“If you look at the deepest pictures ever taken by the Hubble Space Telescope, they show literally thousands of galaxies when the universe was really young. People have commented, ‘Wow, look at all those galaxies! I wonder how many civilizations there are looking back at us?’ In that picture, I’d say zero. Thousands and thousands and thousands of galaxies —but zero Earths, because the heavier elements haven’t built up enough yet.”
