Download And time -- 1 -2 billion yrs Astronomical Conditions for Life

Life in the Universe – An Astronomical Perspective
Our only example -- Earth
Geological and biological record -- fossil record
simplest lifeforms - 3.5 billion years ago
 ~ 1 billion years after formation
All life on this planets shares a common chemistry
amino acids and nucleotides (H,N,C, O )
amino acids  proteins
Nucleotides  nucleic acids -- DNA, RNA
How universal is this chemistry – slushy ice mixture of
solar nebula, comets, IS molecules in GMC
Miller – Urey Experiment 1952
Simulated atmosphere of young Earth -- water, ammonia, methane, hydrogen
Passed an electric discharge through liquid mixture
Produced amino acids
Biology and chemistry – life
could appear in any favorable
environment
Require – liquid medium
And time -- 1 -2 billion yrs
Astronomical Conditions for Life
1. Nature of parent star -- lifetime
require
1 – 2 billion years
2. in life or habitable zone of the star
depends on temp and lum of star
3. size and mass of planet
sufficient surface gravity to hold atmosphere and liquid medium
Chemical conditions -- solar nebula type composition
complex organic molecules -- comets, IS molecules from GMC
Biological conditions
--- Time!
Interstellar Travel or Interstellar Communication ?
SETI -- the Search for Extraterrestrial Intelligence
http://www.seti.org/
http://setiathome.berkeley.edu/
Some interesting papers that have appeared
“A New Empirical Constraint on the Prevalence of Technological
Species in the Universe” -- Frank and Sullivan
adsabs.Harvard.edu/abs/2015arXiv151008837F
“The Age Distribution of Potential Intelligent Life in the Milky Way” -Legassick
adsabs.Harvard.edu/abs/2015arXiv150902832L
“Observational Signatures of Self-Destructive Civilizations” -- Steven,
Forgan and James
adsabs.Harvard.edu/abs/2015arXiv150708530S