As people flock to urban centers where ground space is limited, cities with green walls and roofs and skyscraper farms offer improved health and well-being, renewable resources, reliable food supply, and relief to the environment.

In the winter, I enjoy cross-country skiing and raising orchids and amaryllises. If I could grow tropical flowers as perennials, I would, especially hibiscus and mandavilla.

Nature neither gives nor expects mercy.

Artificial intelligence is growing up fast, as are robots whose facial expressions can elicit empathy and make your mirror neurons quiver.

There is a way of beholding nature which is a form of prayer, a way of minding something with such clarity and aliveness that the rest of the world recedes. It . . . gives the brain a small vacation.

Not much is known about alligators. They don't train well. And they're unwieldy and rowdy to work with in laboratories.

We tend to think of heroes only in terms of violent combat, whether it's against enemies or a natural disaster. But human beings also perform radical acts of compassion; we just don't talk about them, or we don't talk about them as much.