Lately I have been interested in life outside of earth. I don't know if it is because of reading one to many crazy Lost theories or zoning out to the Astronomy Cast postcast, but I've been wondering...
Put aside the fact that I saw a UFO years ago, I don't believe aliens have been spotted by humans. However, I have always believed that extraterrestrial life must exist in a universe this big. In fact, a lot of otherworldly intelligence must be out there, right? Law of averages and all. But then why haven't humans seen them if the galaxy is teeming with life?
I'm obviously not the first person to wonder. The Fermi paradox is the name of the contradiction between high estimates of the probability of the existence of alien life and the lack of evidence for or contact with such civilizations. (Thanks Wikipedia.) Mr. Fermi asked the question and a Frank Drake attempted to answer it.
The Drake equation I find very interesting. It multiplies the factors deemed necessary for our contact with ET, unfortunatly we can only estimate the values of these factors. The factors to consider are the rate of star formation in our galaxy the fraction of those stars that have planets, the average number of planets that can potentially support life per star that has planets, the fraction of the previous that actually go on to develop life at some point, the fraction of the previous that actually go on to develop intelligent life, the fraction of civilizations that develop a technology that releases detectable signs of their existence into space, and the length of time such civilizations release detectable signals into space. Estimates for these fractions range from .0001 to 10,0000 depending on who you ask.
From what I know now, I doubt we will find intelligent life in a long long time if ever, because I think earth is very unique. Earth is a prime breeding ground for life, the likes of which we have yet to see on any other planet. I am not only basing this on the presence of water and atmosphere, or the ideal distance from the sun. The type of sun matters too. Most stars are not like the sun. A star needs at least as much metal in it to support life as we know it. Also, earth is lucky to have Jupiter where it is positioned in our solar system. Without it, the meteors and a asteroids that now are pulled into its gravity would collide with earth on a fairly regular basis.
Thinking back through what we know of our biological history, life almost didn't arise many times over; and then, almost didn't evolve. If the dinosaurs never died off, humans would not be here. As for hoping aliens could develop as far as we have or further, we have to look at history as well. Our civilization as been crippled in the past (fall of Rome) as well as nearly destroyed (nuclear war.) What's to say alien cultures would be as lucky to avoid these growing pains?
My conclusion is this: I now believe that life may be out there, but rare enough for civilizations to never cross paths. Which may very well be a good thing.
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