Hula research while hooping

should be live right come on YouTube right now. Okay. Hello wonderful people of the internet. Welcome back to another episode of Leos Labs. I'm starting just a hair late. I said I would start at 1:00. It is now 1:15. Um there were some technical difficulties getting today's stream to start. Uh just for the record, um what we're going to be doing is going through this paper you see over here on the left. It's geometrically geometric geometrically modulated contact forces enable hula hoop levitation. Now, let me just very quickly calm down a second and let me explain what's going on here. So, this is a hula hoop paper that was accepted in 2024 and published in 2025. Now, hula hoops, if you're aware, are very simple like toys, you know what I mean? It's just a hoop and it's just your hips and you rotate the hips to keep the hoop up. That's it. That's all it is, right? But turns out that the exact dynamics that allow for the hula hoop to levitate, the thing that keeps the hoop up, have not been known until 2025, you know. And when I read that, I was like, what? You know, like this is one of those papers that when I read it, I genuinely thought to myself, wow, that's interesting. Like it's not only interesting from a like, how do I put this? you know, scientific perspective, but this is one of those things that you could like talk to your grandmother about. You know, you could say, "Hey, grandma, did you know that we as a human race did not understand hula hooping until 2025? You know, until this year, you know, that to me sounds incredible and it's one of those things that I really wanted to look into. " Now, the problem was I came across this paper in the month of August. Now, I don't know if you guys are aware with how like Spanish culture works or whatever, but I currently live in Barcelona and the entire country of Spain just shuts down in August or at least the area in which I live in. So, we didn't have daycare, right? Which means I had to take care of my child. Now, okay, I said that like I have to take care of my child. Like, it's a it's a chore. I mean, look, my child is three and I do genuinely enjoy hanging out with them. The problem was it meant that I didn't have time to get work done, right? So, over the past month, I saw this paper. I had an idea. I said, "Hey, I really want to do a live stream where literally all I do is read a paper on hula hooping while hula hooping. " And I thought to myself, "That's got to be a pretty good stream. I'm pretty excited for that. " Um, took a lot of effort getting the stream to start. Um, because when I started hula hooping a month ago, I literally couldn't keep it up. Like I this there's a bunch of different reasons for that. But like this hula hoop is a child's hoop. Okay. Should I be using an adult hoop? Yes, I should. But I'm not. And I could maybe describe the reasons why I'm not in just a second. But um it means that I had to gate my hips a little bit more than like I'd have to if the hula hoop was slightly bigger, right? So I had to train up. And when I say up, it means that I spent like I don't know something like 30 minutes a day just hula hooping and like watching videos. Then I tried to play games. Like I literally tried to play first person shooter games while hula hooping and um I don't know if you can see my hands right now but that didn't work right. So I bought a track ball because I thought the track ball might be might make it slightly easier. No, it didn't help in any way because I don't know how to use a track ball. So I'm at the stage where like kind of doing anything on my computer is incredibly difficult for me right now. Like incredibly difficult. So reading a paper is something I probably can do, but pretty much anything else is out of the picture entirely. However, um as I've gotten better at hula hooping and as I've been training it up, I I'm actually starting to feel like we could like I could potentially do like entire work days while I'm hula hooping. And to me that sounds really cool cuz like imagine, how do I put this? Like imagine having a workout that you can do like just 24/7. like you can consistently do this workout um while you are um like working, typing, streaming in my case, whatever you want to do, you know? I thought that'd be really neat. Um so I kind of went a little bit overboard. Okay, we have a new camera, right? Um this isn't it's new to you. We technically bought it a few years ago um specifically for stream because I realized that Sony cameras in particular allow for you to kind of send the HDMI signal over to your computer. And so I said, let's just use that for streaming as my webcam. Um, and uh, yeah. So, we have a new camera. The camera is like, I don't know, €600 when I bought it a couple years ago. So, that's expensive. I had to completely rearrange my room. That was an expensive change. I got a new microphone stand, you know, specifically for this. Um, I got a new mouse, a whole bunch of new equipment. Like, if you tally all of the new equipment I'm showing off for this particular stream, it's something like $1,000. um specifically to hula hoop while reading a paper on hula hooping which I know sounds really stupid and it is really stupid um but it just sounded like a good idea and san pag pagodala sorry I can't pronounce the last name um is saying in Twitch chat but why I don't know like but why anything you know like the way I see it is like one core element of the stream is getting as many people as possible

interested in scientific research right and I don't know sometimes you got to do some crazy to get people interested, right? Because like everyone is conditioned to believe that research is this kind of boring, arcane, like very difficult thing to understand. But you know, I don't I genuinely do not believe that. So I thought to myself, let's try to find some gimmicks. And yeah, this is a gimmick to get more people involved with the process of reading and dissecting research, right? And so that's where we are. We're today reading a paper on hula hooping while hula hooping. Um, there's a couple other reasons that like I I'm doing this in particular, which will become clear in like a year or two or something like that. Um, basically what I was looking for was some sort of aerobic exercise I could do while streaming, like something I could just do regularly. I'm not saying that hula hooping is necessarily that thing, but in particular, I wanted to be able to um engage my core basically 24/7 with something that would allow me to enable to keep my allow me to keep my heart rate up at about I don't know between 110 120 beats per minute, which is roughly what I get with hula hooping for a while. So anyway, long story short, lots of good reasons to do hula hooping while like also um uh like doing other things as well. And I just thought, why not just try it? Why not try to read a paper while hula hooping and again this stream is going to suck. Like I'm already sweaty and I've only been streaming for like 5 minutes, right? What's the longest you've been you've done this before? The longest I have hula hooped while also playing a video game. Uh which is like I it's not the same as um like streaming because streaming is obviously more energy. But the longest I have kept the hula hoop up um while also doing some other activity is about an hour and a half. Um, I just while my kid was napping, he slept for an hour and a half one day and I was able to keep it up the entire time. So, I have reason to believe that it is totally possible to do the stream, but I don't know if you can see from the camera, I am very sweaty right now and it's only going to get worse. So, we are going to see how this goes. Um, now as far as this paper is concerned, let's go ahead and start dissecting it, going into it, right? Um, geometrically modulated contact forces enable hula hoop levitation. Again, the really interesting thing here, I think, comes in the abstract even, not even in the introduction, right? They basically say that this is the first paper in the history of the planet, like hula hooping as a thing people have been doing. This is the first paper that actually analyzes and explains how the hula hoop stays up. It is the first time people have talked about what allows a hula hoop to levitate, right? And that is impressive. That's really cool. I mean again 2025 and we're just now figuring that out. That is amazing to me, right? Um the claim that they make is that the reason the other papers on hula hooping, because of course there are why wouldn't there be? Um they claim that the other papers on hula hooping do not necessarily go into um sufficient depth because they constrain themselves to two dimensions, right? And this is the first fully three-dimensional analysis of hula hooping, right? Which is obviously necessary. you've got an XY um plane where we're rotating and a Z plane which is you know the hula hoop rising and falling right so I don't know like it is kind of a bold claim to me that they are saying that there has been no other papers um modeling hula hooping in three dimensions like that seems weird to me um and in fact as we read this paper I don't think they actually do full modeling I think what they do is they do experimental um like how do I put this they do experimental setups like they do like a visualization and then they try to model that mathematically. And so it's not the same as doing like a like finite ele finite element model or something like this. So there's actually some wiggle room here. And as I'm reading this paper, I a little bit selfish here, but I would love to find a way to essentially extend this paper so that we can say that we as a community have done hula hoop research. I just think that's funny. I don't know why, but like imagine you have a whole bunch of like really interesting scientific achievements. I do not, but I imagine you did, right? In that situation, saying that, "Oh, by the way, I did hula hoop research. " I don't know. It's kind of funny and I think it's something that we could get people involved in. You know, like the way I see it is, like I said at the start of stream, um, one of the core goals of this stream is to get as many people as possible involved with as much research as possible, right? Like I want people to dissect, read, engage with research, right? And um hey TS just um and to do that I I'm willing to you know make myself a little bit of a fool maybe a lot of myself a lot a fool in order to make that happen right and so yeah I'm hula hooping while stream while streaming and reading papers and stuff but I think I hope that you know the clickbait will allow some people to get in uh to um I don't know like I'm just hoping to get more people involved with the process of research. That's genuinely the entire point. Also, this stream is going to suck. It is going to suck so much because I'm already super

sweaty and I just I just started like we haven't even started reading the paper. Um TJ says, "People two people of two welcome internet wonderful back Leos Labs episode of another hello. Hey, how are you doing? " So, um I guess we should start reading the paper, but first I'm going to kind of go through it and I want to talk about a couple things. So, number one, this paper um was actually edited by someone at Harvard, but I don't know the affiliation of uh Zing Tongju or Olivia uh Pomerink or these guys. Let me go and see if it says it anywhere. Um I don't know if it does. I think we'd have to dig into where they are. No, it has to be A. Where are they? A and one. Where are the affiliations here? I haven't read a penis paper in such a long time. I don't actually know where you they put the affiliations. Um it doesn't matter too much like the point here is just like you know there are people from prestigious universities who actually looked at this paper and said hey it's worth publishing this thing right like one thing is as we're reading papers and stuff like this I think I need to oh and the acknowledgements all right let me take a look at that well I can look at in just a second what I want to do is take a second and talk a little bit about peer review see when it comes to scientific papers right um we're in this kind of like weird era of science right now where like there's always been the archive. The archive is here. I mean, I can just go ahead and show you. Um, can I show you? Let's see. archive. org. It's kind of a list of all the papers. Well, all the prepins for papers. So, papers that are not yet published, but are intended to be published that are coming out every day, right? I love the archive. It's one of the places I go to very regularly. Um, and honestly, it's like almost an everyday type of thing. Uh, Cat says, "I have I leave YouTube for 3 months and come back to you doing hula hoops. " Well, hey, thanks for coming back to YouTube specifically to watch some random person who's slightly chubby uh do hula hooping while reading a paper. Like that. To me, that sounds like a win in my book. You know what I mean? Okay, so point is the archive is a place where people put a lot of preprints. Now, what is a preprint? A preprint is I mean it is what it says. It is basically a paper before it's printed, right? Before it's actually put into an academic journal, right? So this means that these papers have not undergone peer review. Why am I talking about this? Because obviously the paper that we are talking about has undergone peer review and it is published in um to be honest a slightly a pretty good journal you know pretty like a journal I would trust in general right um the reason I talk about this is because we're in kind of a weird era when it comes to science right now where like there is a lot of people there are who are AI generating like slop. That's what they're doing. They're AI generating slop. You find a lot of this lop on the archive, right? Um Oh. Ah, I dropped the hoop. Okay, one second. I got it. All right, dropped the hoop. Switch sides. Ah, dag nab it. I had it going for a good while there. Like I think I've been hooping for 26 minutes or so. Okay, sorry. Uh what did I join? I love the vibe. Hey, I love it that you're here. So, um yeah, the site's free. org. Um you can see it in the top um left middle. You can see in the top middle of my screen also like I have to realize that like I think you guys see okay what a weird Anyway um I'm reading a paper hula wall hula hooping that's exactly what we're doing. So anyway, when it comes to the archive, right, the reason I'm bringing up all this stuff when it comes to peer review and all this kind of stuff is just because there's a lot of people who don't understand how the academic process works. And we've talked about it a lot on this stream. stream, but it's it it's worth repeating again and again because I mean the fact is like I would argue the majority of people who are watching this stream right now, even though you're watching some guy hula hooping while reading a paper on hula hooping, probably don't read that many papers. Like I I'm just going to come out and say it. I doubt that even most academics read a paper a day, you know, and that's something I used to read like 10 papers a day, you know, during the PhD. Um, by the way, hula hooping this way is much harder than hula hooping the other way for me. I don't know why. Um, maybe this paper will help me understand that. So, um, what I'm trying to say is that um, I think we're in the state where a few years ago we had this thing called the replicability crisis. That is to say, if you find a random paper that has even been published, it's likely that paper cannot be replicated. Like if you follow the steps in the paper like step by step, it is very likely that you actually cannot get the same results, right? Um mark the time every time it drops. You can if you want. Um so my point is the following, right? Um, my point is that um, this paper has been peer- reviewviewed, but remember that peer review isn't like necessarily indicating that this paper is like 100% correct in in every single way, shape, or form, right? All peer review is saying is that other experts have reviewed it and they generally say that it's fine, like the paper seems logically consistent, right? Um, and that's kind of it. Yeah, the Linux

works on my machine type of thing. That that's genuinely what peer review is doing. It's basically saying that look um these guys publish something, right? It works on their machine. We verify that it probably should work on their machine and that's it. That's the entire peer review process for the majority of papers, right? And so we can sit here and squabble about like, you know, what does it mean to be published in this journal and that journal and how impactful the research is. We don't really know how impactful research is until like 10 years down the road, right? When this paper is highly cited by a number of people. The problem is when it comes to hula hoop research, there just aren't that many people doing hula hooping, right? Let me go over to Google Scholar. Um Scholar, let's look up Hoola. Okay. Um look, the most cited paper in Hoola has actually been cited 529 times. But keep in mind, this is not about hula hooping. It's scalable load balancing using programmable data planes, right? Um when we talk about hoola hooping, I think we have to specify hoop up here in the title. Oh, come on. Ah, I lost it again. All right, let's go back. Well, you find a paper from Yeah, 2011 on how to twirl a hula hoop. Um, and there's another one from like 1960. Yeah, I think it's this one. Hula hoop an example of heteroparametric excitation. So, that's the one that I think everyone cites, right? Um, and if you look at that, even being the one that everyone cites, it only has 63 citations, right? So, when it comes down to it, um, this is not a field that's expanding very quickly, right? And because it's there's really no incentive for people like to to go into it. However, I would like to say the following, right? The paper is as rigorous as you can expect a paper to be, right? It is about hula hooping, right? While most papers are talking about like, oh, I don't know like the intermolecular dynamics of zinc molecules uh in some sort of like non-newtonian fluid, right? Like what I'm trying to say is a paper is very difficult for people to understand. Everybody understands hula hooping. And I really do strongly wish that more scientists, more researchers would spend a little bit of their time doing research that's not necessarily like the most academically interesting, but is interesting for other people, right? So yeah, that's all I want to say. Okay. Um that was a bit of a ramble. Again, today's stream is going to be a little bit tough. So let me just go ahead and hop into the paper and we're going to see how far we can get. Um, again, I'm going to be keeping up on chat, but today just because I've got the hula hoop up. Uh, chat's not going to be on screen. So, I am reading it, but it's just not on screen. If you're on Twitch, you'll see it on the side. If you're on YouTube, Um, uh, Cat says, "Some papers are just unreadable. Some or the majority filled with ungodly amounts of those gear rhetoric. I don't understand. " So, sometimes h look, I know exactly what you're talking about, right? Like there is an insane amount of academic jargon that appears in most papers. I'm sure we're going to find a lot even in this paper as well. Um now the thing is I generally like jargon. I feel like it's a pretty good idea to have jargon because it allows for experts to read the paper faster and at the end of the day the point of a paper is to basically accelerate people to the boundary of human knowledge and the fastest way you can get from point A to point B is usually through jargon, right? On the other hand, it is certainly true that a lot of academics are like kind of purposely writing their papers in such a way that it's very difficult to follow. And that's no doubt like we're going to find some of that in this paper. I have no doubt about it, right? And so like it's like I like reading papers. I like writing papers. So I'm totally fine with this type of stuff. But if you're not someone that reads papers a lot, then it's jarring. It really is jarring, right? It's like reading poetry for the first time if you've never read poetry before. like you're not going to understand it. Like it's it's a fundamentally different mode of reading that you have to get used to, right? Um and the same is true for scientific writing and like poetry, some poems are really good and some poems just frankly not that good, right? It really depends on the author and like a whole bunch of other things. Okay, so let's go and get into the paper. Um in wait, increment counter, not drop counter. Wait, wait. Oh, I see your the naming conventions of how many times I'm going to drop the hoop. So, so far we dropped it twice. Um, sorry. I'm working on it. No, I'm going to show you guys a trick that I've never been able to do. Um, that is to drink water whilst hula hooping. I can't do this. It's impossible. Actually, I actually got a little bit there. That was pretty good. Usually I I've been trying to do that like all month. Genuinely all month. It's impossible. Okay, so let's go. Man, all these other streamers are showing like these trick shots and stuff and I'm like, "Look at me drink water. Like there's a reason my stream isn't like the most popular stream on Twitch, right? Um, speaking of which, let me see how Twitch is doing. I haven't Are we doing okay on Twitch? Yeah, we're doing okay. All right.

So, uh, again, if you guys have any comments, questions, concerns, anything like that, feel free to let me know. And look, yes, Zan, I hear you. I can definitely use a straw. hear you, but I'm not going to out of like pure spite, you know. Okay, so geometrically modulated contact forces enable hula hoop levitation. Let's go. Um, I think the first thing I want to do is actually go down to the bottom and what I want to do is um see these guys' affiliation just because I want to know where they are. It's not because I have any like I don't feel like it really matters that much, but I do want to know where these guys are from. So, you guys said it was in the acknowledgements um up here. So, acknowledges we jank uh we thank Jay Eaton for early work on motion tracking and modeling and M. Holmes um wait where is it? I thought it was in the acknowledgements. Um, it is through the US NFS grants, which is interesting because like this is one of those things I would not expect the NF NSF to actually like do anything with, but it's fine. Also, what is this? Oh my goodness. I saw 7D over here and figure 7D and I thought this is a seven-dimensional problem. Holy cow. Seven dimensions. That doesn't count as a drop. I caught it. Other streamers never seen a streamer hula hoop. Yeah. Here on Leos Labs, you see new content every day. Yeah. Okay, let's keep going. Okay. Um, right. I guess one more thing before starting. I mean, we've been rambling for a bit, but this is the last ramble, I hope. Um, I actually have a lot of plans for things that I want to do. Drop counter updated 2. 5. I have a lot of things that I want to do in the next few months, and I'm just going to try it. Like, the way I see it is this upcoming year, basically from hooping, pause counter three. Uh, so basically from September to September, like from 2025 to September 2026, um, I'm kind of going all in on Leos Laps. I'm doing everything I can to make the stream and this channel and everything about this successful. So, I'm going to be trying like a bunch of just weird things, right? Some of it is reading papers while hula hooping. I have a lot of like really interesting videos that are coming up. Um, again, I want to try to make sure that every single one of my videos kind of pushes the boundary of what you can do somehow, right? I want it to be novel. Um, what this means is that when it comes down to it, videos will still take a while to produce, but there will be videos coming out, right? And part of the reason I'm reading this paper is because I kind of want to see if there's a way to push boundaries in hula hooping, you know, like just, you know, I I don't know. Is there a way to push boundaries in hula hooping? Who knows, you know? And so that's one big reason why I'm reading this. Um, I just saw the word mat lab and I got triggered. Okay, let's go through um let's start actually with the significance. So um it says significance. This study explains the physics and mathematics of how and why hula hooping can be suspended against gravity. Cool. We identified this activity as an example of more of a more general form of mechanical levitation maintained by rolling points of contact on which and which depend strongly on body shape. Um, specifically, we use robotic experiments that show um to show that keeping a hoop at a level requires a sloped surface with hips and a curvy waist. Really? So, you're telling me that if I just had a rod, like a cylinder, like my body, look, I don't got any hips. I'm just got to I got to be honest. I don't. Um, you're telling me that this paper says that if you're just a rod, you're not going to be able to keep the hoop up at all. Or are they saying that if you rotate the rod in just the right way, you can actually create a like a stable point that allows for the hoop to go up, right? They're also saying that like people whose fat distribution allows for like an hourglass figure, right? Right in line to mat lab every time you drop the hoop. Oh, no. I'm not doing that. Um, basically you're saying people whose fat distribution allows them to have an hourglass figure should in principle be better at hula hooping than people who don't have that, right? Um, I don't know what that means, but I guess we keep reading it from here. Um, okay. So, uh, and we present dynamical models that explain our observations and generalize the different shapes and motions. In addition to explaining a familiar but poorly understood activity, our findings may inspire and inform robotic applications for transforming motions. um extracting energy from vibrations and controlling and manipulating objects without gripping. Um so I think are they trying to say that from now on people are going to try to find a way to like reshape packages as hoops so that you can hold the hoop up. Like what I'm trying to say is like imagine you've got a load like some sort of physical load like a I don't know 5 kilogram weight or something like this right you could imagine a robotic assistant that is constantly rotating in order to maintain that 5 kg weight right in principle I could imagine that happening but like I

mean let's be honest right the primary motivation for reading this is because it's about hula hooping right like that's what it is like we're not reading this because of its like underlying significance to the field of robotics we're reading this because it's about hula hooping and it's kind of fun, right? All right, let's keep going. So, one thing I don't really understand is and this is me just not understanding, you know, the Pass journal, right? Maybe I just don't understand it. Why is there a difference between the abstract and the significance here, right? Like to me, you should be mentioning the significance in the abstract. Like that that's kind of the point of the abstract, right? Um, also guys, I may have made a mistake. Um, before stream, like literally just before stream, because I'm realizing that basically nobody can watch stream in the morning times, I decided, hey, I'm going to drop my kid off at daycare. Actually, not daycare. He's now in preschool. And uh then I'm going to go to swim, right? So, this is actually like I know I'm sweating a lot here, but this is like in a sec in a sense my second workout of the day. Um, yeah. And at no point during the last month was I ever this sweaty. Yeah. I started swimming in in well none of my kids going to preschool. I can like take an hour a day or something to go back to the pool. Okay, so let's go. Mechanical systems with moving points of contact, including rolling, slinging, and impacts are common in engineering applications and everyday experiences. The challenges in analyzing such systems are compounded when object dynamically explores the complex surface shape of a moving structure. Let me read that again. The challenges in analyzing such systems are compounded when an object dynamically explores the complex surface of shape of a moving structure as arises in familiar but poorly understood contexts such as hula hooping. So I think what they're exploring here is not so much the levitation itself but how the levitation dictated by body shape. I think is what they're doing here. Um, and I think I've heard I've read, but again, I was saving this paper for stream, so I didn't read too much into it, but I've read that this whole like hula hooping on a rod thing is kind of like a well-known, not necessarily unsolved problem in physics, but it's a well-known problem in physics that like at the very least is like interesting for some reason. And I don't know if it's like interesting at the graduate level or if it's like a new area of research or something like that, but I've definitely heard of it being a difficult problem to solve for various reasons. Um, okay. So, why can we hula hoop in the first place? Is it innate automatic response or a more deliberate set of actions? Yeah, I don't know actually. Like, this is one of those things where like, you know, it's like a children's toy, right? And so, you like to believe that we as people understand how it works, right? Like you just you want to believe it's like bicycling, right? Like we as people like to believe that we understand simple toys, right? And yet this is a simple toy that when you ask if you would have asked me how does a hula hoop levitate like how does it rise? I don't know what I would have told you. I think maybe said is that like we I would have modeled humans as a like as a rod. Okay. And then what I would have said is that by rotating this rod, you're creating what essentially looks like a um a cone, like a conical surface, right? Where there's like an X in the middle, right? So this is the bottom of the rod rotating and that's the top, right? And by creating that point right there, you create a stable region um by which the hula hoop wants to like exist. You know what I'm saying? So that's what I would have said. I don't know how true that is. Um because here they're clearly saying that a waist and hips are absolutely necessary for hula hooping. So I don't know maybe how can you even concentrate or understand what hula hooping that was really difficult to do over the past month as part of my training. Um specifically this hoop I'm rotating way faster than what most people like again I should have a hoop that's way larger. So I I'm actually using expending a lot more energy here than like again I spent like an hour a day. Like I could have spent that time doing actual work while my kid was sleeping cuz that's the only time I had but instead I spent the time hula hooping. I don't know. I just like the stream took a lot of effort you know um for no reason either. Okay so let's keep going. Um, we studied this activity as a unique form of mechanical levitation against gravity and identified the conditions required for the stable suspension of an object rolling around a gyrating body. So, there's also a couple things here that they're mentioning that is okay, maybe they'll talk about it later, but one thing I'm a little bit worried about is something I mentioned earlier in stream, right? I mentioned that um this hula hoop will not stay up until I get sweaty. And I'm sweating now, so it's staying up a lot easier. But um the reason for that is that the coefficient of kinetic friction, or maybe just friction, I actually don't know the difference between coefficient of kinetic and static friction. I guess I should know, but I kind of forgot. Anyway, the the friction between my

body and the hoop is not enough um because my shirt is slippery. You know what I'm trying to say? Like because my shirt's slippery, it's harder to hoop, right? And I'm wondering how they model this because this is an applied math paper, right? So, how actually do you model that slippiness? I don't know. I mean, I assume it's just a coefficient of friction, blah blah, but there might be more to it and I'm interested to see how they do that, you know? Um, okay. We combine robotic experiments involving hoop twirling uh on surfaces of various geometries and a model that links the motions and shapes of the contact forces generated. I'm interested to see how that happens. The inplane motions of the hoop involve synchronization to the body geration that is shown to require damping and sufficiently high launching speed. Um, I believe that. Yeah, you can't start a hula hoop without giving it some sort of like I can't just start hooping, right? I have to give it this kick, you know. Um like that. Yeah. Um okay. So the in place motions of the hoop involve synchronization of body duration. Uh further vertical equilibrium is reached only for bodies with hips for a critical slope of the surface. While stability requires an hourglass shape with a waist and whose curvature exceeds a critical value, analysis of the model reveals dimensionless factors that successfully organize and unify observations across a wide range of geometries and kinematics. What does that mean? Analysis of the model reveals dimensionless factors that successfully organize and unify observations across a wide range of geomet geometries and kinematics. Okay, so basically they're saying they tried a whole bunch of different like they created a mathematical model. They tried using robotics like some sort of robotic test um to see which of these shapes work and which ones don't and then they showed that the model does actually accurately reflect like what they would expect, right? Cool. Okay. By revealing and explaining the mechanics of hula hoop levitation, these results motivate strategies for motion control via geometry dependent uh contact forces and for accurately predicting and the resulting equilibria and their stability. Again, there's a whole bunch of like implicit claims here in the abstract that I do want to I want to spend a little bit more time like diving into. Um sorry, my camera is blinking. So, I was trying to make sure that it was actually running. Okay. So, um like for example, again, I I'm very interested in this like rod versus like hourglass figure uh discussion. Like how much of a hip do you need to make it possible that you can actually hula hoop? The answer is I have no idea. We're going to have to see, you know. So, let's go ahead and read through and see what we can do. So, seemingly simple toys and games often involve surprisingly subtle physics and mathematics. You're telling me you needed four citations for that sentence? Anyway, a prime example uh from classical mechanics is the spinning top as related to threedimensional rotations of rigid do bodies and complex couplings between different freedom different degrees of freedom as well as non-inertial reference frames and fictitious forces. Okay, what does that mean? So basically they're saying a spinning top um related to the three-dimensional rotations of rigid bodies. Let me take a look at citation five. What is that? um classical dynamics of particles and systems. Okay, that looks like it's a book. I'm not going to read a whole book for this. Okay, I don't actually know what specific problem they were referring to there and probably I should. But it's okay. We'll get through it. Um because again, we're not interested in that problem. We're interested in hula hooping, right? Um hula hooping involves these issues. Um and others associated with rolling points uh with the rolling point of contact on the body surface which itself is actuated with gyrating hips with girration motions and whose what with what where are we giration motions and whose geometry is expected to strongly affect the hoop dynamics. Okay so it looks like we should be reading some prior six and seven. Let me take a look at six and seven here. So, an example of heteroparametric excitation uh with the hula hoop. That's what I was talking about before with 1960. And then parametric spin resonance for a spinner with an orbiting pivot. I that just sounds like hula hooping. Like they just made hula hooping sound more complicated. Give me a second. I need some more water. What a stream, guys. They didn't need for citations like that. They had four citations for that, right? All right. One second. Oh man, I am sure this room is like 10° hotter than anywhere else in my apartment right now. I am sure of that fact. One second. Um, right. Let's keep going. And we go up. Where are we? Here we are. Up, up, up. Okay, so let's keep going down. Oh, uh

also on the Twitch side, guys, um, I I've mentioned this many times before. I don't really know where I want to go with this information, but I really want it to be that we have more people doing like streams and science and tech. I just feel like the science and tech category on Twitch, it's like I don't know how to put it, but I feel like all the technical people go to software and game development and we kind of lost the space for like all of the science streamers. I I'm pretty sure the reason this happened is because all the science streamers went on just chatting instead of science and tech because they immediately saw science and tech as a like uh how do I put this? immediately sell science tech as a dead category, but I kind of want to revive it. So, I understand that my Twitch viewership is it's just not going to be as high as it could be otherwise, and it's just a risk that I'm willing to take because the hope is as we start creating better science and tech streams and as people start seeing science and tech as like a real category. Um, the hope is that more people get involved and we start to create a community in this category, right? Um, so I'm just letting you guys know on Twitch and on YouTube if you wanted to go to Twitch that like that's kind of where I'm at. Um, is your mind trained for both anti- and clockwise or is there a difference in the ability between the two? Um, there is a difference in ability. Um, you can actually see it in heart rate. So, my heart rate when I'm going I guess this is clockwise. clockwise is about 120 beats per minute. And my heart rate when I'm going counterclockwise, which is this way, is about 125 beats per minute. Um, so it's slightly more difficult to do the other direction. But actually, there are certain things I can do going this direction that I can't do as well in the other direction. Like I can move my arms more freely. That was a very weird dance I just did there. Um that in when going that direction. Um how was the view number after the bot purge? I feel like my stream never had too many bots. And to be honest, I don't really know what I don't know anything about the bot purge. I actually this is like I read about it for a second and I have heard nothing about it since then. So, like if you could tell me more about what the bot purge is, let me know. Can you change direction midway? I don't think it's possible to change the direction midway because I think the only way you can start hula hooping is with a significant kick. Um, and so the question is, how would you like let's say I stop spinning, right? It's going this direction. Well, how do I give myself a kick in the opposite direction, right? Or enable the spin to go that way, right? I don't know how that would happen. I don't really know how you would give yourself that. like you need to double the momentum in the opposite direction for that to happen. I think it's possible for a human to like move their hips this way and then stop and move their hips that way. But the question is how do you enable the hoop? Well, maybe it's possible. So, you're going this way and then you just want to ah no, I mean, you're not going to be able to get the hoop to move the other way, but you might be able to maintain rotating in the same direction while your hips are moving the other way. That could be possible, I think, depending on the points of contact and that kind of stuff. Okay, so let's keep going. Are you kidding me? That was a drop. That one that's drop number 3. 5. I I'll give you guys that one. Um okay. Uh let's keep reading. So Hulooping involves these issues and others. Uh hence this familiar playtime activity can serve as an archetype of the challenging class of problems involved uh involving parametric excitation by driven supports. Sure. And the mechanics of dynamic contact points with frictional and normal forces. Good. So they are actually going to talk about frictional and normal forces. That's great. That's exactly what I wanted to make sure they did. Um, such issues are fundamental to related robotic applications for controlling positioning, transforming motions, and harvesting energy from vibrations. So, let me just think about this really quick, right? What they're basically saying is that because we don't have a proper understanding of hula hooping, there are certain types of rotations that robots simply have not been able to do, you know, like types of rotation. Now, I don't think it's types of rotation. I h there's certain types of just movement that a robot hasn't been able to do when they should have it, right? And so in principle, you could imagine like uh a simple toy model of a hula hoop being used to I don't know just to me like the hoop is so light. I wonder this is something I've been very interested in but I haven't had an answer to. Right? Like okay very clearly right let me just put it this way. Right? If you're lifting a heavy object, right, let's say the heavy object, let's just say a 5 kg object versus a 1 kilogram object. It takes more energy to lift the 5 kilogram object than it does a 1 kilogram object. Um, but it's unclear to me whether a 5 kg hula hoop would necessarily be more difficult to hoop than a 1 kg hula hoop. And the reason for that is because the heavier the hoop is, the larger your kinetic your coefficient of friction is between you and the body, which means the less movement it will take to actually keep up. And also your gyration orbit will be slower which means that the amount of energy you're expending like decreases. You know what I'm trying to say? Like the reason this is so hard for me is because I have to rotate so quickly. But if I were to increase the hoop size or increase the

weight, either of these would actually drop the amount of rotation that I'm doing. And the question is like it's like the question if you go up a flight of stairs versus like walking up a ramp, which one uses more energy? Physically they use the same amount uh same amount of energy, right? Because like mgh right that's the potential energy at the with the height difference right we have a formula for that so your change in potential energy is the same therefore the amount of energy you expend should be roughly the same but we I don't believe that to be the case right like you know because like it depends on a lot of different kinematic forces you have within your body and these are very difficult to actually model physically you know so how often do you watch Twitch I came across a rather interesting channel in science and tech some other rather other unknown math channels. Yeah, I just feel like I used to watch Twitch a whole bunch and I kind of stopped because I just haven't had time to watch anything. Like I don't watch Twitch, I don't watch YouTube, I don't watch anything. You know, you might need a wide enough hit base for a hoop to rest on before it falls to the floor. Wait, what are you specifically talking about? So when you were talking about like because my opinion right now as someone who hasn't read the paper is that how do I put this that while gyating you will create that hip base because you're like imagine a rod right if you're rotating the rod how do I put this the bottom part of the rod will naturally flare out and become that bottom part of the base that you need right uh would it be possible for you to hula hoop if you're a spherical cow, actually, I don't think you could. I think you could not hula hoop as I mean, unless this the cow is squishy. If it's a squishy cow, I think you could. But if you're a sphere, I don't think you can actually create the necessary. See, that's the interesting thing here, right? Like, because when you're hula hooping, right? What are you doing? Your body, let me see if I can draw this. Your body's going, "Oh, I can't draw anything. Oh, Jesus. " Your body is going to be going bowing out. I can't do this. Your body's going to be bowing out like this. And like that. Okay. Your body's bowing out, right? And you are Where is the hoop? The hoop is going to be here while you're facing this way and way. Right. Let me watch myself in the camera. So, it is Oh, that's impossible to see, isn't it? It's too fast. So, where is it? It's when I go this way. Actually, when I go that way, the hoop is here. Why is that the case? But I guess it's more What I'm trying to say is it's weird because like as your hoop hips are like bowed out like this. The hoop is against the bowed out hip, not the interior hip. Which means that actually I might be thinking about this incorrectly. Like maybe I'm not maybe I think need to think more deeply about like how this would actually work. My thought is that you can't switch directions in the middle of hooping. So you can't keep the hoop off the floor. That's correct. Like certainly you cannot keep the hoop you cannot switch directions of the hoop mid rotation. I don't think that's possible. But I think the question is hm my question is how does it stay up to begin with? Because like a spherical cow is obviously not a good metric. Like it's not a good I don't think you can hula hoop if you're a sphere. I don't think you can. I think if you're so chubby that you've become perfectly spherical. First of all, go to a doctor. And second of all, I don't think you can keep a hula hoop up. I think there's a limit to that. Um, but the on the other hand, like as I'm rotating, right? Like I'm modulating a spherical person, right? Like it's going like this, right? So as I'm over on this side, like I'm essentially only showing it the outer like I don't know. This is interesting. I have no idea. Okay, let's keep going. Um so the physics of hula hooping was first studied as an excitation phenomenon soon after the toy became a fad. Um so I guess it became a fad in six which means 1960 right? Um the more recent interest and more recent interest has come during its renewed popularity as a form of exercise and performance art. The challenges presented by 3D problem by the 3D problem have restricted previous studies to consider idealized planer or 2D settings without gravity that pertain to an extended mass freely hinge on oscillating support. What a crazy limitation. So they're saying that every other study and this is something I mentioned before because I had read this and I thought this is insane. I'm reading it again and I still think it's insane. They're saying that the challenges presented by the 3D problem have restricted previous studies to consider idealized planer or 2D support. So, you're telling me that this inherently threedimensional problem, again, you need three dimensions because you have an XY plane of rotation and then you have a Z direction, which is the thing that causes the levitation of the hoop to go up, right? This inherently threedimensional problem, has only been studied in 2D until now, right? Again, this is in part because like nobody studies hula hooping, right? I'm sure if this was a field that like people genuinely cared about like you would certainly have people who would

have looked into this before but uh yeah it's quite interesting right but there's cylindrical symmetry though the cylindrical symmetry you're talking cylindrical symmetry for what the sphere um because again we only really care about the point of contact right it doesn't matter does matter this paper is arguing it does matter the shape of the actual object like it matter is my shape because they're saying specifically I should have a hip which again I don't I mean I guess maybe a little bit of I'm not I I'm a little chubs right now you know I don't really have much of a hip um so but it is true right like if it is a cylinder it could rest anywhere but it does naturally go to here which is technically where like my hip is you know there's a phase symmetry and height phase and height for specifically the rod Okay. Um, rich dynamics are displayed even with such simplified systems including a multiplicity of motions for the case of a ring on a circle. Okay. The ring on a circle which dynamics are displayed even within such simplified systems including with multiplicity of motions for the case of a ring on a circle. H. So they're saying in principle a sphere is fine. No way a sphere is fine, right? No way. fine. I mean just intuitively it doesn't make sense. While 2D settings can provide insight into planer twirling, they leave unressed such basic issues as how a hoop remains suspended against gravity. Of course, that's what I was saying before. It's inherently 3D. Weight support is not a goal of the classical analysis of tops um and related rotational systems, but it is fundamental to hula hooping and related applications. What are the related applications to hula hooping, guys? What are they? Hula hooping and related applications. Uh, coordination modes and multi-segmented dynamics of hula hooping. Um, dextrous manipulation through rolling. Um, dynamic analysis of a motion transform mimicking a hula hoop. A hula hoop energy harvesting system. Okay, let me take a look at this one. See what we got here. I am interested in this one. Let's take a look at this PDF. Uh open I guess. I assume they're talking about the study of 2D pendulums around points, right? I assume so as well. But you know, in principle, a 2D sphere is the same as a 2D rod. And so in principle, they're saying it should be possible. So if you wind your stance, you put your feet apart from each other, you might be able to sustain hooping. Um it on your thighs just enough to pull it off. So, one thing I was doing last month is the following. I was doing this hooping, right? As you do, hooping and then I do squats while hooping, right? So, this is one thing I was doing to kind of like train my ability to uh you know, hoop. I don't know. Um, so what you're saying is if you have a wide enough base, how do you get a wide enough base? I don't think it's possible because you can't start from here. This is impossible. I Okay, maybe it's possible for other people, but you can't start from here. And so, you're saying you have to somehow give it I don't know how you do it. Now, do a chin up, too. I thought about it. Man, the lighting here is insane. I got The problem is I have a window right over here and like lights here and like depending on the time of day, like in the clouds outside, it I need to figure out how to fix the lighting. Um, it's okay. It's fine. It's very bright though. Let me try to fix it. One second. I remember doing this as a kid at least. Maybe it requires a bunch of athleticism. Maybe. I don't know. I just don't know how to do. Also, I'm new to hula hooping, right? I've only done it like this month, right? Um Okay. So, let's see. I want to go here and there. Maybe this. Let's try that. Is that better? Do I look more normal now or am I too dark? I think I'm okay. I need layer size random sweatb bands. Yeah, I'm a sweaty Betty today. I'm a sweaty Betty. Maybe one day we'll go. No, I'm not going to do that. I'm not I shouldn't have said that. That was a joke and I didn't even finish the sentence. Okay, let me take a look at this hula hoop energy harvesting system. I I'm very interested in this one. Um here we go. What is this? A hula hoop energy harvesting system from 2011. All right, let me see. This paper proposes a hula hoop energy harvesting system. Where is this published? I e transactions on magnetics. Okay. Um that integrates a

hula hoop motion transformer with electromagnetic generator. The converts the linear motion from the environment. convince can converts environment machinery or even human body into rotational onto a rich into a rotational one under specifically designed dynamic conditions. Then the system can generate power through electromagnetism after combining the electromagnetic generator with the rotational motion. The equations prescribing the relation between induced voltage and power for the systems um are derived according to Faraday's theory. Sure. Okay. Meanwhile, the physical model of energy harvesting system is established and the governing dynamics equations are derived as well as via the Lrange equations. Good agreement of induced voltage and power between theoretical and experimental results is obtained. The maximum power that the system can generate is approximately 5 mills when the frequency and amplitude of the external exertations are eight hertz and 1. 2 Newtons respectively. Couple questions. One, are these the same authors? Right? Because if they are the same authors, I have a lot of questions for these people. Like So that's one thing. Other thing, I want to take a look at these figures. What are they? So they have an experimental setup that does this. What are they saying? They're saying that you generate energy while hooping. That's fine. That's actually really good to know. You generate energy while hooping, right? I had a question which was how much work do you generate? Like how do you how much energy do you use to keep the hoop up? That was a question I had. Um if we all do hula hooping, we can have free energy. That is my question. My question is, is there a way to take this hoop, right, the one that I'm using right now, and to turn it into a generator? Like could I just stick a battery in here? You know what I'm trying to say? charge the battery via hula hooping. I guess I could. That'd be interesting in a sense. I charge a battery via hula hooping. It's not something I have the skills to do because I don't have a machine shop. But it might be interesting for like a future video if I ever do get a machine shop. But I don't see it as like fundamentally interesting research wise. It's more like just an interesting thing you could do. I'm more excited about the hoola machine. What's the hoola machine? Is that the paper that we're reading about right now? Okay. Uh let me just kind of read the conclusions as well because we have this other paper to get through. Um a design of the hula hoop energy harvesting system was conducted both theoretically and experimentally in this paper. The system is composed of a hula hoop motion transformer and electromagnetic generator. Um the physical model of the hula hoop motion transformer was first established which was followed by dynamic analysis to find a wide range where the hula hoop motion occurred under certain excitation initial conditions. Furthermore, the equation of induced voltage for the electromagnetic generator was derived from Faraday's law. Okay, this is literally the abstract. The induced RMS voltage root mean squares voltage and power of the energy harvesting generator were obtained from both the experiment and numerical simulation. Good agreement between them was obtained which verified the effectiveness of the proposed design of the Huloop energy harvesting system. Come on. It's a machine that hoops. Yeah. Yeah. I'm interested in this too. Like but what I said is I can't fundamentally do this study because I don't have a machine shop to make but there could be an interesting thing here right like I mean imagine you power your house via like hula hooping robots you know like but the only way that would work great because you expend energy to keep the hoop up obviously otherwise I wouldn't be sweating you know so you must the question is could the energy harvested um it's easy to harvest energy right the question is it possible to um like generate energy over the amount of energy you're expending to keep the hoop up. And maybe in parallel it is like you could imagine a system where you have right like if you take a bunch of rods right and you have and they're all hooping right they're all doing this thing right so you can imagine a bunch of rods I guess hourour hourglass rods which is what we're learning from this paper that we're reading right now um you if you move one rod right and they're connected via a support then all the rods must move the Um, so the question is how much energy could you like could you what could you meaningfully power with this? You know, I think I got to be honest, this is quite interesting and I think I'd love to make a setup like this, but h so linear mounted stage. What is this model of the hula hoop energy? I don't understand what this is saying at all. Let me read these graphs down here. So induced root mean square voltage frequency and power. It's not giving us a and of course it wouldn't but the question is can it give us a like the

power difference like how much energy we put in versus get out. I don't know if we should have counted some before but I think we're at least 5. 5 now. Sorry I am uh not doing the best at hooping today. That's okay. We'll get there. Um also I need more water. I I know you can tell in the camera and I'm so sorry about that but I am sweaty. I am a sweaty betty today. Um, let me get some water. Okay, so first I want to check to see if these authors are the same. I think that's the most interesting thing here. If the authors are the same, that means that they're ramping up to create a battery via hula hooping, which is interesting, right? If they aren't the same, then maybe creating a battery via hula hooping might be something we do in the future because that sounds kind of insane. Okay. Oops. All right. I mean, a hula hoop battery. Come on. Oh, okay. It's not a hula hoop battery. It's a hula hoop generator. But even so, let me take a look at these authors. So, Chlu, uh, Wang Sun, and Cao. What do we have over here? We have Zoo, Zu might be the same. No, I'm just racist. I read Lou and then I read Jew here. I was like, "Oh, must be the same, right? Must be the same person. " No, these are different people. Um, so that means in principle we could imagine a device that runs a lot of these hula hoop generators in parallel and maybe that's enough to generate some meaningful energy from it. You know what I'm saying? Like that could Oops. That could be interesting. I mean, a hula hoop battery or hula hoop generator sounds fun. Like I don't know how I do it in my current like I barely have enough room to hoop, let alone hoop and also do experiments. Um, what is this dream turning into? Imagine all I do is hula hooping from now on. Um, okay. Yeah. Anyway, I'm still very interested in this paper. I want to read through it. Um, the other thing I want to do is check over here really quick. Sorry, I got some notifications to check out. Okay, good. Again, if you guys have any questions, comments, concerns, ideas, anything like that, feel free to let me know and I'll totally address it as soon as I see it in chat. Okay, so um let's keep going. Did we read this paragraph? 2D settings can provide. Um, so at issue at issue is how equilibrium and stability are determined for free objects whose dynamic point of contact can explore the potential complex surface geometry of an actuated surface. Here we aim to determine the necessary conditions for levitation through experiments on robotic hula hoopers and the models that relate contact forces to shapes and motions uh of the hoop and body. This relatable and concrete context also provides an opportunity to understand a more general issues involving the geometric modulation of forces um on moving context and how these might be exploited to induce motions um position stability, suspend or otherwise manipulate objects. Okay, so let me go back to this hula hoop energy harvesting system because I'm still on this whole hula hoop generator thing. Um, do they give Can I make this bigger? Oh my goodness, this sucks so much. Okay, can I make this bigger? Move this over here. Come on. There we go. Make it a little bit bigger over here. Come on. So, on the one hand, I'm not using my tablet, so it's a little bit easier, but on the other hand, I'm using a track ball, which makes it a little bit harder. Zoom into this figure. All right. What are we doing here? Um where's the hoop? So linear motor stage energy harvesting generator spring. Okay. So occurrences of hula hoop motion obtained from the direct numerical integration experimental setup of the hula hoop uh energy harvesting system. I think we're going to have to go through this paper a bit more in a bit more detail um because I don't think I understand it. Um I really don't. Um, I'm not saying I'm an experimental physicist either. Like I'm I did an experimental physics rotation. So it's not like I'm completely like I don't understand this at all, but I didn't like laser physics and you know, like I'm not going to sit here and pretend I understand this deeply. Uh, but this is an interesting paper that I might want to look into later. So let me go ahead and grab the link here and put that in the paper pile. Um, I guess we just click here. No, that's not the one I was looking for. No, wait, wait. Where's for? No, no. I was looking for U. Uh, H. Uh, this one. So, I'm going put this in the paper pile. Uh, there's a bunch of citations to it as well. Where are the citations? Um, a comprehensive review of energy harvesting from kinematic energy at low frequency. Is this from the same group? No, it looks like from a different group. Um, geometric contact forces enable hula hoop levitation. That's the one we're currently reading. Let me go ahead and grab a link to this. Put it in the paper pile. All right, go back over here in the Where are we? Paper pile. There we go.

And that might be for later. Okay. Uh, let's keep reading. So, um, here we have the robotic experiments that they're showing. And I think what they're trying to show here is that they have ABCD. And just looking at the figures, they're saying that like simply modulating the hips, like if you're if you are a rod and you're just rotating like this, then you're not going to be able to keep the hula hoop up. That's a b is saying that depending on the velocity, I suppose it will either go up and down on a conicle surface, and if you have this hourglass shape, it should rest itself on the hip. I mean, I guess that makes sense. vertical motions of hoop of hoops on robotic gyators of different shapes. You can just tell this is a better journal. Like you can tell based on the figure and the figure caption alone that this is a better journal. Um this is like immediately understandable whereas the other one was just kind of like the figure captions might as well not have been there in the other paper. I don't want to like sit here and pretend that this like I don't want to be like that guy trashing someone's research um because I I'm it's better than what I did, you know? I'm not going to sit here and say that. Like this tells me nothing these figures you know whereas at least the figures in the other paper tell me something you know like what is this figure two occurrences of huloop motion obtained from direct numerical integration like what is one and two I mean I know I haven't read the paper some kind of like I am judging too harshly but still you know what moves a hula hoop in the first place asks and I don't know um I guess this is a generator where the rotary is like a hula hoop yeah that makes the most sense to me as well Um anyway, we're reading the paper right now on what moves the Hulu. So, let's go through there. So, our robot experiments in motion tracking. I'm most interested in the motion tracking. Well, I'm not most interested, but I am interested in the motion tracking as well for something I want to do a little bit later. I have like See, I don't think you understand. I spent the entire month of August thinking about things that I could do for like the Hulu phase diagram. That is exactly what we were just looking at. But I spent a significant amount of time in August um just thinking about ideas for the future. And because I was spending a lot of that time hula hooping. A lot of these ideas involve hula hooping somehow. And I'm not saying like we're going to turn into a hula hoop stream, but what I am saying is that like lots of ideas here and reading papers genuinely makes me excited. Like I know you guys probably aren't the same way and like it takes time to get there, but like for me when I read papers like every sentence is like, "Ooh, that's interesting. That's interesting. " You know what I mean? And so reading this paper on hula hooping is like I'm getting so many ideas of things that I want to do in the future. like the hula hoop generator, like a bunch of these hula hoop generators in parallel, you know, like I don't know. I don't know what to say. There's just a lot of these really interesting things that I want to pursue. Um the question is, are they novel? Are they interesting? The answer is I don't know. Um but like are they interesting to the general public? Yes. And like I said, um I think researchers should do a better job of finding ways to engage the general public with their research. Um, and I think this is one of those things that would allow me to do that, you know. Okay, let's keep going. So, our experimental apparatus consists of bodies of prescribed shape that are driven with prescribed motions and on which a hoop is released. Cool. We consider rigid axis symmetric bodies formed as surfaces of revolution about the vertical axis and which are manufactured by 3D printing. Cool. All this is saying is they created a bunch of different shapes. That's it. shapes via 3D printing. Um, these shapes are symmetric. That is to say like you know there is no like bumps along them at least rotationally and that's it. That's basically what it's saying. Um the surface is rubberized to achieve high friction with a thin rigid hoop made plastic. See that's the thing I don't have. I need a thin rigid hoop made of plastic. I think everybody needs one to be honest. Um a vertical shaft running through the central axis of the body connects to a motor via uh appropriate hardware in order to release realized girration. a term used here to mean purely translational revolution um of the body in a closed trajectory without any rotation or spin about its axis. So what does that mean? So that means the body is going like this. It's not twirling like a top. That's what that means. Okay. Um the hoop is launched by hand and the resulting motions while in contact with the body are recorded by high-speed videography and quantified with custom motion tracking algorithms. So um lots of questions here. Um, does the velocity by which you launch the hoop, does that actually change your hoop, I don't think that changes the overall speed of the hoop? Because I think it hits a stable equilibrium velocity based on the movement like the rotation of the hoop of the body itself, right? So like for example, I can spin it really quickly, right? Right. There we go. Really quickly. And what does that do? No, I mean at the end of the day, we still have the same RPM for the hoop, right? So, that doesn't change anything, right? Um, the other thing that is an important point here is that obviously if I rotate faster, the hoop goes up, but I can't really show it cuz I'm going to hit my desk. So, let me take a step back.

It's hot. Can you see me? I still don't know if I can do it here, but you should be able to I turned on the lights. Try that again. So, I should be able to get it all the way up. I don't know. As a kid, I used to be able to get it up to my neck that way, you know. Um, okay, let's keep going. Give us unrelated anecdote. The latest thing that's kind of blowing my mind from Linux is that when a window pops up asking for admin permissions for the system update or whatever, the rest of the screen dims. does not actually pause. So, I don't miss any stream, for instance. Huh. I guess you're talking about a specific Windows manager like uh Gnome or something. Oh my goodness. I didn't I I've never seen on Linux someone asked for admin rights. I guess because I run everything through the terminal. So, I specifically chose this shirt because I thought if I got really sweaty like it wouldn't show that much on stream. Um I think that's probably true because I'm very sweaty and like I hope that like the shirt is so incredibly full of sweat that no one notices. Um I probably should stop talking about sweat. Like that's definitely going to lose me viewership, right? Like I can tell you this, I'm the only science and tech streamer uh on Twitch who is currently hula hooping on stream. Like that is a true statement. So, let's keep going. Uh right. Oh, the other question was about uh so the question about the rubberized bit here. I had the other question about um like the frictional contact forces and obviously you want to maintain the highest friction possible. I think that's just what this is saying. Is it really hot there? I don't know. I guess how hot is it in Barcelona? and then add two degrees to that. Probably three degrees to be honest. It's quite hot in this room. I mean, I've got a fan on me. But it's still really hot. It's got to be 32. Uh, where are we at? 26. It's No way. It's only 26. You're kidding me. It can't only be 26. That said, like I got to be honest, guys. I don't want to probably we shouldn't talk about it. Okay, that was another what are we? Seven and a half. Okay, I got to be honest. I probably should not like say this so much on stream cuz like I don't think it's you know like there's certain things you should talk about on stream, certain things you shouldn't. And I think sweat probably is not one you should talk too much about on stream. You're definitely going to lose viewership. Anyway, point is um this weekend I was hanging out with my kid and all of his old friends from his old daycare, right? Um it was I don't know 27. It wasn't that hot. Um but it was humid. You know, sometimes it gets humid in Barcelona and I was sweating. I was sweating through my undershirt. overshirt. There was not a single other person there besides my son who was sweating at all. No sweat whatsoever. I was like, "How how are they not sweating at all, you know? " Like I was genuinely sitting there like like, you know, doing this motion, you know, doing everything I could to keep myself dry, you know? Uh and they were just no problems, you know? Like I'm sure some of them were like, "Why is this guy so sweaty? " You know, I don't get it. I guess I just sweat a lot. Maybe I drink too much water. I don't know. Um, okay. So, uh, right. So, I do have a question about their motion tracking algorithms, and I'm wondering if we could replicate that as well. I have this dream of like doing, uh, some Vtubing software. Um, and I think it'd be super funny if in the V tubing software, I use this motion tracking software so that I could hula hoop in the Vtubing stream. I think that'd be funny. Okay. So, we first ask where the levitation of the hoop can be achieved by simple body shapes. Figure 1 A is a case of a circular cylinder that is driven in circular girration um in which the vertical axis sweeps out a circular cylinder. So just moving the rod like this. Okay. Selected images from video are overlaid to show the gradual descent of the hoop. The faster orbiting motions of the hoop around the body can be seen in movies S1 through S3. Can I just click on these? No, I can't because I'm not on Firefox. Um I do want to take a look at those movies though. Um, that's not the one I want. I think I need to go back here to hula hoop and I want to find um, where are we? If I go from 2024, I'm sure I'll find it. Come on. So, then we go this one. Click, click, click. Come on, please. There we go. And now, let's scroll down to the videos. Uh, full text. There we go. And let's scroll down. Uh, this one is the one I'm looking for. Movies S1 through S3. Come on, baby. Okay. Um, there we are. So, movie S1, S2, and S3. So, this is what they're showing. Let's go and take a look. I think it's literally Yeah, that's it. It's just a rod. But the weird thing I see here that I'm not fully understanding is why they're modulating you see the velocity of the hoop is changing. You see what I'm saying? Like why is it not a constant velocity? Why

is it like rotating really fast and then slow and then fast again? You know what I mean? Like I think what they're trying to do is show h movie S1 is supposed to show the What is it supposed to show? It's supposed to show that it's instable, but I'm not getting that from the video. Like just watching the video does not intuitively make me believe that this is an instable. Like it it's you're not able to keep the hoop up, right? For me, it feels like if you were to have the appropriate velocity, see here the hoop is staying up, right? Like at a constant velocity of rotation about its axis, it looks like the hoop is also staying up. Um, I think they are testing various velocities, but the my question is why are they testing various velocities? Why not keep a constant velocity just to keep it up? We take a look at S2. Me remove this really quick. There we go. S2. All right. So, here. Yeah. This is what I kind of expect. Like, this is what we're doing as humans, you know? Like I have a base. You see what I'm saying? I'm not like a rotating rod, you know what I mean? I'm actually a like I have a singular base that is rotating like like this rod is doing, you know. So, it's seeing if this is stable, which I don't know if I would expect it to be stable or not to be honest. I need to think about my intuition doesn't work here. Like I haven't spent years of my life studying hula hoops, you know what I mean? Um, okay. Let's take a look at S3. Okay. So, this one, what is this one showing? Oh, it's just showing that if So, the first one showed that uh that rotating with a stable base is not sustainable. And this one's showing rotating from the top is not sustainable either. Okay, sure. Sure, let's keep going uh for this and other representative cases including various forms of conical gyration in which the central axis of the body sweeps out a cone. Right? So that was my argument before. My argument before was that our bodies when we're hula hooping will create a conical structure. Right? Like that was my argument. And because we're creating this conical structure, I assume that there was a point like a stable point around our hips. It happens to be around our hips. Um that allows for the hula hoop to stay up. Um, but like keep in mind I can rotate here. I need to think about that actually. So my stable point, right? Like I don't have an hourglass figure, right? I've got a slight hip here and then another dip here, right? And so you'd expect this to also be a stable point, right? But for some reason this is way more stable than that, but I feel like the dip is greater here just because I'm chubby. You know what I'm saying? So like the question is, man, what a stream. You guys are watching a chubby guy hula hoop. Well, talking about hula hoop research. What a stream, guys. Thanks for being here. Um, Give me a second. All right, let me get some water. I'm so thirsty. I'm so tired. I really thought we could get through this entire paper today. I really genuinely thought we could, but it's looking like we're on page two and I only have 30 minutes left, so I don't know how far we're going to get here. Uh, thanks for doing the stream. No, thanks for being here. I really do appreciate you guys being here. Um, okay. So um uh are you any tired? Is it tired? Is tired the correct? Yeah, tired is the correct adjective. I just joined confused how this has anything to do with VI. Unfortunately, today we're not talking so much about VI. We're talking about hula hooping and hula hoop research. But maybe tomorrow we'll talk well actually tomorrow hopefully we'll do a stream on uh the language that shall not be named called well brain if I just don't like saying that word because cursing and also demonetization. demonetization is a case that the hoop moves towards the biggest diameter moves towards the it should move towards the smallest diameter, right? Like that should this that's what I expect, right? Wait, wait, wait. I see what you're saying. You're saying that don't model me because I'm not a cylinder. Model me as instead a blob that kind of looks like this. Right? In that case, as I'm rotating, right, the blob is also rotating and the point where the cone is the smallest is also the point where I am the biggest, right? And so in that case, the hoop moves towards the biggest diameter. I do see what you're saying there. Um, I don't know. I don't think they model that very well. But the question is, could someone who shaped like that actually have a hula hoop? Hm. I want to do some numerical experiments of this. at see like here they're showing that their mathematical model allows for certain shapes and these shapes are valid. But I'm wondering what it would take to create other shapes that are also valid. You know what I'm trying to say? Like if we're creating a theoretical hula hoop generator, right? Like do you parallelize with a bunch of different, you know, hoops or do you paralyze with

one hoop with a bunch of different divots? You know what I'm trying to say? Like what's the best parallelization structure? Or is it both? Probably it is both, right? Um I don't know. Let's keep looking. And I realized I did. Yeah, technically there's a double cone. Smallest at the foot, highest at the belly, smallest at the head. Is that true? The answer is I think yes, because the head and the feet are stable points and then the body is moving around. Yeah. Okay, I need to think about this a bit more. Please do numerical simulation. I'll watch that stream. Imagine doing hula hoop simulations while coding or doing hula hooping while simulating hula hooping in C. What a stream that would be. Um and I'm considering it. I'm genuinely considering it. It sounds fun. I kind of lost count how uh there may have been some ambiguous cases. Maybe around six to seven, right? We'll say seven and a half. I think we're at wonder if you could stab a hoop on a cone and if you do it slowly so that instead of stabilizing on a local minimum waist, it stabilizes because the rising force is equal to gravity. Isn't that always where the stable point is? where the rising force is equal to gravity. Isn't that by definition what levitation is? I don't know. I need lots of stuff to think about here. So, um all the trials with a cylindrical body failed to suspend the hoop. Again, I question that, but let's keep going. The further tests of figure 1, B, and C for conical body in a in circular giration reveal the surprising outcome that the hoop may descend or ascend depending on its initial height at release. That's interesting. Let's take a look at four and five. Where's my mouse? Okay, so they said in four and five, depending on where you release the hoop, it may or may not be stable. Let's take a look at these videos. Okay, so here's video four. We release the hoop a little bit low. And again, they're doing this thing where they're varying the rotational velocity of the object, which I don't maybe it's not really their fault. Like maybe there's an experimental reason as to why they're doing this. I mean, it looks stable to me, but maybe I'm just not like, you know, well, maybe my eyes can't actually see what hula hoop stability looks like. Maybe I haven't like ascended to the sul like the hula hoop gods. You know what I mean? Like maybe I just don't understand it deeply enough. What this is saying is that like I think a fundamental limitation of this study is I think the hoop size is the same all the time. But very clearly your hoop size dictates the velocity by which you are allowed to maintain um you can maintain a hoop in the air if that makes sense. Right? So we're seeing a bunch of interesting directions where we could take this. You know one is a bunch of numerical simulations which we'd have to do no matter how we were to do research. Um, but also there is the theoretical possibility of like a hula hoop generator which would be interesting, but also just like mod like finding a good way to study how much energy is spent based on like hoop diameter and hoop weight and stuff like this. This is another thing that I'm very interested in and something I could not find online. I was genuinely trying to find that uh last month and I couldn't figure it out. That local minimum waist would be why an hourglass shape might be required. I mean, look, I don't have an hourglass shape. I'm just going to be honest, like it's clearly not required. Um, but it might help like tremendously, you know. Um, but there's also possib So I would argue that what I would argue before or what I was arguing before was that like the way in which you're rotating this cylindrical body will create a an unstable equilibrium point. Like I called it an equilibrium point, but I acknowledge that it would be unstable. It would also explain why you couldn't hoop the hula past your waist. We tried that earlier. So, what you're saying is I've moved my hips more such that that's Let's give it a shot because that's true, right? So, if I do more of a hip thrust action instead of a an overall, you know, undulation. Yeah, obviously that's stable, right? I mean, yeah. So, like Oh, well, I say obviously that's stable, but then it fell. But like there's a way to make that stable. Hula hoop flinger. Spin a hoop so fast it shoots out a high velocity. Boom. Instant defense contract. What? Wait, wait. What? Let me think about this. You want to create something that allows for us H. There might be something here. There. 8. 5. Thanks, Yan. There might be something there actually like I'm trying to think of it like you know like a rail gun type of thing but for hula hoops. A hula hoop rail gun. Isn't that something? Yeah, you could imagine it. Um the question is like the way the rail gun works is it allows for you to store a bunch of energy in such a way. So the interesting thing about the hula hoop rail gun is that it's not necessarily doing it with like a real physical hoop. it'd be doing it with a

vortex ring because vortex rings are consistently stable for a very long period of time. So, finding a way to accelerate a vortex ring well beyond its intended pace, you know what I mean? That could be very powerful and very vi like very useful for a bunch of people, right? Okay, maybe not good to people, but it would be interesting at the very least, right? And so, finding a way to accelerate a hooplike structure um in such a way that it would allow for a velocity field around the hoop, you know what I mean? like in such a way that you could accelerate a vortex ring. That could be quite cool actually. I could imagine that being like a very h I don't think there's a situation. No, I mean there are certainly situations, but you could imagine it as a non-lethal like option akin to a taser or something if you could get it small enough. Um or maybe like a at least a child's game or something like that, like a paintball type of situation. Um, again, the thing about it is is a vortex ring is stable and so that stability could be I don't know. There's something there as well. So, so this actually gives us three good ideas so far. Let's just go ahead and write down those ideas. This is my favorite thing about reading papers, by the way. Like, as you're reading papers, you come up with a huge number of ideas of things that you can do with the information you're learning from the paper. And then you have to think, okay, which one of these do I actually want to do? You know what I mean? We're reading a stupid paper about hula hooping. Okay, it's not stupid. It is an interesting paper about hula hooping. But nevertheless, like we're not reading about climate change. like, you know, I don't know, super fluid simulations of of, this is not difficult for average people to understand, I would say. And yet, even so, we're coming out of it with a bunch of really interesting ideas of research directions we could pursue in the future, right? So, let me just go and scroll down to the bottom here, and let's start typing these guys out. Uh, so let's do journal. Oh, come on. Uh, new page after this time. Scroll down. Okay. Where did it go? Hello. Uh, where is that page? I thought I just created one. Oh, it copied. I see what happened. Okay. I'm going to have to Huh. Um, well, erase that, aren't I? I don't know how to do that exactly. So, let me try this and that. So, it basically copied the previous page for some reason. I don't know why it would do that, but I think I can just do journal uh page layout journal paper background uh and just do plain. There we go. Okay. So, what are the things that we talked about here? So one is the So one which is still quite interesting I would say is um hula hoop generator uh in parallel. Okay that's one. The other thing is a study on hoola with varying oh come on hoop sizes. And then finally, the third one we talked about was a hula hoop rail gun, which is uh what Hannah said over here. Um uh like flinginger type of thing. So you create a body uh that allows Oops. All right, that we're at 10. We have to be at 10, right? Uh I'm going to finish typing this because typing while hula hooping is impossible. Okay, so um create a body that allows for the maximum for maximizing velocity of um let's say maximizing upward thrust. Um and then we'll say I want to put like a little addendum here because I think the interesting part here is if this can be used for um vortex uh vortex rings. Yeah, that would be the interesting thing. 9. 5 it was okay. 10 it is. That's fine. Uh what's up Twitch? Okay, let's keep going. Uh so we're going to keep reading and we're on where are we? We are right over here or something. So we just looked at movies four and five and we said the hoop sinks if it sets free from lower point in the body and rises if released successfully high sufficiently high but it never keeps a level. I guess I would I would believe that in the case of the cone man I have if I were reviewing this paper I would have so many questions you know like I like there are already things here that I'm like does this actually like I would I'm not saying it would still pass peer review because I find it very interesting and I'm not saying that research is bad but like I would have ask them to do so many things you know I'd be like hey why is the video why is this video like the velocity varying so much um as a function of time it shouldn't right like I mean not to show what you want to So, um, ideally the velocity should stay the same in all in that particular video because the idea was that it's trying to show that it's unstable for the hoop uh with a

um with a rod. So, these failed attempts using shapes and motions uh that vary linearly in height motivate more complex geometries. Uh, figure 1D shows that an hourglass shaped body of hyper hyperboloidal form successfully suspends the hoop. shown is a case in which the hoop is released low on the body and thereafter rises up to the height just below the waist of the narrowest point. Movie six and seven show a robust tapping. Trapping for different release locations either above or below the waist. Trapping. Trapping is an interesting word there that has a lot of interesting um like now I'm thinking of an atomic hula hoop, right? Because when you say trapping, I always think atom trapping. Like I don't want to be like that guy who always thinks of atoms, but like imagine a hula hoop atomic trapper. Like what does that look like? You know what I mean? So let's take a look at six and seven. Okay, that didn't work. Try that one again. Um six and seven. So I think this is showing you start low and it will automatically No, start high and it goes down to the waist. Um again, I'm not really liking Maybe it's just buffering. Maybe that's the problem. Let me go back and look at S1. Maybe the problem was buffering. Maybe it wasn't moving at the same velocity the whole time and just it wasn't No, it's definitely changing velocity, right? Is it changing velocity or is the hoop size just wrong, right? Because like I said, the if I rotate slower, the hoop falls. If I rotate faster, the hoop goes up. Right? Uh up to the stable point, which are my hips, right? And so the question I have, you could imagine what they're doing here is they are using some sort of optimal control algorithm to figure out what the optimal velocity is to maintain the hoop on the uh rod. Right? I don't think that's what they're doing. I I feel like they're just modulating the velocity willy-nilly, but there must be something here, right? I think as we start looking at the experimental setup, we'll understand it a bit better. Okay, let's keep going. To better characterize these results, we compared the dynamics of conical and hyperboloid hyperboloidal bodies as representative examples of failed and successful hula hooping as shown in movie S8. S8 I think that's last movie, isn't it? Oh, there's a couple more. Okay, so what is this looking at? Um, high-speed video of a hoop in a on a hyperbolade where an angled mirror provides a top view. So, this just one video then. That's interesting. Um again we have to remember that like the velocity by which they're rotating these bodies does radically change a lot right like the hoop size dictates your velocity uh of hip movement right so if the hoop size dictates the velocity of hip movement right like I just have so many questions as to how they chose the velocity for the rotation right because I feel like or how they optimized it such that you could get an optimal rotation speed because I feel Like I I'm not going to lie. Let's drop it. So this rotation speed for my lower hip down here is faster than for up here. You know, here's slower, right? And so the question is how did they how' they find that velocity, right? Spinning. I think the spin speed of the tube is constant. It's just a hoop that's spinning at erratic speed creating the effects of the tube spinning at erratic speeds. Let me take a look at S1 again. I see exactly what you're saying. Let me look at S1 again. So, you're saying that actually it's the hoop that's wrong. the hoop is wrong. Can I full screen this and can you guys still see it? Just barely. You're saying the hoop is wrong. You might be right, but this goes back to what I was saying before. This means that the velocity was chosen incorrectly, right? Because a velocity of stability, your stability region, right? Like each hoop has a different velocity for which it is optimal to rotate your hips, right? And so like what this indicates is that it doesn't indicate to me that they chose it's unstable. It indicates unstable at this velocity. And there's more evidence that needs to be given to provide that it's unstable at every velocity. You know what I'm saying? That's what I'm missing from this. I want it to show that it's unstable at every velocity, not just at this velocity, right? And I just my headphones came out. Oh my goodness. Oh my goodness gracious. One second. Oh jeez. Um, right. By the way, um, so my kid speaks four languages, right? This maybe this is an addendum. I don't know. Maybe I shouldn't be talking about this on stream anyway. Like why should I talk to my children on

stream anyway? Um so at daycare he spoke Catalan um and a little bit of Spanish. At home he speaks English and a little bit of Japanese, right? Um the thing is that um as of the past month he was just with us, right? So lots of English learned, right? Um I don't know how much his English improved, but it he started saying like really funny stuff like oh my goodness gracious is something he says all the time. And then he also says um like the fiercest dinosaur of all when it comes to T-Rexes, which means we must be saying that a lot, but I don't remember saying it too much. He watched one Curious George episode where like it said fiercest dinosaur of all. And now like every time he sees a T-Rex, he's like fiercest dinosaur of all. You know, like it's just super funny this kid. He's great. Um like the thing about children, and I knew this, everyone knows this going in is like when you have a child to begin with, I got to be honest, they're hard to take care of, right? Because like you're giving, and they aren't really giving too much back. You know what I'm trying to say? Like it's it's very much you're, you know, taking care of them when they go poop, when they go pee, when they uh they need food, they need water, they need everything, everything. They need everything. But, you know, it is kind of worth it when you hear your child like seeing a T-Rex and going, "Fiercest dinosaur of all. " You know, it's funny. It's really good, you know. Um, and I just feel like, you know, I know someone here, I don't remember who, but someone here is a new parent. I would like to say that my child at three is genuinely fun to hang out with. Like I really enjoy hanging out with my child. He still sometimes cries and is a little bit, you know, tough as kids are, but like generally positive. Like it's a lot of fun. Not saying I didn't have fun at one and two. I'm just saying like the amount of enjoyment I have over having a child has increased this past year. Specifically this past month, even though it was a lot of effort and a lot of work, you know. Um that's all I want to say. I don't weird addendum to a hula hooping stream. But um guys, it is 3:45. 2:45. I cannot stream much longer than three and we are nowhere near getting anywhere with this paper. We're on page two out of 10 and I realize like one of the pages is just citations and stuff but we got to get through something right. So let me at least get through this section and let's talk a little bit. So um the schematics of figure 2 A and B define the key quantities and the data are compiled in figure three. The movement of the hoop after being launched by hand are initially somewhat erratic but later show regularity. This is exactly what Gibbus was saying before. Notably, the vertical translations of figure 1 are corroborated by the by time series measurements of the height Z of the hoop as shown for six trials on a conical body. In figure 3A, the hoop descends if released low and ascends if released higher. These motions are reminiscent of an unstable equilibrium point in vertical in the vertical dynamics. Is that a reference to 24? Okay. Um, the case of hyper the case of a hyperbooid is shown in figure 3D. Following the release from different heights, the hoop ascends or descends to arrive at the final location below the waist at Z equals Z. These motions are consistent with stable equilibrium. Okay, let's take a look here. Oh my goodness, what a figure. Is this a good figure or is this a bad figure? I don't know. Okay, I see what they're doing here. So uh at different starting heights uh they are showing that very clearly it doesn't matter what the starting height here is for the hyperbooid over here in uh figure 3D because no matter what the starting height is it will eventually hit that stable point whereas for the cone it will always go to either the top or the bottom. Again, I feel like this is very dependent on your velocity. And what they need to do is find some way to optimize um they need to that velocity. I still uh maybe I'm a naysayer here, but I'm still of the opinion that any object can be a hula hoop if spun at the appropriate velocity. I still have that opinion. I'm waiting for this paper to prove me wrong. Okay. Now, what's B here? What is sag of sigma? What is this deviation? Sure, deviation is fine, but what's this middle? What's B? What is B in this case? Um, because I'm struggling to find the difference between B and E. What are the differences? I don't know. Maybe you'll never know. Maybe it's one of those great mysteries of life, you know. Oh my goodness gracious. We are nowhere near getting done with this paper. Yeah. All right, let's keep going. Um Um, where are we? We should at least get through this section. So, threedimensional aspects include a slight angle for the plane of the hoop which is supported at its contact point while sagging under gravity and being slung outward by centrifugal action. The sag angle theta. Oh, it's a sag angle measured relative to the horizontal is plotted in 3B and E uh where small values are attained after transient fluctuations. So, the sag angle is this angle here, how far it goes down. Um

and the argument is the sag angle for the hyperboloid is smaller than what it would be for the cone. Again, all I'm seeing here is that they got the wrong velocities. I'm not seeing here that they have I don't know. I feel like I'm being a Debbie Downer. Like I'm a sweaty Betty Debbie Downer right now, guys. I feel like I'm missing something. I don't feel like I it's like one of those things where it's like, man, I just they're missing. Again, I came into this feeling like this paper would adequately explain to me how hula hoop levitation works. And even now, as I'm on section two, I have a lot of questions. And it might solve all these questions. As we get further, these questions might be answered. I just don't know if they will or will not. And I'm hoping they will, but again, there's a high chance they aren't, right? Um, okay, let's keep going. The inplane motions consistent of twirling uh consist of twirling in which the loop the hoop center orbits around the body while maintaining continuous contact by rolling without slipping. Right? Again the slipping bit I I want someone to study the slipping bit. Um the hoop orbits in the same sense as the body gyration which is termed direct twirling and any object can be sweeping uh any object can move sweeping a hyperbolade. Right? That's what I thought as well. Right? Anyway, okay let's keep going. The hoop orbit in the same sense as a body girration uh which is okay turn direct twirling. Further our measurements document a synchronization phenomenon in which the orbits of the hoop and body eventually converge towards the state in which the uh in which the girration body and hoop um centers are nearly collinear throughout the cycle um with a contact point on the inner side of the body and the hoop center located outward of the body relative to the geration center. This direct outward twirling state is defined by the deviation angle um sigma being small in value and nearly constant in time. The time series data of figure 3, C and F show that for both body shapes and over repeated trials initially large oscillations in sigma of t gradually decay out to small values. The results suggest that direct outward twirling is an attractor of the in of the planer dynamics. Again, attractor here is quite an interesting term for various reasons which corroborates a recent hypothesis. Observations counter the more common depiction of a hula hooping of hula hoop ringing as inward twirling, right? Uh with the hoop center located inward of the body center and contact point on the outside of the body. Okay? Right? Because the reason this is interesting is because um when I were if I were to describe if some undergraduate came to me and asked how does hula hooping work, I would have said exactly that. that as you're rotating your body, you're sweeping out of hyperbooid, right? And that sweeping out of the hyperbooid allows for a stable and um unstable equilibrium around the hips and that allows for the hoop to stay up. This paper is directly contrasting that by saying what it's saying that direct outward twirling is an attractor of the planer dynamics which corroborates a recent hypothesis. The results suggest so what is 19 here? What is 19? Physics of a hula hoop in 2021. There's a paper on 2021 about physics of the hula hoop. H was in physics education, which is fair enough. I don't I' I've never read physics education as a journal. I'm not saying that it's not a good journal. I'm just saying that I don't typically read physics education papers. This is one of my first ones. Okay. I unfortunately I don't think we have enough time to go through the next section because I'm going very slowly through this paper. But I want to talk for a bit. Um, because again, I got to leave in like I mean I got to take a shower and then I got to pick my kid up. Wait, wait. It's 3 and we have to be there at 4:45. That means I have to leave at 4:15. And if 4:15, I can go until probably 3:15 3:30 probably. That's okay. Uh, do you get many undergraduates asking you how hula hooping works? No, but you I used to teach lab, you know, physics lab and you get a lot of good questions in physics lab and you try to answer them all the time. I used to um Wait one second. Sorry, I was looking at my volume levels down there. Um, I used to uh do this kind of seminar thing at Oist where I would ask anybody in Okinawa, anybody that came in Okinawa to ask me a question, right? It was kind of a science show, but primarily I was treating it as a Q&A. I'd do the science show for like 40 minutes and then I'd spend 20 minutes just answering people's questions, right? And you'd get various questions about like string theory. I know nothing about string theory, but I'd give it a shot, you know, like this type of stuff and I'd answer it, right? Um, and yeah, sometimes you get questions about hula hooping, right? Or that could be vaguely like you get interesting questions and you could imagine that someone could ask a question like that, right? Um, yeah. Anyway, okay. So, here's the thing. Um, I don't know how much further I can get. Uh, let me just kind of skim

the rest of this paper and see what they actually go through. See, this picture C and D, I'm very interested in this just cuz I don't know what they are. Like, I mean, it looks like the eye of Sauron for hula hooping. You know what I mean? like why would you need this, you know? Um, steady oscilly, over twirling, and anti- twirling. Okay, so it does look to me like they are somehow simulating or like yeah, simulating is the right word here. Um, uh, the rotating velocity, right? Otherwise, they wouldn't have over twirling and anti- twirling. Oh, sorry. Over twirling and under twirling. They don't have an under twirling. You'd expect them to also have an under twirling, but maybe that's what oscillatory means. Um, and then steady, right? Man, these figures are quite hard to parse if I'm being honest. Um, I I'm not saying that they should be easy to parse. I mean, again, this is an academic paper, which means this is on the boundary of human knowledge as far as we understand it for hula hooping. But, um, yeah, it's it still doesn't quite feel like I'm understanding this as deeply as I should. Um, at the end of the day, a lot of academic papers are picture books, right? This is no different. like all academic papers, you know, you should be able to. I'm not saying this is always the case, but okay, maybe this you shouldn't be able to do this in all cases, but in a lot of cases, you can just look at the figures and that will give you a good enough understanding of the um uh of what the paper's trying to do and all this kind of stuff, right? And I'm not getting that with this paper here. Yeah, quite with this paper. Um, so model results and stability mechanism. look, there's a lot of really interesting research that went into this. I'm nowhere near finishing this up. I'm nowhere near I have so much further to go and the text gets smaller as we start going to materials and methods. Um, model stability in 3D. Consider equilibrium away from which the loop is perturbed in height thereby perturbing r of b of z and beta of z. The upsetting and upsetting the vertical force balance. We wish to know whether the system responds with a corrective change in height that restores the hoop to equilibrium or not. We posit that the hoop ascends if f of v of z is greater than mg where that must be mass and gravity. Um let's see. It is therefore sufficient to assess the so-called stability derived uh df of z over dz at equilibrium where the positive values indicate instability and negative values indicate stability. What? Okay. I this is a bit too much for me right now. I think I need to take some time to look at that. Body geometries and formulas. Ah I've been streaming for two hours guys. How long have I been streaming? Two hours right? Let me take a look at my Twitch stats. It says an hour and 50 minutes I've been streaming here and we have not even touched the surface. We haven't even gotten started with understanding hula hooping. Um, all right. Let me ask you guys some questions before we go any further. What do you guys want to do? I actually want to learn more about hula hooping. I think it's kind of fun. Um, just because it's like one of those things that like again I think it's super funny to be like, "Oh yeah, I'm a quantum physicist. My most recent paper is in hula hooping. " You know what I mean? Like I think that's funny. There's a lot of questions I have here. Like when they say trapping and they say attractor, what do they mean? You know, like what kind of traps are allowed here? Could you do an atomic hula hoop? Is that something that's possible or is it not possible? I don't know. Um, so Atomic Trap, would that be a viable? Would you want to do that? I guess not, right? Um, lots of questions like this that I don't really have answers to. Um, atomic hula hoop, like atomic trapping via hula hoop. Does this already exist? I feel like I've heard of something like this before. I mean, essentially all you're doing, why would you want to do this? You'd want to do this because it would create a stability region in Z to create a ring like shape. Yeah. No, this is exactly what you want. Hey, Yeah. So, I did a paper a long time ago. Let me go here. Uh, actually, not a bad idea. So there's this paper where are we that I a controlled creation of threedimensional vortex structures PDF from HBS. Let me just take a look at this bad boy. Uh yeah sure all right bring this over here. Okay so there's this paper that we did where we basically simulated a BEC around a nano fiber and I know and pretty much everyone who did this paper know that this paper is not possible. We can't do this right. um because it would require maybe two traps. some understanding of how to do an atomic fiber trap. But what if you rotated the fiber, right? So the idea here is that this fiber this this thing is sitting in the middle of Oh my goodness. So uh one second.

No, one second. There we are. I need to remove that from the playlist. I hate that song. So, um, anyway, what I want to say is the following. Um, so the idea is that we have like this uh nanopiber, right, which is a very small fiber and you send light through it like you would for the internet or something like this. The light basically the wavelength of light is larger than the fiber uh diameter, right? Which means that the light kind of I can't explain this fully right now, but it leaks out of the fiber creating an artificial magnetic field in these blue regions in here, right? Cool. um those blue regions will then create vortex structures around the fiber. We can't exactly um we can't exactly explain like how an experimentalist would get this trap. We just kind of vaguely said oh it's you know imagine a cylindrical trap. Um but the fiber itself can trap stuff and you could imagine a rotating fiber, right? Um fiber to create a uh like um some form of uh some form of trap that would allow for like the cylindrical structure. So, in principle, we could find a way to experimentally like validate this paper or like more closely experimentally validate this paper with a rotating um with a rotating nanop fiber. But I think that's kind of stupid. I think they mean a tractor in pure mathematical sense like how chaos came. See, I don't think they mean that when they mean attractor. I They can't attractor anyway. Uh isn't moving uh the magnetic field a pain? Why is moving Maybe I'm not understanding what would make it a pain? I mean, I understand theoret experimentally it's a pain, but everything experimentally is a pain, right? Why would you want to do this? The only reason this is so you get a better understanding of the vortex structures, blah blah. You could do super fluid. I don't know. Uh, but you know, this is one of those you could technically do this, right? Okay. So, what else do we want to talk about here? So, I think before closing today's stream, we've been streaming for about 2 hours. I honestly thought we'd get through the paper. So, we have a lot left to do. Uh for people who are here on chat, I'll also be looking at the YouTube comment section. I really did want to go through h I want to understand a lot more about Hoola. Obviously, I want to learn it. I there's a reason I did the stream. I thought it was fundamentally interesting. More than that though, um I want to hear some opinions. Uh like I I've been doing this thing where I will sometimes go through papers on stream. I think it's fun. Uh because I love reading papers and I love like the thoughts that come from reading papers. Like we came up with a bunch of new things that we could do just by reading this paper, right? And it's about hula hooping, right? Imagine a more like scientifically rigorous field that we're looking into. You know what I mean? So that that's interesting. I I love the fact that we were able to come up with so many ideas and so many more ideas will come as we start reading the paper. Um I think that's fun. I don't know if Twitch chat thinks it's fun. I don't I mean obviously you guys are here. Um and so I don't know if I should spend too much time thinking about that, but my question is the following. So tomorrow I wanted to do a video on understanding brain I've got some ideas of different things I want to do with that. Um, I'm not going to spoil it because I want I think it's actually going to be a lot of fun for people involved. So, what I might do is I might put a pin in the hula stuff for now, but I might continue hula hooping for future streams. I think is what I'm going to do because um uh I have other things I want to do and I want to come back to this and I kind of want to make sure I'm trained enough that I can just I don't know. For some reason, I liked hula hooping on stream. It was fun. Like I don't know what to say. It was fun. Um but I just I really love this Yeah, theory crafting is a good word for it. I really love this kind of theory crafting idea. I love this this concept of like, you know, just like reading papers, thinking about what we can do with it. And it's especially interesting because it's not like we're theory crafting for a game. We're theory crafting like actual ideas of experiments or like numerical experiments at the very least that we could run. And I think that's really cool. Like that's something that you like it's very hard like for video games. Sure, that is something that people can definitely do. Like I theory crafted different build ideas for Guild Wars all the time. It was very fun. But like specifically here, like we're theory crafting ideas for research, and that somehow makes it feel more I don't know, not fulfilling, but just it feels impactful in a way, you know? Um, so I think I'm going to leave it here. Uh, I'm going to go back to the brain stream tomorrow. I So I'm not going to do Hoola tomorrow, but I might come back to Hoola on Friday or sometime next week. So uh, sorry, not on Friday. Sorry. I only have three days this week because Thursday is a holiday and then Spain um kind of makes you has these things called bridge days I think is what they're called where like if a day is a holiday and it's on like Tuesday or Thursday then you'll take either Monday or Friday off respectively. So you'll take the day off that's closest to the weekend so you just take an extra day off. I don't know why that happens. That's just what happens. So I have two days off this week. Um and so it's only a three-day stream week and then next week or sorry next week we'll come back with a full 5day. So for those who are watching the VOD and managed to get this far for those who are on stream right now um just let me know what you guys think. Again, I want to do brain tomorrow just cuz I don't know very much about it. I want to learn more about it. Um, we call it squeeze days. It could be a generally like European thing. Um, but

yeah, I think I'm going to be hula hooping while doing the brain stream tomorrow. It's going to be an interesting stream. We'll see how it goes. I can only really manage two hours for this week, but maybe in subsequent weeks I'll be able to manage more. Um, as always, if you like the stream and you want me to do more of them, just let me know. Um, I'm very interested in doing more. Um, like I said, we're currently streaming on the science and tech category on Twitch, which is Look, I gotta be honest, it it's not a dead category, but it it's not as popular as I would like. Um, so let's go twitch. tv. Let's just go to science and tech. I think I can just go to You see who I'm watching now, which maybe I shouldn't have done. Let's go to science and tech. How do I even get there anymore? I know I can do browse and I can go to IRL and then I can do um sorry creative. Where is science and tech sovereign game development? IRL music. Where is it? Music and DJs. I thought it I swore it was IRL. ASMR. Is it just not popular enough to even be on the list of recommended IRL categories? Is that where we're at? Um maybe that is where we're at. So, how do I find it? I used to be able to just search science and tech and then I'd find it, but I don't think that's how I can do it now. It's not popular enough. That's fine. Well, here I am. Anyway, um again, if you guys have any questions, comments, concerns, ideas, anything like that, feel free to let me know. Um but again, I really do want to see more people doing like science and stuff like that on Twitch. I want to see more people doing streams where like they're engaging with things that are academically interesting, right? Um and I feel like the science category is the right way to do that. Uh, you can hula hoop and pools and hot dog category. I guess that would there's like a fitness category as well. I could do the hula hoop streams there. I could just go to just chatting, but again, I'm not so focused on like increasing my own viewership. What I want to do is increase the viewership of people who want to do uh like science and tech streams in general, right? I want to increase the number of people who are doing these types of streams. And so, like, if I get a bunch of views, that's fine. But more importantly, I want more people to be engaged with streaming this type of content and watching this type of content. And I don't feel like I can do that if it's all just going to be in uh in Just Chatting. You know what I mean? I feel like Just Chatting is like where everyone goes. Yeah, I follow Iron Mouse. I think she's cool. Okay. Um I Yeah, I follow a couple like normal people. It's like Iron Mouse and COVA are both really cool people that I follow. Okay, so um overall I consider the stream to be relatively successful. Um I mean like the fact that I was able to stream and talk while streaming the whole time without losing my breath too much. I mean, obviously I lost my breath a bit, but actually I think I don't know. I today I think was a relatively successful stream. Tomorrow I'll be back with brain and I'll be listening to the comments and hear what you guys say about whether you guys want another um like uh hoola stream or if I should like just look at other more interesting research. You know, I've got a bunch of other things I want to do. Um I really thought I could get through this paper in 2 hours, but you know how it goes. So that's it. Thank you guys so much for watching. Have a wonderful day, night, afternoon, morning, evening, whatever time it happens to be your time. And I will see you guys around next time for the next episode of Leo Labs. Uh, which should be tomorrow. We'll do Brain and then we'll see what we want to do on Friday. Um, or sorry, um, Wednesday. All right, bye guys. Thanks for coming in.