Carl Sagan on the Drake Equation; Aliens!

Posted in Science by jukeboxparables on March 11, 2009

Here’s a youtube excerpt from Carl Sagan’s Cosmos: A Personal Voyage. A 13 part television series first broadcast in 1980. It’s apparently been seen by over 600million people in 60 different countries[1] The series covers everything from the beginning of the Universe to the formation of stars and planets to the evolution of life on earth. It then continues through the physiology of the brain to our human history, the history of Science and then onto other planets, space travel and extraterrestrials. It’s utterly awe-inspiring and if your not one for reading then definitely grab the series on DVD.

Anyway back to this excerpt, which is about the Drake equation which is one of the more well known equations that attempts to calculate the amount of Alien life in our galaxy. It was developed by Frank Drake at the time from Cornell University.

The equation is as follows:

N = R* × fp × ne × fl × fi × fc × L

R* is the average 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.

Back in 1961 When Dr Drake first developed it the parameters used were;

N = 10 × 0.5 × 2 × 1 × 0.01 × 0.01 × 10000 = 10

10 Advanced civilizations in our galaxy? That seems fairly plausible. The wikipedia page on this topic has compiled a recent review of these numbers using various sources and comes up with the following:

N = 7 × 0.5 × 2 × 0.33 × 0.01 × 0.01 × 10000 = 2.31

2.31 I’m not a fan of that at all mainly because although it uses updated parameters for R and fl it keeps others unchanged.

What do you all think? I thought I’d have a go at two differing versions based on the following. The first is an optimistic calculation but I still think it’s based in reality. I’ve increased the planet per systems (I just think planets will be found to be more frequent) However I’ve dropped the amount of those that are capable of supporting life to just above half, fl should be one because If a planet is in the ‘Goldilocks zone’ then why shouldn’t it have life? Just as you’d expect a planet extremely far from the sun with all the wrong elements to not have life. I think intelligence is probably inevitable given enough time. Natural selection is powerful and produces endless forms. Lastly I think if a certain species begins an arms race in intelligence stakes then it should naturally reach its endgame, real and flourishing high-intelligence.

N = 7 × 0.6 × 0.6 × 1 × 0.3 × 1 × 1000 = 756

Optimistic indeed. Plausible though. And here’s my flip-side;

N = 7 × 0.5 × 1 × 0.5 × 0.05 × 0.3 × 500 = 13.1

I just don’t see intelligence developing as such a far-off. Obviously calculations have been made by looking at our Earth and perhaps the percentage of intelligent life (us) versus how many species there are. But that would mean it’s much much lower than 0.01. But I’m basing all this on a theory I have that Aliens will look A LOT! like us and that high-intelligence doesn’t co-develop on a single planet. Just as our ancestors wiped out our early hominid competitors making sure that only one intelligent species roam the lands.

Intelligence develops amongst all social animals that care for their young. Mammals are only one group in this branch. I think the other pre-requisite is being bipeds. When our ancestor hominids started walking on 2 legs, it free’d up their hands for using tools and I think this lead to a positive feedback loop of increased brain capacity which then lead to more complex communication and so on. It’s a distinct pattern that I think will repeat throughout our galaxy and the Universe. Anyway I should probably do a proper write-up on this theory with citations and what not. But for now it’s just wild speculation.

[1] http://en.wikipedia.org/wiki/Cosmos:_A_Personal_Voyage


2 Responses

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  1. Dan said, on March 11, 2009 at 10:52 pm

    This makes me think of one of my favorite Douglas Adams’ quotes: “It is known that there are an infinte number of worlds, simply because there is an infinite amount of space for them to be in. However, not every one of them is inhabited. Any finite number divided by infinity is as near nothing as makes no odds, so the average population of all the planets in the Universe can be said to be zero. From this it follows that the population of the whole Universe is also zero, and that any people you may meet from time to time are merely products of a deranged imagination.”

  2. jukeboxparables said, on March 12, 2009 at 8:13 am

    haha. Douglas Adam’s is great, I still haven’t gotten around to reading Hitchhikers yet unfortunately :s I’ve heard it quoted so many times though along with his other work.

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