In 1950, during a lunchtime conversation with colleagues at the Los Alamos National Laboratory, famed physicist Enrico Fermi asked the question that launched a hundred (or more) proposed resolutions. “Where is Everybody?” In short, given the age of the Universe (13.8 billion years), the fact that the Solar System has only existed for the past 4.5 billion years, and the fact that the ingredients for life are everywhere in abundance, why haven’t we found evidence of extraterrestrial intelligence by now? This came to be the basis of Fermi’s Paradox, which remains unresolved to this day.
Interest in Fermi’s question has been piqued in recent years thanks to the sheer number of “potentially habitable” exoplanets discovered in distant star systems. Despite that, all attempts to find signs of technological activity (“technosignatures”) have come up empty. In a recent study, a team of astrobiologists considered the possible resolutions and concluded that only two possibilities exist. Either extraterrestrial civilizations (ETCs) are incredibly rare (or non-existent), or they are deliberately avoiding contact with us (aka. the “Zoo Hypothesis“).
The program includes a survey of the one million closest stars to Earth, the center of our galaxy and the entire galactic plane, and the 100 closest galaxies to ours. In a recent paper, members of Breakthrough Listen presented the results of their radio technosignature search of the centers of 97 nearby galaxies observed by the Robert C. Byrd Green Bank Telescope. This search was one of the largest and broadest searches for radio evidence of extraterrestrial intelligence ever undertaken, surveying trillions of stars at four frequency bands. Unfortunately, no compelling candidates were found.
The Search for Extraterrestrial Intelligence (SETI) has evolved considerably in the past sixty years since the first experiment was conducted. This was Project Ozma, which was conducted in 1960 by Dr. Frank Drake and his colleagues using the National Radio Astronomy Observatory (NRAO) in Green Bank, West Virginia. While the experiment did not reveal any radio signals from space, it established the foundation upon which all future SETI is based. Like Ozma, the vast majority of these experiments have searched for possible technosignatures in the radio spectrum.
Unfortunately, this search has always been plagued by the problem of radio interference from Earth-based radio antennas and satellites in orbit, which can potentially flood SETI surveys with false positives. In a recent study, an international team of astronomers (including researchers with Breakthrough Listen) recommended that future technosignature searches rely on multi-site simultaneous observations. This has the potential of eliminating interference from terrestrial sources and narrowing the search for extraterrestrial radio signals.
It has been over sixty years since the first Search for Extraterrestrial Intelligence (SETI) survey occurred. This was Project Ozma, a survey led by Dr. Frank Drake (who devised the Drake Equation) that used the National Radio Astronomy Observatory (NRAO) in Green Bank, West Virginia, to listen for radio transmissions from Epsilon Eridani and Tau Ceti. While the search revealed nothing of interest, it paved the way for decades of research, theory, and attempts to find evidence of technological activity (aka. “technosignatures”).
The search continues today, with researchers using next-generation instruments and analytical methods to find the “needle in the cosmic haystack.” This is the purpose behind Breakthrough Listen Investigation for Periodic Spectral Signals (BLIPSS), a collaborative SETI project led by Cornell graduate student Akshay Suresh to look for technosignatures at the center of the Milky Way. In a recent paper, Suresh and his team shared their initial findings, which were made possible thanks to data obtained by the Greenbank Observatory and a proprietary algorithm they developed.
This naturally raises the all-important question: are we going about the business of SETI wrong? Instead of looking for technosignatures within our galaxy, as all previous SETI surveys have done, should we look for activity beyond our galaxy (from possible Type II and Type III civilizations)? This premise was explored in a recent paper led by researchers from the National Chung Hsing University in Taiwan. Using data from the largest SETI project to date, Breakthrough Listen, the team looked for potential radio technosignatures from extragalactic sources.
E.T. managed to call home with a Speak and Spell, buzzsaw blade, and an umbrella. The reality of interstellar communication is a bit more complicated. Space is really, really big. The power needed to transmit a signal across the void is huge. However, rather than using super high power transmitters, recent research by Stephen Kerby and Jason T. Wright shows that we could make use of a natural signal gain boost built into solar systems – the gravitational lensing of a solar system’s star. Networking a series of stars as nodes could get signals across vast tracts of the Milky Way. And we may be able to detect if our Sun is already part of an alien galactic communication network.