Billions and billions.
For years I've been stressing with regard to UFOs that extraordinary claims require extraordinary evidence.
On the day that we do discover that we are not alone, our society may begin to evolve and transform in some incredible and wondrous new ways.
Science is a way of thinking that helps you not to fool yourself.
Imagination will often carry us to worlds that never were. But without it we go nowhere.
It will not be we who reach Alpha Centauri, and the other nearby stars. It will be a species very like us - but with more of our strengths and fewer of our weaknesses.