"I, for one, am not so immensely impressed by the success we are making of our civilization here that I am prepared to think we are the only spot in this immense universe which contains living, thinking creatures, or that we are the highest type of mental and physical development which has ever appeared in the vast compass of space and time."

This passage of humble insight is an excerpt from an essay written in 1939 by Winston Churchill, an 11-page article titled ‘Are We Alone in the Universe?’, in which the famous statesman discusses the possibility of the existence of life on other planets. Aside from having been revised by Churchill in the late 1950s, the essay has never been published, and just recently came to the attention of astrophysicist Mario Livio. Livio received the essay from Timothy Riley, the director of the US National Churchill Museum in Missouri, who wanted to hear the opinion of an astrophysicist on Churchill’s article.

Livio was fascinated to find that the famous statesman employed a scientific approach to the question of life in the cosmos, an attitude that runs contrary to the anti-science stance that many modern world leaders have adopted. Indeed, Churchill was known to enthusiastically embrace science throughout his career: As an example, during World War II England’s Air Chief Marshal Arthur Harris complained, “Are we fighting this war with weapons or slide rules?” Churchill reply was, “Let’s try the slide rule.”

Churchill begins ‘Are We Alone in the Universe?’ by defining life and its requirements, including “all living things of the type we know require water”, the key element in today’s search for extraterrestrial life. He then defines what we know today as the Goldilocks Zone, the region around a star that is just the right distance away to allow water to remain liquid on a planetary surface. A given planet’s gravity, atmosphere, and the ability to retain that atmosphere over long periods of time are then factored into Churchill’s equation.

Churchill’s conclusion was that Venus and Mars would likely be the only bodies in our solar system to be able to support life as we know it — bear in mind that at the time, we knew comparatively little about these two planets, with what we knew of Mars being made from observations through telescopes, and Venus being a near-total enigma, as her surface is concealed beneath a dense blanket of cloud.

Churchill does concede that it’s possible that our own Sun may be unique in the universe, but in the absence of any evidence toward that idea, he remained optimistic that life elsewhere might one day be found. Drawing on Edwin Hubble’s discovery of the multitude of galaxies that exist beyond our own, Churchill posits that “with hundreds of thousands of nebulae, each containing thousands of millions of suns, the odds are enormous that there must be immense numbers which possess planets whose circumstances would not render life impossible.”