ARE we alone in the universe? For centuries that question has been purely speculative, but now, for the first time, there is genuine cause for hope of getting an answer.
The first results from NASA鈥檚 planet-detecting Kepler space telescope suggest that Earth-sized planets are more common than we dared hope. Its survey of some 150,000 stars has already found 68 such planets, some of which are in their star鈥檚 鈥済oldilocks zone鈥� 鈥� neither too hot nor too cold to support life. Given that it鈥檚 early days for the Kepler survey, and given the limitations of its detection methods (see 鈥淲hat鈥檚 an alien solar system like?鈥�), it is reasonable to conclude that the Milky Way is teeming with planets like ours.
This is real progress. When Kepler was launched less than two years ago, nobody could predict with confidence how many Earth-sized planets it would find.
Advertisement
Of course, finding potentially habitable Earth-sized planets is a million miles from finding inhabited ones. Kepler is not fitted with instruments capable of seeing evidence of life and it will be many years before we can search for unambiguous signs of life on distant worlds.
Optimists suggest that we will have an answer within two decades. If so, people alive today may become the first to wrestle with the knowledge that Earth isn鈥檛 the only living planet in the universe.
鈥淧eople alive today may be the first to wrestle with the knowledge that Earthlings aren鈥檛 alone鈥�
What are the implications of such knowledge? One school of thought has it that it doesn鈥檛 matter: alien life is unlikely to be intelligent, and even if it was it would be too far away to communicate with, let alone visit. We might as well accept that for all practical purposes we are alone.
This 鈥渕isanthropic principle鈥� is rather mean-spirited. The mere detection of life elsewhere would be one of the most profound discoveries of all time.
After all, if an alien civilisation that thought itself alone in the cosmos had spotted Earth any time between 3.8 billion and about 5000 years ago it would have concluded that there was no intelligent life on the planet. But you can bet that the discovery of even basic Earth-life would have been met with the awe and wonder that comes with knowing, at last, that you are not alone.