For millennia humans studying the stars had no idea if there were any other planets outside our solar system, let alone ones similar enough to ours to sustain life. The first extra-solar planet – or exoplanet – was only discovered in 1995. Now, a new space-based telescope has discovered thousands more, and some of them may be just like Earth. If the Kepler Space Telescope’s discoveries are verified, and if what is true for this one tiny randomly chosen area of the cosmos is true throughout, then our universe is probably chock full of habitable planets. This discovery would have enormous implications for the possibility of extra-terrestrial life. We would move from slim chance to great likelihood in one giant step. And we’re about to take that step.