A supernova is when a star explodes. If our sun were to go supernova, we wouldn't know what hit us. That's not going to happen in your lifetime. But what about a star outside our solar system? That's been happening since the early days of the universe. Supernova explosions are usually too far away to affect earth much, although they can leave evidence we find millions of years later. Kurzgesagt gives us various scenarios for stars at difference distances from Earth, and what would happen if they exploded into a supernova. As the theorectical distances get closer, the process of a star dying is pretty complicated for relatively nearby planets. There is a distance that's a "sweet spot" that will rain destruction on Earth over the course of centuries, leading to a future dystopia. Closer than that, well, that's it. The last two minutes of this video is an ad.