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Here is the Seth Shostak interview by Sander Olson. Dr.Shostak is the senior astronomer at the SETI institute. Dr. Shostak has written a number of books on extraterrestrial intelligence, including Sharing the Universe: Perspectives on Extraterrestrial Life and Confessions of an Alien Hunter: A scientist's search for Extraterrestrial Intelligence. Dr. Shostak is also the host of SETI's weekly radio show titled Are We Alone?
Question: You have been searching for the existence of extraterrestrials for several decades. Are you more or less confident of the possibility of extraterrestrial life than when you started?
Answer: I am considerably more confident than I was three decades ago. Several decades ago we didn't even know if most solar systems had planets. Now we have already spotted more than 400 extrasolar planets, and we are finding more all the time. If we find out that 3% of all solar systems have terrestrial planets, then there should be 10 billion earthlike worlds in the galaxy. That isn't even counting the 100 billion other galaxies out there.
Question: The WOW signal found in 1977 has never been properly explained. What is your assessment of the source of that signal?
Answer: There have actually been numerous signals similar to the WOW! signal. That particular signal has been searched for numerous times subsequently, and no one has found anything. So I strongly suspect that the signal was not extraterrestrial in origin.
Question: some have argued that we should be searching specifically for optical beacons near the center of the galaxy. Do you agree?
Answer: I actually began my career searching for radio signals at the center of the galaxy. A message sent from a beacon near the center of the galaxy would need to be at infrared wavelengths in order to get through all of the dust between there and here. But the idea is a good one.
Question: What computing resources does SETI have to search for alien signals? To what extent is SETI limited by the lack of computing power?
Answer: SETI does most of the processing of signals in real time, on-site. Initially, the SETI program was hindered by a lack of computing power and the need to use specialized digital filters. But we are increasingly employing conventional off-the-shelf computers for these tasks. SETI is continuing to benefit from Moore's law, so we should be able to double the number of signals we analyze every 18 months or so, at least on average.
Question: How many SETI projects are currently in operation?
Answer: There are actually a number of SETI projects, and not all of these projects are associated with the SETI Institute. The seti@home project is run out of Berkeley and does excellent work. They currently have a multi-petaflop computer, courtesy of all of the seti@home participants. This supercomputer is used to analyze signals as a result of all of the participants who donate computer time. Harvard has a SETI project, as do the Italians at the University of Bologna.
Question: What single technological invention would most expedite the search for extraterrestrial life?
Answer: A two-dimensional detector able to detect nanosecond optical pulses would be invaluable to our search for optical signals. We suspect that if intelligent alien life exists it might try to contact us by employing either optical or radio waves. Such a detector could be developed within the next five years and would be a boon to astronomy as well as to SETI.
Question: How is construction of the Allen Telescope Array progressing?
Answer: It is up and running. There are currently 42 antennas, and we hope to eventually have 350. We plan on upgrading and expanding the array in stages. The first stage will expand the array to one or two hundred antennas, and that should cost about $20 million. The basic concept of the Allen array is that one can use many small antennas to simulate the performance of one huge antenna at a fraction of the cost.
Question: If you had a billion dollars to invest in searching for extraterrestrials, how would you spend it?
Answer: With a billion dollars I would place an observatory on the back side of the moon. That would be an ideal location for such an observatory because it would be fully shielded from terrestrial interference. Such an observatory would provide a very clear and noise-free window for both radio and optical studies of the cosmos.
Question: What effect will the Kepler telescope have on the search for extraterrestrials?
Answer: The Kepler telescope was launched in 2009 and is specifically designed to search for earthlike planets in the habitable zone of solar systems in our galaxy. It has been fully operational since the summer of 2009, and has already detected hundreds of planets. Within the next three years, it should tell us how commonplace earthlike planets actually are. If it turns out that such worlds are prevalent, as expected, that will substantially raise the likelihood of ET’s existence.
Question: Carl Sagan postulated that there might be 1 million intelligent species in the galaxy, and Frank Drake speculated that there might be 10,000. What is your best guess?
Answer: I see Drake's estimate as plausible. If 3% of the solar systems in our galaxy have earthlike planets, then there are 10 billion earthlike planets in the Milky Way. Even assuming that only one in a million of these planets harbors intelligent life, that still leaves 10,000 civilizations. We should have precise numbers available by 2013.
Question: In Rare Earth, Peter Ward and Donald Brownlee argue that the "principal of mediocrity" for earth is inaccurate, and that intelligent life in the galaxy is probably exceedingly rare. Do you think their arguments are flawed?
Answer: Rare Earth is a well written book and it has generated much discussion, which I consider a good thing. I have engaged in numerous debates with Ward on this issue, and it comes down to this - what single factor would make intelligent life rare? We know or suspect that all of the inputs necessary for life, such as water and carbon, are abundant in the universe.
Question: One could argue that the combination of factors - the need for jupiterlike planets, the "habitable zone" requirements, along with the requirement for water and a certain gravity, and the need for a moon - together add up to a compelling case against the likelihood of life.
Answer: I'm not at all convinced that moons are needed to support life. Without the moon, the tides would be different and the poles would migrate every so often. But that wouldn’t wipe out life. Regarding gravity, there are already two planets with earthlike gravity in our solar system, and even Mars could probably have supported life earlier in its history (and maybe even today). And we are now fairly certain that Jupiter sized planets are commonplace - we have already located hundreds of them. So I just don't find the argument that complex life must be rare in the galaxy to be compelling.
Question: How confident are you that we will find evidence of extraterrestrial intelligence by 2030?
Answer: I'll bet you a cup of coffee that we will. Our ability to monitor the heavens for signals has been and will continue to increase exponentially. The combination of Moore's law and the Allen telescope array will massively increase the likelihood of finding intelligent life. So I am optimistic.
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