We only give that answer to questions that haven't been answered yet. We know how the earth formed.If I search Google by asking, “How did planet Earth form?”, what do you think I’ll find? Will I find science saying, “We don’t know”?
They might seem like guesses to you, but they're not. I just finished explaining why the critical thinker isn't interested in guessing andcalling it fact.They offer guesses.
And what would be your criticism if it were only a guess? You're guessing that it's only a guess and you're guessing that a god exists. What argument are you offering against guessing?