Through the Looking Glass

Reflections on a mirror universe.

There are more things in Heaven and Earth, Horatio, than are dreamt of in your philosophy.

Alice ventures into the mirror world. Illustrations: John Tenniel, Alice in Wonderland
How can she tell which side of the glass she’s on?
An asymmetry of nature: Neutrinos spin in just one direction, so they would all spin in the opposite direction in the mirror world.