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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