In 1939, Winston Churchill wrote an 11-page article on the prospect of life beyond Earth. Shortly afterward, events kept him otherwise occupied and the paper was not published. After the war, Churchill updated the paper, but for unknown reasons it didn't get run then either. The lost document was rediscovered last year and has now been analyzed in Nature, revealing that even as Churchill tried to warn the world of the dangers of fascism, he had time to think deeply about this topic. His conclusions largely match those of astrobiologists today.
Astrophysicist Dr Mario Livio, the first scientist to get to examine the paper, wrote: “At a time when a number of today’s politicians shun science, I find it moving to recall a leader who engaged with it so profoundly.” Today, with thousands of planets known around other stars, discussion of life elsewhere in the universe is widespread, but Churchill was writing long before any exoplanets had been discovered and well before the Drake Equation attempted to quantify the chances of life elsewhere. Although he included discussion of the habitability of planets in our Solar System, he also looked further afield.
The dominant theory of planetary formation in the 1930s proposed that a passing star had pulled material from the Sun. Such an unusual event would have made planetary systems like our own very rare. Churchill acknowledged this, but expressed skepticism about the model, pointing out that double stars are common and writing: “If they could be formed, why not planetary systems?”
In line with modern thinking, Churchill argued that the presence of liquid water was the prime requirement for life on other worlds. Although he acknowledged other liquids might provide substitutes, he stressed that “nothing in our present knowledge entitles us to make such an assumption.” From this, he drew the idea of what we now call the “Goldilocks Zone”, which is that life cannot exist either too close or too far from a star, and that planets must fall within a narrow size range. Even Churchill's definition of life, and discussion of whether viruses should count, is evidence of how well he understood the topic, Livio argues.