The nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in our apple pies were made in the interiors of collapsing stars. We are made of starstuff.

Even today the most jaded city dweller can be unexpectedly moved upon encountering a clear night sky studded with thousands of twinkling stars. When it happens to me after all these years it still takes my breath away.

Books are like seeds. They can lie dormant for centuries and then flower in the most unpromising soil.

Whatever the reason you're on Mars, I'm glad you're there, and I wish I was with you.

I believe that in every person is a kind of circuit which resonates to intellectual discovery-and the idea is to make that resonance work

Some 5 billion years from now, there will be a last perfect day on Earth... then the sun will begin to die, life will be extinguished, the oceans will boil and evaporate away.

Who are we? We find that we live on an insignificant planet of a humdrum star lost in a galaxy tucked away in some forgotten corner of a universe in which there are far more galaxies than people.