This recent toy is an amazing optical illusion. It is apparently based on a display piece housed in several Science Museums around the world costing many millions of dollars.
Descending droplets of water appear to defy gravity. Perfect water droplets can be suspended in mid-air within the backlit display box and then made to magically rise upwards. Impossible to describe – seeing is believing. No wires, no tubes.
How does it work? Well the device produces a steady stream of water droplets, falling under gravity. Just inside the frame of the box is a series of strobe lights, and if these flash exactly in time with the falling drops, then the droplets appear to be stationary. A small adjustment of the strobe timing can make the drops appear to be moving up or down. Magic!