It’s incredible that in our lifetime we will know how many earth-like planets there are in the galaxy. The NASA Kepler mission has been staring at one patch of sky for more than a year now, looking for winking stars. These are the kind that dim ever-so-slightly when a planet passes between them and us. Finding Jupiters is relatively easy; finding Earths … not so much. But Kepler has shown that it is up to the task. A few weeks ago, the first results were published, and it turns out that out of about 150,000 stars, 54 of them have planets in the habitable zone – the distance from the star that might support liquid water on the surface. Is that incredible, or what? — 54! — It may not sound like much, but for all the centuries of people looking up into the sky and wondering if there were…