If there is no God, “the big questions” Why is there something rather than nothing?

so how do we answer the following questions: Why is there something rather than nothing? This question was asked by Aristotle and Leibniz alike – albeit with differing answers. But it is an historic concern. Why is there conscious, intelligent life on this planet, and is there any meaning to this life? If there is meaning, what kind of meaning and how is it found? Does human history lead anywhere, or is it all in vain since death is merely the end? How do you come to understand good and evil, right and wrong without a transcendent signifier? If these concepts are merely social constructions, or human opinions, whose opinion does one trust in determining what is good or bad, right or wrong? If you are content within atheism, what cirstances would serve to make you open to other answers?