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Search for Life: SETI by Robert Nemiroff Michigan Technological University Physics X: About This Course • Officially "Extraordinary Concepts in Physics" • Being taught for credit at Michigan Tech o Light on math, heavy on concepts o Anyone anywhere is welcome • No textbook required o Wikipedia, web links, and lectures only o Find all the lectures with Google at: "Starship Asterisk" then "Physics X" o http://bb.nightskylive.net/ o asterisk/viewforum.php?f=39 The Drake Equation: • N = R* x fp x ne x fl x fi x fc x L • N is the number of civilizations in our Galaxies that are contactable • R* is the rate of star formation • fp is the fraction of stars that have planets • ne is the number of habitable planets per above star • fl is the fraction of above planets that develop life • fi is the fraction of above life planets that develop intelligent life • fc is the fraction of intelligent life planets that are contactable • L is the expected lifespan of such a intelligent life civilization The Drake Equation • Possible plausible values: o o o R*=10 stars/year; fp=0.5; ne=2 fl=1; fi=0.01; fc=0.01; L=10,000 years • Then N~10 • Where are they? The Fermi Paradox If life is abundant in the Universe • where are they? • why don't they communicate? Question made famous by Enrico Fermi in 1950 • over lunch The Fermi Paradox Possible solutions: • • • • Human civilization is unique o chance o theology High tech civilizations destroy themselves High tech civilizations destroy each other o when two civilizations meet, one always militarily superior The Universe is naturally dangerous o ask the dinosaurs The Fermi Paradox Possible solutions: • High tech civilizations choose to remain quiet o self-preservation o Star-Trek like prime directive (zoo hypothesis) o energy efficient (like Cable TV) • We can't understand their communications o they are too alien o we don't know how to search o signals look to us like noise Fermi Paradox: von Neumann probes • • • • • Self-replicating spacecraft that travel the universe. Make the Fermi paradox less restricted. Might absorb large fraction of rocky planets. Astrochicken: Might be part biological RJN ponderable: vN probe = DNA ? Radio, The Big Ear, And The Wow! Signal Credit and Copyright: Rick Scott APOD: 1998 September 17 The Very Large Array of Radio Telescopes Credit: Dave Finley, AUI, NRAO, NSF APOD: 2006 May 14 A Big Dish at the VLA Radio Observatory Credit & Copyright: Victor Bobbett APOD: 2006 November 29 Arecibo: The Largest Telescope Credit: NAIC, Cornell U., NSF APOD: 1998 November 29 How to Search for Aliens Credit: SETI@home, UC Berkeley SETI Team APOD: 1999 May 17 An Anomalous SETI Signal Credit & Copyright: SETI League 2004 March 7 The Voyagers' Message in a Bottle Credit: Voyager Project, JPL, NASA APOD: 2002 August 31 A Message From Earth Credit: Frank Drake (UCSC) et al., Arecibo Observatory (Cornell, NAIC) 2005 March 13 A Cosmic Call to Nearby Stars Credit & Copyright: Yuvan Dutil & Stephane Dumas 2006 April 2 M13: The Great Globular Cluster in Hercules Credit & Copyright: Eddie Guscott APOD: 2004 May 11