Stephen Hawking

Imaginary time is a new dimension, at right angles to ordinary, real time.

There is nothing bigger or older than the universe.

One can't predict the weather more than a few days in advance.

We define ourselves as intelligent. That's odd, because we're doing the definition - We're creating our own definition and saying, 'We are intelligent!'

Well, I actually wrote her a letter a couple of days ago congratulating her. The tone I tried to convey in the letter is, look, you are a part of a great American historical process.

An economist is an expert who will know tomorrow why the things he predicted yesterday didn't happen today.