Carl Sagan Explains the Drake Equation

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The most famous American astronomer and astrophysicist Carl Sagan explains the Drake equation.

The Drake equation (rarely also called the Green Bank equation or the Sagan equation) is a famous result in the speculative fields of xenobiology, astrosociobiology and the search for extraterrestrial intelligence.

The Drake equation states that:
N = R* × fp × ne × fl × fi × fc × L, where:

N is the number of civilizations in our galaxy, with which we might hope to be able to communicate;

R* is the rate of star formation in our galaxy
fp is the fraction of those stars that have planets
ne is the average number of planets that can potentially support life per star that has planets
fl is the fraction of the above that actually go on to develop life at some point
fi is the fraction of the above that actually go on to develop intelligent life
fc is the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
L is the length of time such civilizations release detectable signals into space.

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[charvelgtrs]

Carl Sagan makes us look better as a species.

[skiwinter01]

Wow, sometimes i like to read comments to get a general idea of each layman's view. Recently, i can't help feeling like I'm living in the movie titled "idiocracy":

An "average American" is selected by the Pentagon to be the guinea pig for a secret hibernation program. Forgotten, he awakes 500 years in the future and discovers a society so incredibly dumbed-down that he's easily the most intelligent person alive..Seems we need to add an f(d), the fraction of planets that are "dumbed-down"

[MrNotoriousNinja]

Every star is confirmed to have a planet around it. If there are 400 billion planets, 2/3rd or so are earth-sized, 1 in 10 are terrestrial , so 27 billion terrestrial planets. Why does he multiply it? sorry i'm a bit confused. Shouldn't he be dividing it? :S and imho the guesses he makes (like 1/2nd of terrestrial planets have life) are a bit off...

But who am I to judge :)

[scifi75]

It hasn't even been a hundred years since we discovered that other galaxies existed and that they are in movement. The stars that we looked are but a few. We could be in an area of the galaxy considered "rural" to others or we could be overlooked as uninteresting or as an undeveloped race still prone to aggression. We also base the development a sentient race along our own conceptions. It all sums up that we still have much work to do and we need to get out in the stars to find out.

[Strangerinasland]

@worktosser The Fermi Paradox & the Drake Equation have no basis for an answer. They are based on unsupported biased supposition.

[knoxvilleguy2]

Just my opinion, but some intelligent life forms might still be just getting out of their equivalent of the Stone Age or the Iron Age. Maybe some are just now learning how to build the type of tools & devices for mass production. Maybe some species & civilizations didn't develop contentious religions like humans did.

Assuming they're actually out there waiting.

[worktosser]

@Strangerinasland There is a difference between a guess and an estimation. For example, my step father was a sailor and asked me how high I thought a bridge 2 miles away was. I asked him how high the mast of a typical sail boat is (similar to ours). I projected that distance into an imaginary perspective line and counted by an estimated 10 units (for speed purposes). I came within 10 feet of the actual hight.

A guess is 'heads or tails'? - where you have no basis for an answer, just a gut feel

[9hello123]

@Strangerinasland The Drake Equation is exact, it is not in the slightest bit a guess.

The values we enter into it, some are guesses, some are exact measurements. However the ones that are guesses we can give very reasonable guesses and even with incredibly conservative guesses that we are almost sure are guessing much too low, still give life being certain.

[sit001]

Wow, the possibilities! Simply wonderful to marvel at. However, it seems the likelihood of us destroying ourselves is high (with people like "terrorists" around). I hope people get their stuff together and stop trying to destroy the world.

[CirqueDuCloud]

This video is really chilling.

[angrygrunt]

@Strangerinasland the final result is a guess, not the equation itself. sorry, i get what you meant, i'm being overly technical

[Strangerinasland]

@angrygrunt Put 1 or more guesses into it then the result is a guess.