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The Drake Equation; Lets solve it!
Topic Started: Jun 22 2009, 05:52 PM (963 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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Xenophile
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Formerly known as alienboy.
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Are you saying we may not even recognize intelligent life?
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Empyreon
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Are you plausible?

That's a distinct possibility, I think.
Take a look at my exobiology subforum of the planet Nereus!

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food for thought
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ATEK Azul
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Transhuman
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Yes life and intellegent life may be unrecognizable for a good amount of time even after we start traveling places.
I am dyslexic, please ignore the typo's!
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