A total lunar eclipse happens when the sun, Earth and the moon perfectly line up. The most spectacular part about a total lunar eclipse is that when the moon is fully in Earth’s shadow it turns red. This has earned the phenomenon the nickname of blood moon.

The red colour happens because sunlight is deflected through Earth’s atmosphere. The process is called refraction and it bends red light from the sun like a lens into the space behind Earth – and so on to the surface of the eclipsed moon.

The precise colour of the moon depends on the atmospheric conditions in Earth’s atmosphere. The clearer the atmosphere, the brighter and lighter the red colour appears to be.

If Earth had no atmosphere then the totally eclipsed moon would be black. As it is, we stay alive because we have air to breathe and as a bonus we get a beautiful celestial phenomenon to watch. So, a win-win.