It's 100% certain that extraterrestrial life exists. Think of the ISS.
Life outside of our solar system? Near 100% certainty. Assuming humans are the only life form possible would be pretentious. There's so much theoretical proof pro-extraterrestrial life that I don't think this thread is debate-worthy. I don't think anyone's gonna come in here and proclaim there is no extraterrestrial life.
Originally Posted by
Thellian
I second what NoGood said. Given what we know about life and the conditions needed to support it, it is very likely that the universe is teeming with life. However, I don't know if much of that life would evolve beyond a microbial state, so I don't find it very likely we've been visited by extraterrestrial life.
The universe is more vast than you could imagine. The chances for a more advanced life form than us humans are near 100% too.
I like Neil DeGrasse Tyson's reasoning on this.
Our world is full of life within an arm's reach. Do you go outside and look at the ants? Do you go out and examine their "technology"? No. Either you look briefly and then go on or stomp them. You aren't going to put effort in trying to figure them out, what they do, what drives them. A similar thing could be going on in our galaxy. There could be life forms that know we exists, but we are as trivial to them as ants or worms are to us. We're simply not worth their time.
There's a scale of "advancement" called the "Kardashev Scale", based on how much energy a civilisation has at its disposal. A type I civilisation has power over all energy of its planet. A type II has power over the energy of the star it orbits around. A type III civilisation has power over its galaxy. Type IV can take energy from anywhere. Type V has transcended the universe. We're type 0.7
Last edited by Arglax; Aug 11, 2013 at 11:59 AM.