At sunset on a late summer weekend in 1924, crowds flocked to curbside telescopes to behold the advanced alien civilization they believed to be present on the surface of Mars.
“See the wonders of Mars!” an uptown sidewalk astronomer shouted in New York City on Saturday, Aug. 23. “Now is your chance to view the snowcaps and the great canals that are causing so much talk among the scientists. You’ll never have such a chance again in your lifetime.”
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During that weekend, Earth and Mars were separated by just 34 million miles, closer than at any other point in a century. Although this orbital alignment, called an opposition, occurs every 26 months, this one was particularly captivating to audiences across continents and inspired some of the first large-scale efforts to detect alien life.
“In scores of observatories, watchers and photographers are centering their attention on that enigmatic red disk,” the journalist Silas Bent wrote on Aug. 17, 1924. He added that it might be the moment to “solve the disputed question of whether supermen rove his crust, and whether those lines, which many observers say they have seen, really are irrigation canals.”
Scientists plotted for years to make the most of the Martian “close-up.” To aid the experiments, the U.S. Navy cleared the airwaves, imposing a nationwide period of radio silence for five minutes at the top of each hour from Aug. 21 to 24 so that messages from Martians could be heard. A military cryptographer was on hand to “translate any peculiar messages that might come by radio from Mars.”