The Drake equation devised by Dr. Frank Drake in the 1960s, the equation supposedly allows a person to calculate the number of extraterrestrial civilizations in the galaxy that might be close enough to communicate with Earth. To use the Drake equation, a person must first estimate the rate of star formation in the galaxy, the number of stars with planets, the average number of planets around each star that might be able to support life, the fraction of those planets that might actually support life, the fraction of those life-supporting planets that might actually have intelligent life, the fraction of those planets with intelligent life that might have a civilization able to communicate with Earth, and the number of years such a civilization might have been in existence.
Basically Drake equation takes the form:
X stars in the Galaxy, of which
Y % have planets, of which
Z % can support life, on which
A % intelligent life has arisen, with
Then with the manipulation of the numbers you arrive a figure that gives you how close on average the nearest intelligent life-forms are.
All these fractions would then be multiplied by each other; the resulting product’s numerator would be divided by the denominator to arrive at the final answer, which varies depending on the original estimated numbers in the equation.
There are various mathematical expressions for this formula, and there are variations on how many terms the equations include.
The problem, of course, is that some of the variables are easy to pick (e.g., stars in the Galaxy), some are under study (e.g., how many stars have terrestrial-like planets), and others are just flat-out guesses (e.g., duration of civilization, where we are currently running an experiment to test this here on Terra of Sol).
Basically Drake equation takes the form:
X stars in the Galaxy, of which
Y % have planets, of which
Z % can support life, on which
A % intelligent life has arisen, with
Then with the manipulation of the numbers you arrive a figure that gives you how close on average the nearest intelligent life-forms are.
All these fractions would then be multiplied by each other; the resulting product’s numerator would be divided by the denominator to arrive at the final answer, which varies depending on the original estimated numbers in the equation.
There are various mathematical expressions for this formula, and there are variations on how many terms the equations include.
The problem, of course, is that some of the variables are easy to pick (e.g., stars in the Galaxy), some are under study (e.g., how many stars have terrestrial-like planets), and others are just flat-out guesses (e.g., duration of civilization, where we are currently running an experiment to test this here on Terra of Sol).
If you take reasonable numbers for everything up to the average duration of technological civilizations, then you are left with three possibilities:
1 - If such civilizations last a long time, "They" should be here (leading either the Flying Saucer hypothesis -- they are here and we are seeing them, or the Zoo Hypothesis -- they are here and are hiding.
2 - If such civilizations last a long time, and "They" are not "here" then it becomes necessary to explain why each and every technological civilization has consistently chosen not to build starships (since the first civilization to build starships would spread across the entire Galaxy on a time scale that is short relative to the age of the Galaxy), perhaps because they lose interest in space flight and building starships.
3 - Such civilizations do not last a long time, and blow themselves up or otherwise fall apart pretty quickly.
People who do not believe that extraterrestrial life exists at all end up with an answer of zero, but those who are certain there are many extraterrestrial civilizations have been able to make it come out to five thousand or more. But despite this element of subjectivity, positive results from the Drake equation were used in part as justification for the creation of the Search for Extraterrestrial Intelligence, or SETI, a project that searches for intelligent life by using radio telescopes to pick up radio waves from space.
Sources:
The Greenhaven Encyclopedia of Paranormal Phenomena by Patricia D. Netzley;
UFO Dictionary A to Z
1 - If such civilizations last a long time, "They" should be here (leading either the Flying Saucer hypothesis -- they are here and we are seeing them, or the Zoo Hypothesis -- they are here and are hiding.
2 - If such civilizations last a long time, and "They" are not "here" then it becomes necessary to explain why each and every technological civilization has consistently chosen not to build starships (since the first civilization to build starships would spread across the entire Galaxy on a time scale that is short relative to the age of the Galaxy), perhaps because they lose interest in space flight and building starships.
3 - Such civilizations do not last a long time, and blow themselves up or otherwise fall apart pretty quickly.
People who do not believe that extraterrestrial life exists at all end up with an answer of zero, but those who are certain there are many extraterrestrial civilizations have been able to make it come out to five thousand or more. But despite this element of subjectivity, positive results from the Drake equation were used in part as justification for the creation of the Search for Extraterrestrial Intelligence, or SETI, a project that searches for intelligent life by using radio telescopes to pick up radio waves from space.
Sources:
The Greenhaven Encyclopedia of Paranormal Phenomena by Patricia D. Netzley;
UFO Dictionary A to Z
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