Transcript Slide 1
SETI: The Search for Extraterrestrial Intelligence Terry Bridges Queen’s University What is SETI? SETI asks: are we alone in the universe? SETI scientists are using optical and radio telescopes to search for signals from alien civilizations The Beginning of SETI 1959 How do we search? Radio waves can travel large distances … but there’s a lot of radio “real estate” to cover! One Magic Frequency Hydrogen is the most common element in the universe. H atoms emit radiation in the radio spectrum at a wavelength of 21cm and frequency of 1420 MHz (compare CBC radio at 107.5 MHz) The “Waterhole” Water (H20) is also special. OH emits radiation at 1721 MHz. So “waterhole” between 1420-1721 MHz is a good place to search SETI Searches: Past and Present Radio Project Ozma, 1960: Frank Drake looks at Tau Ceti & Eridani SETI Institute opens in 1985 META, BETA: 1986-1999, 60-70% of sky, using Harvard 26 metre telescope -- searched 80 million frequencies! -- dish now dead as is BETA (1999) -- a good survey to detect rare but powerful transmitters Project Phoenix: 1993-2004, funded by SETI Institute targeted search of 1000 nearby stars like the Sun used several telescopes including Arecibo and Parkes Project Serendip:onto 1997-present piggy-backed other telescopes, 150 million freq some of the data goes to SETI@home Project Phoenix: 1993-2004, funded by SETI Institute targeted search of 1000 nearby stars like the Sun used several telescopes including Arecibo and Parkes Project Serendip:onto 1997-present piggy-backed other telescopes, 150 million freq some of the data goes to SETI@home The “Wow” Signal The Future of SETI: The Allen Telescope Array Privately funded by Paul Allen and Nathan Mryhrvold 350 x 6m telescopes linked together Search 100,000 to 1,000,000 stars, at 100 million frequencies 42 dishes now, 350 eventually (if funded!) The Allen Telescope Array The Allen Telescope Array The Allen Telescope Array Optical SETI look for optical laser pulses: very focused, can travel across 1000s of light-years, easily detected Several programs around the world (Berkeley, Harvard, Lick, Mt. Wilson, Australia Harvard AllSky Optical SETI Project 1.8m telescope Sending Signals! In 1974, Frank Drake sent a message to the globular cluster M13 The Drake Message Can you figure it out? Should We Send Messages? Pro: detecting another civilization would be very exciting we could learn a lot from an advanced civilization Con: will they be friendly or nasty? What if we detect a signal? -- it would be checked carefully by the discovering scientists -- it would have to be verified by other observatories -- if real, all astronomers and governments would be notified. -- how would the public react? Would there be panic? Probably an internet meltdown … -- could we figure out what the message says? -- should we respond to the message? -- if so, what do we say? -- what would the long-term implications be? Fermi-Hart Paradox: “Where are They?” We have searched for 50 years with no detection: statistically, probably less than 10,000 broadcasting civilizations If there are advanced civilizations, would expect one of them to have colonized the galaxy: so “they” should be here now! Fermi asked: where are they? Presumably means there's not many of them ... Useful Resources The SETI Institute: www.seti.org The Planetary Society: www.planetary.org “Confessions of an Alien Hunter” by Seth Shostak “If the Universe is Teeming with Aliens …” by Stephen Webb “Life Everywhere” by David Darling SETI@home: http://setiathome.berkeley.edu/