SETI stands for the Search for Extra-Terrestrial Intelligence. It is an interdisciplinary scientific effort to try to detect electromagnetic signals that are indicative of intelligent life. By this we mean that the signals (radio waves, visible waves such as laser signals, infrared waves, microwaves) are not those one would detect from the regular cosmic background “noise”, but rather, these signals are EM waves that are constructed, or similar to those created by human beings. They are manipulated in such a way that we can infer that some intelligent being(s) did such a manipulation. This is similar to the radio waves heading out into space from our tv networks, radio channels, etc. If other intelligent life exists, it might do something similar. Detecting and locating such signals would be strong evidence for intelligent life.
People have been wondering if we are alone ever since we realized that those bright dots in the sky are other stars similar to our Sun. The actual search for ETI commenced when our technology advanced enough to start searching. Modern SETI began with Cocconi and Morrison’s publication in Nature, “Searching for Interstellar Communications”. Published on Sept 19, 1959, it discussed a strategy for scanning nearby stars for non-natural microwave radiation. At around the same time, radio astronomer Frank Drake was about to perform the same experiment Cocconi and Morrison drafted: This was Project Ozma, the first SETI experiment conducted that gave way to further experiments and searches.
The first SETI meeting was held by Drake in Green Bank in 1961. Here he wrote the famous Drake Equation, which spurred a search into figuring out the components that make up the equation, furthering the SETI aims.
SETI is the search as a scientific practice (see “What is SETI?), while the SETI Institute is a private nonprofit corporation founded in 1984 dedicated to the SETI search, among other missions. The Institute works in SETI Research as well as other projects involving Astrobiology and Education and Public Outreach. The SETI Institute is independent of, but collaborates with, researchers here at the Berkeley SETI Research Center.
Messaging to Extraterrestrial Intelligence (METI), also called Active Searches for Extraterrestrial Intelligence (Active SETI), refers to the act of using high power communications equipment on Earth to transmit various messages to unknown extraterrestrial intelligences.
The BSRC has never engaged in any activities involving intentional transmission of communication signals to advanced extraterrestrial life and has no intention to do so in the future. It is the position of the BSRC that intentional transmissions to known or unknown extraterrestrial intelligences should not be undertaken until such time that the world community has carefully considered the potentially enormous implications and consequences of such actions.
Several scientists at the BSRC, along with others, have released a more detailed statement on this topic here.
Earth’s radio waves at certain times and frequencies outshine all other sources in the Solar System. The waves from our broadcasts leak outwards in a spherical shell. These could potentially be found by distant detectors. Since they travel at the fastest possible speed (the speed of light), it takes much less time to reach far distances than physical travel. If other intelligent civilizations have similar technologies, they too would leak out radio waves which we could then detect with our antennas.
Ever since we realized that there were other stars out in the universe, we have been haunted by the question of “Are we alone?”. Curiosity is a natural human driving force. Simply knowing if there are other intelligent beings out there is a major reason for searching. In the vastness of our universe, how could we not wonder if there are others like us that we could potentially communicate with? The only way to find out is conducting experiments and looking for that signal. SETI research also helps to develop new detector technologies, and provides valuable experience in digital hardware development and training in astronomy for students working with us.
No unambiguous signals from extraterrestrial intelligence have yet been found. Our main challenge is distinguishing candidate ETI signals from emission from natural sources, both terrestrial and astronomical. ETI signals must repeat in order to be confirmed. In previous years, SETI scientists found signals that were compatible with our expectations for ETI but did not repeat, or were later found to be interference from our own terrestrial technology. However, SETI has new experiments that capture a vast amount of more detailed data than previously, allowing us to confidently rule out terrestrial signals much faster.
The lack of a signal does not rule out the existence of intelligent life forms in our Galaxy. There are many reasons why we might not even detect the signal. Limitations include the frequency coverage and sensitivity of our detectors, and the sheer vastness of the Galaxy. We might be receiving a signal, and not be tuned in to the right channel, or be looking in the right spot. The search is really just beginning; we have probed such a small region of the Galaxy that we can't yet make any strong statement about the prevalence of ETI. But a signal could come at any time, so it's important to keep surveying the sky!
We have several SETI programs operating at multiple wavelengths, from radio, through infrared, to visible light. These include SERENDIP, SEVENDIP, NIR-SETI and SETI@home. We are also involved in the development of new telescopes and instrumentation.
Our team includes professors, researchers, graduate students, and undergrads. Here is some more information about some of our members.
Our group uses data from a wide range of observatories to search for planets around other stars, and to scan the skies for signs of life:
The main telescopes we use for our SETI searches are listed here.
Researchers attempt to detect EM waves indicative of intelligent life (see “What is SETI?). These signals are likely very weak, so we use large radio telescopes to gather signals. Given that we do not know where the signals may come from, what frequency they might be at, or in what format (FM, AM, pulsing, etc), we need to search many channels and many locations across the sky to gather large amounts of data, which requires a lot of computing power to process and analyze. Computers all around the world help in this effort via the program SETI@home (see“How can I get involved in the search?”)
We also search for evidence of extraterrestrial engineering such as Dyson Spheres.
Since about 2001, our group has made all of our peer-reviewed publications available for free on arxiv. Older publications and non-peer-reviewed publications can be accessed on NASA Astrophysics Data System.
Researchers from universities all around the globe contribute and participate in SETI efforts. UC Berkeley is notable for its work with SETI@home and radio searches, among other efforts. A Harvard team works on optical SETI and operates the Planetary Society funded All-Sky OSETI Telescope.
Kepler is a telescope that searches for planets around other stars. Recent Kepler results suggest that there are billions of Earth-like planets in our Galaxy, which make for promising places to search for signs of life. In particular, planets within the “Habitable Zone” where liquid water could exist on a planet's surface are good candidates for SETI searches. Read more here.
Professor Geoff Marcy, co-investigator of the Kepler Mission, is a major contributor and participant in SETI at Berkeley.
Here is a talk by Professor Marcy on Kepler and its relation to SETI.
In the late 1970s, SETI programs were established at NASA’s Ames Research Center and the Jet Propulsion Laboratory. In 1988, after years of study and designing, NASA Headquarters adopted the programs and provided funding. Observations started four years later, but within a year Congress terminated the funding.
NASA is not directly involved in a SETI program but many affiliates of NASA work with SETI via private efforts and funding. SETI is primarily a privately funded project. There is no specific government agency program devoted to SETI.
One easy and very helpful way to contribute is downloading and installing the SETI@home program on your personal computer. This helps analyze the enormous amount of SETI data simply by letting it run as your screen saver. You can also make a tax-deductible donation to help fund our programs and support our students and researchers.