Nasa's search for 2nd Earth?

The US space agency's first mission to look for habitable, Earth-sized planets has begun, or has it?

The launch of the Kepler spacecraft from Cape Canaveral in Florida today marks the beginning of the most ambitious hunt for planets like ours in distant solar systems.

The Kepler telescope will spend three-and-a-half years staring deep into a starry region of the Milky Way, in the direction of the constellations Cygnus and Lyra, in the hope of spotting Earth-sized planets as they pass in front of their stars.

Every half hour, Kepler will record the brightness of 100,000 stars using a 95 megapixel camera built by the British firm e2v.

The camera is so sensitive, it could spot the imperceptible dimming of a car headlight as a fly wanders across it.

(lets hope they don't turn it towards earth!)

The mission will focus its attention on planets in the "Goldilocks region" of space, where conditions are just right for liquid water to exist. Some of these worlds could potentially be home to life as we know it.

By the end of the mission, we may have a clearer idea of our place in the universe, and whether warm, wet rocks like Earth are the exception rather than the rule.