A hoopy frood

By Phil Plait | February 10, 2012 7:00 am

I caught this video on Geekologie, and it made me laugh. This is a brilliant idea: a woman put a camera on a hula hoop, and then, well, hula’ed:

[WARNING: some folks might feel ill watching this. I will not be blamed if you have to wipe vomit off your keyboard.]

[Note: at the end of the video there are links to other videos like it.]

I found this fascinating. For one thing, the motion is slower than I would’ve expected. I suspect that may be due to an illusion when you watch from the outside as a hula hoop being used; humans are notoriously poor at judging rotating reference frames. After all, people still try to argue with me that centrifugal force isn’t real, when it it quite clearly is.

Even more amazing to me was that I didn’t get ill watching that video. I tend to get a seasick on a kid’s swing or when reading in a car, so the fact I was fine watching this is weird. But I have pretty good 3D spatial reasoning, and have a lot of practice swapping reference frames — trying to figure out when the Moon rises, what configuration planets are in, and how to point a telescope give you a lot of practice there — so maybe that helped. Beats me.

But I wonder what other weird change-of-frames would benefit from using this camera technique? That might make a fun series of videos.


Related posts:

When I say centrifugal, I mean centrifugal!
Space station gives physics a boost
You spin me right round baby right round
xkcd, wherein Randall Munroe and I agree

CATEGORIZED UNDER: Cool stuff, Science

Comments (60)

  1. NewEnglandBob
  2. HappyHead

    Spatial reasoning and sense of balance are two separate things – for example, I have an excellent sense of balance. I can spin around in place for a long time without getting dizzy, and if I’ve looked at a room that I’m in, I can usually navigate around all of the furniture and pick things up that I want while blindfolded. On the other hand, 3D-shooter style games make me dizzy and nauseous, and the better the video quality, the sooner it happens. (Modern HD video game systems can have me running for a bucket in seconds. It’s not fun.)

    One thing this video has going for it that reduces that effect though, is the constant frame of reference of the other side of the hoop, with the striped coloring, it gives you a steady, non-moving object to focus on, instead of the rapidly passing background. Thus, while you do see the background whipping past repeatedly, you don’t get the same sense of motion, because of that steady, unmoving striped bar across the screen. If the camera was facing outwards and the hoop wasn’t there, the effect would be very different.

  3. Wow, that’s is very cool! Didn’t make me sick either!

  4. Gaebolga

    And I think it needs to be said:

    She’s damned good with a hula hoop….

  5. Kevin
  6. Ben

    Significant portions of the video are in “slow motion”. If you watch the speed at which she moves her arms, or the way her hair moves it becomes pretty obvious. Also I noticed a slight choppiness, as the frames were spread out.

  7. Sam

    Do that in front of a greenscreen & you could capture some pretty neat simulated zero-g acrobatics for a low-budget sci-fi flick.

  8. James

    Re-read over your centripetal/centrifugal post and the comments. Spirited debate! I use your explanation in class and the kids get it right away. We also talk though about it being a non-inertial reference frame. I once threw a volleball while inside a rotating carnival ride at Six Flags called the spindle top. People outside said it went straight. To us inside it curved! Sweet demo.
    I’m going to show this video in class today. Very cool! It does look “slower” and I was wondering how she made it so smooth, then I realized I was focused on the hoop and not the outside view, which was much more jerky.

  9. Chris

    Looks more ‘stop motion’ than ‘slow motion’. I suspect a fake. Notice she rarely moves out of view, which she should often do when hula-ing. Plus there’s almost no distortion of the hoop, especially when it suddenly changes direction or torques. Fascinating, perhaps, but definitely not what it appears to be.

  10. Gregory Ruderman

    I can’t believe how easy it is to hula in a different reference frame! ;-) I mean, it’s just dancing around a stationary bar, how hard could that be?

  11. Russ Barrett

    She is certainly skilled with the hula hoop, but I was most impressed by her ability to change clothes while using it.

  12. Keith

    The thing that I found interesting, other than the entire video itself, was that the hula hoop appears to be enormous.

  13. ctj

    she doesn’t just change reference frames, but she changes clothes a couple of times too.

    oh, and she must really know where her towel is.

  14. Gary Ansorge

    Yeas, it looked to me as though that hoop was 12 feet across.

    Ah, altering ones frame of reference,,,something DeadHeads are well know for doing,,,

    Gary 7

  15. JamesE

    From Roy Bishop’s “Orbital Motion” in the RASC Observer’s Handbook 2012:

    In the case of orbits, the common misconception is that the inward gravitational
    force is balanced by an outward “centrifugal force.” Newton’s view is simpler: There
    is only one force, the inward pull of gravity. There is no physical agent to cause
    an outward force. (Note that forces cause accelerations, not vice versa.) Also, if
    there were an outward supporting force, the two forces would cancel and, as Galileo
    realized, the body would then move along a straight line. If you choose a rotating
    reference frame and then ignore the rotation (mistake no. 1), you have to pretend there
    is a “centrifugal force” (mistake no. 2) in order to make sense of motions occurring
    within this frame. The two mistakes effectively cancel, but the description has been
    made needlessly complicated, and if you do not realize what you have done, you do
    not understand the motion.

  16. The hula hoop doesn’t just rotate; it also travels around the person inside it. That’s got to affect the motion of the camera and the difference between that and the apparent motion when viewed from outside.

  17. Osian

    There is a Radiohead music video – can’t remember for what song but it’s from In Rainbows – which is shot entirely from cameras strapped to the band members’ heads (looking back at their faces); so their heads remain stationary with respect to the view while everything else moves. Similar idea to this, and looks really odd; found it difficult to relate the swaying background with the head motions they must be making.

  18. Trebuchet

    This is the camera angle the television folks need to make the Olympic event called “rhythmic gymastics” interesting. It’s a complete snooze otherwise.

    As soon as I saw a reference to “rotating reference frames” my first thought was “No, Mr. Bond, I expect you to die!”

  19. ASFalcon13

    …dangit, can’t resist.

    “After all people, still try to argue with me that centrifugal force isn’t real, when it it quite clearly is.”

    Still trying to use Newton’s laws to make arguments about reference frames in which Newton’s laws don’t apply, I see…

    Edit: Also, what JamesE said.

  20. Jay

    The reason you get sick while reading in a car is due to your eyes having to constantly adjust every second (if not more) while trying to focus on the words you are reading. It’s just motion sickness. Happens to me after only a minute or so of reading in the car.

    Now…trying and watch this video while your in moving vehicle…

  21. Richard

    The video made me think about the geocentric model of the solar system. From the camera’s perspective, everything is revolving around it when it’s clear the camera is moving.

  22. cms

    Wish I could watch the whole thing, but 10 seconds of it still has me queasy 45 minutes later!

  23. Jenna

    I was immediately attracted by the H2G2 title, then thoroughly wowed by the video!

  24. Was gonna ask if she knew where her towel was, but ctj done beat me to it. Amazin’ what sticks in me brain fer 30 years, but I cain’t remember where me car keys is :P

  25. John EB Good

    I guess if you can’t watch this without feeling perfectly normal and well, you just failed you first test to become an astronaut!

  26. Travis

    Chris, it is not fake. Parts of it are slowed down and there are clearly multiple takes involved (hence the changing of clothes), but this is actually how hula hoops rotate. Also, the kind of hooping she is doing isn’t what most kids do, it’s a performance art where the hooper commands the hoop in a much more precise way than a normal person would.

    Also, with the camera facing inward, she shouldn’t be leaving the camera’s view unless she is OUTSIDE the hoop.

    Also, the reason why it looks like the hoop is moving all crazy while she isn’t moving much in comparison is because of how hoops work. When we spin them around, the point of contact of the hoop changes very little over time, this is how the hoop has traction and is able to rotate instead of falling straight to the ground, and is why the stuff outside the hoop is moving fast, while the stuff inside the hoop is moving slow. Another thing is that many hooping tricks involve grabbing the hoop which is why she’s able to stop it without violent torque. Watch instructional videos on hooping and you’ll see all the interesting techniques they do and it should make sense.

  27. Musical Lottie

    Ooh, that was fun! I have terrible balance, get carsick, have mediocre spatial reasoning, and 3D films make me feel really weird – but I didn’t feel at all sick watching that. As someone mentioned above though, it probably makes a difference that the hula hoop is always in shot!

    [Also, what’s happened with your RSS feed? It keeps truncating posts now, which is annoying but not a disaster – I was just wondering why it does.]

  28. Eleri

    Didn’t even have to start the video to know that watching it would cause breakfast to reappear. Sucks to have whatever it is that causes my massive motion sickness, but I can’t even watch live Merry-go-rounds. And forget 3d and first person games. Managed to watch hubby play Portal for 3 whole minutes before I had to flee…
    What really sucks is, I’m probl’y one of those people that has issues with ‘local vertical’ and would never handle free-fall. No space for me!

  29. MeganMcC

    That was really quite beautiful not to mention hypnotic. And yes, she is good with the hoop.

  30. oh! She might have found what was missing in the Theory of Everything: the entire Universe revolves around a hula hoop!

  31. Amazing video, and not a fake. Anyone who’s ever spent any amount of time hooping recently should recognize that this is how hoops move, even when switching directions and angles. And she doesn’t really change clothes – just puts on a sweater and takes it off again which isn’t so magical as the video isn’t continuous anyhow. And speed changes…they really just make it easier to appreciate the movement.
    Love it, and I’d love to see something like this with aerial dance, especially lyra.

  32. Jeffersonian

    Boo. I thought she was actually going to hula, not just hold onto it.

  33. HvP

    Oh c’mon people. She’s trying to inject a bit of variety into the performance. If she just stood in the center and spun it around her for three minutes like we might do then I’d figure it would get pretty boring.

    She’s doing tricks and generally trying to be entertaining in her video performance – this is not a bad thing.

    Also, the mass of the camera may have unbalanced the hoop, throwing it to the outside, which probably explains why she spends so much time near the center of the picture. Or, alternatively, the views in which you could see her in the frame helped to show off the tricks she was trying to do, which was the point of the video, so she edited it accordingly.

    It’s a piece of performance art not a scientific experiment. It’s meant to be fun.

  34. Jim

    Dr. Plait,

    “After all people, still try….” Your grammar is usually impeccable, and I’m only pointing this out because it made me laugh. I couldn’t help but point it out.

    Perspective truly is an amazing thing!

  35. CR

    Watch the video on YouTube, and read her own description of the video. I did so, and found out the camera has a 180 degree field of view, which enhances the effect as the hoop spins around her. This was an experiment by her to test the camera (in multiple takes), and according to the notes, she plans to do more videos/routines as summer arrives.

    I, for one, look forward to seeing more! This was cool, and I even enjoyed the music.

  36. MadScientist

    I disagree that the motion is slower than expected – the motion would be related to the ratio of the hooper’s waist to the inner perimeter of the hoop. I would expect virtually everybody who’s played with a hoop to have noticed that. Spinning the hoop on a leg or wrist shows the comparative effect nicely.

  37. I’d also like to point out that the fish-eye lens helps create the slow-motion effect; objects have to cross a wider angular arc to appear to move the same distance across the screen. Our field of view is roughly 90 degrees, so cropping the video down to half the original resolution and filling your eyeballs with it should be more accurate to what you’d see!

    HJ Hornbeck
    (PS. Yes, I tried it. Yes, I felt somewhat sick afterwards…)

  38. Stephanie
  39. Cathy

    You some some hoopy froods? Go to a rave and watch a hoop performer like this one using their full LED setup with tape for streaks. It’s preeeeeetyyyyy and you don’t need to actually take any drugs to get the awesome trippy patterns.

  40. db26

    If you thought that was a hula hoop with a camera on it, I’m afraid you are all morons.

  41. JB of Brisbane

    @db26 – Of course it isn’t. Anyone can see it’s a camera with a hula hoop on it!

  42. slang

    Cute. But how was it done? Which camera?

  43. Wayne on the Plains

    Okay, I probably shouldn’t have tried to multitask reading the text while watching the video. I read “how to point a telescope” as “how to point a teapot” and got really confused for a second there…

  44. Wayne on the Plains

    … not that I doubt Phil’s ability to point a teapot correctly.

  45. Tom Callahan

    Get out a slo-mo cam and I think you’ll find that the speed the hula hoop rotates around the body and the speed it rotates relative to itself are not the same thing. It swings around your hips pretty quickly but because it’s also “walking” along your body, the rate at which a specific point on it goes around is much slower. I noticed this once at a father-daughter dance where I had to embarrass myself badly in the hula-hoop competition. The hoops they had were junk and the one I had had duct tape holding the seam together. I noticed that the duct tape moved around a lot slower than I would have thought. Camera==duct tape in this case. Add in the wide-angle effect mentioned earlier in the comments and you have the effect as seen.

  46. Helen

    I made this video, and just happened to come across this article. I just wanted to say that it’s nice to hear some intelligent discussions going on and to read the scientific debate. I was just messing around with my camera, so it is fascinating to me to be confusing so many people!

    When there is a larger portion of me inside the hoop (i.e. my waist) you’ll notice that my body fills the screen and momentarily blocks the view, and this happens about once every 3 seconds.
    When you spin a hula hoop around your hand (a much smaller portion), you will notice that it takes a significantly longer amount of rotations for the hoop to get back to where it started.
    When you are hoop dancing in actuality you can quite often have the same part of the hoop in your hand for a while, even though to the outside viewer it appears to be spinning pretty fast.

    If you also pay attention to my grip, there are times when I am moving my body with the hoop, and actually holding on tightly to the hoop, rather than letting it spin round me. At these points of the dance I deliberately gripped the hoop opposite the camera so I would be in the frame, to give a more interesting perspective, and also because the balance of the hoop was off by having a camera attached to it!

    And in respect to the slo-mo debate, parts 0.55-0.58 and 2.10-2.28 are slowed down to half the speed, the rest is in realtime. I wasn’t trying to mess with people’s heads, just make a cool film!

    Special brownie points to Travis for nailing it on the head.
    I don’t even understand Chris’ comment about it being fake- I have no idea what technology you would use to fake something like this, but strapping a small camera to a hoop seems to me to be a much easier and probably cheaper option!

  47. Kim

    The hoop looks huge because she’s using a fisheye lens which distorts the edges. She also combined two videos, which is why she has two different outfits.

  48. Rogerio

    one simple idea and a awesome effect

  49. Mike Torr

    Yay! @Helen – thanks for taking the time to drop by and explain all that, much appreciated. Love the video :)

  50. thew

    Phil said:
    “But I wonder what other weird change-of-frames would benefit from using this camera technique? That might make a fun series of videos.”

    I saw a video once from a camera mounted on the end of a sword, facing toward the hilt, so the blade and swordsman were in view, but they seem to have used an unlicensed song in the video and now it’s blocked.

  51. Joreth

    For those who are complaining or confused by why she doesn’t just stand there & let it spin around her waist, who have never seen a hula hoop dancer, or think that hula hooping is all about super-fast spinning, I recommend watching this video of another hoop dancer who performed at Skepticon: http://www.youtube.com/watch?feature=player_embedded&v=59BP3HjjfIE

    You’ll notice that for the majority of her hooping time, the hoop is actually spinning pretty slowly, and several times she spins along with the hoop, which also can account for some of the “slowness” that appears to be in the above video.

  52. Hi Phil,

    What struck me most about this video was how apparently disconnected and haphazard the movement of everything outside of the reference frame (camera view) was.

    Throughout the video, I couldn’t help thinking how many observations we make of our Universe are just as confusing until we view them from the proper frame. What is so amazing is that we have the cognitive ability to study these observations and imagine different plausible frames until we understand the underlying science.

    Shawn

  53. I just read the comments and like the way Richard (comment 21) compared the apparent motion of the outside to the geocentric view of the Universe.

  54. Nigel Depledge

    James E (15) said:

    From Roy Bishop’s “Orbital Motion” in the RASC Observer’s Handbook 2012:

    In the case of orbits, the common misconception is that the inward gravitational
    force is balanced by an outward “centrifugal force.” Newton’s view is simpler: There
    is only one force, the inward pull of gravity. There is no physical agent to cause
    an outward force. (Note that forces cause accelerations, not vice versa.) Also, if
    there were an outward supporting force, the two forces would cancel and, as Galileo
    realized, the body would then move along a straight line. If you choose a rotating
    reference frame and then ignore the rotation (mistake no. 1), you have to pretend there
    is a “centrifugal force” (mistake no. 2) in order to make sense of motions occurring
    within this frame. The two mistakes effectively cancel, but the description has been
    made needlessly complicated, and if you do not realize what you have done, you do
    not understand the motion.

    Nevertheless, denser particles will settle to the outer end of a centrifuge tube when it is spun.

    Newton also stated that every action has an equal and opposite reaction.

    Centrifugal “force” is the inertial reaction to centripetal acceleration.

  55. Nigel Depledge

    Helen (46) said:

    I don’t even understand Chris’ comment about it being fake- I have no idea what technology you would use to fake something like this, but strapping a small camera to a hoop seems to me to be a much easier and probably cheaper option!

    Sure, just like actually going to the moon is easier and cheaper than faking it on a soundstage in Arizona . . .

    j/k ;-)

  56. I really enjoyed Helen’s control over the hoop, particularly when changing hands, and moving from inside the hoop to outside. It looked so simple, so it had to have taken a hell of a lot of practice to make it look so “easy”!

    Believe it or not, the hand control actually reminded me of learning the quarterstaff a few years ago. The hands have to be quick, precise, and firm, all at the same time, *and* know where to ‘expect’ the wood (hoop) to be.

    I wonder if this unusual camera viewpoint would make a good training video?

  57. Zhorik

    Helen, I really enjoyed the video. If you make another video like this what I would love to see is to have a separate camera filming you at the same time from the outside and then do a split screen view with the synchronized hoop-centric and outside views.

    -George

  58. Zhorik

    Helen, I really enjoyed the video. If you make another video like this what I would love to see is to have a separate camera filming you at the same time from the outside and then do a split screen view with the synchronized hoop-centric and outside views.

    -George

  59. Zhorik

    Helen, I really enjoyed the video. If you make another video like this what I would love to see is to have a separate camera filming you at the same time from the outside and then do a split screen view with the synchronized hoop-centric and outside views.

    -George

  60. James

    “Sure, just like actually going to the moon is easier and cheaper than faking it on a soundstage in Arizona . . .

    j/k ;-)

    How’s that a joke? Going to the moon for real IS easier than faking it. Rocket science is EASY.

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