The Legendary Frank Drake Shaped the Search for Alien Life

The influential astronomer led the hunt for extraterrestrial signals and helped make the field of astrobiology what it is today.

Frank Drake, a leading figure in planetary astronomy and astrobiology who inspired the search for extraterrestrial intelligence, or SETI, died Friday, September 2, at the age of 92. “Frank essentially pioneered the field of SETI as a scientific endeavor by being the first to actually conduct a SETI experiment,” says Bill Diamond, president of the nonprofit SETI Institute in Mountain View, California.

Drake was born in Chicago in 1930. He studied engineering physics at Cornell University and then served as an electronics officer on a Navy cruiser for three years. Afterward, he earned his PhD in astronomy at Harvard.

His SETI quest began in 1960, when he was working for the National Radio Astronomy Observatory at its telescopes in Green Bank, West Virginia. Unbeknownst to him, in 1959 a pair of physicists had published a research paper speculating about how far radio signals sent by extraterrestrial civilizations might travel and still be detectable by a receiver on Earth. “It turns out the distance is light-years,” says Seth Shostak, senior astronomer for the SETI Institute, a nonprofit research organization focused on the origins of, and the search for, alien life. “Maybe the sky is filled with signals, but we’ve just never looked for them.” 

Drake had already begun leading an effort to do just that. In 1960, he secured approval from the NRAO for Project Ozma (named after the princess in The Wizard of Oz), the first attempt to systematically hunt for alien signals. For a few hours every day, he pointed the facility’s 85-foot radio telescope at Tau Ceti and a handful of other nearby star systems, searching for bumps or wiggles above the background noise that might be signs of an intentional broadcast. He tuned in to a particular range of frequencies, notably one near the 21-centimeter emission line of hydrogen. This is normally a quiet part of the radio spectrum—most worlds would have few emissions in that range—so one could use it as a natural “hailing frequency.” But aside from one false alarm that was probably due to an aircraft, he and his colleagues heard only static.

Although the Green Bank experiment didn’t spot any alien messages, it showed how one could look for them, so the National Academy of Sciences approached Drake to help organize a conference about SETI there. That pivotal 1961 meeting brought together an influential and eclectic group of scientists, including the chemist Melvin Calvin (who was notified of his Nobel Prize win at the meeting), a dolphin intelligence researcher, the authors of the 1959 paper, and a young Carl Sagan, who would become a frequent collaborator with Drake.

At that conference, Drake began developing a seminal formula that later became known as the Drake Equation. Still in frequent use in various forms today, that formula tries to reach a ballpark figure for the number of alien societies that could exist within our galaxy and that might be trying to message us. Its variables include the birth rate of stars, the abundance of planets orbiting them, the fraction of those that are habitable rocky worlds, the portion of those on which life could develop, the fraction of alien civilizations that might transmit signals that can be detected, and the estimated lifetime of those civilizations.

While the variables about stars and planets can be constrained with some precision, no one really knows how long intelligent civilizations typically last. (After all, we have only earthling civilizations to extrapolate from. Although some have flourished for millennia, humans are just babies, cosmically speaking—and they’ve already threatened their very existence with nuclear war and climate change and still don’t know how to deflect killer asteroids.) “Most of the important terms of the equation are unknown. You could say, ‘The equation is useless,’ but that’s not true, because it is a good way to organize your ignorance,” Shostak says. It shows that questions about intelligent life and our efforts to listen for it need to bring together other fields, too, including astrophysics, geology, biology, and sociology.

Scientists ultimately built the field of astrobiology on the groundwork of that equation, Diamond argues. It showed how they could approach the search for alien life itself—not just scanning for its telltale radio broadcasts—from a variety of angles, including investigating the emergence of complexity and the development of intelligence and consciousness, studying evolution and the biochemical origins of lifeforms, and understanding the challenges of interstellar communications.

Drake’s efforts to make contact with other worlds didn’t stop when Project Ozma ended. Since the invention of broadcast radio, earthlings have accidentally sent signals into the heavens, via shows and songs. But these signals scatter in different directions and might not be detectable from afar. So in 1974, while serving as the director of the Arecibo Observatory in Puerto Rico, Drake used the radio telescope to broadcast the first interstellar message deliberately sent from Earth. With 1,679 binary bits representing ones and zeros, he used frequency pulses to send a message in the direction of the star cluster M13, which included pictograms of a DNA double helix, a diagram of the solar system, and pictures of a human being and Arecibo. (His daughter Nadia Drake, a science journalist, later covered the telescope’s 50th anniversary for WIRED.)

He also participated in two efforts to send tangible messages into space. In the early 1970s, Drake, Sagan, and others designed the small metal plaques carried aboard NASA’s Pioneer 10 and 11 spacecraft, which depicted a pair of humans and Earth’s location in the Milky Way. They also collaborated on the Voyager Golden Records project. The two spacecraft each carry a metal record containing sounds, images, and music from Earth, as well as a player and instructions—should aliens find them one day. Today, all of these crafts continue to fly billions of miles beyond the solar system, carrying Drake’s messages with them.

In the 1960s and ’70s, Drake played a major role in driving astrobiology—then called exobiology—into becoming a systematic field of study of the origins and evolution of life on alien worlds. “Everyone was just beginning to muse on the role of liquid water. Could there be another liquid solvent—ammonia, chlorine—at an atmospheric pressure different than on Earth?” recalls Bill Nye, CEO of the nonprofit Planetary Society, which was cofounded by Sagan in 1980. “You could make an argument that all astrobiology speculation is a formal or informal form of the Drake Equation.”

In 1984, Thomas Pierson founded the SETI Institute in an effort to gain funding for and to support SETI research by astronomer Jill Tarter and others. Drake later served as president of the institute, a role he held until 2010. The institute launched a number of groundbreaking projects, including the Allen Telescope Array—42 antennas devoted solely to the SETI search—and the LaserSETI project, which scans the night sky for flashes of light that aren’t coming from astrophysical sources. (Their collaborators, the Berkeley SETI Research Center, ran one of the most well-known searches for extraterrestrial signals: SETI@home, a project that until 2020 let people devote their home computers’ downtime to crunching SETI data.)

In 2006, Drake became the inaugural director of the Carl Sagan Center, which supports more than 75 scientists advancing SETI work and studying astrobiology, and he served on the SETI Institute’s board of trustees into his seventies. Diamond and Shostak, who frequently worked with Drake there, described him as quiet, gracious, observant, and very intelligent. “He was a very humble gentleman for somebody who’s had such an impact on science and astrobiology. He was just a lovely human being,” Diamond says.

In recent years, scientists have begun fleshing out the Drake Equation and measuring its terms more precisely. For example, astronomers now better understand the lives of stars. Thanks to research with NASA’s Kepler telescope, they know that planets are more ubiquitous than previously thought, including ones in the “habitable zone” where it’s neither too hot nor too cold for liquid water.

Researchers are also exploring the equation in new ways. “The Drake Equation is iconic for describing and illustrating the search for signs of life by way of civilized aliens that have radio communication tools. I took his equation and recast it in the search for signs of life, not by intelligent aliens but by perhaps bacteria giving off a gas that accumulates in the atmosphere of a planet,” says Sara Seager, an astronomer at MIT working on multiple exoplanet-searching projects. Seager worked on a team that explored whether phosphine on Venus could be a sign of life. Other biosignature efforts include NASA’s Perseverance Rover, which is tasked with looking for traces of past microbial life on Mars, and planned future missions to Jupiter’s moon Europa and Saturn’s moon Enceladus. Separate teams have also looked for technological signatures of alien civilizations, like smog on distant planets.

New space telescopes will surely help too, like the Transiting Exoplanet Survey Satellite, which launched in 2018 and will find thousands of new worlds, and the James Webb Space Telescope, which could be used to scope out water vapor in planets’ atmospheres and potential signs of life on the worlds below.

But the most important part of Drake’s legacy, says Nye, is that people now frequently ask big and profound questions about humanity’s place in the universe. “Where did we come from? Are we alone in the cosmos?” Nye says. “All this speculation was because of Frank Drake. The guy changed the world.”

The Legendary Frank Drake Shaped the Search for Alien Life

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