Just the Facts: Three SETI Myths
Many common ideas about SETI just aren't true, but that doesn't prevent them from popping up in popular articles, blogs, books, and even movies. Here are three of my favorite fallacies about SETI.
Myth #1: The "National SETI Agency"
Remember the scene in the movie Starman when government officials examine a crashed spaceship? One late-arriving character, flashes a badge, says "I'm from SETI" and is immediately let through the police line. This is my favorite portrayal of a mythical "National SETI Agency;" maybe it's the badge. Sadly, far more common examples of this myth abound in most media reports on a particular SETI project. A typical such article will report that "SETI is using millions of personal computers" or "SETI opened a new search for laser signals." As a result, many people believe there is an organization called simply, "SETI" that coordinates and controls all SETI work around the world. Some people are certain that it is a semi-secret, US government organization -- basically the interstellar version of the National Security Agency.
In reality, SETI is a field of research pursued by a handful of independent groups conducting SETI projects in a few countries. World-wide, there are about 30 scientists and engineers working more or less full time in SETI. The largest SETI research group, roughly a dozen people, is at the SETI Institute. However, the SETI Institute is not the "National SETI Agency." There is no such agency or organization.
Myth #2: "All radio telescopes do SETI, all the time"
The idea of dedicated radio telescopes searching the cosmos for sign of ET has long been the persistent siren song of SETI research. In the early 1970s NASA funded a summer research study to design a system to detect interstellar signals. The study, Project Cyclops, produced a report outlining an ambitious system, an array of antennas and signal processing electronics that could be expanded in stages as needed over many years. Dramatic artwork showing the various stages of the project accompanied both the report and a plethora of popular articles about Project Cyclops, all of which used the most dramatic image showing a thousand large antennas in the desert. The artwork was so memorable that many people assume the array was built -- but it was not.
Perhaps the power of the imagery and myth it inspired also led many people to believe that all radio telescopes spend most of their time doing SETI, with occasional breaks to look at a pulsar or quasar. (I once talked with a man who is convinced that the rest of radio astronomy is just the "cover story" and that we are already communicating with many civilizations.) In reality, astronomers use very little telescope time for SETI. Project Phoenix used about 5% of the time at the Arecibo Observatory (a total of 2,400 hours) during the period from September 1998 through March 2004. Ironically, while that may not sound like much, it was the largest allocation for a single project at Arecibo. Project SERENDIP optimizes its search time on the Arecibo telescope by observing the sky wherever the telescope happens to point during other research projects, but these other projects control the instrument.
SETI programs on radio telescopes are rare. The VLA (Very Large Array), used in the movie Contact and sometimes confused with Cyclops, has done only a single, very short SETI project. In Australia, a "Southern SERENDIP" program operates part of the time on the Parkes radio telescope. "SETI Italia," a group at the University of Bologna, uses a 32 meter VLBI telescope part of the time. So the actual amount of SETI observing done around the world is much, much less than most people assume, and a tiny (vanishingly small) percentage of radio astronomy observations world-wide.
Myth #3: "SETI has been listening for nearly 50 years..."
Actually, this is not really the myth -- what it implies, however is. A recent book by historian George Basalla and an article by political scientist Peter Schenkle have inspired a flurry of articles about the "failure" of SETI. The argument goes as follows: SETI has been listening for nearly fifty years and hasn't discovered ET, so SETI is a failure. This conclusion is based on Myths 1 and 2 combined with many incorrect assumptions of how telescopes and signal processing systems actually work.
Since 1960, when Frank Drake searched a few radio channels in the direction of two nearby stars, about 100 independent SETI projects have carried on searches of various levels of capability, for various periods of time, and most with very limited sensitivity and frequency coverage. In aggregate, the searching has been, well, spotty. To say that SETI (Myth #1) has been listening for nearly fifty years conveys the image of continuous listening (Myth #2). The phrase "listening for ET" may evoke the SETI goal, but does not accurately describe how SETI is done. In the first twenty years of "listening," twenty-three targeted radio SETI projects conducted a total of ninety days of searching.
Assumptions hide in the verb "listen." As an analogy, consider this statement: "Pablo Picasso painted for over fifty years." Common sense tells us that Pablo put down the brush at least to eat and sleep. What are these hidden assumptions? "Listen" automatically conveys the idea of continuous listening; after all, our ears are always listening. Our ears also hear sounds with a wide range of pitch, from a deep rumble to a high-pitched squeak, coming from any direction. We also listen to the radio and for most people, SETI means listening with radio telescopes. "Radio" is another assumption loaded word. In most locations we can easily tune in dozens of stations on a small portable radio.
So, we need to forget what we know about familiar terminology when it's applied to SETI. Telescopes are not like ears nor AM/FM radios. Radio telescopes are extremely directional. The Arecibo antenna is very sensitive to radio waves coming from one ten-millionth of the sky, the direction where it points. It is thousands of times less sensitive to signals from other directions. High tech receivers and electronics process the radio waves from a relatively small range of frequencies (the pitch in audio terms). For SETI, the prime real estate of the radio spectrum, the "microwave window," extends from roughly 1 GHz to 10 GHz and contains about 9 billion channels. Current SETI signal processing electronics can "only" process about 100 million channels at a time. This means that each sky position searched needs at least 90 observations to cover all channels. So, SETI observations are not as easy as the term "listening" implies.
There's one final incorrect assumption hidden in Myth #3: "all SETI projects are equal." The vast majority of the roughly 100 projects were very limited in frequency coverage, directions searched, and/or sensitivity. If you consider the number of stars (or sky positions) observed and the number of frequency channels searched at high sensitivity, only two projects have done a significant amount of searching. UC Berkeley's SERENDIP project (parent to SETI@Home) has searched the sky visible with the Arecibo telescope (about 30% of the entire sky) in the radio spectrum's water hole*. In a complementary approach, the SETI Institute's Project Phoenix searched about 800 stars out to a distance of about 250 light years, covering six times as many frequency channels, with sensitivities up to ten times that of SERENDIP. And even with impressive statistics such as these, we've only scratched the surface.
New SETI projects offer deeper searching of more of the sky at more frequencies. SERENDIP is working with a new feed system at Arecibo and will get more sensitivity. The SETI Institute's SonATA (SETI on the Allen Telescope Array) will observe a million stars over an unprecedented range of frequencies at high sensitivity. The idea that we've been listening for decades is indeed a myth but the future holds promise. We are just beginning to really listen.
*The "water hole" is a 300 MHz wide section of the radio spectrum, from 1420 MHz to 1720 MHz. These boundaries correspond to radio frequencies emitted by Hydrogen (H) atoms and Hydroxyl (OH) molecules. Since H and OH combine to form water (H2O), the basis of life as we know it, this region of the spectrum may be favored by water-based life for interstellar communication.
The Cyclops Report recommended conducting a SETI program, starting with a single dish. If that search was unsuccessful, the array would then expand in stages to conduct searches of ever increasing sensitivity, until a signal was found. The artwork for the final phase, with 1000 antennas, was the most widely used. The array was never built.
- Mars Analog on Earth: Taking a Trek in the Outback
- VIDEO: Figuring Out the Odds of ET Existing
- VIDEO: Reflections of Fermi's Paradox
- VIDEO: Listening for Life
- GALLERY: Scenes from SETI at Arecibo
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