is the chances pretty rare that advanced and intelligient life exists somewhere else in our universe, I mean it seems like we got pretty lucky here on earth to get these conditions to have such abundant life. I am not doubting that bacteria and other simpler organisms exist elsewhere but it almost seems like the chances of advanced life forms is quite small.
russ_watters
Nov18-08, 11:53 PM
It is virtually impossible to evaluate the odds with much accuracy due to the existence of only a single data point. What we do know is this:
1. Life arose quickly on earth, but took a long time to evolve to get to us. That *may* imply that you are correct.
2. Current detection methods are only good for finding large planets orbiting close to stars. And we've found an awful lot. What this tells us is:
a. Most stars have planets.
b. A substantial fraction of planetary systems - perhaps most of them - are likely incapable of supporting life.
The combination of those facsts/inferences leaves a lot of wiggle room in our estimates of the odds. It is not inconceivable that as much as a few percent of stars could harbor intelligent life. If that is the case, there could be millions in our galaxy alone. Such a thing would not contradict our currently available data. But it is also still conceivable that it is a billion to one shot, in which case there could still be a hundred in our galaxy. I doubt many scientists believe the odds to be much lower than that, though.
CaptainQuasar
Nov19-08, 12:22 AM
Not that it necessarily influences the likelihood of there being life elsewhere, since there are a variety of conditions such as a Europan environment it might develop in, but I remember coming across two other points in addition to Russ's:
That amongst the extrasolar planets we've been looking at, nearly-circular orbits like those of the Sol system are relatively rare. Most planets we can see have wildly eccentric orbits, some like those of comets in this solar system.
Evidently it's thought that the oceans somehow provide something like lubrication for plate tectonics? And it's speculated that plate tectonics may have something to do with the presence or maybe diversity of life on Earth.
⚛
jim mcnamara
Nov20-08, 05:51 AM
Read about the Drake Equation.
http://www.setileague.org/general/drake.htm
which attempts to estimate the number of advanced communicative civilizations nearby.
N, the number of civilizations, as Russ said, is already proven to be at least 1, and considering the incredibly immense sample size, it is very unlikely that N is truly 1,
and it is not unreasonable at all to assume N > 1. We have no proof of this of course.
mplayer
Nov30-08, 05:15 PM
Take a look at this article:
Brin, Glen David. 1983. The 'Great Silence': the Controversy Concerning Extraterrestrial Intelligent Life (http://www.brin-l.com/downloads/silence.pdf), Quarterly Journal of Royal Astronomical Society, 24: 283-309.
Its an interesting and detailed discussion on the topic that I think you and many others would enjoy.