First Shape Found That Can’t Pass Through Itself
A geometry problem that originated with a royal bet has been solved after more than three centuries.
Imagine holding two equal-size dice, and consider whether it's possible to bore a tunnel through one die that’s big enough for the other to slide through.
In the late 1600s, an unidentified person placed a bet to that effect with Prince Rupert of the Rhine, who spent his later years studying metallurgy and glassmaking.
The mathematician John Wallis proved mathematically that a straight tunnel in the direction of one of the cube’s inner diagonals can be made wide enough to allow another cube through.
Author's summary: Geometry problem solved after 300 years.