'Blood Moon' Eclipse Will Be Century's Longest

July's total lunar eclipse will turn the moon a ruddy red as it passes through the Earth's shadow. (Photo: Francisco Carlos Calderòn/flickr)

If you happen to be in Europe, Africa, Australia or anywhere else in the Eastern Hemisphere on July 27, you just might find yourself standing under this century's longest lunar eclipse.

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This spectacular event, which occurs when the moon passes through the Earth's shadow, will feature a length of totality of 103 minutes. Unlike a "blue moon," which doesn't actually have anything to do with color, the "blood moon" that will glow in the night sky will, in fact, be a ruddy red color.

The total lunar eclipse of January 2018 as viewed from Siberia.
The total lunar eclipse of January 2018 as viewed from Siberia. (Photo: Aleksandr Yuferev/flickr)

The reason for this phenomenon is more spectacular than you might think. The moon, within the shadow of the Earth, is reflecting the collective light of every sunset and sunrise around the globe. As NASA points out, if you were standing on the moon during a lunar eclipse, the view of Earth's dark side would be quite beautiful.

You might suppose that the Earth overhead would be completely dark. After all, you’re looking at the nightside of our planet. Instead, something amazing happens. When the sun is located directly behind Earth, the rim of the planet seems to catch fire! The darkened terrestrial disk is ringed by every sunrise and every sunset in the world, all at once. This light filters into the heart of Earth's shadow, suffusing it with a coppery glow.

The moon reflects that amber color and –– voila! –– we get red moonlight back on Earth.

The phases of the total lunar eclipse from January 2018.
The phases of the total lunar eclipse from January 2018. (Photo: Christian Gloor/flickr)

So why does the length of this total lunar eclipse differ from the 85 others that have or will take place this century? July's full moon, also nicknamed the Buck Moon, will take place during the monthly lunar cycle when the moon is at its furthest point from Earth. It will be the opposite of a supermoon (when the full moon is closest to Earth) and will instead be a full mini-moon.

Because the moon is farther away from Earth, it's both smaller and moves slower through the nearly 1 million-mile wide shadow (known as the umbra) cast by the planet. It also helps that the moon will pass through the center of Earth's shadow and not to the north or south like previous total lunar eclipses.

Those outside the viewing area for July's eclipse won't have to wait long for their own chance to peer up at a full blood moon. The next total eclipse, visible over northwest Africa, Europe and the Americas, will take place on Jan. 21, 2019.