For as long as humans have looked to the night sky to divine meaning and a place in the universe, we have let our minds wander to thoughts of distant worlds populated by beings unlike ourselves. The ancient Greeks were the first Western thinkers to consider formally the possibility of an infinite universe housing an infinite number of civilizations.

We've talked in this space in the past few months about detecting the existence of Earth-like planets in other solar systems, and on the educated guesswork which goes into putting a number on the probability of intelligent life existing out there as well. You may remember that the discovery of terrestrial planets is well on its way as technology improves; and that the Drake equation—with all its assumptions—has proved to be remarkably accurate.

Radivoje Lajic thinks aliens don't like him. The Bosnian man says his home has been hit by meteorites no less than five times. He took the rocks to experts at Belgrade University, who confirmed that they are the real thing. But they haven't been able to verify that Lajic did anything to anger the extraterrestrials, or that he's the target of some extra-planetary prank. Still, Lajic seems sure this isn't just a coincidence.

Astronomers can say with near certainty that there are no moons with moons in our solar system. But that doesnt mean its physically impossible. After all, NASA has successfully put spacecraft into orbit around our moon.

SETI@home—part of the Search for Extraterrestrial Intelligence—is one of the earliest successful distributed computing projects. Its intent is to discover the presence of extraterrestrial life by analyzing radio signals from deep space. I remember the excitement of joining in late 1999, watching the candy-colored bars make their way across the client screen as my computer worked to detect meaningful variations in the cloud of noise. SETI has not yet been successful—that would be pretty big news—but the distributed computing model that has come out of it has.

When we catch up with the robot, it is poking along in a herky-jerky and rather flummoxed fashion through the Atacama Desert, which covers much of far northern Chile. The Atacama is reputedly the driest place on Earth, with rainfall measured in millimeters per decade. It is a rough place for man or robot, a tawny maze of high plateaus and shaley foothills under constant sun and an enormous cobalt-blue sky.