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The Drake Equation; Lets solve it!
Topic Started: Jun 22 2009, 05:52 PM (962 Views)
Xenophile
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Formerly known as alienboy.
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What are your estimates on the famous drake equation? Here are mine from my astrobiology report. The following paragraphs also give a good description of Drake's equation for anyone who does not know it.

As interesting as microbial life or multicellular alien life would be, what scientists would really like to find is intelligent, communicable aliens. One scientist named Frank Drake organized a meeting in 1961 with about a dozen scientists with specialty areas ranging from astronomy to biology to talk about the possibilities of life beyond Earth. At this meeting Dr. Drake came up with an equation used to estimate the number of intelligent civilizations in our galaxy. The equation , N = R*Fp x Ne x Fl x Fi x Fc x L is know as the Drake equation.
In order to find N (the number of intelligent civilizations) we must know the number of sun like stars that are born each year or the R* rate of star formation. Sun like stars are yellow g-type stars. We know that about 20 new stars are born each year. NASA has estimated that around 7 sun like stars are born each year.
The next element of the equation is Fp, the fraction of stars with planets. As I discussed earlier about 200 planets have been found outside of our solar system. Only one of these planets was small and rocky. The technology today is very limited in its ability to find Earth like planets. The situation is only going improve as technology advances such as with the launch of the Terrestrial Planet Finder and the Kepler spacecraft. I’m going to agree with Drake's original guess of 0.5 or half of the sun life stars have planets.
Ne , the number of Earth like planets. Within our own solar system at least 3 planets other than Earth possibly could have life of their own, or at least could support it. The word planet is misleading though because their are "moons" possibly capable of supporting life as well. Mars certainly is a planet within the habitable zone but Titan and Europa are denoted as "moons" of Saturn and Jupiter. This raises the value of Ne to at least 2 or every solar system with planets will have at least 2 planets capable of supporting life.
Fl , the frequency life actually arises on a planet. One of the main problems with the Drake equation is that the farther to the right you go the more uncertain we become about the value of the variables. We have yet to find any form of alien life so we can only speculate on the value of the term Fl. Life on Earth is capable of surviving a variety of difficult conditions, amino acids were found on meteorites, and organic molecules have been found on the surface of Titan. As amino acids are the building blocks of life this opens up more possibilities. Given the right circumstances, I am fairly optimistic that live would and could arise on another world. I will guess that Fl is 1 or all planets capable of supporting life will develop life at some point in their lifetime.
Fi , The fraction of planets with intelligent life. In the 4.6 billion years life has existed on Earth, humans have only existed for about 100,000 years, a blink in the evolutionary history of life on Earth. This means that planets will probably have to have to host life for a fairly long time before intelligent life develops. However, if we look at the example of the octopus, a relatively old species, we realize that it has the largest brain of all invertebrates. The octopus’s brain is in fact even larger than some vertebrates. This means that planets could possibly develop smart creatures earlier in their history. The fossil record has also demonstrated that some creatures gradually evolve to have larger brains. Clearly intelligence has an obvious advantage. I think that given enough time a planet with life will develop an intelligent species, leaving the value of Fi at around 100 percent or all planets with intelligent life will, in time, develop intelligent life.
Fc, the fraction of intelligent species capable of interstellar communication. A few species on Earth are considered to be intelligent, like the dolphin, the chimpanzee and the gorilla, the parrot, and the octopus. As an example of this group of animals, the dolphin is able to communicate with other members of it's speices and is able to do many different tricks and other sophisticated actions humans associate with intelligence. But although the dolphin is intelligent it lacks the ability to create tools so it will never be able to develop technology, a neccessity for interstellar communication. As a human civilization we have only very recently developed technology that allows us to communicate between the stars. The inventions that let us accomplish this are the radio and the laser. Could alien life develop these technologies? Assuming the intelligent species has some way to manipulate tools, some form of "graspers", and has some way to communicate with other members of it's species it is very likely to develop science. If you look at human history on Earth, many early civilizations had science. For instance the highly religous Aztecs had extremely accurate measurements of the planets. All it takes is for one person to make a monumental discovery, like Albert Einstein's Theory of Relativity. I believe that the course of science in any alien civilization will eventually lead to the radio, the laser or some other form of interstellar communication. But the question remains even if a species does develop technology capable of interstellar communicatication, will it communicate? Skeptics of the Drake equation have said that very few societies will broadcast signals because they are not interested in talking to other foriegn civilizations or because they may fear alien invasion. I personally believe that one of the aspects of intelligence is curiosity. For example, if James Clerk Maxwell had never been curious about the nature of electricity we would not have cars, computers, IPODs, lightbulbs, ovens, televisons, or any other modern inventions. If primitive societies had never been curious about fire we would still be living in the stone age. I think it is reasonable to assume that intelligence and curiousity are connected. So if there are other civilizations out there they probably are searching for us! The alien invasion concept, although possible, is unlikely ( more on this next ). With this reasoning I believe the value of Fc to be about 0.95 or 95 precent of intelligent species will communicate.
L the lifespan a civilization communicates. After the invention of the radio in 1895 by Guglielmo Marconi, an incredibly destructive device was tested in Alamogordo, New Mexico. With the force equivalent to 22,000 tons of conventional high explosives, the atomic bomb was born. The device was so powerful that J. Robert Openheimer in observing it said "Now I am become Death, the destroyer of worlds." a quote derived from the Hindu scripture. Humankind now has numerous weapons capable of destroying life on a massive scale and even destroying our own species. The varible L in the Drake equation deals with how long humans as a species will broadcast detectable signals into space. In the history of life on Earth life has come very close to being destroyed on numerous occasions. In the Permian era roughly ** million years ago, 90 precent of life on Earth was completely wiped out by a massive meteoroid impact. But life recovered. One of the most amazing abilities of life is its skill of being incredibly adaptable. As I talked about in my first section, we have found lifeforms adapted to an array of incredibly harsh conditions where they continue to thrive. The animals and plants that did survive the Permian extinction went on to reclaim the planet and eventually evolved into modern humans. People too have faced epidemics, earthquakes , famine, nuclear disasters, tidal waves and war yet still have been able to establish themselves as the dominate vertebrate on the planet. How long as a species will we survive and thus continue to communicate? On our current evolutionary path we've been communicating by radio for just over 100 years. This is likely to be the miniumum ammount of time a species will communicate. Of course the lifetime of our civilization , which serves as an example for other civilizations, is likely to be much longer. Dr. Drake's estimate was 100,000 years. For this varibable I will give a high of 100,000 years and a low of 1000 years.
N the number of intelligent civilizations in our galaxy. After multipling every varibable in the equation for both the pessimistic and optimistic veiw of the equation , I came to an interesting conclusion, the varible L greatly effects the answer to the equation. For the opptimistic answer I came to 665,000 intelligent civilizations within the milky way galaxy. With this estimate we will probably find direct evidence of an alien civilization with the next 25 years. But with the pessimistic estimate of 6650 civilizations we are not likely to contact an alien race unless we discover a way to travel to other star sytems within a resonable amount of time. Beacause of the large diference between the two values of N , the drake equation does not give a solid answer to how many civilizations are within the milky way , but more of an educated guess. As our understanding of the different factors that contribute to the drake equation incresses so will the accuracy of our guess.
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ashwinder
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Well thought out.

I guess I disagree with your estimates of Fl and Fi.
Fl: You say that any planet able to support life will at some time have life, I think that's rather over-optomistic. You say yourself that there are 3 other planets/moons capable of supporting life and yet earth is the only one that for the entire history of our solar-system has. I would say that life not only needs the right environment it also needs certain 'accidental' or 'lucky' circumstances that are rather rare.
Fi: Intelligence is not the natural progression in evolution, indeed the development of our extremely large brains involved a number of factors. For example if we had never began walking on our hind legs then we would never have freed up our hands and I doubt our brains would have got any larger than a chimps. The reasons we walk bipedally, unlike all other mammals (which are at best habitual bipeds) is because we happened to be in a certain place at a certain time. Evolution doesn't favour intelligence, while our intellect was a boon getting there was an uphill struggle.

Therefore I would argue that neither life nor intelligence are natural progressions, therefore I would argue that you overestimate these values somewhat.
Edited by ashwinder, Jun 23 2009, 07:33 AM.
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Xenophile
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You have some very good points Ashwinder, but I beg to differ. Although life and intelligence are not natural progressions, we do not know if Titian, Europa, Mars or even Io support there own biospheres. These moons are also in a much earliar stage of their development. I know that intelligence is not a natural progression of evolution, butit has been shown to be incredibally useful in the development of a species. Again the problem we are dealing with is time. I think that givin enough time a planet hosting multicellular life will eventually develop intelligence.
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ATEK Azul
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You know I see the point of this but i completely dissagree with the set up of the equation along with the probability to any where near accurately predict the evolution of life in the universe when 1: we only have our world to use which can contradict this equation all by its self and 2: this equation only operates on earth like planets in the habitable zone with our form of star with carbon based life.

Bottum line for me is that life is unpridictable in many ways(along with planets and the universe) and this equation is far to limated and speculative to mean any thing reliable.
I am dyslexic, please ignore the typo's!
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Xenophile
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Agreed. NASA says its focas will be on carbon based life. I need to contact my friends at SETI to see what they have to say on this.
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ATEK Azul
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Do you really have freinds at seti?

Only carbon based life is being looked for? That sucks and might be very mislead and stupid we should look for all life. I mean who knows we could find silicon based life that works better than most machines! And that could be very useful and yet we are just gonna ignore them!
I am dyslexic, please ignore the typo's!
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Xenophile
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Yep, Nasa has screwed the pooch. But then again they don't get nearly as much money as our military. And yes, I have a friend at seti.
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Water addicted Carbon-based life Narcissism. The prejudice of xenobiology.

As for the equation, here's my statistics:
Ne = Well, I'm optimistic so I have to say seven. I know someone is going to say 'look at our solar system', but I think life can evolve much easier then we give it credit for.
fe= Much fewer, since random chance would appear to go against it. Assuming that the debated meteorite from Mars did contain life, let's say two. But, possibly more.
fi= This is where I may tick people off. All of them that survive long enough, not because intelligence is the natural development of life but do to how low my standard actually is. If it can show deductive reasoning and/or tool use, then I'll count it. So on Earth we have corvids, cetaceans, mollusks, hominids and friends, and elephats and- there's othes but I can't remember. So, my estimate is high. Half.
fc= much lower. One at most from what we've seen.
L= Also low, since that species is naturally self-destructive. Think about it, as a species we are very war-like, that in and of itself is unlikely to be a universal characteristic, but we are also less and less likely to reproduce. Abortion, safe-sex, and deciding to focus on careers instead of families lead to more and more people NOT reproducing, and the trend is on the rise. Beyond that we have to deal with Darwin's comment, we allow the detrimental genes to live and continue on even though they have no point, creating a very hazardous gene pool. Our use of medicines leads to our viruses and diseases to evolve and become more effective killers. We ruin our ecosystems. While it didn't happen, we have came close to wiping out entire races which would lead to us loosing genes that may become important for survival. Our technology is leading to more and more health problems (obesity, high cholesterol, I already mentioned the viruses, plus untrained immune systems). Then there is the problem of civilizations meeting, if we go by Earth's history that probably kills off one of them, or puts it through hell one. Civilization, as it advances, makes it's species more fragile, it is it's own Great Filter.
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Empyreon
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Are you plausible?

The biggest problem I've had with this equation is that it's so arbitrary. If you want there to be a high probability of alien life then you just pick numbers to reach that end. I've never seen much necessity to nail down a specific number of probability to this, I've just said I'm optimistic that there is indeed life out there, and that we may just be surprised where we actually find it.

That said, carbon-water chauvinism might not be such a bad thing to look for, as far as SETI is concerned. If we're going to search for life, it might be a good idea to search for life as we know it. Searching for life as we don't know it might have a higher probability of existence and proliferation, but we might not be able to recognize it for what it is, so discovery might be more difficult.
Take a look at my exobiology subforum of the planet Nereus!

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food for thought
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T.Neo
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but we are also less and less likely to reproduce. Abortion, safe-sex, and deciding to focus on careers instead of families lead to more and more people NOT reproducing, and the trend is on the rise


Access to reproductive rights is a threat to human survival? Even though populations are decreasing in certain countries, the number of humans on the planet is rising alarmingly. It isn't dwindling population that is the threat, but a growing one.

Survival is all about balance.
A hard mathematical figure provides a sort of enlightenment to one's understanding of an idea that is never matched by mere guesswork.
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No, not alone. But when combined with the others yes, since the survival of fittest is gone evolution is gone. You've heard of the Red Queen right? Well, we're avoiding it now. Evolution isn't running anymore but stumbling around drunk, in any and every direction including the mutations that are detrimental to the species, meanwhile the people who are hard working money-makers (the fittest) are trying to keep from reproducing.

Ever read 'The Marching Morons'?
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T.Neo
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Sorry, not convinced.

Especially since the people who are breeding more are of economic/political distinction, not a genetic one.
And I'm also not entirely convinced that people with successful careers are genetically superior.

The most plausible human extinction scenario is that the majority of the population is killed by a nuclear conflict/world damaging natural disaster, and the surviving humans never rebuild civilization, becoming extinct over a long period of time.

Either way, humans are very adaptable organisms, and although civilization might be vulnerable, humans could be far safer from extinction then one might think...
A hard mathematical figure provides a sort of enlightenment to one's understanding of an idea that is never matched by mere guesswork.
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Xenophile
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The variable L is the hardest of all of the variables in the equation to estimate because we have no examples on which to base it on. As I wrote, I gave two different variables to the equation and the end result was dramaticly different. Does anyone else have any estimates/ reveiws of my estimate and the equation?
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Xenophile
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Here's what wikipedia has to say on the equation, http://en.wikipedia.org/wiki/Drake_Equation .

-P.S. I would really appreciate if someone reviewed my estimate of the equation. :)
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ATEK Azul
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With how much life I beleave is possible in this large galaxy alone your high would most likely be my low or close to it even without the equation. This does not mean that I think intellegence is always going to happen but becouse in my opinion life will be super abundant in this and most other galaxies. Though it will most likely be unrecognisable in most instances.
I am dyslexic, please ignore the typo's!
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