Do you believe in first love - or should I pass by again?

A theory is a good theory if it satisfies two requirements: it must accurately describe a large class of observations on the basis of a model that contains only a few arbitrary elements, and it must make definite predictions about the results of future observations.

A million million million million (1 with twenty-four zeros after it) miles, the size of the observable universe.

If I have questions about the universe on my mind when I go to bed, I can't turn off. I dream equations all night.

A model is a good model if first it interprets a wide range of observations in terms of a simple and elegant model, and second if the model makes definite predictions that can be tested, and possibly falsified, by observation.

Using e-mail, I can communicate with scientists all over the world.

What is important is that we have the ability to create.