The idea of water flowing backwards, or stopping all together is the thing of science fiction. Right? Wrong. As the video shows, a subwoofer producing a 24Hz sine can be used to create a very cool optical illusion, with the water caught ‘frozen’ or running backwards simply by varying the frame rate on the camera. Basically your camera’s frame rate is synced up with the rate of the vibrations of the water so it appears to be frozen or still. Now if you play a 23 hz sine wave your frame rate will be off just a little compared to the sine wave causing the water to “move backward” or so as it appears. You can play a 25 hz sine wave and cause the water to move slowly forward. Mind. Blown.
Click the pic to watch it happen.