NASA has explained what a lunar eclipse is, where and how to watch it, what stages to expect, and the scientific reason behind the Moon's reddish color.

A total lunar eclipse will make the moon appear red during the across the Western Hemisphere during the "Blood Worm Moon" this week.

In a lunar eclipse, the Earth's shadow — called the umbra — blocks the sun's light from hitting the full moon, resulting in a dimmer moon with a distinct red and orange cast. It's also called a blood moon.