The COSETI Observatory

R* = Rate of star formation.

s = Fraction with good suns.

p = Fraction with planets.

e = Fraction earth-like.

l = Fraction with life.

• The subscript “o” accounts for the matching of electromagnetic transmitting and receiving technologies.

i = Fraction with intelligence.

c = Fraction wishing to communicate.

o = Fraction using optical means.

L = Lifetime of civilization.

• If all ETIs use laser technology to transmit and we use microwave technology to receive, the number of detectable civilizations falls to zero!

The Modified Drake Equation

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