1. Mick West

    Mick West Administrator Staff Member


    Source: https://www.youtube.com/watch?v=SD1FJUJdi6M


    In a recent presentation, Dane Wigington, the Lead Researcher at Geoengineeringwatch.org showed what he said was the effect of "radio frequency" on water, and spoke of his concern on the effects on human health.

    The problem is it's not radio frequency that's making the water freeze in mid air. It's not even being frozen by sound. It's actually a harmless trick of the camera called the wagon wheel effect.
    Metabunk 2018-01-26 11-49-15.

    The wagon wheel effect was first noticed when filming coach chases in old westerns. This effect can freeze objects, like a wagon wheel, if their rotation speed is synchronized with the speed of the camera. You can replicate this effect yourself.

    In Wigington's example a water hose is attached to a speaker that's playing a 24 hertz tone, so it's moving the hose back and forth 24 times a second. Seen here in slow motion
    Amazing-Water-&-Sound-Experimen.

    The camera is recording at 24 frames a second so this has the effect of making the water look like it has stopped. But it hasn't, it's just an optical effect, the Wagon Wheel effect

    It's unfortunate the Wigington is using this cool science experiment to frighten people, but maybe when people see how easily mistakes can be made it might prompt them consider other claims more carefully.
     
    Last edited: Jan 26, 2018
    • Like Like x 4
  2. deirdre

    deirdre Moderator Staff Member

    Here's the video Dane is using. It specifically says you need a specific camera [setting].

    upload_2018-1-26_15-34-14.

    Source: https://www.youtube.com/watch?v=uENITui5_jU
     
    Last edited: Jan 26, 2018
  3. Mick West

    Mick West Administrator Staff Member

    It's not a special camera. The iPhone can shoot at 24fps. And if you camera shoots at a different speed (like 30), you can just use that tone.

    24 is preferred, as you get more movement. But you can use an iPhone for the camera. You could even use it for the tone generator.

    It's a popular experiment:
    Metabunk 2018-01-26 12-36-22.
     
    • Like Like x 2
    • Agree Agree x 1
  4. Mick West

    Mick West Administrator Staff Member

    Here's a high school student discussing how they did it in school:

    Source: https://www.youtube.com/watch?v=npw22YDWywg

    (Note: "shutter speed" is a different thing to frequency/fps, lower frequency is still best.)
     
  5. deirdre

    deirdre Moderator Staff Member

    point taken. i'll change it to 'camera setting'.
     
  6. Mick West

    Mick West Administrator Staff Member

    A win for science is that this one video has twice as many views as Geoengineering Watch's entire channel!

    Metabunk 2018-01-26 13-01-27.
     
    • Like Like x 2
    • Agree Agree x 1
  7. deirdre

    deirdre Moderator Staff Member

    he says as he races out to Best Buy to get a speaker. :)
     
    • Funny Funny x 1
  8. Mick West

    Mick West Administrator Staff Member

    • Like Like x 5
  9. Doesn't the wagon wheel effect make true virtual reality impossible?
     
  10. Trailblazer

    Trailblazer Moderator Staff Member

    Not sure what you mean - that the effect lnmoving objects would be a giveaway? I suppose you could work around it by controlling the speed of objects or using motion blur etc.

    I've noticed the "wagon wheel" effect with the naked eye before, with no special set-up other than an electric LED light which has a fast flicker due to the AC power supply. The flicker rate is faster (typically 100-120Hz, twice the frequency of the AC supply), so you need a fast-spinning wheel to match the rate.
     
    Last edited: Jan 27, 2018
  11. Ravi

    Ravi New Member

    Interesting you mention that. At work I use a 500Hz image acquisition system and in combination with a LED torch, you can (not naked eye) see the effect of the frequency of the LED in the frames as black, horizontal rectangles moving top down. Bit annoying, as I always need to use incandescent lamps..
     
  12. I suppose I should amend that to recorded media. No matter how fast the frame rate is, a spinning, marked wheel could be timed so it strobed.
     
    Last edited: Jan 27, 2018
  13. I am almost certain that you can overcome the LED-flickering with battery-driven ones; or a better stabilised (aka expensive) AC-to-DC-power-supply.
     
  14. FatEarther

    FatEarther Member

    I was going to say this isn't new as I saw this water affect on the Don Lane Show here in Australia in the late 70's/early 80's using a strobe light.

    These people (geo...) are pathetic.
     
  15. Hevach

    Hevach Senior Member

    Many video games have motion blur, but there's a cleverer trick with things like wheels and rotors: When they're above a particular speed, switch the texture from the static one to a pre-blurred version. It's less resource intensive than motion blur and doesn't have the unwanted side effect of making rapid twitch camera movements (common in first person games) smear the whole screen, and it handily prevents the wagon wheel effect. Alternately it can build the effect in so it's not ruined by framerate fluctuations, some games use this to make helicopter rotors more visible.

    Perfect virtual reality is vastly beyond current technology, but we can already do a pretty good job of faking it with some spit shine on the rough bits.
     
  16. Agent K

    Agent K Active Member

    There's a toy that uses a strobe light instead of a camera to make water drops appear to levitate or even float upward.

     
  17. Agent K

    Agent K Active Member

    It's a general problem of undersampling in time or space, which causes aliasing. It's the same thing that causes Moire patterns in photos of striped shirts, due to insufficient pixel resolution. To prevent it, you need a sampling rate that's twice the highest observed frequency, or you need to perform anti-aliasing that removes the high frequencies by blurring the observed signal before sampling it.
     
  18. Mick West

    Mick West Administrator Staff Member

    Or do the blur naturally by having the exposure time (1/24th of a second) match the frequency (24 fps/Hz). That's why the best examples are done in bright sunlight, when the camera is forced to use a very short exposure (1/1000th or so). There's some much less impressive examples done indoors by the less scientific viral video crowd, where you get a kind of "blur with gaps" effect.
    Metabunk 2018-01-29 05-34-01.
     
  19. The experiment testing the fidelity of virtual reality video could be done. Set up a room with a window next to a bicycle race then switch between live and recorded views. To move the goal posts, perfectly replicating the experience of skiing suncups in virtual reality looks impossible.
     
  20. Leifer

    Leifer Senior Member

    ...or the videos were shot under a strobe light, which could have a wider frequency range for the same effect (mentioned before) and not reliant on video frame-rate, and therefore observable to the naked eye.
     
    Last edited: Jan 29, 2018
  21. Tedsson

    Tedsson Member

    • Like Like x 3