Sending Extraterrestrials a Message
A little over 25 years ago, working at Space.com, I interviewed astronomer Frank Drake about the “Arecibo message,” humanity’s first attempt at interstellar communication, which he’d organized 25 years prior, in 1974. It was a radio transmission from the Arecibo Telescope in Puerto Rico that encoded a visual diagram with representations of the human body, the DNA molecule, the solar system and more. It was targeted at M13, a star cluster 25,000 light-years away, because that was conveniently overhead at a time when the telescope wasn’t fully steerable, though it will pass near other stars on the way.
The signal was “about a million times stronger than the typical TV transmission,” Drake said, brighter than the sun at a comparable wavelength and detectable by technology with capabilities like those of Earth’s radio telescopes. Despite his role in this, Drake thought listening for signals was more important. “Transmitting is very costly,” he said. “Receiving is not.” He had a low-key deportment over the phone. Any extraterrestrials hearing from him might’ve been impressed by his just-the-facts demeanor.
The search for extraterrestrial intelligence (SETI) until the late-1970s was called communication with extraterrestrial intelligence (CETI). A separate moniker, METI, for messaging, is now used for efforts, such as the Arecibo transmission, aimed at outreach rather than listening; these are rare, as they’re not only expensive but controversial (on grounds that hostile aliens might become aware of our existence; although how significant the risks are, given the distances and timescales involved, is debatable).
Science historian Rebecca Charbonneau’s new book Mixed Signals: Alien Communication Across the Iron Curtain is a fascinating look at how C/SETI (as she calls the field when describing aspects unfolding over time) arose during the Cold War and was shaped by geopolitics. I became aware of Charbonneau’s book through reading a November Scientific American article in which she was quoted, by science writer Nadia Drake, daughter of the late astronomer (he died in 2022); the article marked the Arecibo message’s 50th anniversary and included an image of the elder Drake’s hand-drawn first draft of the encoded diagram.
Charbonneau’s interest in C/SETI was piqued when, as a history student at Oxford, she came across a “dusty book” in the library. It was Intelligent Life in the Universe, by Carl Sagan and I.S. Shklovsky, and she was struck by certain oddities: that it was published in 1966, when Sagan wasn’t yet well-known, and was out-of-print unlike his other books, and had a Soviet astrophysicist as co-author at a time when Cold War tensions were high, with the superpowers giving high priority to outperforming each other in the Space Race. The friendship between these two scientists, both iconoclastic personalities, was a factor in getting C/SETI established as a scientific activity, her subsequent research indicated.
More broadly, a mix of competition and cooperation between the U.S. and the Soviet Union shaped the field, with political and cultural preoccupations on each side. American scientific institutions propounded the idea that science should be “apolitical.” Soviet scientists were influenced by “cosmism” and Marxist dialectical materialism in thinking intelligent life exists beyond Earth. Both sides had connections between their scientific establishments and their military/intelligence agencies, though Charbonneau notes that the Soviets were more restrictive in oversight of scientists and data. Anxieties about nuclear war and other potential catastrophes also shaped research efforts, as scientists began to speculate that an absence of alien signals might mean that technological civilizations quickly destroy themselves.
Efforts to convey information to potential aliens always had terrestrial audiences in mind. This was the case with the plaque placed aboard the Pioneer space probes, which brought criticism for showing naked humans, both in showing a man’s genitalia but not a woman’s, and in supposedly portraying the woman as submissive. The Golden Record placed on the Voyager probes contained sounds and images intended to put humanity’s “best foot forward,” rather than depicting problems on Earth. Considerations of messages to aliens also influenced other fields, such as efforts to communicate with dolphins, and proposals for long-lived markers to warn future people away from radioactive waste.
Reading Mixed Signals, it occurs to me, even amid Cold War ideology and propaganda, scientists such as Drake and Sagan operated in a society that was more fact-based than ours. If new projects to transmit messages to extraterrestrials occur in the next few years, I imagine they might be shaped by people such as Elon Musk, Donald Trump and Steve Bannon, such that the latter’s exhortation to “flood the zone with shit” could become a lasting human legacy, extending thousands of light-years from Earth.
—Kenneth Silber is author of In DeWitt’s Footsteps: Seeing History on the Erie Canal. Follow him on Bluesky