Archimedes' Lab Experimental Geometry

Tetrahedron marble top

This incredible marble top, when spun on its base as shown below (fig. A), will tip itself over automatically and continue spinning on its "stem" (fig. B) -- a behaviour caused by sliding friction effects with the ground.
How to make a tetrahedron marble top
Take 4 standard marbles and glue them together with a strong quick-setting glue by assembling them into a two layer tetrahedron (kind of pyramid). It's all.
How to spin your tetrahedron marble top
Grap one marble between your thumb and forefinger and... spin!