In this way, Edwin Hubble worked out the distances to nine different galaxies. We now know that our galaxy is only one of some hundred thousand million that can be seen using modern telescopes, each galaxy itself containing some hundred thousand million stars.

We explore because we are human and we want to know. I hope that Pluto will help us on that journey.

You may see a cup of tea fall off a table and break into pieces on the floor... But you will never see the cup gather itself back together and jump back on the table. The increase of disorder, or entropy, is what distinguishes the past from the future, giving a direction to time.

I've noticed that even people who believe in fate look both ways before crossing the street.

I don't want to write an autobiography because I would become public property with no privacy left.

The downside of my celebrity is that I cannot go anywhere in the world without being recognized. It is not enough for me to wear dark sunglasses and a wig. The wheelchair gives me away.

But a machine that was powerful enough to accelerate particles to the grand unification energy would have to be as big as the Solar System - and would be unlikely to be funded in the present economic climate.