What I have learned from life is to make the most of what you have got.

One can see from space how the human race has changed the Earth. Nearly all of the available land has been cleared of forest and is now used for agriculture or urban development. The polar icecaps are shrinking and the desert areas are increasing. At night, the Earth is no longer dark, but large areas are lit up. All of this is evidence that human exploitation of the planet is reaching a critical limit. But human demands and expectations are ever-increasing. We cannot continue to pollute the atmosphere, poison the ocean and exhaust the land. There isn't any more available.

Someone told me that each equation I included in the book would halve the sales.

Any physical theory is always provisional, in the sense that it is only a hypothesis: you can never prove it.

One cannot really argue with a mathematical theorem.

I think those who have a terminal illness and are in great pain should have the right to choose to end their own life, and those that help them should be free from prosecution.

It's clearly possible for a something to acquire higher intelligence than its ancestors: we evolved to be smarter than our ape-like ancestors, and Einstein was smarter than his parents.