We've probably all done it, and our ancestors did, too: looked up at the night sky filled with innumerable stars, planets, and faraway galaxies and wondered whether there was something like us out there. In the twentieth century, this collective sense of wonder has become a global scientific enterprise—the search for extraterrestrial intelligence, also known as SETI—but it remains nevertheless firmly rooted in the annals of human history.
We began our quest to bridge the heavens and the Earth in the early 1600s, with the invention of the optical telescope. Less than two centuries later, by the late 1800s, the prospect of contacting intelligent extraterrestrial life had begun taking hold of the human imagination. The inventor Nikola Tesla, in 1896, proposed a technology for contacting alien beings on Mars. By the early 1900s, pioneering scientists Guglielmo Marconi (a Nobel laureate and the inventor of the radio), Lord Kelvin (namesake of the SI unit of absolute temperature), and David Peck Todd (an eminent American astronomer) were advocating for the search for extraterrestrial intelligence, and a radio listening experiment was even conducted by Todd with the assistance of the U.S. military in 1924.
A Number of Firsts
In 1932, a new window opened on the universe with the birth of modern radio astronomy, at Bell Telephone Laboratories, when Karl Jansky first observed electromagnetic radiation emanating from the Milky Way, confirming several decades of scientific speculation that radio waves could be detected from astronomical sources. In 1959, Cornell University physicists Philip Morrison and Giuseppe Cocconi described the possibility of using radio waves for interstellar communication in the first scientific paper on SETI, published in the prestigious journal Nature. In 1960, the first modern SETI search was conducted by another Cornell scientist, Frank Drake, using a 26-meter radio telescope at the National Radio Astronomy Observatory in Green Bank, West Virginia. In 1961, Drake convened a meeting at Green Bank with a cadre of SETI leaders and made the first probabilistic estimate of the number of active, communicative extraterrestrial civilizations in the Milky Way Galaxy—what came to be known as the Drake Equation and is still guiding SETI today.
The 1970s saw an explosion of activity, including NASA’s funding of its first SETI study and the development of much of the technology still used by radio astronomers today. But the 80s brought the beginning of the budgetary battles over NASA’s funding of SETI, beginning in 1981 and continuing until all federal funding for SETI was eliminated in 1993. Without government support, still SETI soldiered on, backed instead by private funding, although these efforts were mostly small and run on shoestring budgets. A notable exception, the SETI Institute received substantial financial support from inventor and Hewlett-Packard executive Barney Oliver and other philanthropists; Microsoft cofounder Paul Allen, namesake of the Allen Telescope Array, would later become another significant benefactor.
Then, in July 2015, billionaire tech investor Yuri Milner and a number of leading scientists, including Frank Drake and the late luminary physicist Stephen Hawking, announced the largest and most comprehensive search to date: the Breakthrough Listen Initiative, based at the Berkeley SETI Research Center in the Department of Astronomy at the University of California, Berkeley, and funded by Milner to the tune of $100 million over 10 years. Breakthrough Listen would utilize telescopes at observatories around the world, including one of the largest and most powerful radio telescopes on Earth—the 100-meter Robert C. Byrd Green Bank Telescope. SETI, once again, seemed to be on the verge of big discoveries.
In the years leading up to this SETI resurgence, other initiatives in more-mainstream astronomy had been indirectly advancing pieces of the SETI puzzle. NASA’s astrobiology program brought together scientists from diverse backgrounds—planetary science, biochemistry, and geomicrobiology, among others—to search for life and its signatures throughout the universe. Over the course of nine years, from 2009 to 2018, NASA’s Kepler mission discovered nearly 4,000 exoplanets and, in the process, revealed the relative abundance of potentially habitable worlds beyond our own solar system.
Thanks to Kepler, we now know that nearly every star hosts planets, roughly one in five of which orbits in its host star's habitable zone, where life as we know it could evolve, and has a solid surface that could contain water. Kepler’s successor, TESS—the Transiting Exoplanet Survey Satellite—has discovered another 81 confirmed exoplanets and nearly 2,400 new candidates, which astronomers are now studying with ground-based telescopes, including the 10-meter Hobby-Eberly Telescope at McDonald Observatory and the 3.5-meter WIYN Telescope at Kitt Peak National Observatory, both Penn State partnerships.
Up to now, SETI has been focused primarily on detecting radio and, to a much lesser extent, laser signals coming from these exoplanetary systems. But in the era of big data and multimessenger astronomy, SETI scientists increasingly will analyze existing data troves collected across the observational spectrum—from visible light, radio waves, and other forms of electromagnetic radiation to gravitational waves, neutrinos, and cosmic rays—for possible communications or other technosignatures. Since 2013, Penn State's Astrophysical Multimessenger Observatory Network (AMON) has been collecting these data from observatories worldwide to identify and study transient cosmic phenomena; now SETI scientists across the globe can begin putting them to use, as well.
Penn State SETI
Also at Penn State, Jason Wright, Steinn Sigurdsson, and colleagues are working to develop different and unique implementations of SETI, devising new and novel search strategies to look for signals beyond the radio spectrum, and shaping the University's curriculum to reflect those evolving methodologies. In 2018, Wright launched the University’s first SETI graduate course, which has since been added to the curriculum of the Astrobiology doctoral program. Wright and several of his graduate students also collaborated with renowned SETI scientist Jill Tarter and others at the SETI Institute in creating a new tool to track SETI searches, called Technosearch, which was released in January 2019. And along with scientists in AMON, the Astrobiology Research Center, Center for Astrostatistics, Institute for Gravitation and the Cosmos, and Center for Exoplanets and Habitable Worlds—including Alex Wolsczan, who co-discovered the first known exoplanets—Wright and Sigurdsson are building a global SETI hub at University Park: the PSETI Center, supporting SETI faculty and doctoral students at Penn State and around the world.
Already at the PSETI Center there are several graduate students leading innovative and noteworthy research projects. Sofia Sheikh is leading a collaboration with Breakthrough Listen and Penn State’s Institute for Computational and Data Sciences to expand the search methodologies of radio SETI. Macy Huston is leading work to look for Dyson spheres, hypothetical solar power–collecting megastructures that would indicate the presence of advanced extraterrestrial civilizations. And Shubham Kanodia is searching for extraterrestrial laser signals, using two Penn State–built spectrographs: NEID on the WIYN Telescope and the Habitable Zone Planet Finder on the Hobby-Eberly Telescope.
Joining the ranks of SETI powerhouses like Breakthrough Listen, the Berkeley SETI Research Center, and the SETI Institute, Penn State and the PSETI Center have the potential to help shape the future of SETI in unimaginable ways. Now, maybe more than any other time in history, it’s incredibly exciting to wonder what—or even who—else is out there, awaiting discovery.
Hero image (at top): The tip of the wing of the Small Magellanic Cloud (SMC) galaxy is dazzling in this new view from NASA Great Observatories. The SMC is a small galaxy about 200,000 light-years way that orbits our own Milky Way spiral galaxy. Credit: NASA/CXC/JPL-Caltech/STScI