Why is an American Eclipse of the Sun So Rare?

by | Feb 8, 2016 | Eyeglasses

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In August of 2017, the United States will experience a rare total solar eclipse. In fact, this is the first American eclipse since 1979. It is creating a lot of excitement in the country and many people are already making plans for parties, gatherings and special events. But why is this upcoming eclipse so rare and what makes it so special? Here are some of the reasons why.

A Closer Look at Solar Eclipses

Did you know there are four different kinds of eclipses? In addition, the moon casts three different kinds of shadows during this period.

Moon Shadows

 * Umbra – this moon’s shadow is cast on the earth like a cone. The smallest part of the cone is the darkest, and is cast toward the earth.

 * Penumbra – opposite of the umbra. The penumbra is cone shaped with the largest area of the cone shadow cast upon the earth. This is the lightest area of the moon’s shadow and only blocks out part of the sun.

 * Antumbra – this shadow appears as the moon gets farther from the earth. It blocks out all the sun except for the outer rim.

Eclipse Types

 * Total or complete eclipse – during this event, the moon totally blocks out all of the visible light from the sun. This can only occur while the moon is in a certain position called perigee.

 * Partial eclipse – just the penumbra shadow is cast and only covers up part of the sun.

 * Annular – when the moon is in an apogee position, it will cast an antumbra shadow which covers the sun but allows for the outer rim to be seen.

 * Hybrid eclipse – this is an extremely rare event when an annular eclipse turns into a complete or total eclipse of the sun.

The American Eclipse

Many total solar eclipses are not visible from the US or only in small sections of the country. This depends on the position of the earth, moon, and sun. There are at least 2 solar eclipses every year, so why are they so rare in the US?

The United States is a large country and most eclipses can be seen in specific regions only. For example, in 1972 only the Northern sections of Alaska could experience the rare event. In 1991 Hawaii was the only region affected. Yet, in late August of 2017, an American eclipse will be seen across the country and this does not happen very often. Take the time to enjoy it, and make sure to use safe and approved viewing devices.

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