Using the properties of previously discovered exoplanets (that is, planets outside of our solar system) and their dates of discovery, Sam Arbesman and Greg Laughlin predict that the discovery of the first Earth-like exoplanet will likely occur in early May 2011.

Of course, it's a bit more complicated than that, but here's an overview of what we did. Using the properties of previously discovered exoplanets, we developed a simple metric of habitability for each planet that uses its mass and temperature to rate it on a scale of 0 to 1, where 1 is Earth-like, and 0 is so very not Earth-like. Plotting these values over time and taking the upper envelope yields a nice march towards habitability.

The authors don't address this directly in their paper, but I wondered what the Moore's Law for planetary discovery might be — e.g. every X years (or months?), the habitability of the most habitable planet discovered doubles. So I emailed Sam Arbesman and he said that his quick back of the envelope calculation would be "half a month or so"...which is an astounding pace.