James Propp wrote:
...I propose that someone build a tetrahedron...
Michigan artist David Barr designed his "Four Corners Project" in 1976. It is an Earth-sized regular tetrahedron that spans the planet, with just the tips of its four corners protruding. These visible portions are four-inch tetrahedra, which protrude from the globe at Easter Island, Greenland, New Guinea, and the Kalahari Desert. Barr traveled to these locations and was able to permanently install the four aligned marble tetrahedra between 1981 and 1985. For details, see: Sandra L. Arlinghaus and John D. Nystuen, Mathematical Geography and Global Art: the Mathematics of David Barr's "Four Corners Project" Institute of Mathematical Geography monograph series 1986 http://www-personal.umich.edu/%7Ecopyrght/image/monog01/fulltext.pdf George http://www.georgehart.com