As you pass from sunlight into darkness and back again every hour and a half, you become startlingly aware how artificial are thousands of boundaries we've created to separate and define. And for the first time in your life you feel in your gut the precious unity of the Earth and all the living things it supports.

Anytime we can save lives or prevent the destruction of property, we should do it.

While we didn't know the dinosaurs personally, we do know that they were wiped out by an asteroid impact.

If we do our homework right, never again should an asteroid that can do damage on the ground impact the Earth. We're living in a time-with our technology-we have the capability to eliminate that major shaper of evolution . . . the evolution of life on this planet.

By preventing dangerous asteroid strikes, we can save millions of people, or even our entire species. And, as human beings, we can take responsibility for preserving this amazing evolutionary experiment of which we and all life on Earth are a part.

As you pass from sunlight into darkness and back again every hour and a half, you become startlingly aware how artificial are thousands of boundaries we've created to separate and define. And for the first time in your life you feel in your gut the precious unity of the Earth and all the living things it supports.

There's no accepted global policy on what to do about asteroid impacts.