Rare total lunar eclipse will happen over US and UK THIS month – here’s how you can watch

the effect as "if all the world’s sunrises and sunsets are projected onto the Moon."

This principle is called "" and it also explains why the sky is blue - different colored light rays have different wavelengths and properties.

Blue light has a shorter wavelength and scatters easily, filling the sky with its soft blue - red light passes more cleanly through the atmosphere and, during a lunar eclipse, lands on the face of the Moon.

The apex of the next lunar eclipse, or the totality, is when the Moon is fully caked in its reddish hue.

An entirely red moon will be in most of the Western Hemisphere an hour after the lunar eclipse begins at 10:30PM on May 15.

The rarity of the total lunar eclipse can be expressed by looking to the future or the past.

Nasa projects that there will be 228 lunar eclipses over the course of the 21st century - just of them will be total eclipses while a chunk of them are partial eclipses.

In the last eight years, there have been just six total lunar eclipses.

Added together, the Earth has seen just under six hours of visible total lunar eclipses in that span.

Nasa expects this May's total lunar eclipse to be the last until November 2022.

After November's eclipse, the Earth won't see another total lunar eclipse until March 2025.