# Why does this object periodically turn itself?

See below gif image taken from here.

1. Is this a real effect?

2. Why does it seem to turn periodically?

3. Can it be explained by classical mechanics alone?

4. Is there a simple equation that models this behaviour?

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Related post Dzhanibekov Effect on MO –  Pratik Deoghare Nov 27 '11 at 10:34
Wow, this is awesome. And just in Chapter 2 in my undergrad physic's book :-) –  Martin Ueding Nov 27 '11 at 15:27
L. D. LANDAU and E. M. LIFSHITZ, "MECHANICS": The asymmetrical top –  Martin Gales Nov 28 '11 at 8:06
The answer! –  Dale Jun 20 '13 at 19:06

It's a classical mechanics effect for sure although a really interesting one. Following links on "Dzhanibekov effect" one gets at Marsden and Ratiu's "Introduction to Mechanics and Symmetry" Chapter 15 Section 15.9 "Rigid Body Stability" treating this with use of the Casimir functions.

From remark 1: A rigid body tossed about its middle axis will undergo an interesting half twist when the opposite saddle point is reached.

Here is another and more profound example under weightless conditions.

This seems to be a home experiment where a guy throws the spinning object upwards.