1For many centuries, human beings have wondered whether we are truly alone in the vast universe.
2So far, we have found no certain proof of life anywhere beyond our own planet.
3However, during the past thirty years, scientists have discovered thousands of planets circling far distant stars.
4Some of these distant worlds lie in the special zone where liquid water could possibly exist.
5Astronomers carefully study the faint light that passes through the thin air of these planets.
6Certain unusual gases hidden in that light might be clear signs of simple living things.
7Giant radio telescopes also listen patiently day and night for any messages from other intelligent civilisations.
8So far, the great sky above us has remained silent, but the careful search continues.
9Perhaps one quiet day in the future we will finally receive an answer from the stars.
10Until that day comes, the great question keeps us looking up at the night sky.