Evaluating the Odds Optimistically
NIC = RIC
x LIC = Rstar x Pplanets
x Phabitability x
Psimple life x Pcomplex life x Pradio signals x Lradio
era
Optimistic
Estimates
Rstar observed rate: 10 per year
Pplanets observed discoveries: 0.5
Phabitability
extreme
life: 0.5
Psimple life rapidity of life on Earth 1.0
Pcomplex life
long
time on Earth 0.2
Pradio signals who knows? 0.02
NIC = Lradio
era/100 pick your favorite
duration…
So if Lre is greater than a few hundred years, there’s
probably
somebody out there.
Lre needs to be a million years
for them
to be neighbors
(meaning
within 1000 ly).
The Galaxy’s a big place, and
its been
around a long time!
