I often reflect on what an extraordinary time (pun intended) it is to be alive here in the beginning of the twenty-first century. It took life billions of years to get to this point. It took humans thousands of years to piece together a meaningful understanding of our cosmos, our planet and ourselves. Think how fortunate we are to know this much. But think also of all that's yet to be discovered. Here's hoping the deep answers to the deep questions-from the nature of consciousness to the origin of life-will be found in not too much more time.

The most serious problem facing humankind is climate change.

If you have this idea that the earth is only 6,000 years old, you are denying, if you will, everything that you can touch and see. Youre not paying attention to whats happening in the universe around you.

The more you find out about the world, the more opportunities there are to laugh at it.

Burning carbon-based substances like oil, gas, and especially coal, produces billions of tons of extra carbon dioxide each year. Methane gas from cows and pigs and other animals on our large farms ends up in the atmosphere as well, trapping more of the sun's energy as heat.

We should educate more women and girls. Because that is the surest route to controllably, manageably reducing the human population. Educated women have fewer kids. And the kids they do have are better cared for and are more successful. As I like to say, it's not one thing that we need to focus on. It's everything all at once.

The natural world is a package deal; you don't get to select which facts you like and which you don't.