History of the SETI Program
The modern search for extraterrestrial intelligence began in 1960 when astronomer Frank Drake conducted Project Ozma at the Green Bank Observatory in West Virginia. Using an 85-foot radio telescope, Drake pointed at two nearby Sun-like stars, Tau Ceti and Epsilon Eridani, and listened for artificial radio signals at the 1420 MHz hydrogen line frequency. While no alien signals were detected, the project established the scientific methodology for SETI research.
NASA funded SETI observations through the 1970s and 1980s, but Congress eliminated the program's funding in 1993 after critics derided it as wasteful. The SETI Institute, a private nonprofit founded in 1984 by Thomas Pierson and Jill Tarter, continued the search using private funding. The Allen Telescope Array in northern California, partially funded by Microsoft co-founder Paul Allen, was designed specifically for SETI observations and began operations in 2007.
Technologies Used in the Search
SETI primarily relies on radio telescopes to scan the sky for narrowband signals that could indicate artificial origin. Natural astrophysical sources produce broadband radio emissions, so a tightly focused signal at a specific frequency would be a strong indicator of intelligent transmission. Researchers typically focus on frequencies between 1 and 10 GHz, known as the "water hole," where background noise from the galaxy and Earth's atmosphere is minimal.
In recent years, SETI has expanded beyond radio to include optical and near-infrared searches for brief, powerful laser pulses that an advanced civilization might use for communication. The Breakthrough Listen initiative, launched in 2015 with $100 million in funding from billionaire Yuri Milner, employs some of the world's most powerful radio telescopes including the Green Bank Telescope and the Parkes Observatory in Australia. Breakthrough Listen surveys the 1 million nearest stars, the entire galactic plane, and the 100 nearest galaxies across a wide range of radio and optical frequencies.
Notable Signals and Candidates
The most famous candidate signal in SETI history is the "Wow! signal," detected on August 15, 1977, by Jerry Ehman using Ohio State University's Big Ear radio telescope. The signal was a strong, narrowband burst at 1420 MHz that lasted 72 seconds and has never been detected again despite numerous follow-up observations. In 2019, the Breakthrough Listen project detected a signal designated BLC1 coming from the direction of Proxima Centauri, which generated significant excitement before being attributed to terrestrial radio frequency interference.
Fast radio bursts, first discovered in 2007, initially sparked speculation about alien origins due to their immense energy and mysterious nature. However, the detection of a fast radio burst from a magnetar within our own galaxy in 2020 confirmed that at least some of these signals have natural astrophysical origins. Despite decades of searching, no confirmed extraterrestrial signal has ever been detected, but each new technology and survey improves our sensitivity and expands the parameter space being explored.
The Future of SETI
The next generation of SETI research will benefit from dramatically more powerful instruments. The Square Kilometre Array, currently under construction in Australia and South Africa, will be the world's largest radio telescope and will have the sensitivity to detect airport radar-strength signals from nearby stars. Machine learning algorithms are increasingly being used to sift through the enormous volumes of data generated by modern surveys, identifying candidate signals far more efficiently than traditional methods.
Beyond electromagnetic signals, researchers are exploring new detection strategies including searching for signs of megastructures like Dyson spheres through infrared surveys, looking for industrial pollution in exoplanet atmospheres, and even detecting the gravitational effects of large artificial structures. The growing field of technosignature science, which received its first NASA funding in 2018 after a 25-year gap, aims to systematically catalog all the ways an advanced civilization might be detectable across interstellar distances.