Asking, "If there is no God, what is the purpose of life?" is like asking, "If there is no master, whose slave will I be?".
Scientists do not join hands every Sunday and sing "Yes gravity is real! I know gravity is real! I will have faith! I believe in my heart that what goes up, up, up must come down, down, down. Amen!" If they did, we would think they were pretty insecure about the concept.