The Drake Equation: My Estimates
R* = 7 (7 stars formed per year, averaged over the life of the galaxy)
fp = 0.6 (just over half of all stars formed will have planets)
ne = 0.5 (only half of solar systems with planets will have a single planet capable of developing life)
fl = 0.75 (75% of these planets will develop life)
fi = 0.001 (.1% of which will be intelligent life)
fc = 0.2 (20% of which will be able to communicate)
L = 10,000 years (which will last 10,000 years)
N=3.15 (there are between 3 and 4 communicable civilizations in the galaxy at any one time)
R* is pretty much safely scientifically established.
fp I think is a conservative estimate; current observations seem to imply that this is actually closer to 1 (even binary systems have planets!), but, just in case our searching has been unique, I want a lower estimate.
ne is the first hard estimate to make; a planet with lower mass, liquid water, in the star’s habitable zone… I tend to think that possibility is low, much lower than the “2” value estimated by Drake (that two planets in every solar system with planets will be capable of developing life.)
fl is a little misleading; if a planet is perfect for life, why wouldn’t life arise? Well, I want to account for contingencies, such as a catastrophic impact destroying the planet’s ability to produce life before that life has arisen.
fi is a dramatically low number, which deserves to be dramatically low; the difference between monocellular life and complex consciousness is huge.
fc is much higher than Drake’s estimate of only 1%, but I think that if intelligent life arises, its selfish need to continue its existence would at least 1/5th of the time allow for technological communication to arise. This is the number I have flip-flopped most on.
L is the most arbitrary number of all; we aren’t talking the 10,000 or so years of recorded history here, we are talking about how long a civilization that has developed intersolar communication will last. Seeing as how we are still here, but have only had communicative ability for… say… 50-200 years (depending on your definition), this number is entirely guesswork.
fp = 0.6 (just over half of all stars formed will have planets)
ne = 0.5 (only half of solar systems with planets will have a single planet capable of developing life)
fl = 0.75 (75% of these planets will develop life)
fi = 0.001 (.1% of which will be intelligent life)
fc = 0.2 (20% of which will be able to communicate)
L = 10,000 years (which will last 10,000 years)
N=3.15 (there are between 3 and 4 communicable civilizations in the galaxy at any one time)
R* is pretty much safely scientifically established.
fp I think is a conservative estimate; current observations seem to imply that this is actually closer to 1 (even binary systems have planets!), but, just in case our searching has been unique, I want a lower estimate.
ne is the first hard estimate to make; a planet with lower mass, liquid water, in the star’s habitable zone… I tend to think that possibility is low, much lower than the “2” value estimated by Drake (that two planets in every solar system with planets will be capable of developing life.)
fl is a little misleading; if a planet is perfect for life, why wouldn’t life arise? Well, I want to account for contingencies, such as a catastrophic impact destroying the planet’s ability to produce life before that life has arisen.
fi is a dramatically low number, which deserves to be dramatically low; the difference between monocellular life and complex consciousness is huge.
fc is much higher than Drake’s estimate of only 1%, but I think that if intelligent life arises, its selfish need to continue its existence would at least 1/5th of the time allow for technological communication to arise. This is the number I have flip-flopped most on.
L is the most arbitrary number of all; we aren’t talking the 10,000 or so years of recorded history here, we are talking about how long a civilization that has developed intersolar communication will last. Seeing as how we are still here, but have only had communicative ability for… say… 50-200 years (depending on your definition), this number is entirely guesswork.