The search for ET may soon yield an answer

MOST SCIENTIFIC research has practical ends. But some still pursues goals better described by the field’s original name: “natural philosophy”. One of its most philosophical questions is, “Is there life elsewhere in the universe?”

It is philosophical for two reasons. One is its grand sweep. If there is life elsewhere, particularly of the intelligent sort, that raises the question of whether humans might ever encounter it, or its products (see article). If there is not—if all the uncountable stars in creation waste their light on sterile, lifeless worlds—then life on Earth must be the result of a stroke of the most astronomically improbable good luck. As Arthur C. Clarke, a science-fiction author, is reputed to have said: “Two possibilities exist. Either we are alone in the cosmos or we are not. Both are equally terrifying.”