The Kepler is a one-ton satellite set to be blasted into orbit around the Sun, far away from all the distracting background noise of Earth - in any aspect of the search for intelligent life, it's important to be as far from American Idol as possible. The probe will make over six billion stellar measurements in order to detect any Earth-alikes hiding in the stars.
At the moment our main method of planet-detection is the "wobble method", which sounds awfully unscientific for an interplanetary investigation. It's based on observing how much the planet pulls its host star - the problem being that stars are very big, while planets are pretty small, so we've only found unusually huge and close-in planets this way. Planets which couldn't possibly support life as we know it.
Kepler will instead observe stars steadily for forty two months, measuring every single one every half hour. If a planet passes in front of the star the brightness will dip by a tiny fraction, only one part in fifty thousand, but detectable by Kepler's ninety-five megapixel camera. Any number of things should cause such a dip - but only planets will do so on a regular schedule (once a year to them, of course).
Kepler can only see planets whose orbits line up between the star and the satellite, but with a hundred-thousand candidates some certainly should. We may make out many, meaning that We Are Not Alone. We might see nothing, in which case make friends with your neighbor because we're All There Is. Either way, our place in the universe will be radically redefined.
Posted by Luke McKinney