Shedding Light on the 2017 Solar Eclipse

Or, don’t fear the toad

On August 21st, 2017, those of us living in the contiguous 48 states in the US will be treated to a rare astronomical event. Or maybe we’re doomed. Either way it should be an interesting day.

What’s the reason for the celebration and/or lamentation? It’s because on that day, much of the United States will be in prime viewing territory for a total eclipse of the sun. The last time a total solar eclipse was visible in North America was back in 1979. If you miss this one, you’ll have to wait until 2024 before you can see another total eclipse in the US, and that one will primarily be visible in the eastern half of the continent.

The Science Behind the Shadow

At it’s most basic, a solar eclipse occurs when the moon blocks the light from the sun, casting a shadow over parts of the Earth. Because the moon’s orbit is tilted about 5 degrees with respect to the orbit of the Earth around the sun, solar eclipses are more rare than you might think.

While we get most excited about total solar eclipses, there are actually four kinds of solar eclipses:

Total Eclipse — This is when the moon completely blocks the sun. If you’re in the path of a total eclipse, that shadow cast by the moon is called an “umbral shadow.” Scientists get particularly excited by total eclipses because they create a unique opportunities to view the sun’s outer atmosphere, or “corona.”

Partial Eclipse — This is when the moon’s path doesn’t quite go across the center of the sun and only partially covers it. That shadow cast by the partial obscuration is called the “penumbra.” Most of us in the US will see this penumbral shadow as we’ll be in the path where 50–90% of the sun will be blocked by the moon.

Image from NASA

Annular Eclipse — Because the moon’s orbit is elliptical, it may be far enough away from the Earth that it appears smaller and doesn’t quite fully cover the disc of the sun even when centered. When that occurs it’s called an “annular eclipse” because it appears that there is a ring or annulus of fire around the moon’s shadow.

Image Credit: NASA/Hinode/XRT

Hybrid Eclipse — This is a combination of a total eclipse and an annular eclipse. At certain times during the eclipse or at certain locations on earth, it may appear to be either annular or total. These types of eclipses are relatively rare and only occur roughly once per decade. For perspective, most calendar years have two or three solar eclipses with one of them being a total eclipse.

“Mythology” or “Who Ate the Sun?”

While we see solar eclipses as a really interesting astronomical phenomenon, you can imagine that our ancestors, who didn’t understand all this fancy science stuff, might have viewed the sun disappearing as a cause for concern. For many ancient cultures, a solar eclipse was believed to happen when some creature tried to eat or steal the sun. In China, it was a dragon, the Vikings thought it was a pair of wolves, Koreans believed it was fire dogs, and in Vietnam it was a giant frog or toad (which, you have to admit, makes it sound a little less scary). In Hindu mythology it’s the head of the decapitated demon, Rahu, that tries to swallow the sun. Fortunately, since he has no body, the sun just slides out of his throat. Close one!

For me, I would be more inclined to credit a voracious, furry, blue monster with a reputation for gobbling circular objects.

Even in our modern society there are still pockets of groups that see eclipses as bad omens. One particularly persistent superstition is that a solar eclipse can be dangerous to pregnant women and their babies. For example, in parts of India women are warned to stay inside during an eclipse. In Mexico some women believe they must protect themselves and their babies by carrying something metallic, like a safety pin, pinned to their undergarments.

Eclipse Safety

In reality, the main danger you face from a solar eclipse is the risk of damaging your eyes if you don’t view it properly. Never look at an eclipse with unprotected eyes. You can readily purchase eclipse glasses or solar viewers on-line, but look for those that say they meet the ISO 12312–2 international standard for solar viewing safety. That will ensure the proper protection. If there are scratches or other marks on the lenses, don’t use them!

An alternate method of viewing the eclipse is to make a simple, pinhole projector. This will allow you to watch the progression of the eclipse indirectly, and very safely.

If you want to record the eclipse for posterity, you can find many resources on the Internet with useful tips on how to safely photograph this event.

Traveling for the Eclipse

Since this eclipse will cross the entire continental United States, you have plenty of locations to choose from to get a good look. The totality of the eclipse will run a path from Oregon, though Wyoming, Nebraska, Missouri, Kentucky, Tennessee, and South Carolina.

On the west coast, the eclipse will start around 9am local time. On the east coast it will start around 1pm. The entire event will last about three hours. To find out where and when the eclipse will happen, check out this nifty interactive map.

If you haven’t already made your travel plans, you better move fast. Prime viewing locations are filling up quickly and going for a premium. Still, many locations have been gearing up to handle larger crowds and with the umbra of the eclipse tracking almost 3000 miles chances are you can find an interesting spot for an eclipse vacation!

Teaching Moments

Solar eclipses present great opportunities to learn more about the sun and to explore the intricacies of the dance of orbital mechanics our sun, moon, and Earth share. However, we can turn back to ancient mythology for another learning opportunity that’s still relevant today.

Not all ancient myths about solar eclipses inspired fear and dread. The Batammaliba people of Togo and Benin have a different kind of story they tell during solar and lunar eclipses. In their mythology, solar and lunar eclipses are caused by an ongoing feud between the sun and moon (you can listen to the full story here). To the Batammaliba people, eclipses are a reminder of the cost and futility of sustained conflict. Eclipses are seen as times for reconciliation, to resolve arguments and come together. They serve as a reminder that unresolved conflict and anger brings darkness to all involved.

As we here in the US marvel at the August 21st solar eclipse, here’s hoping we can also use that celestial event as an opportunity to resolve ourselves to bring a peaceful end to our own feuds and fights.

Now that would be something to see!


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