What is an Eclipse of the Moon?

Of all the celestial bodies in the universe, the Moon alone ventures into Earth’s shadow. When that happens we see a lunar eclipse. Since this is the only time we can observe the effects of our shadow on another world, it’s a unique experience. Making it even eerier, our planet’s shadow is not black, but red, so the Moon normally turns a vivid coppery color when the eclipse is total. But all lunar eclipse are not the same. The Moon can partly hit our shadow, or it can plunge fully into it. SLOOH sets up its remote telescopes to capture the best of these spectacles – the total lunar eclipse.

How Rare Are Lunar Eclipses?

A total lunar eclipse is never visible to the whole world – only the side that has the Moon in their sky at the time. Moreover, during most years there are no total lunar eclipses at all. After the event of December 11, 2011, there will be none at all during 2012 and 2013. But total eclipses of the Moon will happen in 2014, 2015, 2018, 2019, and 2021. A little more than half of these will be visible from any given place on Earth.

Why is a Lunar Eclipse Special?

Eclipses of the moon are fascinating, and shouldn't be missed. Children of almost all ages become intrigued when they learn that, yes, there's our planet's shadow in space, swallowing the moon. There's proof we really live on a ball. And look at how strange it looks, and how odd is the color of totality!

As the partial eclipse progresses, the shadow goes from the inky black that begins the event as a first bite is taken from the moon's edge, to a deep reddish-orange. Anyone on the moon would then see the black cameo of a "new Earth" surrounded by a brilliant crimson circle, with the dazzling Sun hidden behind it. No astronaut's ever been on the moon when this happened, but what a sight it must be: All our planet's sunrises and sunsets combine into a single blood-red ring around the pitch-black Earth, its ruddy light alone illuminating the otherwise-gray lunar surface.

But the Moon varies from eclipse to eclipse. If Earth has undergone recent, intense volcanic eruptions, like the Pinatubo event in the Philippines in 1991, the thick dust in our atmosphere can paint our shadow black, and that becomes the Moon’s color during the eclipse. On the other hand, when the limb or edge of Earth has been unusually un-cloudy, our shadow can be so filled with bright sunlight that the fully eclipsed Moon barely darkens.

It is this unpredictability that adds to the magic of lunar eclipses. For, here is the one time when we can look at another world to get an environmental report card about ourselves!

History of Eclipses

Total solar eclipses have enormous scientific usefulness, since we then see dramatic solar phenomena like prominences and the corona that are simply invisible at all other times. Lunar eclipses, by contrast, offer little of scientific value. But this wasn’t always the case.

It’s a false if widespread idea that Columbus was a maverick in believing the Earth to be round. The better educated knew for many centuries, since the ancient Greeks, that our planet is a sphere -- and the primary evidence were eclipses of the moon. For, every time the moon wandered into the spot of space that was directly opposite the sun - the place where our planet’s shadow must be cast - it always went into eclipse. It never failed. And the shadow was always round.

But couldn't our Earth then merely be a flat disk? No, for that would mean that the disk must somehow always lie perpendicular to the Sun and Moon. Seen even slightly edgewise, a disk throws an oval shadow. In actual eclipses, the bite taken from the moon is forever round, and only a sphere always casts a round shadow.

It is this knowledge - that the sight before us is our own shadow - that has elevated the event since time immemorial.

SLOOH's Live Coverage

This total eclipse of the Moon will not be seen at all from most of Europe, the eastern half of the United States, or any part of South America. It will be visible in its entirety from Australia and New Zealand, and easternmost Asia. From the westernmost United States, the Moon will set while the eclipse is still in progress. SLOOH, however, will set up remote telescopes to optimally webcast the event, along with narration by experts, from locations that will allow the entire event to unfold.