A scan of a color copy of the original computer printout, taken several years after the 1977 arrival of the "Wow!" signal. It was a strong narrowband radio signal detected by Jerry R. Ehman on August 15, 1977, while he was working on a SETI project at the Big Ear radio telescope of The Ohio State University. The signal appears to have come from an area of the sky with no stars or planets, northwest of the globular cluster M55. Image Credit: The Ohio State University Radio Observatory and the North American AstroPhysical Observatory (NAAPO).



Why the “Wow!” signal is so special? How much it differs from the other ordinary signals we receive every day?



Vakoch: In the SETI Institute's ongoing search for radio signals from other civilizations, we find promising signals all the time. The critical difference is that we can immediately follow-up to see whether the signal is really coming from a distant star, or whether it's caused by a satellite in Earth's orbit or a radio transmitter on Earth. When the "Wow!" signal was detected in 1977, such real-time follow-up was impossible.



Shostak: It's special because the name is appealing. There were more than 100 other types of signals back then, before we had equipment able to quickly follow up on signals.



Shuch: There are about a half a dozen tests that can be run on received signals to mark them as being of possible extraterrestrial origin. Many detections pass one or a few of these tests, and remain interesting SETI candidates. The “Wow!” signal was the first detection to pass all of the tests to which it was subjected. Of course, even that is not conclusive evidence, because there was no independent confirmation, a necessary condition for certainty.



Harp: It isn't at all special or different from signals that we observe every day at the ATA. I hope you're not disappointed that I'm not so impressed by the “Wow!” signal. I think you will find that many professional scientists in the field do not find the “Wow!” signal very convincing. But that doesn't mean that SETI isn't a good thing to do. There is still a 50% chance, by my estimates, that our first discovery of life off of our planet will be a discovery of a transmitting civilization.



Do you think that we will receive similar signals in the future?



Shuch: We will in the future; we have in the past. We continue to see a few interesting candidates every year. The “Wow!” was merely the first such phenomenon to be observed, and then extensively sought in follow-on experiments. Until such time as they can be independently verified, all signals are enigmas.



Shostak: Less probable. Many SETI experiments, including ours, have the ability to "follow up" almost immediately. When you can do that, "Wow" type signals don't seem to occur!



Harp: We see such signals all the time. To answer a different question, we do sometimes observe signals that look even more interesting, from our perspective, than “Wow!” Sometimes the signals that repeat – “Wow!” was not repeatable - that carry on for some time and then disappear. I wish I knew more about such signals, but if we can't prove a signal really is ET, it is our duty to not make a big deal about it.



Vakoch: We receive promising candidate signals every night, but so far, they don't repeat, so we have to assume they're made by humankind.



How close is SETI today to finding signals from extraterrestrial civilization?



Vakoch: We could find a signal from extraterrestrials any day now. And the search will get better as technology advances. In the next twenty years, we should be able to look closely at about a million stars for signs of advanced civilizations, and that's a large enough number to have a reasonable chance of finding intelligence in the cosmos, if it's really out there and trying to make contact.











Harp: Although I am rather conservative about when we will find ET, there is always a chance we will find it today or tomorrow. We are observing with the ATA every day, 12 hours a day. It could happen any time.



Shuch: We are in the phase of developing hardware, software, and other tools for designing and conducting our experiments. We are still in our technological infancy.



What needs to be done to better detect potential signals from ETs?



Shuch: We need to dramatically increase our coverage of the search space, by bringing online many more observing stations, monitoring a wider portion of the electromagnetic spectrum, operating around the clock, and coordinating among themselves to provide independent verification of candidate signals.



Shostak: The real problem is lack of adequate money to do the experiments.



Vakoch: SETI searches through the cosmic static, looking for signals that stand out from the background noise as distinctly artificial, signals that nature can't create. We need a lot of computing power to sort through all that data. The good news is that computing power increases every year, so the normal trajectory of technological progress is on SETI's side!



Harp: We need faster signal processing. The ATA is actually not sensitivity limited. We are limited by the large amount of so-called radio frequency interference in our observations. In order to find ET faster, we need to be able to process a larger number of candidate signals and this requires a lot more computational power. If I were king, I would upgrade the electronics at the ATA with a $10 million dollar analysis system to increase our observing speed one hundred-fold. Then we'd crank through observations of the entire sky and find ET in a lot less time.







Seth Shostak is the Senior Astronomer and Director of the Center for SETI Research. He also heads up the International Academy of Astronautics’ SETI Permanent Committee. He’s co-authored a college textbook on astrobiology, and has written three trade books on SETI. In addition, he’s published more than 400 popular articles on science - including regular contributions to both the Huffington Post and Discover Magazine blogs - gives many dozens of talks annually, and is the host of the SETI Institute’s weekly science radio show, “Big Picture Science.”



Paul Shuch is the Executive Director Emeritus of The SETI League, Inc. He is also the principal investigator for the Invitation to ETI, a web-based SETI experiment. He developed the San Marino Scale, an analytical tool for quantifying the significance of transmissions from Earth into Space. He’s the author or editor of more than 650 publications, including a dozen books and roughly 300 papers in various conference proceedings, technical, scholarly and popular journals.



Douglas Vakoch is the Director of Interstellar Message Composition at the SETI Institute. He leads the SETI Institute's project to compose interstellar messages of the kind that may some day be sent in reply to a signal from extraterrestrials. As a member of the International Institute of Space Law, he examines international policy issues related to sending such responses. He serves as Chair of both the International Academy of Astronautics (IAA) Study Group on Interstellar Message Construction and the IAA Study Group on Active SETI: Scientific, Technical, Societal, and Legal Dimensions.



Gerry Harp is the Director of the Center for SETI Research. Most of his effort is still focused on doing SETI with the Allen Telescope Array (ATA), a radio interferometer telescope owned by the SETI Institute. The technical side of this work involves automated control of the ATA and ultra-high speed digital signal processing systems to isolate weak signals potentially from outer space, from the sometimes strong human-made signals all around us.

is the Director of Interstellar Message Composition at the SETI Institute. He leads the SETI Institute's project to compose interstellar messages of the kind that may some day be sent in reply to a signal from extraterrestrials. As a member of the International Institute of Space Law, he examines international policy issues related to sending such responses. He serves as Chair of both the International Academy of Astronautics (IAA) Study Group on Interstellar Message Construction and the IAA Study Group on Active SETI: Scientific, Technical, Societal, and Legal Dimensions. is the Executive Director Emeritus of The SETI League, Inc. He is also the principal investigator for the Invitation to ETI, a web-based SETI experiment. He developed the San Marino Scale, an analytical tool for quantifying the significance of transmissions from Earth into Space. He’s the author or editor of more than 650 publications, including a dozen books and roughly 300 papers in various conference proceedings, technical, scholarly and popular journals. is the Senior Astronomer and Director of the Center for SETI Research. He also heads up the International Academy of Astronautics’ SETI Permanent Committee. He’s co-authored a college textbook on astrobiology, and has written three trade books on SETI. In addition, he’s published more than 400 popular articles on science - including regular contributions to both the Huffington Post and Discover Magazine blogs - gives many dozens of talks annually, and is the host of the SETI Institute’s weekly science radio show, “Big Picture Science.” ------ We need faster signal processing. The ATA is actually not sensitivity limited. We are limited by the large amount of so-called radio frequency interference in our observations. In order to find ET faster, we need to be able to process a larger number of candidate signals and this requires a lot more computational power. If I were king, I would upgrade the electronics at the ATA with a $10 million dollar analysis system to increase our observing speed one hundred-fold. Then we'd crank through observations of the entire sky and find ET in a lot less time. SETI searches through the cosmic static, looking for signals that stand out from the background noise as distinctly artificial, signals that nature can't create. We need a lot of computing power to sort through all that data. The good news is that computing power increases every year, so the normal trajectory of technological progress is on SETI's side! The real problem is lack of adequate money to do the experiments. We need to dramatically increase our coverage of the search space, by bringing online many more observing stations, monitoring a wider portion of the electromagnetic spectrum, operating around the clock, and coordinating among themselves to provide independent verification of candidate signals. We are in the phase of developing hardware, software, and other tools for designing and conducting our experiments. We are still in our technological infancy. Although I am rather conservative about when we will find ET, there is always a chance we will find it today or tomorrow. We are observing with the ATA every day, 12 hours a day. It could happen any time. We could find a signal from extraterrestrials any day now. And the search will get better as technology advances. In the next twenty years, we should be able to look closely at about a million stars for signs of advanced civilizations, and that's a large enough number to have a reasonable chance of finding intelligence in the cosmos, if it's really out there and trying to make contact. We receive promising candidate signals every night, but so far, they don't repeat, so we have to assume they're made by humankind. We see such signals all the time. To answer a different question, we do sometimes observe signals that look even more interesting, from our perspective, than “Wow!” Sometimes the signals that repeat – “Wow!” was not repeatable - that carry on for some time and then disappear. I wish I knew more about such signals, but if we can't prove a signal really is ET, it is our duty to not make a big deal about it. Less probable. Many SETI experiments, including ours, have the ability to "follow up" almost immediately. When you can do that, "Wow" type signals don't seem to occur! We will in the future; we have in the past. We continue to see a few interesting candidates every year. The “Wow!” was merely the first such phenomenon to be observed, and then extensively sought in follow-on experiments. Until such time as they can be independently verified, all signals are enigmas. It isn't at all special or different from signals that we observe every day at the ATA. I hope you're not disappointed that I'm not so impressed by the “Wow!” signal. I think you will find that many professional scientists in the field do not find the “Wow!” signal very convincing. But that doesn't mean that SETI isn't a good thing to do. There is still a 50% chance, by my estimates, that our first discovery of life off of our planet will be a discovery of a transmitting civilization. There are about a half a dozen tests that can be run on received signals to mark them as being of possible extraterrestrial origin. Many detections pass one or a few of these tests, and remain interesting SETI candidates. The “Wow!” signal was the first detection to pass all of the tests to which it was subjected. Of course, even that is not conclusive evidence, because there was no independent confirmation, a necessary condition for certainty. It's special because the name is appealing. There were more than 100 other types of signals back then, before we had equipment able to quickly follow up on signals. In the SETI Institute's ongoing search for radio signals from other civilizations, we find promising signals all the time. The critical difference is that we can immediately follow-up to see whether the signal is really coming from a distant star, or whether it's caused by a satellite in Earth's orbit or a radio transmitter on Earth. When the "Wow!" signal was detected in 1977, such real-time follow-up was impossible.