It is characteristic of all deep human problems that they are not to be approached without some humor and some bewilderment.

One of the memorable moments of my life was when Willard Libby came to Princeton with a little jar full of crystals of barium xenate. A stable compound, looking like common salt, but much heavier. This was the magic of chemistry, to see xenon trapped into a crystal.

Climate change is part of the normal order of things, and we know it was happening before humans came.

In the long run, the only solution I see to the problem of diversity is the expansion of mankind into the universe by means of green technology... Green technology means we do not live in cans but adapt our plants and our animals and ourselves to live wild in the universe as we find it... When life invades a new habitat, she never moves with a single species. She comes with a variety of species, and as soon as she is established, her species spread and diversify further. Our spread through the galaxy will follow her ancient pattern.

Many of the technologies that are now racing ahead most rapidly, replacing human workers in factories and offices with machines, making stockholders richer and workers poorer, are indeed tending to accentuate the existing inequalities in the distribution of wealth.

The technologies which have had the most profound effects on human life are usually simple. A good example of a simple technology with profound historical consequences is hay. Nobody knows who invented hay, the idea of cutting grass in the autumn and storing it in large enough quantities to keep horses and cows alive through the winter. All we know is that the technology of hay was unknown to the Roman Empire but was known to every village of medieval Europe. Like many other crucially important technologies, hay emerged anonymously during the so-called Dark Ages.

We won't really understand the brain until we can make models of it which are analog rather than digital, which nobody seems to be trying very much.