In the mid-19th century, Bernhard Riemann conceived of a new way to think about mathematical spaces, providing the foundation for modern geometry and physics.

Whenever someone talks about black holes, they almost always talk about the event horizon and the singularity. After all, ...

The setup is simple. One partner points out a bird to the other — or in a common variation, recounts a fake bird encounter from earlier in the day — and awaits a response. A partner who responds with ...