If the rate of expansion one second after the Big Bang had been smaller by even one part in a hundred thousand million million, it would have recollapsed before it reached its present size. On the other hand, if it had been greater by a part in a million, the universe would have expanded too rapidly for stars and planets to form.

When something is made idiot proof, they will just make better idiots.

Nothing is fool-proof to a sufficiently talented fool.

I believe everyone should have a broad picture of how the universe operates and our place in it. It is a basic human desire. And it also puts our worries in perspective.

The progress of the human race in understanding the universe has established a small corner of order in an increasingly disordered universe.

The human capacity for guilt is such that people can always find ways to blame themselves

If any one of about 40 physical qualities had more than slightly different values, life as we know it could not exist.