You cannot prove that God exists, at least by normal scientific methods. If it is beyond our five senses to examine, then you cannot use science to either prove or disprove. But think about it, no one has ever seen love, yet we all know it is real. No one has ever smelled freedom, but it exists. The key is to look for evidence that would support whether or not it is reasonable to believe in the existence of God.
Christians believe that such evidence exists in abundance.
Then, roughly 4 billion years ago, there was a huge explosion. From that explosion, all of the matter that today forms our planets and stars was born. Imagine you came upon a space shuttle sitting in the middle of the desert. You could reason that it came together by chance through a chaotic sandstorm. But your initial thought would likely be that someone made it and placed it there.