The Hubble Space Telescope has shown us distant galaxies and planets orbiting other stars, deepening our knowledge of the Universe. Nobel prizewinner John Mather works on Hubble's replacement, the James Webb Space Telescope. He believes we are in a golden age of astronomy. But the young researchers he meets are not convinced. There are too many unanswered questions, they say. For example: what's causing the accelerated expansion of the Universe? Hear how Mather and fellow laureate Brian Schmidt, who first observed this expansion, handle their queries.