How Will Your World End?

Stories need conflict and what better conflict than the end of the world? So, how will your fantasy world end? Or even better what world ending disaster will your heroes avert through their skill and cunning?

What about... The Sun Will Kill Us

Life as we know it wouldn't exist without the Sun, but let's be honest. The Sun has it out for planet Earth. Even if none of the other catastrophes on this list ever happen, the Sun will end us. Stars like the Sun burn brighter over time as they fuse hydrogen into helium. In another billion years, it will be about 10 percent brighter. While this might not seem significant, it will cause more water to evaporate. Water is a greenhouse gas, so it traps heat in the atmosphere, leading to more evaporation. Sunlight will break water into hydrogen and oxygen, so it can bleed away into space. Should any life survive, it will meet a fiery fate when the Sun enters its red giant phase, expanding out to the orbit of Mars. It's not likely any life will survive inside the Sun.

But, the Sun can kill us any old day it wants via a coronal mass ejection (CME). As you can guess from the name, this is when our favorite star expels charged particles outward from its corona. Since a CME can sent matter any direction, it doesn't usually shoot directly toward Earth. Sometimes only a tiny fraction of particles reach us, granting us an aurora or a solar storm. However, it's possible for a CME to barbecue the planet.

The Sun has pals (and they hate Earth too). A nearby (within 6000 light years) supernova, nova, or gamma ray burst could irradiate organisms and destroy the ozone layer, leaving life at the mercy of the Sun's ultraviolet radiation. Scientists think a gamma burst or supernova might have led to the End-Ordovician extinction.

Now that is food for thought :D