Green flash

Green flash is a phenomenon where a tiny bit of green light appears briefly just at the moment when the sun is setting. This happens because of the Earth's atmosphere and how light is bent by it. When light enters Earth's atmosphere, it gets bent a little bit. Because of this, when the sun is just barely below the horizon, the light coming from it hits the edges of the atmosphere at a different angle. This means a little bit of the green light in the sunlight is bent, so it travels a bit farther to your eyes than all the other colors of light. That's why you can see a tiny bit of green light right before the sun sets.