"We must realise that there are other worlds in other parts of the universe, with races of different men and different animals." That was the Roman poet Lucretius, writing in the 1st century BC.
Only in the past few decades have we grasped the truth of the first part of that statement, thanks to planet-hunters such as NASA's Kepler space telescope. Almost 5000 suspected planets have already been spotted outside our solar system, and stars nursing planets seem to be the rule, not the exception. With hundreds of billions of stars in our galaxy alone, that's an awful lot of worlds.
Surely, then, it's only a matter of time before we confirm the second part by finding signs of life.
Perhaps. Life on Earth has required billions of years to evolve organisms capable of asking such questions, and that process has been anything but inevitable. Other life, ...
To continue reading this article, subscribe to receive access to all of newscientist.com, including 20 years of archive content.
