The idea that excites me the most concerns the two greatest puzzles in science: the origin of the universe, and the origin of consciousness. The origin of the universe is what I do for a living, working on string theory. But I am also fascinated by consciousness.

The human brain has 100 billion neurons, each neuron connected to 10 thousand other neurons. Sitting on your shoulders is the most complicated object in the known universe.

You can mass-produce hardware; you cannot mass-produce software - you cannot mass-produce the human mind.

When we're born, we want to know why the stars shine. We want to know why the sun rises.

Aging is basically the build-up of error: error at the genetic level, error at the cellular level. Cells normally repair themselves; that's why you heal when you get a cut. But even the mechanism of repair eventually falls apart.

Eternal life does not violate the laws of physics. After all, we only die because of one word: "error." The longer we live, the more errors there are that are made by our bodies when they read our genes. That means cells get sluggish. The body doesn't function as well as it could, which is why the skin ages. Then organs eventually fail, so that's why we die.

As Heinz Pagels has said, The challenge to our civilization which has come from our knowledge of the cosmic energies that fuels the stars, the movement of light and electrons through matter, the intricate molecular order which is the biological basis of life, must be met by the creation of a moral and political order which will accommodate these forces or we shall be destroyed. It will try our deepest resources of reason and compassion.