Euler's Spinning Disk Euler's Disk amazes as it demonstrates the math and physics of spolling (spinning and rolling) of rigid bodies Spin the included disk on the concave mirror and watch as the disk spolls for remarkably long periods of time As it spolls, its appearance changes and it begins to generate a mysterious hum until the motion abruptly ends A fascinating and entertaining toy for any scientifically minded child or adult; Makes a great desk toy