We are made of star stuff. For the most part, atoms heavier than hydrogen were created in the interiors of stars and then expelled into space to be incorporated into later stars. The Sun is probably a third generation star.

What an astonishing thing a book is.

And after we returned to the savannahs and abandoned the trees, did we long for those great graceful leaps and ecstatic moments of weightlessness in the shafts of sunlight of the forest roof?

After I give lectures-on almost any subject-I am often asked, "Do you believe in UFOs?" I'm always struck by how the question is phrased, the suggestion that this is a matter of belief and not evidence. I'm almost never asked, "How good is the evidence that UFOs are alien spaceships?"

One trend that bothers me is the glorification of stupidity, that the media is reassuring people it's alright not to know anything. That to me is far more dangerous than a little pornography on the Internet.

Chlorine is a deadly poison gas employed on European battlefields in World War I. Sodium is a corrosive metal which burns upon contact with water. Together they make a placid and unpoisonous material, table salt. Why each of these substances has the properties it does is a subject called chemistry.

Writing is perhaps the greatest of human inventions.