[My study of the universe] leaves little doubt that life has occurred on other planets. I doubt if the human race is the most intelligent form of life.
Harold UreyI looked for it [heavy hydrogen, deuterium] because I thought it should exist. I didn't know it would have industrial applications or be the basic for the most powerful weapon ever known [the nuclear bomb] ... I thought maybe my discovery might have the practical value of, say, neon in neon signs.
Harold UreyAll of us who study the origin of life find that the more we look into it, the more we feel it is too complex to have evolved anywhere. We all believe as an article of faith that life evolved from dead matter on this planet. It is just that life's complexity is so great, it is hard for us to imagine that it did.
Harold Urey