I really want to try a string shooter with variable speed because I think there will be some interesting behaviour at the boundary of instability! Maybe I can modify this one... You can also discuss this video on REDDIT: stvmld.com/7htxvr_f The sponsor is KiwiCo: Get your first month free here: kiwico.com/stevemould

I used to think my cat was real stupid for finding such entertainment in a piece of string, but then here I am, wanting to buy one of these.

Bruce Yeany is a treasure. Also I can't believe that opening clip is real. I've wanted a string thing for a while myself. I had forgotten about it.

Hi Steve, thank you for kind words for my video and suggesting my channel This piece has been one of my favorites for years and also one of the most baffling. A far simpler analogy that I like to use to describe the wave movement is somewhat like a throwing a rock in a pond and seeing the waves move out in all directions at the same speed. Now try throwing a rock in a moving stream and the waves moving down stream will move very quickly and the waves going upstream tend to move very slowly. This suggests that at some point where string speed and the wave speed match there would be no wave moving through it. I have a similar piece that produces slow moving waves through hanging string, ribbons, or chains ( 2 videos on this are on my channel) I can easily vary the speed on these pieces and it's much easier to observe the speed of the wave changing as the speed of the chain changes, also fascinating as to how rigid the chain becomes or string on the opposing side. However I have not been able to match the chain speed and wave speed to get a standing wave where I thought it would have. I suspect that as the speed increases the tension increases enough to keep this from occurring (I'll have to get a faster drill and try it again). Another interesting note, is that the string flies due to lift created by drag as it moves through the air (studies have shown this doesn't work in a vacuum). I used to build these and sell them and we noticed that the old worn string fly better than newly made strings. We found that by rubbing new string with sandpaper, little hairs form on the string surface increasing the drag force, thus allowing for longer loops, my longest loop is about 20 feet of string. I do have some additional thought on the string's strange behavior and hope to share more on it in a future video.

Brilliant. But I’ve got all the way to the sponsor read and not a single String Theory gag. I’m not angry, I’m just disappointed.

I'm beginning to think that you just want as many scientific papers as possible to mention a "Mould effect"

We just saw your video! What a great explanation! ZipString on a drill was so cool. Love seeing others use creative ways to solve a problem🔥🔥🔥

Reminds me of the idea of an active support structure like a space fountain or orbital ring. It's particularly interesting that it has such incredible stiffness.

I have so much respect for this KZfaq channel not only does he do informational informative and great content with science. But he also gives full credit where credit is due and that you don't see very much and I appreciate that in a channel

I feel like a stationary one that would plug into the wall and quietly keep a randomly-rotating string in a corner of you living room like a sculpture would be really cool...

I think you can colour a part of the string so that you can keep track of the string speed compared with the wave speed. Also, I think it would be an interesting wave equation to solve with periodic boundary conditions and setting a moving 0 displacement point where the rollers are.

This is what I love about the KZfaq science community; the rivalries are entirely friendly in the spirit of discovery, everyone supports each other and promotes great content and genuinely wants every other content creator to succeed and build off of each other, causing all of us to go down this rabbit hole of real science from what started as essentially a school demonstration. Bravo everyone involved

Steve 'put it on a drill' Mould.

Being able to vary the roller speed will help explain the wave speed "doppler" effect better. If you could slow it enough and still have a loop, the wave may propagate both ways.

That bit at the end with your kid explaining how his new gadget works was so wholesome :') thanks for sharing your random but intriguing knowledge once again!

It seems to me that we've forgotten to account for the difference between linear displacement and angular displacement when trying to explain the behavior. When you move or rotate the device, you impart a discrete change in velocity to each discrete part of the loop. To simplify things, we will make a few assertions- 1. Our side-to-side movement is at a constant velocity, and our rotation is at a constant rate. 2. Our acceleration is applied in a single discrete unit of time. In other words, the velocity instantly changes from 0 to the final value. 2. The displacement is propagated to all points in the loop quick enough that we will consider it instantaneous. In the case of linear displacement, the same velocity (in both magnitude and direction) is applied along all parts of the loop. As a result the entire loop moves together with the source (i.e. the device). In the case of angular displacement, all points along the loop move through arcs of equal length (since we are still applying the same change in linear speed to each point), but arcs farther away from the source radially will sweep through smaller angles, thus causing the loop to appear to curve. It is also worth noting that there is probably some interesting relationship between the forces that cause the loop the hold its shape, and the torque applied to rotate it about the device. I suspect we could see some interesting phenomenon by tweaking both the rate at which the device "generates" the loop, and the rate at which we rotate it about the device.

The sideways movement vs turning thing does seem quite gyroscope-y; if it was a solid ring of material that you were rotating in front of you, it would behave like the disc of a gyroscope - resisting its axis being turned, but not resisting movement along its axis. The resistance to turning is, I think, the same thing that manifests the effect of the furthest part appearing to move in unison with the nearest part - if it didn't do that, it would require turning the axis of rotation. However, I was wrong about the chain fountain thing, so... pinch of salt and all that.

So instead of attaching the sting shooter to a drill, what if you connected it to a speaker and played different tones? What patterns would the tubes impart in the string?

I absolutely live how you take the time to see if anyone else has done a video on a subject and even go the distance to tell us some of the differences between your videos and the others. The way you present the information is really cool makes it amazingly entertaining, have you ever thought about being a teacher?

When in motion the string is exerting a force (using energy) to leave the loop and the resistance of the string is greater so the loop is maintained in a centrifugal wave a bit like gyroscope but more significantly, like a flywheel. When you move sideways you are maintaining the axis of the flywheel which generates negligible turning force. When you pivot the handle around it’s axis you introduce a new flywheel that opposes the existing flywheel. The time it takes for the pre-existing flywheel to dissipate and catch up with the new flywheel is not instantaneous because the loop is flexible. Since the loop is an affect and the motor is the cause, the affect must fall in line with the direction of the cause and re-establish equilibrium. If the flywheel were fixed like a sold piece of metal, when you pivoted your would experience measurable resistance from the flywheel. The energy of the resistance has to go somewhere and if moved fast enough, tends to want to move upwards... sufficient is the upward force away from the fixed point, that it will overcome gravity. I think you wave theory is correct btw and is affected by the tension of the string in the flywheel. Like a guitar: the tighter the string, the higher frequency the wave and shorter duration of vibration... String theory lol.

Actually, I was taught that this effect and the gyroscope are the same effect, but in the other order. The gyroscope is much easier to onderstand is you first make one from a chain, connected to a hub by a number of strings, a bit like a bicycle wheel. When you try to change the direction of that while it is spinning you see where all the links are trying to go. When you make the system rigid then and integrate over the wheel, you realize that that is where the gyroscope's precession comes from.

7:29 When the string falls off it looks like a lagged out desynced object in a game!

Something about him lying on the ground and watching the wave spin makes me so happy about the love he has for the beauty of the laws of physics.

The behaviour of the waves reminded me of the way the surface of a surf wave smooths out as the wave builds and pitches. Not the same effect, which is simply the surface 'stretching', but eerily reminiscent of the string's behaviour.

im gonna be honest i didnt understand a single thing u said but i watched the whole thing to see u play with the string thing

A string with a checkered pattern might be interesting for visualizing the waves’ speed relative to the string’s.

The top string is being fed through between two wheels, those wheels straighten the string and fire it out at high acceleration, which makes the wave extremely long and hard to see, but it is there.

When you pivot around the handle, the far end of the string has to travel along a much longer arc than the handle does. The string itself isnt rigid so the small force you apply to move the handle a few inches can only move the far end of the string an equal distance in the same amount of time, it takes more time for the far end of the string to complete its arc ater you stop rotating by reacting against your now stationary hand. When you move in a straight line from left to right the near and far ends of the string are travelling the same distance. Not sure if thats actually the reason, but it makes sense intuitively. You can also consider how a slack line would behave if you held it in your hand and rotated. The far end of the line would only be moved by an amount equal to the distance your hand travelled. The more i think about this the more complex it gets. The string is experiencing a centrifugul force thats perpindicular to the rotational force you apply when you rotate the handle, theres gyroscopic procession involved, possibly some sort of mechanical advantage, the role that the speed of the string has on the propogation of waves...

Loved the Doppler effects reference for explaining the wave. The beauty of it gets clear when you realise the string is in a loop and basically the handle is “approaching” and “distancing” at the same time towards and away from the wave and that’s why the wave length is different. What makes it interesting is that the amplitude also changes

When you move side to side you are adding a vector to velocity of the string so the effect propagates at the speed the string is moving. When you rotate you are changing the vector of acceleration of the string which propagates as the new acceleration vector overcomes the inertia of the previous one.

This was really cool. Thank you. I wonder if a heavy rotating belt could support a fairly light gadget on rollers at the top? Maybe you'd need two belts rotating in opposite directions to keep the gadget at the top and twisting might also be an issue.

Very cool of you to give Bruce Yeany the credit he deserves! He has inspired so many, as do you, Steve!

It’s so satisfying to watch Steve getting amazed by a toy, feels like we’re never old enough to stop questioning why stuff happens. Great video!

Have you tried moving the shooter quickly towards/away from you? I was thinking that maybe *lateral* motion is fast but linear motion might be different, which might account for the rotational motion effect (a combination of the two). Additionally, does the time taken to restore the string to the standard location under rotation increase linearly with additional motion? (or alternatively, does the deflection increase linearly with rotation rate) If it's instead superlinear, that would make sense with slower restroation under forward/reverse motion.

I love that you're talking about it as if you're personally interested, and then in the video you're completely tuned out, just looking at your phone. It's like your a hot back stage that has to shake a tree or something, and you're just sitting there shaking randomly, with no real concern or discernment

The stringthing is not even the earliest iteration of this idea. In the late 60's the Museum of Modern Art in NY had an exhibit where they showed a number of robotic, mechanical, and technological artworks, and one of them was giant model of the stringthing that used a 30ft long 1" wide ribbon to do the same thing, with the additional feature that it rotated the whole mechanism on a motorized turntable sending the ribbon loop in a giant circle. The ribbon rose and fell and warped and twisted as it described a giant arc over the crowd. It was mesmerizing. I saw it when I was about 8 years old, and it remains one of my strongest memories.

when I was 10 years old my mother took me to Disney land. The first day she picked one of these string rollers. I played with that thing non-stop for the entire trip. Rolling it all over walls, ceilings, anything I could find. I lost it on that trip and I haved never found a toy more simple and fascinating to play with as a child.

I think your gyroscope analogy actually really explains it well, where there is momentum stored in the string that resists being distributed. It’s response differs because it’s a competently flexible gyroscope. I’d be interested to see what happens if you put it on a mechanism that allows it to pivot freely👀I suspect you’ll see a very similar response to a rigid gyroscope

Love how Drill Steve looks at the camera exactly the way a dog looks at you when it is shitting. Now THAT is a great mystery.

Steve Mould is the best KZfaqr because he ALWAYS gives credit and references and suggestions. Most KZfaqrs never give credit where credit is due. They act like all knowing and all insightful. Not Steve. He says "this guy's video is already in existence within the universe, so go watch this brilliant individual/channel and gives them views, new fans, and a huge connected network of education between people, regions, and counties across the globe.

The difference between the side-to-side steps and the turning really seems to be an agular momentum issue. Something that big moving in a circular path has a lot of angular momentum. Side to side is simply not as much momentum to overcome. Great vid!

I think the second clip from the end is where you'll find your answer, because there you can see two different types of waves transitioning into each other. I think it's going to be more of the same as what you've already mentioned: the difference between one side being in tension and the other side not, vs coordinate change of the equal tension zone.

Those drill demonstrations are great. They have such a 7 yearold trying to make his first video energy. Really improved my day

I’m glad you decided to stay on here and making videos.

Me looking at the title: oh no, mould effect 2.0?

Dang. I had a handheld one of these at least 15 years ago my dad found at an airport. Thing was cool

Bruce Yeany is an excellent human being, glad to see him being recognized.

When hovering the thumbnail I thought that was CGI or effects or something. But wow that makes sense and looks so unreal. Coolest thing I've seen in a good while

Looks like I've been enchanted by Steve's big, blue, anime eyes. Mehdi's words had been deeply planted into my mind and I can't get rid of it.

You should make another video on this topic. About the waves. Explaining wave's group velocity and phase velocity in detail. You can also include slowing down of light in this way. Waiting for that.

The real string theory

I would be interested in seeing a scaled up version that can shoot ball chain to see if there is any differences with the extra mass and the more rigid structure.

Lol, "and here we have a wild mould in his natural habitat, playing with his effects"

The string shooter should be tested in a vacuum conditions to see how much of air pressure with molecules coming from the roller are affecting the path.

You and mehdi both started with an understanding of some but not all the causes of the chain fountain. There was a tiny but significant downwards pressure from the chain on the container which helped the chain rise, and there was also another force effectively trying to keep the loop stable. When the weight of the chain or the flexibility of the chain changes, the relative magnitude of these forces change, and this alters how the forces essentially balance. I think part of the reason the rotation last longer is one of the causes of the chain fountain - you are changing the direction of the string, so it wants to hold the shape of that curve, and changes only slowly. On the other hand, when you shift side to side, there is less of a direction change, so it resolves much faster. I did see a minor wave effect once when you were shifting the shooter back and forth rapidly. You have to shift the string left 1 foot to get a 1 foot shift in the furthest point of the string, but a relatively small turn will move the furthest point even more than that. And given the speed the string is moving, you need to shift quite fast to have an appreciable impact, whereas twisting even 10 degrees has a large impact on the furthest part of the string.

NO WAY! I saw the original video in a random compilation video months ago and the video disappeared on me, and I've been trying to google it since! I immediately wanted to buy it off the creator as well. I'm super happy to hear that he is going to produce them! :D

The string still has inertia. When you move it sideways, you're moving the whole system in translation, and it is very light so it moves quickly. When you rotate it, it has to change the angular position of the string. It has a moment of inertia, and conservation of angular momentum dictates that the whole string needs to transfer its angular momentum to you and the ground via the device you're holding. It doesn't generate much torque immediately when you twist it so it takes time for the dynamics to propagate. I know invoking conservation laws doesn't give much insight of the dynamics of the system, but it lets you understand that it has to evolve more slowly given that it's not a rigid body. Thinking 'out loud' so to speak, the impedance-matching picture isn't a bad analogy. The impedance of the system determines how quickly the wave propagates. For rotation, the wave propagation likely slows down as you go out, because while you're at the center of rotation, an angular change requires a larger displacement as it goes out. When you twist the handle, the system isn't a rigid body. It can't respond with any knowledge of the length of the string (and therefore has no knowledge of the necessary translation at the end)....it just has to propagate outward based on the local tension and velocity until the wave reaches the other end and meets its counterpart.

I'm thinking that this analysis would benefit a lot from slow-motion footage! Also, I love the mesmerizing images from the double spinning demos.

Your drill set up PROVES the 'wave on top" issue VERY clearly. As you move the device back and forth, the wave length on the bottom is very short and is clearly visible, but the wave is there on the top, obviously as you are moving your hand or body back and forth thru space. the issue is, the wave length is just much longer than the top half of the string arch so the end seems to follow you, but it is truly just following its very long (3m+ im guessing) wave.... Just as when you spin this device at a higher speed, it makes that top wave (or coil now) tighter and now visible, but clearly shorter, as always, than the 'tension' or bottom half wave (or coil). I love how you expand then blow my mind every video! great stuff, and umm.. i want a rope thrower too!!

Steve, interesting video as always, thanks! Re the wave not propagating along the top half when moving from side to side, I think you already explained it. When you demonstrated plucking the top half of the string (7:36) the wave seemed to move away from the handle which as you explain is actually the wave which is moving towards the handle only the string is moving faster than the wave so it appears to travel slowly ( the wrong way ) along the string away from the handle. Hopefully that is correct. When moving from side to side the wave which is moving away is whisked away very quickly by the string making it invisible due to its speed, the wave which is moving the other way should emerge upstream of the rollers only again it is not moving fast enough so it travels downstream as before, but immediately meets the rollers all the time so any vibration in the upstream direction is immediately dampened to zero by the rollers themselves. maybe....

As for why the string looks like it doesn't have waves when moving side to side, I think I may have an explanation: When you pluck a string on the top part the one coming to you is slowed enough that it start going away from you. However when you move side to side, the origin of that movement is at the string shooter's rollers. So that wave still exists it just goes down the string fighting against the speed (higher tension at the rollers give it the boost to not go up), meanwhile the part of the wave that goes with the string just goes around so fast you don't see it. I also think you might be wrong about the turning, it's not that you impart a wave on top and bottom at the same time, that still works just like translation. I think it is essentially the gyro effec of the string, and the reason you don't see any procession, is because you're holding onto the string shooter. I think what's happening is that you have the linear momentum of the string coming out of the shooter trying to fight the angular momentum of the entire string, and as you keep adding linear and angular momentum on one end, and rooting yourself to the world so you don't counter-spin eventually the angular/linear momentum from the string shooter wins. Still I wonder if when you turn if the string rolls along its movement axis, would make sense to me as that's yet another way of preserving the original angular momentum.

8:10 And "they" said: *"yOu cAn'T pUsH a StRiNg!"* and here is proof of how wrong they were! :D

I was not prepared for the sheer beauty of attaching it to a drill. Wow

Hi, Steve. One thing to point out is that linear velocity of the string is of the same value both coming from the shooter and towards it. Because otherwise string would either stretch or contact. To me the difference in behavior seems to do with different tension of the string in those areas. The string coming from the shooter is under compression, the string coming towards it is under tension. Same offset in both strings provides waves with different amount of energy. The string under higher tension will move faster to is initial position, the one under lower tension - slower and as a result will fade faster.Waves coming from the shooter as well have higher wave length, are more spread out. This looks like a transverse wave. It's velocity equals to frequency times wave length. Given the same initial offset both areas receive and same absolute medium velocity (linear string velocity differs only in direction), in both areas waves of equal length would be produced. String under tension produces wave of higher frequency (like in a guitar string), thus wave produced in area before the shooter will actually move faster than wave after the shooter, if measured from fixed point on a string. But string in the area before the shooter is moving in the direction opposite to the wave's, slowing it down if measured relative to the shooter itself. A similar example would be to throw rock off the bridge into a flowering river. As point of impact is moving away from thrower, wave propagates "outwards" (the circle grows), and if you would measure speed of the wave at points closest and furthest from thrower the values would be different. The wave at the closest point is carried away by the medium, but propagates towards the thrower. The wave at the furthest point is carried away just the same, but also propagates in the same direction. The difference in behavior to stepping sideways and turning may be explained by difference in impulse's vector it produces. While moving sideways each piece of string as it moves through the shooter receives impulse of the same value and direction, the difference is only in point of origin. While if you turn, the point of origin is the same, values of the impulse is the same, but the direction is not. In a case of sideways offset the tension between two pieces of the string stays almost constant, thus as offset point travels away from the shooter pieces move towards each other only a little. Given that speed with which string departs the shooter is much higher than speed with which shooter is offset, this effect is barely observed. But if two pieces are provided with impulse of different direction, as they move away from the shooter they'll stretch the string between them more and more, pulling string towards mid point. The section between them will grow in length over time and will be observed much easier. At the same time, you can observe as those pieces of string move towards each other. A similar experiment would be to throw rocks from the moving train perpendicular to it's direction of motion. If train moves in straight line, trajectories of the topics will produce parallel lines if observed from the top. But if train is turning, those trajectories will produce lines converging in center point of the road turn. An interesting experiment would be to vary string shooter speed and observe how it affects waves' behavior. Perhaps you could build one.

I think we actually *do* see the wave propagating from the top of the string when you move the shooter laterally. The problem is that the wave originates from the shooter itself so unlike when you pluck the top part of the string, the wave is only propagating AWAY from the shooter and moves far too fast to see. In fact, I think what you're interpreting as the string following the shooter when moved laterally, is actually just the propagation of the wave away from the shooter till it hits the vertical "boundary region". Would be interesting to see slow-mo of the shooter being moved laterally to see if we can verify/disprove this hypothesis.

I think it would be incredibly useful to dye a bit of the string so that we could easily see the direction that the string is moving. It's not easy to tell, and I keep getting confused about what direction it's spinning.

Yus! Glad for the shoutout to Bruce!

String theory resolved. This is quite interesting behaviors of strings that I doubt anyone would have guessed... keep them coming friend :D

I love the faces Steve makes when he's testing stuff like "wtf is going on here"

Wave speed on a string is sqrt(T/mu) and the chain's tension varies with height; so exactly what point in the chain is the chain speed equal to the wave speed? In fact, the tension in a vertically dropped chain (suspended from one end and dropped) is zero if you neglect earth's tidal force. Immediately after the rollers the tension approaches zero -- possibly is negative for some circumstances -- in which case wave speed is zero (or possibly imaginary and dissipative); thus no wave propagates. Applying friction to the top of the loop increases tension after the touch and greatly increases wave speed... the wave is then reflected by the rollers and the reflection is inverted. The string motion is the sum of these two waves.

This reminds me of electricity, quiescent draw, instrument amplification, and signal-driven changes in impedance against a coil. The speed of the string is a "voltage", the energy of the moving mass is kind of like a big battery/capacitor/filtering network, and there's a "quiescent draw" against that constant charging of the system like a bias against a tube passing current, which I think is a result of exterior forces imposed onto the system (friction and gravity). Your impressions onto the string and the movements/axis accelerations of the shooter/spinner would be changes in the control grid voltage of either a triode or pentode, and the behaviour of the string demonstrates changes in impedance. The simpler demonstration is in just touching the top or bottom of the string as it moves along. This is most like a triode, in my opinion. I like to see this like resolving the signal path and draw characteristics on a circuit. When tapping from the edge of spinner's top, you can see the effect/signal amplify at the "peak impedance point" for a moment. If you keep your finger in place, you've create a new bias/impedance point; and if you waggle it, we can see an amplified waveform. Plus, we can see the draw can be seen/felt at the returning edge at the bottom of the spinner. When tapping it from the bottom, I think this is what might me a "cathode follower" in tube circuits. I think the bottom taps and friction slows the string down, and drags the whole system down (increasing the system's impedance), like adding a resistor to restrict cathode flow, affecting the global bias point. Not to get super nerdy about it, but this "cathode follower" design is a common low-impedance drive circuit in tube amps, and is known for smoother overdrive characteristics. Tapping from the top is maybe like a later Fender design (AA864 circuits) which sound a little harsher and blockier, exaggerated even when overdriven. When you tap the outside edge (where impedance is greatest), it's more like a microphone, or, your finger effectively turns into a resistor/capacitor, eating some voltage/speed, feeling current/heat on your finger, and ability to sense other waves travelling through the system in the form of reductions and increases in voltage/speed and friction/current/heat. The less obvious/probably incorrect effect I'm seeing here is in the side-to-side motion. I feel this looks like pentode behaviour, where the voltage is held more constant (we're not messing with the spinner's Y-axis), and we're applying a considerable X-axis. Watching it be resolved, I want to say there's a smaller drop in speed/voltage/Y-axis energy for a considerably larger distance travelled across the X-axis, and the system resolves the energy on the X-axis as if it were "capacitively" more efficient as a result of your arm become a part of the impedance network. Which is a mixed blessing. Smaller forces might not require any extra input from your arm to control the system gently. Just as well, too strong a swing would overwhelm beyond reasonable correction, and your string turns into a whip (this is when vacuum tubes arc). Also, when you're rotating the string-spitter with a drill on your back, I think this is maybe a "visual" of a parasitic oscillation. With guitar amplifiers especially, it's sometimes possible to produce a high-pitch parasitic ring with too much high frequency bypass. It's also possible to produce oscillating hums with over-filtered or poorly arranged power filtering schemes (usually an inaudible low 4-Hz up and down drift that shows up on the speaker output).

I'd not seen these fancy electric ones before. As a kid I had a much simpler toy: a pipe you put in your mouth went to a short chamber with small holes top and bottom. A loop of woolen yarn was fed through the chamber. When you blew into the pipe it caused the yarn to loop around. I remember being fascinated by the patterns in the loop.

My first reaction when I saw this was "oh no, it's another Mould effect".

It looks like the speed/tension work as a parameter in a low pass filter. Reminds me of guitar strings... or rubber bands - if you don't put too much tension the amplitude of vibration is high and the frequency is lower. I also think that the velocity makes that string "tenser" in one axis.

I'll be honest, your videos are a treasure and delightful to watch.

I ordered a Zipstring in the US on November 21, 2021 and it FINALLY arrived today! It is lots of fun.

I have questions. Have you tried to rotate the strinthing, so that up goes down ? Could you manage to build this into a device, with a very, very long string? What would happen to the wave?

Just gonna keep milkin that chain fountain, eh Mr. Mould Effect?

He actually did it! I took a university course with one of the inventors. I sat near the front off the room and heard him discuss some ideas he had for the string shooter with our professor after class. I am very impressed with what he has managed to accomplish

Steve , you asked why the string doesn't have a wave on the top, but I think you did provide an explanation for this: the wave is propogating out from the handle both top and bottom. On the bottom the wave speed is faster than the string speed, so it propogates slowly. At the top, the wave speed is combined with the string speed, so the string motion elongates the waves -- so long that you cannot visibly perceive them. However, you actually can see the super long wave if you step back and think about the horizontal movement as the entire wave.

When you attached it to thd drill, the helix shape was pretty interesting. The frequency in the z direction of the outside string is far less than the frequency of the inner string.

You already have a Mould Effect named after you. Once you figure this one out, you can't have another Mould Effect. Unless, this is an extension of the same physics, which would be interesting.

I definitely saw the wave in the top string mentioned around 11:40. The key is that the wavelength is far longer than the string, so all you can see is a small part of the waveform at any given instant. If you pause the video during the side to side perturbation, you can clearly see the curvature of the string that is indicative of a wave. If you could capture the discrete coordinates of the string along the top of the curvature, you could do a discrete Fourier transform on it and that would give you the frequency of the Doppler shifted hand movement. After accounting for the Doppler shift, the frequency of your hand movement would be the primary frequency remaining.

Bro I've been following him since like 50 followers, this was by far the invention I've been most excited about and now your doing a video about it, thats crazy.

Some of this would be easier to communicate if, instead of saying the top and bottom string, you called them the departing and returning parts of the string. A dark mark on the string would also make the movement of the string more clear

I had one of those toys as a kid. It had flashing lights and played music too! I loved it until my friend "borrowed" it and I never saw it again sadge 😔

I thought that maybe the waves dont travel along the top part of the string, because the waves starting point depends on the change in position of the two rolling pieces. When you move your hand in one direction the lower part of the string moves with you in that direction and since the string moves away from you, the position of that moved Part of the string keeps moving forward. On the other hand the string on top moves towards you and so the part that is right in front of the rolling pieces will be pulled in and its change in its physical position will come out of the lower part. When you move in one direction the part of the string that is the furthest away will „feel“ that motion after all the positions before notice it. As you move your hand, the gadget pushes the the new position and you see the wave you created with your hand. Great video as always!

Instantly pre-ordered one. I have ideas for this already. I need a strobe light too. And some glow in the dark string would be cool.

Im just curious if a cat can play with it. Can you imagine the hours of bonding you would have with your cat over string? Top comment has a point lol

I think you made an incorrect assumption that the tension in the top of the string is lower. The device is NOT the only source of tension here! The tension along the length of the string travels at high speed (maybe a hundred miles an hour or something), the weight (and momentum) of the string itself creates tension. The bottom is actually at LOWER tension. And that's why you can see the waves. The waves at the top go too FAST, and are likely being damped out by the air and the string itself, as well as being carried along with the motion, at the bottom they are somewhat under-damped, and move much more slowly. The rotation effect is basically gyroscopic-but there's no strong bearing. If you look at the string entering the device, it lags, and it leaves leading. That's the device creating the precession. Note that the loop is angled to the vertical, that's the wobbly string version of precession.

An old physics teacher of mine would frequently say "it's all a matter of inertia" each element of mass in the string/chain is still exhibiting the momentum of the previous condition and will have a delay on taking the new momentum condition. Each element gets impulse from the adjacent elements. (In a chain, these elements are more clearly discrete)

Fascinating! The trajectory of the rotating string shooter looks similar to that of some strange attractors - particularly the Sprott attractor which has a central rather tight spiral and returns via wider loops around the outside. Coincidence???

I've never seen a youtube video say uploaded 20 seconds ago, cool

I saw this item on a french channel. The man spoke about chain fountain as well. But he didn't mention the "Steve Mould effect". Which was disappointing.

You are such a gentleman. I honestly watch your videos and try to incorporate your frank/open approach into my classroom.

The reason for no seeming propogation on the top string with the side to side motions is the fact that a wave it does propogate but the rapid movement of the string shooting away makes any action applied to it relatively subtle and weak. You would need to shake it from side to side more forcefully which would perhaps be difficult if it tangles or dislodges in that event. But the reason tapping it with your finger works is that if you think of the string zooming past your finger as your touching it, you're essentially putting a force on a greater surface area and creating a larger impact to generate a wave.

Jes🙌, I've massaged you on Instagram about this and i already know it's gonna be such a cool video

I NEED ONE!!!! I have a transcendental experience planned and this thing is an essential piece of entertainment.

2:43 You can see the wave in the top string, because of the angle of the spring to the camera compressing the appearent wavelength, it stands out.

Just found your channel Steve and it is awesome. Just pure information and explanation from a kind humble guy, even shouting out other yt channels. Pleased keep up this good stuff.