In days gone by the event often filled people with fear and dread.
To see the sun, which reliably shone day after day, disappear from view as though devoured by some great monster or at the hands of a disgruntled deity would have sent any observer into panic.
Fortunately, today we understand what's happening when the sun disappears from view and thankfully don't resort to human sacrifice to bring it back!
A solar eclipse has to be one of the most amazing natural displays and they happen just a few times each year. Because of the conditions that cause the eclipse you need to be in very specific locations on Earth to see them, unlike the lunar eclipses that are visible over half the Earth at a time.
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These quite surreal events occur due to very specific alignments of the Earth, moon and sun. If the Earth lies between the sun and moon then it will block sunlight from reaching the moon and we see a lunar eclipse or "eclipse of the moon." If, on the other hand, the moon is between the Earth and sun, then sunlight is blocked from a very small patch of the Earth -- this is a solar eclipse or "eclipse of the sun."
Parts of the US (Nevada, California, Utah, Arizona, Colarado, New Mexico and Texas), Japan and China are treated to a solar eclipse on May 20 this year, although it's not going to be a total solar eclipse; it's going to be something a little special between 22:06 and 01:39 UTC (5:06 p.m. and 8:39 p.m. EST).
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The moon's orbit around the Earth isn't perfectly circular, instead its shaped like an ellipse. This means the distance between the Earth and moon varies and with that, the apparent size of the moon in the sky varies a little.
When the moon's disk appears the same size or larger than the sun, we see a total solar eclipse where the bright photosphere of the sun is blocked from view, revealing the intricate glory of the outer atmosphere of the sun -- the corona. On occasions, though, the moon's disk is slightly smaller than the sun as it appears in the sky leading to the strange spectacle of an annular solar eclipse.
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Annular solar eclipses differ visually from total eclipses as the moon isn't large enough to block the entire photosphere from view, leaving the moon surrounded by a ring of bright sunlight (as seen in the photo, top). It's for this reason that annular eclipses must be observed with filters or using projection techniques. At no point of the eclipse on May 20th will it be safe to look directly at the eclipsed sun with the naked eye or with optical aid.
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Taking the right precautions, though, it is well worth taking time out of your day to witness this incredible spectacle. Annular eclipses don't come round often, so take this opportunity and believe me, during the eclipse you will feel a tingle down the back of your neck as the moon and sun engage in their heavenly dance.
In May, I will share some eclipse viewing tips to make sure every Discovery News reader is well equipped to make the most of this spectacular event.
Want to read more about the May 20 event? Read NASA's special eclipse site (including maps).