appreciate you input Hecklerboy , In fact, whole civilisations could have become extinct before we came along.
This actually might be more likely if interstellar travel proves impossible (it certainly seems impossible from where I'm standing).
Anyway if we are not become capable of interstellar travel ourselves in the next millenium or so, our chances of long term survival
might diminish considerably. (implying that colonizing another planet would increase our longterm survival prospects by spreading our bets)
But for now, our live times and this century, I don't see us flying of to alpha-centauri colonizing a earthlike planet.
The distances our simply to vast. Even at lightspeed it would take years to get to the nearest stars. And as you might know,
according to Einstein's theory of reletavity it's not possible to travel at lightspeed.
What is encouring though, is that over the last couple of years astronomers have been finding large planets (comparable to Jupiter, Saturn)
circling stars. At this point in time however it's still impossible to find small earthlike planets because they're too small to detect.
Detecting earthlike planets will become possible in the next decade as a sattelite called the TPF (Terrestrial Planet Finder) will be
launched, I believe in 2007, but I'll get back to you on that.
Bas