There is an alien civilization on any of these worlds?

How likely is it that the Universe Guestbook more technologically advanced forms of life?
In 1961, Frank Drake, astrophysicist at the National Academy of Sciences of the USA and founder of SETI with Carl Sagan, worked out a famous equation to calculate the possibility of existence of "intelligent extraterrestrials."
In an article recently published in the journal Astrobiology, Adam and Frank Woodruff Sullivan, astronomers from the universities of Rochester and Washington, they have revised this equation based on the most recent discoveries of Kepler, coming to an interesting conclusion: we do not know if at the time you they are alien civilizations, but it is very likely that there were before us.
The elements to consider.
Drake devised the equation that bears his name at a conference on the possibility of interstellar communication.
Since the contact with other forms of heavenly life depends on the number of advanced civilizations in the galaxy, he identified seven factors to which this number can depend on.
Here they are, in the order they are to be considered:
# 1 # the number of stars born each year;
# 2 # the fraction of those stars that host planets;
# 3 # the number of planets whose orbit allows the formation of life (ie that are located in the habitability area);
# 4 # the number of planets, including the potentially habitable, on which it has actually developed life;
# # 5 on the possibility that these heavenly bodies "settlements" has evolved intelligent life ...
# 6 and # ... advanced enough to be able to send radio signals;
# 7 # Finally, the average length of life of that advanced civilization.
Little to say.
The Drake equation is not a universal law, but a (great) starting point to guide the reasoning.
That's why for decades, with very few scientific data available - if you exclude the only known for some time, ie the number of stars born each year - the speculations about the existence of aliens have always been reduced to opinion duels between pessimists and optimistic.
more tools.
Today, however, three of the Drake equation variables are known.
We know:
# 2 # the proportion of stars hosting planets (almost all);
# 3 # that 20-25% of these exoplanets are in the habitable zone.
The two researchers also reformulated the question of starting to try to eliminate another factor in the equation, that the duration of technologically advanced civilizations (point 7 of the list).
Representation of a Dyson sphere, hypothetical mega-structure to keep collecting (or far) the energy of a star: a sci-built for us, but might be built with much more advanced technology.
| Science Photo Library
We change perspective.
Instead of wondering how many alien civilizations exist, you wondered
what are the chances that ours is the only technologically advanced civilization ever existed?
In this way, the variable on the duration (and hence on the possibility of meeting) forms of life becomes superfluous, and there are only three unknowns: (4) the probability that has developed life on an exoplanet, (5) that this life is intelligent, (6) that is technologically advanced.
We are not the first.
You may think that the probability that these three factors combine is extremely low.
But what Sullivan and Frank have shown is that even if we assume that it is extremely low, according to the most pessimistic assumptions, the possibility that our not the first technologically advanced civilization are very high.
Therefore, the answer to the problem is duly reformulated ...
unless the probability of an alien civilization has developed on a habitable planet are not less than one in 10 billion Katherine, humans are not the first technologically advanced form of life to have inhabited the observable Universe.
The comfort of the data.
In the past the most pessimistic scientists have theorized that there is one chance in 10 billion for the planet evolve a technologically advanced civilization.
Well, while maintaining this level of pessimism would evolve a gazillion of civilization with these characteristics, in the course of our cosmic history.
In practice, with the knowledge gained so far, I doubt that before us there were any other advanced civilization appears highly irrational.
This does not tell us whether there are now, but perhaps enough to make us feel a little 'less alone.

From Focus