These two astronomers spend their nights in the observatory at Oakland's Chabot Space and Science Center policing the skies for doomsday asteroids; those wider than roughly 3,000 feet.
None have been spotted so far, which is probably not a good thing. Remember the dinosaurs? It's only a matter of time before we have a rock that big thwack us again. It'd be nice to know where it is.
The men are part of a worldwide network of volunteer astronomers tracking 5,000 known asteroids, a thousand of which could cause some serious damage.
One named Apophis is one such headache. This enormous chunk (700 - 1000 feet in diameter) is much bigger than the one that created a quarter-mile wide crater in Arizona. Astronomers won't know until Friday the 13th of 2029 when Apophis breezes by Earth if it will come back and slam into us in 2036.
Don't worry. We're not totally helpless against Apophis. One idea involves NASA launching a "gravity tractor" which would nudge the rock in a different away from Earth.
Gerald's not sweating it. He points out that you have a better chance of getting hit by a car when crossing the street than getting nailed by an asteroid. That's reassuring.