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Estimating
the number of just Right places in the Galaxy
-
What
does it take to be a just right place?
-
need
a star for warmth, energy
-
need
a planet to protect from star
-
probably
need a terrestrial planet
-
possibly
a particular atmosphere
-
stable
or unstable conditions to nurture or stimulate life
-
Some
think land animals got crowded out of oceans
-
etc.
etc.
-
We
know a about how many stars form in the Galaxy every year
-
from
this and other estimates, we can estimate the number of intelligent civilizations
in the Galaxy:
-
The
Drake Equation
N
= Rs fp ne fl fi fc
L
-
N
= number of civilizations (what we are looking for)
-
Rs
=
Rate of Sun-like stars forming in the Galaxy
-
fp
= fraction of these stars that have planets
-
ne
= average number of Earth like planets in these systems
-
fl
= fraction of Earth like planets on which life actually arises
-
fi
= fraction of these life forms that that develop into intelligent beings
-
fc
= fraction of life forms that develop civilization
-
L
= lifetime of civilization
| Variable |
Book Value |
Alternate value |
| Rs |
1 1/year |
1 1/year |
| fp |
1 |
1 |
| ne |
0.1 |
1 x 10-4 |
| fl |
1 |
0.1 |
| fi |
1 |
0.1 |
| fc |
1 |
0.1 |
| L |
100 years |
10,000 years |
| N |
10 |
0.001 |
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