I've been watching a lot of Stephen Hawking lately. He says that planet earth supports life because it just happens to be in the right position from our sun to contain liquid water, and has the proper amount of gravity to keep gases close to the earth's body. They recently discovered a planet that could sustain human life, but it would take something like 200 years traveling at just under light speed to reach them. The reason it doesn't contain its own life forms is because life on earth is very much accidental. Life on earth came about from amino acids forming connections and breaking apart until just the right combination of amino acids just happened to form. Now for all we know this process could be happening on other earth-like planets, but the odds of having "just the right" combination is remarkably low. Now of course as much as we know of the universe is also remarkably limited. I like to think of all the different kinds of planets that could contain life and what they might be like, they don't necessarily have to be that ( ... )