Snakecharma, the chance of us evolving to where we are now is infinitesimally small- and we aren't capable of interstellar travel. Given the odds and the number of things that needed to align perfectly it's stunning that we exist at all.
So what are the chances that someone/ something else has evolved to our stage let alone to the more advanced stage of being capable of interstellar travel?
I think it was 1966 Carl Sagan announced that there were two important criteria for a planet to support life: The right kind of star, and a planet the right distance from that star. Given the roughly octillion — 1 followed by 24 zeros — planets in the universe, there should have been about septillion — 1 followed by 21 zeros — planets capable of supporting life.
As knowledge of the universe increased, it's became clear that there are far more factors necessary for life than Sagan supposed. His two parameters grew to 10 and then 20 and then 50, and so the number of potentially life-supporting planets decreased accordingly. The number dropped to a few thousand planets and kept on plummeting.
As factors continued to be discovered, the number of possible planets hit zero, and kept going. In other words, the odds turned against any planet in the universe supporting life, including this one. Probability said that even we shouldn’t be here.
It's commonly accepted today that there are more than 200 known parameters necessary for a planet to support life — every single one of which must be perfectly met, or the whole thing falls apart. Without a massive planet like Jupiter nearby, whose gravity will draw away asteroids, a thousand times as many would hit Earth’s surface. The odds against life in the universe are simply astonishing.
So no, not a believer in alien life.
