What is the name of the "Egyptian artifact" that will only move counter-clockwise?

Question

Our Earth and Space science teacher showed us today an "Egyptian artifact," and it only moves counter-clockwise. If you try turning it clockwise, it will stop, then move counter-clockwise. They come in 4 colors: pink, red, blue, and green.

Answer 1

They are called a rattleback or wobblestone or dynamic Celt or probably a hundred other names.  There are lots of physical variations, too.

The physics is both simple and complex.  The simple:

The underside of the object looks smooth and symmetrical but it is slightly asymmetrical.  When the object is rotated in one direction it slips as it turns but in the other direction the rotation is unstable.  The object slows down and as it does it stores some of its rotational energy in a wobbling motion.  

After it stops rotating in the unstable direction the energy stored in the rocking motion is then transferred into a reverse rotational motion (the stable direction) through the action of the asymmetrical bottom surface.

Answer 2

It's called a rattleback or celtic stone. Here's an article that explains how it works:

http://en.wikipedia.org/wiki/Rattleback