Making water appear to levitate usually requires a strobe light to trick the eye. If you don't have a fancy system to control water flow, you can run water through a tube taped to a speaker playing very low frequency sound, and again use a strobe light to make the water appear to defy gravity. Or you can ditch the strobe, and sync the sound waves to the frame rate of a video camera to make water drops appear to hover.
posted by filthy light thief on Apr 12, 2012 - 15 comments

See For Yourself - Purves Lab's optical illusions web page with empirical explanations of familiar and unfamiliar illusions.
posted by nthdegx on Nov 16, 2007 - 6 comments

Is the dancer spinning clockwise or counterclockwise? An optical illusion. [more inside]
posted by painquale on Oct 8, 2007 - 133 comments

Your daily dose of perception-bending. Stare at the center of this video (wmv or flash) for a minute or two then look away from the screen at your surroundings. You'll experience an interesting and somewhat disconcerting effect. Not appropriate for anyone prone to headaches or seizures.
posted by brain_drain on Aug 28, 2006 - 51 comments

Rapid Afterimage Optical Illusion
posted by srboisvert on Jun 6, 2005 - 38 comments

Interesting Optical Illusion - and explanation. {It's just a single page with an image. Go on, click it!}
posted by dobbs on Nov 13, 2004 - 24 comments

Utterly terrifying! [Windows Media, from Grand Illusions]
posted by Pretty_Generic on Nov 13, 2004 - 15 comments

This is the coolest optical illusion you'll ever see. Happy Friday. (Warming: .exe format, about 250k)
posted by skechada on Jan 10, 2002 - 17 comments