Researchers at the University of Edinburgh in Scotland constructed a computer model to create a synthetic galaxy with billions of stars and planets. They then studied how life evolved under various conditions in this virtual world, using a supercomputer to crunch the results.
In a paper published recently in the International Journal of Astrobiology, the researchers concluded that based on what they saw, at least 361 intelligent civilizations have emerged in the Milky Way since its creation, and as many as 38,000 may have formed. |CNN|
The obvious question is, if intelligent life is so plentiful, why can't we get alien channels on the TV? To clarify my thinking on this question, I did some back of the envelope math, which I'd now like to share with you.
Let's start with some assumptions. The Milky Way is about 10 billion years old, intelligent species are on the galactic scene for about 100,000 years, and civilizations are distributed roughly equally across time.
I can't justify any of those, but I can say something about the last two. Taking the last first, this makes the math easier. With regard to the other, in the current pulp sci-fi I'm reading the assumption is 50,000 years, but that seems parsimonious. My thought is: it took human kind about 100,000 years to get to radio and surely we'll destroy ourselves within the next 100 milennia.
Given all that, and working with the upper bound of 38,000 civilizations, it turns out that you'd expect that there is an intelligent civilization broadcasting about 1/3 of the time.
What does all this mean? In a word, that even in light of this finding it should be no surprise that we remain mired in terrestrial programming.