When you’re bracing for war, facing down the Nazis and preparing to become the only fighting democracy on the continent of Europe, you’d think have more than enough to think about. But in 1939, British Prime Minister Winston Churchill had one other thing on his mind: extraterrestrials. According to a newly revealed essay that Sir Winston wrote on the brink of World War II, the polymath PM was not only sanguine about the possibility of life on other planets, but anticipated much of the modern science that justifies that optimism.

The essay, described in an article in the current issue of Nature, by astrophysicist and best-selling author Mario Livio, had been filed away for decades at the United States National Churchill Museum in Fulton, Missouri. Last year, Li…