Astronomy 1021 Chapter 19: Drake’s Equation
29 May 2018
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Astronomy 1021
Chapter 19
Drake’s Equation
•Drake Equation- Frank Drake in 1961; N, the number of civilizations capable of interstellar
communication in our Galaxy; useful for not solving, but for contemplating; N = "R"∗ fp np fl fi
fc L
-Makes us think about what factors we need to find life
-N= number of civilizations capable of interstellar communication in our galaxy
-R= average rate of star formation in Milky Way (1-3 stars/year); fp= fraction of stars that have
planets; np= average number of planets per star that can potentially support life; fl= fraction of
planets that develop life
-Fi= fraction of planets bearing life on which civilized life has developed; fc= fraction of
civilizations that have developed communications; L= time over which such civilizations release
detectable signals
•Fl= if Fl is 1, then can develop life easily, if number is 0, it is hard to develop life (we just got
lucky on Earth); we only have one example so cannot extrapolate
•Fi; i stands for intelligent conversation; fi= 0 means unlikely to find civilized life; if number is 1
it is inevitable
•Fc= we are not actively communicating, only passively; only detectable within one light-year
away
•L= can we avoid self-destruction? Is there some point where we, as a civilization, can become
immortal?
•The Numbers: estimates for N range from Earth being the only example in the universe, to 10s of
millions
-Why can’t we explore the stars? Where are the aliens?
•Slow spacecraft speeds
Document Summary
Drake"s equation: drake equation- frank drake in 1961; n, the number of civilizations capable of interstellar communication in our galaxy; useful for not solving, but for contemplating; n = r fp np fl fi fc l. Makes us think about what factors we need to find life. N= number of civilizations capable of interstellar communication in our galaxy. R= average rate of star formation in milky way (1-3 stars/year); fp= fraction of stars that have planets; np= average number of planets per star that can potentially support life; fl= fraction of planets that develop life. Fi= fraction of planets bearing life on which civilized life has developed; fc= fraction of civilizations that have developed communications; l= time over which such civilizations release detectable signals. Fl= if fl is 1, then can develop life easily, if number is 0, it is hard to develop life (we just got lucky on earth); we only have one example so cannot extrapolate.
