"Hey kids," said physicist Tadashi Tokieda, "Wanna see a magic trick?" He pulled out a Slinky and did something that amazed the kids, & their dad Steve Strogatz. Steve, along with Neil deGrasse Tyson, explains what the gravity-defying Slinky trick reveals about the nature of all things great and small (including us).

The mathematician Charles Lutwidge Dodgson posed a big question about mirrors in one of his best-known books: Through the Looking-Glass (yup, Dodgson's pen name was Lewis Carroll). Natasha Gostwick of Storynory reads an excerpt that gets at the heart of the trouble: is mirror milk any good to drink? ...

Just after the Big Bang, the universe was a primordial soup made of light. Then, it started belching out matter. Neil deGrasse Tyson explains how deeply shocking this is, and Marcelo Gleiser reveals an imperfection in the laws of physics that makes our very existence possible.

A mysterious case of the topsy turvies and a return to the question of what felines feel when they fall.

Two stories of falling in everyday life, and one fantastical leap:

6. Falling Asleep: Professor Frederick Coolidge argues that our tree-dwelling ancestors are to blame for a hiccup in our sleeping patterns.

7. Walking as Falling: David Eagleman explains walking as the act of calibrating our steps to turn falls into forward motion.

8. Falling Apart: Neil deGrasse Tyson takes us on a one-way trip into a black hole.