What is a lunar eclipse?
A lunar eclipse happens when Earth passes directly between the Sun and the Moon, casting its shadow on the Moon. It can only occur during a full moon.
In a total lunar eclipse, the Moon moves completely into the darkest part of Earth's shadow, called the umbra. Instead of disappearing, it usually turns a coppery red color, which is why it is often called a blood moon. Totality can last more than an hour and a half.
The red color comes from sunlight passing through Earth's atmosphere. The atmosphere scatters blue light and bends red and orange light toward the Moon, like all of Earth's sunrises and sunsets shining on it at once. Dust and clouds in the atmosphere can make the eclipsed Moon look brighter or darker.
Partial and penumbral eclipses
In a partial lunar eclipse, only part of the Moon enters the umbra. In a penumbral eclipse, the Moon passes through Earth's faint outer shadow, and the dimming is hard to notice. Unlike solar eclipses, lunar eclipses are completely safe to watch with the naked eye.
Did You Know?
A total lunar eclipse can be seen from anywhere on the night side of Earth, so many more people get to see it than a total solar eclipse.