There is a theorem that colloquially translates, You cannot comb the hair on a bowling ball. ... Clearly, none of these mathematicians had Afros, because to comb an Afro is to pick it straight away from the scalp. If bowling balls had Afros, then yes, they could be combed without violation of mathematical theorems.

We should not be ashamed of not having answers to all questions yet... I'm perfectly happy staring somebody in the face saying, 'I don't know yet, and we've got top people working on it.' The moment you feel compelled to provide an answer, then you're doing the same thing that the religious community does: providing answers to every possible question.

I have a personal philosophy in life: If somebody else can do something that I'm doing, they should do it. And what I want to do is find things that would represent a unique contribution to the world-the contribution that only I, and my portfolio of talents, can make happen. Those are my priorities in life.

So while you're getting ripped apart head to toe as you fall into a black hole, you will also extrude through the fabric of space and time, like toothpaste squeezed through a tube. To all the words in the English language that describe ways to die (e.g., homicide, suicide, electrocution, suffocation, starvation) we add the term spaghettification.

The greatest teachers are the ones that turn a B student into an A student, or a failing student into a B student.

The caricature of science is that we hold tight to the theories we have, and shun challenges to them. That's just not true. In fact, we hold our highest rewards for those scientists who can prove others wrong. And by the way, they are famous in their own lifetimes. We don't wait until they're dead.

In any city with lots of skyscrapers, lots of skyline, the moon seems bigger than it is. It's called the moon illusion.