
Amazing optical illusion or "glitch in the Matrix"? - shawndumas
http://www.cbsnews.com/8301-504784_162-57416477-10391705/amazing-optical-illusion-or-glitch-in-the-matrix/?google_editors_picks=true
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acqq
Strictly speaking, it's not an "optical" illusion at all -- you must film the
drops with the camera. You'll see the effect only on the screen.

Still, a clever idea to simply use a sub-woofer to kick the drops. I like it.

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jcampbell1
The same effect can be achieved in real life by adding a strobe light.

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Florin_Andrei
There might be a little bit more to it than that. I think the vibrating
subwoofer actually nudges the droplets and shapes them, controls the flow and
the way each individual droplet breaks off.

Anyway, I'm definitely going to try this.

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MartinCron
I think the idea was to have a vibrating subwoofer and a strobe light, where
the strobe light would simulate the synchronized framerate.

It should work. I would try it but strobelights give me a headache.

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Florin_Andrei
Oh, I see. So then you wouldn't need a camera.

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spatten
I spent a few years of my life staring at this exact effect. I was working on
building a big industrial inkjet printer. The physics behind it is cool too,
but not new. Lord Rayleigh first described it in 1878. Not exactly a glitch in
the Matrix :). I have a patent somewhere on a minor tweak to the concept, but
can't find it right now. Good times.

More info:

Just to clarify for everyone assuming that this is an optical illusion. It's
not. The subwoofer is actually creating vibrations in the water stream that
increase exponentially as the stream travels until their magnitude is larger
than the diameter of the stream. At this point, the stream breaks up into
drops. If you do this with a coloured stream of water (i.e. ink) and run a
piece of paper under it, you will see individual drops of ink hit the paper.

There are two types of inkjet printers. The most common is what you see in
household inkjet printers, it's called Drop-on-demand. You spit out a drop by
doing something to the ink. Ofter you heat up a resistor, converting some of
the ink to steam and pushing out a drop of ink.

The other type is called continuous inkjet. The way this works is you have a
stream of ink, you stimulate it at some frequency which gives you drops at
that frequency, and then you select some drops to hit the paper and others to
miss.

The project I was working on used conductive ink and selectively charged the
drops before sending them between two oppositely charged plates, sort of like
a cathode ray tube with ink drops instead of electrons.

It was ridiculously cool technology, and a lot of fun to work on. The printer
we were designing (never got to market in that incarnation) would have had
paper going by at ~6 meters/second with very high quality, totally variable
output. I thought we were going to disrupt offset printing in a big way. Sigh
:).

[edit] Ooo, found the patent. Great bedtime reading if you're interested:
<http://bit.ly/HXc6o2>

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jblock
If you don't mind me asking, what ended up killing it? It sounds awesome.

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spatten
Two companies doing the same thing both got bought by the same very large
company. The other company kept going. We got shut down. I got to leave and
start my own company (Leanpub), and everyone lived happily ever after.

It was a great project, but I'm much happier now doing the startup thing than
I was being a physicist.

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EvilTerran
You might be able to get a similar effect to the naked eye, if you used a
sound wave at/near the same frequency as your local mains electricity, under
incandescent mains lighting. A harmonic frequency might even work, too.

I recall seeing a tool for fine-tuning vinyl turntable speed that used that
form of the trick - it was basically a cardboard "record" with spokes printed
on it every (* grabs a calculator *) 4.02deg, so as to appear to be stationary
when rotating at exactly 33.5rpm under light flickering at 50Hz. Thought that
was ingenious.

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dredmorbius
s/incandescent/fluorescent/

Incandescent (filament) bulbs glow by black-body radiation as the filament
heats. Mains cycles are too short for the bulb to flicker (though you can get
interesting effects on slower, ~2Hz or thereabouts, voltage fluctuations).

Fluorescent and LED lighting actually flicker multiple times per second,
though this can be tuned somewhat.

If you remember CRT displays and monitor flicker, the problem _wasn't_ so much
the flicker rate of the monitor, but the interference in rates and timing
between your monitor and the overhead office fluorescent lighting. Setting
refresh to anything other than (and preferably above) 60Hz (US) would resolve
this.

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lloeki
Aren't LEDs fed with DC? If so they would obviously not flicker but I'll admit
not cracking my LED bulbs open just to see, as they're expensive enough.

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dredmorbius
LEDs are DC. What I've observed in certain applications, particularly LED
taillights/brake lights, is a flicker pattern which I suspect is either an
AC/DC conversion artifact, or a brightness regulation. I find it quite
distracting.

It's also fairly well known that LED's response to voltage variation is fast
enough to be of concern in highly secure data environments. Demonstrations
have been made of reading line signal from modems, and even Ethernet and other
high-bandwidth networking equipment status/indicator lights.

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essayist
Since water droplets look alike, you get the illusion, at the proper frequency
setting, of water dripping up.

I wonder how it would look if a different dye was injected into the flow every
few seconds, just above the faucet. Presumably, the colors would appear to
flow _down_ as the water appeared to drop _up_.

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sp332
Here's a crazier version: <https://vimeo.com/4041788> The camera takes frames
at 30 fps. But each frame is only exposed for 1/4000 of a second, which lets
you see the string as if it is holding still during the frame. And finally,
the camera has a "rolling shutter" so the bottom of the frame is captured
about 1/50th of a second after the top. This creates the visible wiggle in
each frame, as the string vibrates several times as the frame is recorded from
top to bottom.

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the_cat_kittles
I think the relevant wikipedia terms here are "Aliasing" and "Nyquist
Frequency"

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streptomycin
I would have said "Poincaré map", as that's basically what this is, in some
respect.

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sbarre
Whatever you want to call it, it's a very cool effect.. (edit: but thank you
for providing some educational context! Off to Wikipedia I go..)

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shashashasha
These kind of computer vision illusions are always really fascinating to me.
It's kind of like a natural zoetrope effect.

More: Bass String Video: <https://vimeo.com/4041788> The Phonotrope:
<http://www.jimlefevre.com/?page_id=200>

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marquis
Bill Viola did this using strobe lights in an installation format. You can
recreate this yourself easily with a programmable strobe. Thanks to Edgerton
for the inventions. <http://en.wikipedia.org/wiki/Harold_Eugene_Edgerton>

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yathern
My question is would this be possible with a strobe light? Or even better, a
florescent light? That would make some very impressive shows, if you could
have a whole hallway with different streams, all synchronized to the frequency
that the lights strobe at.

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DanBC
([http://hackaday.com/2011/03/11/water-droplet-sculpture-
using...](http://hackaday.com/2011/03/11/water-droplet-sculpture-using-leds-
and-arduino/))

There are plenty on YouTube. It is an amazing illusion.

I find it hard to understand how "a drop" seems to stay the same shape. I need
to think a bit more about that.

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jfoutz
think about an old tire rolling through paint. you'll see the same artifacts
every revolution of the tire. the key idea is every cycle creates the same
pattern.

so, you could have a mechanical system that hit the tube every /24th of a
second, and you'd get some effect, but i think it would be hard to get the
impact and recovery to be EXACTLY the same, or close enough you don't notice.

If you use sound to squeeze the tube, rather than pushing on it, the
distortion and recovery are much more consistent, so you get the same pattern.
I'd guess you don't have much control over where the drops actually appear.
you'd have to wiggle the tube around on the speaker to get the right
distortion.

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loceng
Does this signal our perception of the universe is structured by the energy's
surrounding us? We did evolve along with all of these energies.

The human mind is malleable and dynamic, not fixed like a 24 FPS camera lens
(I imagine most humans don't have a fixed framerate for incoming sensory) - I
do wonder if other critters with less dynamic minds would fail to some kind of
trick.

I wonder too if it was this kind of dynamic ability that allowed us to
disconnect from a fixed reality, thereby giving us contrast, the ability to
analyze our surroundings, and therefore consciousness.

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bch
zoetropes on bicycle wheels:
[http://www.designboom.com/weblog/cat/8/view/17851/bike-
wheel...](http://www.designboom.com/weblog/cat/8/view/17851/bike-wheel-
animation-by-katy-beveridge.html)

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Blunt
really an optical illusion? I heard two different flows of water splashing in
the bucket which I would not expect if it was just an optical trick.

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JVIDEL
Just another trick like the "hovering" russian helicopter...

The matrix didn't go BSOD when Crysis launched, it wont go because of a
reverse stream of water...

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melvinng
my dog started acting up when I turned this on, any relation?

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nirvana
Camera's are not the same as reality. They take images at a certain number of
frames per second. 24, 30 or 60 are common frame rates for digital cameras.
Thus, the camera is effectively its own strobe.

Since the frequency in the speaker is 24 hertz and camcorders can be set at 24
frames per second, it is likely that this is what is happening here-- the
speaker frequency is causing pressure differentials in the water, the water's
surface tension causes the succession of drops to form similar shapes, and the
camera taking an image at the same frequency of as the speaker makes things
look still because the drops are in exactly the same spot each frame.

You can notice on one of the lower bubbles further away from the spout the
effect is less precise and the bubble seems to be changing shape or moving
around.... this is because the effect of he speaker on the water decreases
over time as the water gets further away and air turbulence causes the drops
shape to pick up more randomness.

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rsanchez1
We can read the description on the video, you know.

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maeon3
Another trick is to take a rope and wiggle it at say 2 to 20 hz and take a
strobe light to light up at 1 to 15 hz. In the dark the rope will show a
perfectly formed sin wave which is spooky to look at.

Another one is putting clear plastic wrap over a subwoofer, making it face
upward, and sprinkling salt on the surface. The patterns it creates look like
alien symbols as you explore the spectrum.

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rsanchez1
This is your universe at 24 Hz.

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pjscott
It usually looks like the universe at any other reasonable frequency, unless
you're doing weird things at a multiple of 24 Hz.

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petegrif
Cool.

