The question for which mankind has sought answers for so long-Are we alone in the universe?Most of you might be thinking,"that is stupid!There is no such thing as aliens!".Well to think that earth is the only planet that supports life in all of the billions on planets in the universe would be rather pessimistic.Of course when considering the essential factors for a planet to support life,one can eliminate a large number of planets from the billions of them out there.The planet should have a sun like star at optimum distance,a big blanket of atmosphere which supports life,certain elements and of course, water.However, even if such a planet does exist,the evolutionary pattern over the years would have been completely different there.Still narrower is the possibility of an advanced civilization like our own to exist there.But don't jump to conclusions just yet!Theories and probabilities aside,there is an equation to predict the existence of advanced civilization on a planet!It is called the Drake equation.
The Drake equation states that:
N = N* fp ne fl fi fc fL
The equation can really be looked at as a number of questions:
N* represents the number of stars in the Milky Way Galaxy
Question: How many stars are in the Milky Way Galaxy?
Answer: Current estimates are 100 billion.
fp is the fraction of stars that have planets around them
Question: What percentage of stars have planetary systems?
Answer: Current estimates range from 20% to 50%.
ne is the number of planets per star that are capable of sustaining life
Question: For each star that does have a planetary system, how many planets are capable of sustaining life?
Answer: Current estimates range from 1 to 5.
fl is the fraction of planets in ne where life evolves
Question: On what percentage of the planets that are capable of sustaining life does life actually evolve?
Answer: Current estimates range from 100% (where life can evolve it will) down to close to 0%.
fi is the fraction of fl where intelligent life evolves
Question: On the planets where life does evolve, what percentage evolves intelligent life?
Answer: Estimates range from 100% (intelligence is such a survival advantage that it will certainly evolve) down to near 0%.
fc is the fraction of fi that communicate
Question: What percentage of intelligent races have the means and the desire to communicate?
Answer: 10% to 20%
fL is fraction of the planet's life during which the communicating civilizations live
Question: For each civilization that does communicate, for what fraction of the planet's life does the civilization survive?
Answer: This is the toughest of the questions. If we take Earth as an example, the expected lifetime of our Sun and the Earth is roughly 10 billion years. So far we've been communicating with radio waves for less than 100 years. How long will our civilization survive? Will we destroy ourselves in a few years like some predict or will we overcome our problems and survive for millennia? If we were destroyed tomorrow the answer to this question would be 1/100,000,000th. If we survive for 10,000 years the answer will be 1/1,000,000th.
When all of these variables are multiplied together when come up with:
N, the number of communicating civilizations in the galaxy.
Scientist Frank Drake, the one who formulated the equation, in 1961 with his students estimated the values of these parameters.He calculated that there may be approximately 10 planets in our galaxy alone that can support life!Though there are many critics for this equation, the U.S government seems to trust Drake and his team.That is how SETI came into existence
SETI(search for extra terrestrial intelligence) institute involves activities to detect extra terrestrial intelligence.Their basic action involves scanning the sky for signals that may be transmitted from intelligent life forms on other planet.In fact you can join them by sharing your computer's idle time processing power.All you have to do is download the SETI@home software package.The system uses idle time processing power of millions of computers all over the world to analyze radio signals from outer space.
For many years, there have been reports of alien and UFO sightings all over the world.Furthermore, some people believe that some countries have already managed to capture alien life forms and secret government organizations have been set up to research on it.However, there are no concrete evidences yet to prove this.Who knows?may be we are not really alone in the universe!
Sources:
http://www.activemind.com/Mysterious/Topics/SETI/drake_equation.html
http://www.seti.org/seti
http://en.wikipedia.org/wiki/Drake_equation
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