Winston Churchill, British prime minister and one of history’s most influential statesmen, was undoubtedly a man with weighty questions on his mind. How best to save the British Empire? he must have mused. What will the postwar world look like? he surely wondered. But the legendary leader also focused his prodigious mind on less pragmatic questions. For instance: Is there life on other planets?

In fact, in 1939, Churchill penned a lengthy essay on this very topic, which was never published. Besides displaying a strong grasp of contemporary astrophysics and a scientific mind, he came to a breathtaking conclusion: We are probably not alone in the universe. The long-lost piece of Churchilliana has just floated up to the surface again, thanks to an article written by astrophysicist Mario Livio in this week's edition of the journal Nature analyzing Churchill's work.

“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,” Churchill concluded in his essay. He wrote these words on the eve of World War II—more than half a century before exoplanets were discovered.

Until last year, Churchill's thoughts on the problem of alien life had been all but lost to history. The reason: His 11-page typed draft was never published. Sometime in the late 1950s, Churchill revised the essay while visiting the seaside villa of publisher Emery Reves, but the text still didn't see the light of day. It appears to have languished in the Reves house until Emery's wife Wendy gave it to the U.S. National Churchill Museum during the 1980s.

Last year, the museum’s new director, Timothy Riley, unearthed the essay in the museum's archives. When astrophysicist Mario Livio happened to visit the museum, Riley "thrust [the] typewritten essay" into his hands, Livio writes in Nature. Riley was eager to hear the perspective of an astrophysicist. And Livio, for his part, was floored. “Imagine my thrill that I may be the first scientist to examine this essay,” he writes in Nature.

Churchill did his homework, Livio reports. Though he probably didn't pore over peer-reviewed scientific literature, the statesman seems to have read enough, and spoke with enough top scientists—including the physicist Frederick Lindemann, his friend and later his official scientific adviser—to have had a strong grasp of the major theories and ideas of his time. But that wasn't what left the deepest impression on Livio.

“To me the most impressive part of the essay—other than the fact that he was interested in it at all, which is pretty remarkable—is really the way that he thinks,” Livio says. “He approached the problem just as a scientist today would. To answer his question 'Are we alone in the universe?' he started by defining life. Then he said, 'OK, what does life require? What are the necessary conditions for life to exist?'”

Churchill identified liquid water, for example, as a primary requirement. While he acknowledged the possibility that forms of life could exist dependent on some other liquid, he concluded that “nothing in our present knowledge entitles us to make such an assumption.”

"This is exactly what we still do today: Try to find life by following the water,” Livio says. “But next, Churchill asked 'What does it take for liquid water to be there?' And so he identified this thing that today we call the habitable zone.”

By breaking down the challenge into its component parts, Churchill ended up delving into the factors necessary to create what is now known as the “Goldilocks zone” around a star: that elusive region in which a life-sustaining planet could theoretically exist. In our own solar system, he concluded, only Mars and Venus could possibly harbor life outside of Earth. The other planets don't have the right temperatures, Churchill noted, while the Moon and asteroids lack sufficient gravity to trap gasses and sustain atmospheres.

Turning his gaze beyond our own solar system raised even more possibilities for life, at least in Churchill's mind. “The sun is merely one star in our galaxy, which contains several thousand millions of others,” he wrote. Planetary formation would be rather rare around those stars, he admitted, drawing on a then-popular theory of noted physicist and astronomer James Jeans. But what if that theory turned out to be incorrect? (In fact, it has now been disproven.)

“That's what I find really fascinating,” Livio notes. “The healthy skepticism that he displayed is remarkable.”

Churchill suggested that different planetary formation theories may mean that many such planets may exist which “will be the right size to keep on their surface water and possibly an atmosphere of some sort.” Of that group, some may also be “at the proper distance from their parent sun to maintain a suitable temperature.”

The statesman even expected that some day, “possibly even in the not very distant future,” visitors might see for themselves whether there is life on the moon, or even Mars.

But what was Winston Churchill doing penning a lengthy essay on the probability of alien life in the first place? After all, it was the eve of a war that would decide the fate of the free world, and Churchill was about to become Prime Minister of the United Kingdom.

Such an undertaking was actually quite typical for Churchill, notes Andrew Nahum, Keeper Emeritus at the Science Museum, London, because it reflects both his scientific curiosity and his recurring need to write for money. It was skill with the pen that often supported Churchill and his family's lavish lifestyle (recall that he won the 1953 Nobel Prize for Literature, with a monetary award of 175,293 Swedish Kroner worth about $275,000 today).

“One recent biography is entitled No More Champagne: Churchill And His Money,” Nahum says. “That was a phrase he put into a note to his wife about austerity measures. But he didn't know much about austerity. He liked luxury so he wrote like crazy, both books and articles that his agent circulated widely.”

That’s not to say that Churchill was simply slinging copy about aliens for a paycheck. “He was profoundly interested in the sciences and he read very widely,” notes Nahum, who curated the 2015 Science Museum exhibition “Churchill's Scientists.” Nahum relates the tale of how as Chancellor of the Exchequer, Churchill was once sent a book on quantum physics, and later admitted that it had occupied him for the better part of a day that should have been spent balancing the British budget.

He not only read scientific content voraciously, but wrote on the topic as well. In a 1924 issue of Nash's Pall Mall Magazine, Churchill anticipated the power of atomic weapons. “Might not a bomb no bigger than an orange be found to possess secret power to destroy a whole block of buildings nay, to blast a township at a stroke?” he warned. In 1932, he anticipated the rise of test-tube meat in the magazine Popular Mechanics: “Fifty years hence, we shall escape the absurdity of growing a whole chicken in order to eat the breast or the wing, by growing these parts separately in a suitable medium,” he wrote.

In 1939 he authored three essays, tackling not just extraterrestrial life but the evolution of life on Earth and the popular biology of the human body. Two were published during 1942 by the Sunday Dispatch, Nahum discovered when reading Churchill's papers at the University of Cambridge. It remains a mystery why his thoughts on alien life went unpublished.

In the rediscovered essay, Churchill admits that, because of the great distances between us and other planet-harboring stars, we may never know if his hunch that life is scattered among the vastness of the cosmos is correct. Yet even without proof, Churchill seems to have convinced himself that such a possibility was likely—perhaps by swapping his scientific mind for one more finely attuned to the human condition during the troubled 20th century.

“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,” he wrote, “or that we are the highest type of mental and physical development which has ever appeared in the vast compass of space and time.”

Seventy-five years after Churchill's bold speculations, there's still no proof that life exists on other worlds. But, as was often the case, his analysis of our own still seems prescient.