me too, thats why i came here again :p

[@n0body550]

I was just listening to a podcast episode of no such thing as a fish and they mentioned this channel

[@zaczac343]

Can you have a quantum slinky where the two ends are entangled? :P

[@Vits2001]

No, it would be pull towards the center, and the center would not move

[@NCMcLaren]

what happens with a slinky in space held at different ends and released at the same time? Does it pull toward its centre? And is it at the same speed as 1G on earth?

[@Vits2001]

It would stretch, but not in the same way as in earth as there would be no other forces interacting with it. It would strech, then bounce a little bit till tension reached 0 and stay like that forever

[@nanusha91]

Actually, in channels like these, the ads are what make these videos possible. Personally, I want to keep watching these videos so I have to put up with the ads.

[@BrilloBrock]

Imagine something like this on an enormous scale. Like dropping a slinky from the very edge of our atmosphere. I know there are a lot of factors that would change the outcome, like wind, and different gravity up there than down here, but it would be so cool to see something like that in a perfect atmosphere. Imagine standing under the base of the slinky and seeing it hover above your head before eventually being crushed by a giant falling slinky.

[@Grogumans]

What happens if you drop the bottom first, will the slinky fully extend and the top won't move? Veritasium

[@malcolmgruber4690]

What would happen if you were to hold a slinky up from the middle so that the the slinky is in the shape of a horseshoe, and then drop it?

[@अंशुमानअवस्थी]

Brain.exe stopped working

[@edgarbleikur1929]

A falling slinky is one method to prove gravity doesn't exist.

[@capitaopacoca8454]

?

[@capitaopacoca8454]

Did you really ignore the whole video lol

[@jahnyguitah7999]

@@capitaopacoca8454 he's referring to Einstein's theory of relativity, in that gravity is an illusion. It's impossible to tell the difference if you were inside a box free falling to the Earth vis a vis a box floating in space. Inversely, if you were in the same box, you wouldn't be able to tell the difference between the box being on flat earth vis a vis a box accelerating through space at ~9.8 meters per second per second. The potential energy of the slinky under tension at the bottom is almost the same as the pull of gravity, so from the frame of reference of the bottom of the slinky, it's under the same force as being on flat ground. Just, instead of the slinky being pushed up by the surface, it's being pulled from above.

[@omgIoIwtf]

@@jahnyguitah7999 you would absolutely notice the difference. being inside a box freefalling to earth, the box is creating friction with the air around it, however insignificant. zero gravity happens at the arch of a curve when gravity is concerned, zero gravity does not occur during a straight line free fall.

[@shobaanand8439]

Let's say we make really really long slinky which strech several miles and drop it holding from a helicrafter. Will the bottom stay still until the top reaches the bottom? Why don't we see similar behavior in the case of rope?

[@AdityaPatil-gi7zo]

the term "information" really makes sense.it is such a beautiful way to xplain it

[@xEpicxSpeed]

WHY IS GRAVITY NOT PULLING THE BOTTOM OF THE SLINKY TOAWRDS THE GROUND? D:

[@mohitthapa7064]

the potential energy in the slinky is way more than the force of gravity

[@DawnsInferno]

BECAUSE......... SCIENCE!!!!!!!! D:

[@brucel337]

It is! It's only that the slinky, free falling and its stretched state no longer in tensile equilbrium, contracts at the same time. Meanwhile, the Slinky's center of mass (i.e. it's mid point) is accelerated by g, just as you'd expect (This is also why it appears to suddenly decelerate once compactified when using it's upper end as reference point). Only thing I can't explain on the spot is why tension and gravity seem to counteract themselves so evenly as to make the bottom end appear static, seemingly regardless of the Slinky used. I'm sure it has to do with equilbrium state under tension being a function of g, as is the fall, but I can't quite formalize it. Also, it's not like the Slinky evenly contracts, but rather compactifies top-down, so consider the above just a basic outline of the effects involved...

[@IMSSEvolution]

Because pulling it up ,How actually the slinky bushing up and down when he hod it(Remember when he hold it he is pulling it up ) ,,, but when he drop it the power of pulling up is more than the slinky weight (Weight of un-collapsing slinky parts) so the half bottom of the slinky is puling the slinky upper half but the upper half pulling more more faster and more power than the free object fall 0.9.

[@glayo_]

I think it's because the bottom of the slinky is still in equilibrium with the tension acting opposite to the weight of the slinky, up the slinky

[@v3Potato]

@4:20 that sweat

[@comic4relief]

The addition of the center of mass bit is cool. No matter what the slinky is doing the red dot falls at g. That's neat.

[@duhskills129]

Wow! not only are your arguments entertaining to read, but they also have branching paths! Much like an RPG game. This is quite fun.

[@thecodeec]

the factor that held the ball stationary is that the tension force of the slinkie is strong enough to pull the ball upwards with almost the same force the ball is pulling it downwards (you might have seen it dropped a bit, it didn't stay completely motionless); if you attached an object with greater mass, the tension force wouldn't be enough to hold it stationary, thus it would fall on the ground before the slinki collapsed.

[@MrTwitch217]

Just stumbled across your channel today while bored at work. I have another scenario for you. Press both the x and o and then explain to everyone why the tube will fly in a loop. Got caught doing this in 1993 in my physics class in high school. Actually had to look it up in a book.. Love your channel man. Keep it up.

[@JustWasted3HoursHere]

What's cool to me is that the bottom doesn't just stay put, it does seems to not move _at all_ until the "information" has reached it. Very cool. JW3HH

[@CapSora]

I believe that you both explain it perfectly well, but with different points of view. Both your explanations are valid; you cannot say that his is 'terrible' unless it is untrue or inaccurate.

[@incendiablo]

no, this is a perfectly good way to explain why it takes nonzero time for the information to travel from one end to the other, information is referenced heavily in physics, it is rigorous, and explains why if you push something at one end, the other end takes time to move, also why information about changes in gravity don't happen instantly, they have an upper bound of the speed of light. Information theory is its own science. You just said what the information was.

[@hgnato]

the music in the start combined with the slinky is just...i don't know, it made me stop what i was doing, i even stopped breathing for a moment

[@Infinitesap]

It's due to the forces of contraction. From midpoint of the spring the forces go in both directions (up an down). Gravety accelerates the top towards the middle of the spring (midpoint mowed because it's always is in center of the spring).the spring contracts with the same amount of force. That's why it's position doesn't change, but due to the always moving center it does.

[@lucinos19]

I have not read the comments to see if someone made a similar one but I would say that a good way to visualize that is as a resultant of two motions. One is a free fall of the whole slinky and the other is the stretching of the slinky. So the top is falling faster for a while and the bottom is staying motionless (until the information reach it). In this view it is somehow similar to a wheel. The bottom of the wheel has velocity zero as it touches the ground.

[@leemarshall9946]

Best way to explain it imho; the parts of the slinky that haven't started falling yet, are holding the ones below them up. Once some part of it starts falling, it's still pulling the lower parts up a bit, just less, because it's moving toward them.

[@cookiemornster]

what i think is that before it is dropped, all the points along the slinky are in dynamic equilibrium, even on the top of the slinky. the fundamental difference is that while other points are in dynamic equilibrium between the tension of the spring and the weight, the point at the top of the slinky is in dynamic equilibrium between the force from the person holding it and the weight of the slinky. so when the person releases the slinky, there is no longer an equiibrium at the top

[@luciddeception]

The reason the spring turns is simple (but I need 2 comments). A spring is a cylinder that has had a minutely thin strip of metal removed from it in a very tight spiral. So now there is physical space between the coils in the cylinder that spirals downward drop it from midair and you release an accelerating wave of potential energy from the top of the coil, being transformed into kinetic energy down the spiral.

[@feyetho9524]

This video of him dropping the slinky in slow motion is still in an exhibit at that building today (called Questacon).

[@ironpirites]

This is explained by the physics of helical springs. The force exerted upward by the spring on the bottom of the slinky is greater than the force of gravity on the bottom of the slinky and remains so until the slinky collapses to that point. The slinky is set up so that an equilibrium is reached between its weight and the force of the helical spring. If it were dropped before fully stretching and reaching equilibrium, then the slinky as a whole would fall, top and bottom, before coming together.

[@DaveKings]

It's cool how background music can really add to a speech!

[@gawayne1374]

I love to see how it appears to float for while as the top is falling, but its actually the top thats pulling it up!

[@thecrow242242]

They've apparently come a long way since the early versions, it works as advertised. Thanks for the suggestion, and also for not being a douche!

[@Karansetiya16]

4:45 I think the bottom of the slinky rotates because of the compression of the slinky which increases with the collapse. When the slinky is stretched, its maximum stretch is a vertical 'cable' which turns into a slinky-shape by rotation around its middle. The more it is collapsed, the more it has 'rotated' thus; when the slinky is dropped, it goes from a stretched state to an increasingly collapsed state, this rotation has to necessarily occur.

[@OlivierDeSillegue]

This is really astonishing. Although this is in slow motion, it's astonishing to see that the lower part of the slinky remains in fact in place while the upper is collapsing. I wonder what would happen if the slinky was caught again before it could complete its fall. I imagine that the lower rings would keep their downward motion and that the slinky would bounce back and recoil.

[@NickRoman]

It's interesting how the information about the twisting of the slinky made it to the bottom quicker than the fact that it was falling. I guess you could say that there's more tension in the rigidness of the material in that direction than in the normal bending direction.

[@gunjubrianaugustinelee8782]

Slinky's power is same amount of force as the Earth's gravity. This is amazing.

[@Graymenn]

lol i see what you are doing and it is the exact same thing im thinking... what are the chances?

[@dooge1992]

You can also selectively disable adblock on youtube. Giving you the best of both worlds.

[@AuthorX]

This is exactly what I was going to comment on - I was wondering if the top is accelerating at 2g. That makes some intuitive sense, if the center of mass is falling at g and the bottom is stationary, but I don't always trust my intuition in physics.

[@KunamaElgar]

I love those coloured slinkies from Questacon!!! They're sooo easy to tangle though... I can't count the number of times I've had to untangle an impossible mess my brothers created with them over the years :P

[@alans172]

I did some frame timing on the demo at 3:35 which seems to contradict your statement that "the top is accelerating faster than that" The vertical speed of the top of the slinky appears to be constant, not increasing. That's surprising!

[@CringeHunterJon1]

Dear frustrated youtube user, I understand your pain, as I went through it a few months ago. Then I got Google Chrome and downloaded the extension adblock. I have no ads on youtube or any website, and I highly recommend it to any fellow youtube user. Sincerely, Fellow Agitated KZbinr.

[@PunkFiddler]

Technically, the force of Gravity is working on the slinky from tip to end. Since the slinky is stretched, the tension is strongest at its middle hence pulling both ends toward the middle. The slinky is still falling, per se, but the force at the other end of the slinky farthest the ground is then affected by two forces, namely Gravity and Tension while the other end opposes gravity which results to it looking like it was stationary. Then the point equilibrium adjusts as it loses tension.

[@Eleathiel]

I think it's awesome that this clip of Derek was used in one of my favourite TV shows QI. :)

[@wuopisht]

At first I was puzzled that the bottom of the slinky did not move down until the rest of it collapsed, but it did experience some recoil well before the total collapse. That is because the overall collapse is caused by transversal waves along the wire, which are slower than the recoil caused by longitudinal waves along and inside the wire material. Therefore, the "information" reaches the bottom at the speed of sound on steel, but the collapse only arrives later. Gravity < Transversal < Longit.

[@murfleblurg]

Absolutely. The amount of weight makes no difference to the principle at work. The car is hanging from a series of points lined up in a coil. Every point has the weight of the car below it exactly opposed by upward strain, and that upward strain is not released until the next section up begins to relax. Since the strain is equal to the mass of the car and is only offset by the mass of the spring, that will translate into enormous acceleration of the spring, as you said. But the car will wait.

[@luciddeception]

The bottom does not fall because the wave has not yet reached it, and the matter is in a state of potential energy still. It's the time it takes for the flexible material the coil is made of to slam against itself, transferring the wave of released energy down the coil. It’s this down part that is important, by moving down the coil, the spring is forced in a spiral. Its plain centripetal force at work, the wave travels in circles, slowly kicking the cylinder to spiral.

[@3dgar7eandro]

In my opinion from my Engineering background from a Physics perspective (Specifically form Basics Mechanical principles knowledge) the slinky apparently falls is because the sum of the Forces of gravity and Elastic force pointing down are grater than just the elastic force between the atoms of the slinky pointing upwards. For me is as simple as its appeared ;)

[@seanking4641]

It's so cool how the bottom of the spring stays still until the part of the spring when it actually touches it!

[@theodorei.4278]

Veritasium do more of this particularly. One of the most interesting things in physics

[@cournt1234]

To be exact the tension exerted on the slinky is equal to the force of gravity so it is suspended in mid-air until the information about it being dropped reaches the bottom causing it to fall.

[@ZomBeeNature]

I don't care about the slow motion but it is interesting that the whole thing does not start falling when you release the top, but has to propagate down. Everyone, please watch my tiny nature videos. There is no talking in them. Shhh!

[@laservampire]

So strange hearing Derek's hybrid Australian/American accent in these old videos