Wednesday, July 2, 2025

Move over, Erdős Pál

h/t Reynolds: the monostable tetrahedron, courtesy Gábor Domokos and Gergő Almádi (and Robert Dawson). The former two names might be reversed in this language off the steppe.

Tetrahedrons are four-sided dice, or as we Dungeon-Masters used to called them: caltrops. They're looking for a loaded die that always falls on the "4" side. John Horton Conway and Richard Guy thought it existed but could not prove it. Now they can: if they hollow out the thing, and overweight the "4" side. Like, by thousands.

In material-science, those proportions can be had by using tungsten on the one side and carbon-fibre on the others.

They want this for Lunar landers which, lately, keep falling over.

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