If you get asteroids about a kilometer in size, those are large enough and carry enough energy into our system to disrupt transportation, communication, the food chains, and that can be a really bad day on Earth.

I never got into 'Star Wars.' Maybe because they made no attempt to portray real physics. At all.

When asked about which scientist he'd like to meet, Neil deGrasse Tyson said, "Isaac Newton. No question about it. The smartest person ever to walk the face of this earth. The man was connected to the universe in spooky ways. He discovered the laws of motion, the laws of gravity, the laws of optics. Then he turned 26.

Photography is a form of time travel.

We're quite happy with our Big Bang description of cosmic origins. But actually, the Big Bang accounts for what happened only after the beginning. The beginning itself, and especially what happened before, remains the biggest mystery of all.

When scientifically investigating the natural world, the only thing worse than a blind believer is a seeing denier.

Something bad happened on both Mars with its dried-up watercourses and Venus with its runaway greenhouse effect. Could something bad happen on Earth too? Our species currently turns row upon row of environmental knobs, without much regard to long-term consequences.