The big questions

Why the universe looks fine-tuned for us — and what that observation can and cannot prove.

A handful of numbers could have been almost anything. They landed in a narrow band that allows atoms, stars, and chemistry.

Martin Rees's dials — gravity, the nuclear force, dark energy, and three more — and what each one does.

The improbability of your existence, stacked from the Big Bang to the specific sperm and egg that became you.

Brute fact, necessity, a multiverse, or design. Each has serious defenders and serious problems.

"The multiverse" isn't one idea but several. Max Tegmark famously sorted them into four levels.

Heat death, the Big Crunch, the Big Rip, and a stranger fate hiding in the vacuum itself.

The word is older than the company by half a century. Here is where it actually comes from.