3
votes
2answers
1k views

Why does a Penrose Stair seem to be correct?

Penrose Stairs seem to be a locally valid but globally inconsistent contraption. I have a couple of questions: Is it physically realizable? In other words, is it possible to build a 3-D structure of ...
35
votes
6answers
2k views

A variant of the Monty Hall problem

Everybody knows the famous Monty Hall problem; way too much ink has been spilled over it already. Let's take it as a given and consider the following variant of the problem that I thought up this ...