Allen Telescope Array, credit: startalkradio.net
At the Astrobiology Science Conference (AbSciCon) in Chicago last month, I heard several talks by scientists involved in the search for evidence of extraterrestrial intelligent life (SETI). Listening to these talks was like being in a parallel universe to the AbSciCon universe.
Many talks I heard at AbSciCon convinced me that the rationale for search for evidence of microbial life in our solar system is strengthening, while the SETI talks I heard led me to think the rationale underlying their arguments to continue the search remains weak, at best (see my posts on the so-called “Drake equation” and prospects for life on exoplanets). See what you think.
Andrew Siemion of the Berkeley SETI Research Center, University of California-Berkeley, advocated using the Square Kilometer Array (SKA) for SETI, claiming it will be “primed” for the search. (The SKA is to be built in South Africa. Construction is scheduled to begin in 2018.) Siemion claimed that SETI surveys – campaigns using radio telescopes to search for radio signals of extraterrestrial technological (that is, intelligent) origin – are not “anthropocentrically biased…making no assumptions about locations, habitable zones, etc.”
Okay. But the overall SETI endeavor is anthropocentrically biased. Deeply. The SETI endeavor rests on a number of assumptions – for example, that terrestrial biology is “universal,” that intelligent life is an inevitable result of biological evolution, that extraterrestrial intelligence would be like human intelligence, that extraterrestrial intelligent life would develop the same sorts of technology that humans have…. These assumptions have no solid basis in science. They are speculations.
(FYI, Siemion was on the witness list for a now-postponed June hearing before the House Science, Space, and Technology Committee on astrobiology.)
In checking its web site, I found that in 2011 the Berkeley SETI Research Center began a search for ETI at the Green Bank Telescope (GBT) in West Virginia, targeting 86 exoplanet candidates detected by the Kepler Space Telescope. According to the Center, “the 86 candidates chosen for the GBT SETI search are those in the ‘Habitable Zone,’ that is, they are just the right distance from their parent star for liquid water to exist on their surface.”
Results? The Center reports that its “analyses have generated a few ‘hits,’ but all are undoubtedly examples of terrestrial radio frequency interference (RFI). … Why are these signals interesting? We know these signals are interference, but look similar to what we think might be produced from an extraterrestrial technology. They are narrow in frequency, much narrower than would be produced by any known astrophysical phenomena, and they drift in frequency with time, as we would expect because of the doppler effect imposed by the relative motion of the transmitter and the receiving radio telescope. Even though these signals are interference, detecting events with similar characteristics to what we expect from ET is a good indication that the first steps of our detection algorithms are working properly.”
Next, I heard Gerry Harp, director of the Center for SETI Research at the SETI Institute, argued for a change in approach to searching for ETI signals. He said 50 years of SETI have focused on looking for radio signals in the so-called “water hole,” 1.4-1.7 gigahertz (GHz) on the electromagnetic spectrum.
(The rationale for searching for signals in this range is that since life on Earth requires water, life elsewhere requires water, and intelligent life elsewhere would send signals in this range so that we would recognize them as a signal from life elsewhere.)
This half-century of searching, Harp said, has shown that the water hole is dry. “Stick a fork in it, it’s done.” It’s time for SETI to look for signals in the rest of the so-called terrestrial microwave window, from 1-10 GHz. The water hole accounts for only 3 percent of the microwave window, and that 3 percent is subject to a lot of radio frequency interference (RFI).
(According to the SETI Institute, “For interstellar communication, a particular range of radio frequencies, “microwaves” from 1 GHz to 10 GHz, are particularly good choices. At lower frequencies our galaxy emits prodigious amounts of radio waves creating a loud background of noise. At higher frequencies the Earth’s atmosphere, and presumably the atmosphere of other Earth-like planets, absorbs and emits broad ranges of radio frequencies. The result is a quiet ‘Microwave Window’ through which efficient radio communication is possible.”)
“If we find a signal, Harp noted, “we have a protocol” for what to do.
(I have a question: Precisely who is “we?” As far as I know, “we” is a small group of people who have been working on a protocol at International Astronautical Federation and International Academy of Astronautics meetings. Emphasis on small.)
Katy Wimberley, an intern at the SETI Institute, reported on her examination of a database of 10 years worth of SETI searching using the Allen Telescope Array. She claimed her research disproves that ETI signals would be distinguishable from RFI and other “noise.” If ETI signals are in the database, then we have to come up with another way to identify them.”
(I must note again that the assumption here is that ETI signals are available to find. The other way to interpret Wimberly’s results is that 10 years of ATA searching has not found any ETI signals.)
I heard Doug Vakoch, director of interstellar message composition at the SETI Institute, present a rationale for “active SETI” – sending powerful, information-rich radio signals out into the galaxy in hopes that “someone” might receive them.
(The assumption here – in addition to the assumptions I’ve already pointed out – is that if “someone” receives our signal, that someone will understand it and care about it.)
The SETI community should pursue active SETI, Vakoch said, to diversify its approach, since 50 years of listening has turned up nothing.
Finally, I heard retired State Department official Michael Michaud say that searching for evidence of extraterrestrial microbial life is not so interesting as searching for evidence of extraterrestrial intelligent life because non-intelligent alien life can’t grant us wisdom or threaten us.
Some members of the SETI community have been advocating for NASA to resume funding SETI. I worked with NASA’s former SETI program from 1988 to 1993 on communication and advocacy planning. I recall that during that time, I argued that SETI leaders needed to articulate a scientific rationale for their program – something that they had not, but ultimately did, put down on paper. It was not enough to save the program from budget cutting. And today, budget limits mean that funding for SETI remains outside the boundaries of NASA’s science portfolio. It’s a bit of a boutique enterprise, and private funding is appropriate.