Watch Secrets of Size: Atoms to Supergalaxies Season 1 Episode 2 Online

In the concluding episode of the series, Jim encounters ever larger cosmic structures to reveal the latest breakthroughs in our understanding of the universe. For example, there's the heliosphere, a vast cloud of solar plasma that surrounds and protects the solar system. Its unique physics help us understand why life is possible. Larger still, Jim comes face to face with our galactic home the Milky Way, a monstrous structure sculpted by the gravitational forces of dark matter. Jim finds out from pioneering researcher Adrian Fabian about the black hole at its centre, whose strange behaviour includes emitting the lowest note that can be heard in the cosmos.