Monday was ‘moon day’ : the anniversary of the Apollo 11 moon landing in 1969, now 46 years ago in the rear view mirror. We may no longer land on the moon (or Mars, as people surely thought back then, we would be by now) .. but we are certainly exploring our galaxy with telescopes and unmanned spacecraft. ‘Our galaxy’ is the Milky Way, of course. And ‘our’ sun is but one of 200 billion stars in the Milky Way. That makes for about 11 billion other planets that are orbiting their suns in the habitable zone : at a distance not too warm and not too cold, so that there could be liquid water on the planet. And where there is water, there may be life.