A galaxy is composed of gas and dust and stars - billions upon billions of stars. Every star may be a sun to someone.

Eratosthenes's only tools were sticks, eyes, feet, and brains; plus a zest for experiment. With those tools he correctly deduced the circumference of the Earth, to high precision, with an error of only a few percent. That's pretty good figuring for 2200 years ago.

And you are made of a hundred trillion cells. We are, each of us, a multitude.

If we are merely matter intricately assembled, is this really demeaning? If there's nothing here but atoms, does that make us less or does that make matter more?

Books tap the wisdom of our species -- the greatest minds, the best teachers -- from all over the world and from all our history. And they're patient.

[One's] inability to invalidate your hypothesis is not at all the same thing as proving it true.

I'm only a four-dimensional creature. Haven't got a clue how to visualise infinity. Even Einstein hadn't. I know because I asked him