Thiis the question I always see, and everytime I see it, it makes me believe in GOD more or some kind of super human/squirle/dog/anything to have created it.
I mean try thinking back of how it begain. What is the first thing ever? The first planet? Was it just nothing, complete blackness for centries? Something had to have started something. I mean my head starts hurting when I get asked this, because I start thinking as hard as I can to come up with anything. But thats the problem, there is nothing. And I doubt scientists will EVER find out how EVERYTHING (planets, universe, where the nothing came from, how long ago that nothing started, and how?) was created. Sure they will most likly get far but no one will ever know how anything was started.