Board Thread:Fun and Games/@comment-24482836-20140131021153/@comment-26832713-20180203145203

In real life, light eliminates darkness. Darkness cannot exist when light is around, but light can easily exist without darkness. After all, light is an effect created by electrons moving closer to the nucleus after energy is added to an atom.

In fiction, they're two equal but opposite forces. Darkness covers light and light covers darkness, etc. They act much like gravitational potential energy and kinetic energy of a falling object in that sense.