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It is not every day that the moon passes between the Earth and the Sun for a total solar eclipse. When it does, the results are stunning to observe if you are on the right part of the globe. It is the only time when the outer rays of the Sun, or corona, are able to be observed.
During an eclipse
The most recent total solar eclipse to be visible throughout the majority of the continental United States took place on August 21st, 2017. The event became a group experience, bringing communities together to watch the skies. Eclipse viewing was so popular that safety glasses for watching the event were hard to find. Traffic jams grew as people drove to get into areas of totality where the fullest effects could be viewed.
As the eclipse grew and totality happened, it was clear the results were worth it. Crowds gathered and looked skyward together, with protective glasses on and cameras recording. As the first moments of totality took place, wonderment was shared by all. The Sun’s beautiful corona appeared with a gem-like solar flare.
The mechanics of a solar eclipse
There are a number of variables that need to line up the right way for an eclipse to occur. These include the size and distance between the Sun and the Moon. Conveniently, the Sun is approximately 400 times larger than the Moon, but the Moon is approximately 400 times closer to the earth. If it wasn’t for this correlation, the size and distance of both bodies would prevent an eclipse as we know it.
Another important element in a solar eclipse is the Moon’s orbital path around the Earth and the Earth’s orbital path around the Sun. Because the paths are not perfectly round, there are only two times per year, known as eclipse seasons, when they can intersect for a solar eclipse.
The third element in a total eclipse is the type of moon shadow that is present. The central part of a moon’s shadow is called an umbra and the outer region is called a penumbra. Total eclipses are visible only in geographies where the umbra to passes over the earth. Areas experiencing only the penumbra will have a partial eclipse.
How does a total solar eclipse look?
The appearance of a total eclipse is much like you may expect. At first, there is a small shadow on the edge of the Sun. As this shadow progresses, it covers the Sun in darkness. At a certain point, the lighted part of the Sun begins to appear as a crescent, much like the way the Moon appears during certain times of the month. Eventually, only the outer rays of the Sun are visible. The skies resemble dusk or nighttime even though it is the middle of the day. Often birds tend to roost as if it is evening.
The UV rays leading up to and following totality have been known to cause retinal burns, so anyone watching an eclipse should take care to protect their eyesight. Eclipses can be viewed safely with projection devices such as pinhole cameras, or eclipse glasses (not regular sunglasses) that have been specifically manufactured for the event. During the minutes of totality, when only the corona is visible, it is possible to safely view the Sun directly.
Total eclipses occur somewhere on Earth approximately once every eighteen months. The next one to be visible in the United States should occur in 2024. There are multiple eclipses expected to appear on other parts of the globe before then and you may want to consider making plans to view one. It is a bonding, educational experience for all ages.