Consider the following object: The exact dimensions are unimportant, but its x, y and z dimensions must not be too similar (so I'm told). I have been told that an object such as the one above will behave strangely when thrown up into the air whilst spinning. If it is sent spinning on its x-axis then it will continue to do so until it falls back into your hands. If it is sent spinning on its z-axis then it will continue to do so until it falls back into your hands. But if it is sent spinning on its y-axis, it will begin to twist in mid-air. At first I didn't believe it, and I certainly could see any physical reason for it to behave like this, but I've been trying this out by throwing my calculator up in the air and it works! What's going on? Is it because the calculator isn't uniformly dense? Is it to do with air resistance? Is it to do with gravity? I'm told that it works in a vacuum with uniformly dense objects too, but I can't check that. Please help to fix my intuition -- this one's baffling me!