If we manage to survive the Sun gradually heating up, though, there might be a bigger problem before the Sun runs out of hydrogen. See, Monty Python and the Galaxy Song have it right; our galaxy is only one of millions and billions in this amazing and expanding Universe. Physics is stunning. The reason is that it exists on so many different scales. On impossibly small lengthscales, we have no idea what’s going on; things are strange, and weird, and quantum. Then we move up towards the scales of subatomic particles; then the world of atoms and molecules; the world of microscopy. The world of us, and the objects we know; and the world of mountains, the world of worlds. The world of stars, and solar systems; the galaxy of stars and stellar systems. The world of galaxies, and, who knows – maybe the world of Universes, too.   This is the story of what happens if we make it through everything; if we survive the 21st century, and all of the centuries beyond. What new risks can we anticipate? And how - to the best of our understanding - does everything, inevitably end?  Theme music: Get Ready for the Apocalypse - Astrometrics Incidental music:  Julie Maxwells Piano Music, Starry Sky Both available via the Free Music Archive