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Comment by acqq | Hacker News Reader

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

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.

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.

Even at high frequencies? Because a strobe light gives you a lot more flexibility.

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

Yes I also think that if you can use strobe light and have the possibility to adjust the strobe frequency you don't even need a subwoofer, but for the proper "matrix-like" effect a lot of "frames per second" are needed and the camera gives certainly nicer result. In my opinion his setup was really quite optimal for what he presented.

See my comment above. You actually need the sound to create vibrations in the stream of water that breaks it up into drops. The coolest thing is that there really are drops here, it's not an optical illusion.

I'm not quite sure I'm following you. You don't need the sound to break the water into drops. You can do it without the sound by just adjusting the flow rate. I've done this.

Are you just saying that by using sound, you can break up an even faster stream, one that would ordinarily be too fast to break up on its own?

With sound, you can break the stream into the same pattern of drop every time

Indeed, when I was at MIT there was a exhibit in the Doc Edgerton hall that did exactly this with florescent food coloring for the water and a strobe. You could turn a dial and change the speed of the strobe, and the 'drops' would change direction into or out of the spouts. There were two spouts with streams hitting each other. A very cool effect.

It's been eons since I've been there, but I believe a reproduction of this is set up at the Boston Science Museum.

There's also one in the Hong Kong Children's Science Museum.

Yes, I was a bit disappointed, I was hoping that the effect was being caused by the AC mains frequency effecting the lighting. Ah well

I wonder if there's any way to make this into a decorative fixture? A strobe would be annoying, and a large LCD shutter in front would be expensive and spoil the effect somewhat. Any ideas?

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