Searching for Extraterrestrials: An Undergraduate's Tale
It's a Wednesday afternoon in a cluttered basement lab on the Case Western Reserve University (CWRU) campus, and I begin running the computer program on a new data set. Maybe this one will be it, I find myself thinking as the program begins to execute. Maybe these data contain the signature we're looking for, one that shows evidence for extraterrestrial intelligence. Maybe I will go down as the first person in history to detect an alien signal!
The run cycles through and returns predictedly unpromising results, as always. Nuts. I give a little sigh, and prepare another data file.
This past semester, I've held a research job at CWRU working on OSETI, the Optical Search for Extraterrestrial Intelligence. OSETI is an effort by scientists to detect laser pulses from other solar systems sent by aliens. Nothing out of the ordinary was ever found on my watch, but it was nonetheless an exciting part-time job. Life always seems a little more exciting when there's the possibility of making extraterrestrial contact after lunch!E.T. Phone Home
When thinking about aliens, flying saucers or B-rated Hollywood movies are the first things that come to mind for most people. Most scientists scoff at the idea of UFOs and aliens coming to Earth. Scientists do not think intelligent life resides on other bodies in our Solar System, and the vast distances between stars makes travel to Earth very unlikely. Besides, why would an intelligent race travel trillions of miles to reach our planet only to conceal itself and draw crop circles in corn fields?
Because of the interstellar distances that make travel between stars very difficult, in the 1960s scientists posed a new method for interstellar communication: radio waves. Electromagnetic radiation can travel effortlessly through space at the speed of light, so a signal from a powerful transmitter could easily travel for hundreds of light years. Even our own modest television and radio signals could be detected from nearby stars by intelligent beings with equipment as sensitive as ours.
Scientists have argued that while no one knows how prevalent life is in the universe- or if there is any other life at all- it is reasonable to assume that the conditions which allowed life to occur on Earth could happen elsewhere in the universe. This means that countless civilizations out there might be sending out signals that could be detected on Earth!
From this logic, the Search for Extraterrestrial Intelligence (SETI) project was born. For the first few decades, the project focused nearly exclusively on listening to radio waves in the microwave region of the spectrum, which propagate best over interstellar distances. Although sporadically funded, SETI is arguably the world's largest distributed computing project of all time: about 5.2 million people have donated two million computing years combined to SETI@home in an effort to analyze all the data.
SETI has also gone through several transformations based on funding and resources. This means that SETI has never been the continuous search that many imagine it to be but is instead a search conducted whenever there is a moment of opportunity.
So far the SETI results have all been negative with a few exceptions that did not prove positive under scrutiny. Despite the lack of results so far, SETI scientists remain optimistic about the project and believe there is still much work to be done. In the words of SETI radio astronomer Frank Drake, "All we know for sure is that the sky is not littered with powerful microwave transmitters."
In the 1990s, some researchers began proposing the idea that aliens may try to communicate not through radio waves, as many believed, but instead through powerful optical lasers. Such lasers would be very directional, meaning the beam would have to be pointed directly at Earth to be detectable, but when the beam was pointed in our direction the star from which it originated from would appear several times brighter. Lasers have improved greatly since the initial conception of interstellar communication: even we could signal a hundred light years away using a modern high-energy laser and a ten meter optical-focus mirror. In light of these arguments, a new subset of SETI was examined which was dubbed Optical SETI (OSETI).
So far, the most extensive OSETI project was led by Harvard astronomer Paul Horowitz, who built a laser detector mounted on a 155 centimeter (61 inch) optical telescope. Between October 1998 and November 1999, the survey observed 2,500 stars with negative results. Clearly, it was time for me to step in!WANTED: Physics major to look for aliens. Must be open to big ideas.
Corbin Covault is a quirky astrophysicist who teaches freshman physics at CWRU, where he is famous for eating chalk to grab the attention of his class and for wearing socks with sandals no matter what the weather or the rest of his wardrobe. I decided very early on that this was a man to be reckoned with, or at least one who would entertain random physics questions during office hours.
Eventually Corbin offered me a position in his High Energy Astrophysics Group. I accepted, and spent the summer of 2006 working on atmospheric data for STACEE (Solar Tower Atmospheric Cherenkov Experiment), a gamma-ray detector near Albuquerque, New Mexico. The detector consists of several solar mirrors, called heliostats, which are used by day for solar energy research and by night to detect Cherenkov light caused by gamma rays hitting the upper atmosphere. These flashes are reflected to a nearby solar tower, where they are recorded for further analysis.
As summer wound down, so did the project I was working on, and Corbin promised me something new for the coming semester. The promised offer arrived a few weeks later via email- "Interest in using STACEE for OSETI has gone overnight from practically non-existent to possibly a major consideration. On a scale of zero to ten, how interested would you be in working on this?"
One quick shout of excitement later, I hit the reply button and quickly responded with an enthusiastic eleven. Who wouldn't want a job looking for aliens?
The OSETI work done by STACEE is a continuation of the work done by Paul Horowitz's group at Harvard. STACEE is a more sensitive detector than the one used by the Harvard group, making this survey the most sensitive ever conducted for OSETI. We collected data by observing nearby Sun-like stars, which were presumed to have favorable conditions for intelligent life, meaning conditions similar to those of the Solar System.
My work on the project focused on observing the difference in the time it takes for an artificial signal to travel from one side of the detector field to the other. We calculated that it would take about one nanosecond, a time just within reach of the instrumentation. Detecting this time difference could help distinguish between an artificial signal and one of the countless signals generated by particles hitting the upper atmosphere because their respective signals would appear differently.
As the semester wore on, nothing much happened and I made the inevitable realization that while finding an intelligent signal is no doubt an exciting and adrenaline-filled moment, waiting to find the signal is boring. Though not a particularly insightful discovery, it is one that many others have undoubtedly noticed since the first SETI surveys in the 1960s, and is probably what has brought funding cuts for the project from various government agencies. (NASA funded SETI work up until the early 1990s when Congress cut it from NASA's budget.)
Despite this drawback, it seems terrible to think of possibly missing a signal from intelligent life in the universe just because we were not paying attention. I stayed with the project over the semester, even though, for a good fraction of the time, I was the only one analyzing the OSETI data from STACEE. I tried my best during these times not to think about how the most sensitive OSETI survey was left solely in the hands of an idealistic undergraduate and what this implied about our civilization.
A semester after STACEE began OSETI work, the much-sought artificial signal has yet to be detected. And time is running out- STACEE will shut down for good in the summer of 2007, and our survey will be over. Do I think we will succeed by then? Logically I have to tell you no: the odds of detecting an alien signal are several times worse than those of winning the lottery. In other words, the chance is next to none.
And yet, the human drive to study the world around us is not based wholly on logic: we do not study stars because we find it practical, nor do we dream of other worlds because it is a sensible thing to do. Pure science is based on a thirst for knowledge without a clear immediate benefit, and I believe my work in OSETI is part of the scientific tradition.
Though I know the odds are slim, I can't help but hope. The universe is a big place, and there is no doubt in my mind that the fantastic is just waiting to be discovered.
By Yvette Cendes