"A hundred years ago, Auguste Compte, ... a great philosopher, said that humans will never be able to visit the stars, that we will never know what stars are made out of, that that's the one thing that science will never ever understand, because they're so far away. And then, just a few years later, scientists took starlight, ran it through a prism, looked at the rainbow coming from the starlight, and said: "Hydrogen!" Just a few years after this very rational, very reasonable, very scientific prediction was made, that we'll never know what stars are made of."