[James]

Originally Posted by Shasown

Ever heard of the Drake Equation?

N = RfpneflfifcL


In this equation, N is the number of detectable civilizations in our galaxy. The other variables are described below:

R is the rate of star formation in the galaxy
fp is the fraction of stars that form planets
ne is the number of planets hospitable to life (i.e., Earth-like planets)
fl is the fraction of these planets on which life actually emerges
fi is the fraction of these planets on which intelligent life arises
fc is the fraction of these planets with intelligent beings capable of interstellar communication
L is the length of time such a civilization remains detectable

The only variable known with any degree of certainty is the rate of stellar formation, R. In the Milky Way, a typical spiral galaxy, new stars form at a rate of roughly four per year [source: Cain]. The variable astronomers feel most uncertain about is L, the length of time a civilization remains detectable. A variety of estimates have been used for L, ranging from 10 years to 10 million years.

Astronomers can make educated guesses about the rest of the variables. For example, of the nine planets in our solar system, only four are what astronomers call terrestrial planets -- those that have a solid surface. Of those terrestrial planets, only Earth supports life. If we take our solar system as representative, then we might argue that ne equals 1/4 or 0.25. Similar guesses have been made about the other variables and, interestingly, they all end up having very similar values, usually in a range between 0.1 and 1.0. So, a typical calculation might look like this:

N = 4 x 0.5 x 0.25 x 0.2 x 0.2 x 0.2 x 3,000,000

which gives us a value of 12,000 civilizations in our galaxy.

Drake's original calculations were very close to this value for N. When he ran the numbers, he predicted that there might be 10,000 detectable civilizations in the Milky Way [source: Garber]. Carl Sagan, a leader in the SETI movement until he passed away in 1996, was even more generous when he suggested that 1 million civilizations might exist in the galaxy [source: Lemarchand]. That's a lot of ETs!

But thats only in the Milky Way, our galaxy, there are billions of other galaxies out there.

Obviously some civilisation or life forms will be more advanced and others less advanced, that reduces the probability down from highly.

There are lots of religions on Earth, there have been a lot more, most talk of an all knowing all powerful merciful God who favours his believers. Thats a joke. Why would God even bother with us, we are insignificant.

A lot of religious beliefs have been shown to have been invented, adapted and changed by man, take for example Christianity, until the Pauline Conversion old JC wasnt really looked upon as being son of god. Followers of him still followed the Jewish faith. People who started following him converted to the Jewish Faith.

It wasnt until Paul was accepted in the Nazareans and pushed out a belief in the divinity of Jesus that there was schism in the "early church" and a belief established that JC was the son of god.

fl, fi, fc and L are guess-timates at best. fl and fc could be much less probable than 0.2 (1 in 5), which reduces the number of potential civilisations in the galaxy considerably.