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Terry Godier

Some Basics to Prepare for the Great American Solar Eclipse 2017

Solar eclipse is exciting not only for the kids and scientists, but also for all across the United States eagerly waiting for August 21st. Even though many of us know about solar eclipse, may are still doubtful about the basics of an eclipse as to how it happens and the effects of it. For those who want to gain some basic knowledge about solar eclipse, here we will discuss some basics.

How eclipse occur?

The primary fact to know about eclipses is that they are caused by some coincidences of the cosmic space. In fact, the sun is almost of the same size of the moon on the sky while we view it from earth. Actually, sun is bigger than the moon by about 400 times in its diameter; however both looks of the same size to us as the moon is 400 times closer to earth than the sun.

You can now imagine how solar eclipses occur. Moon has a relatively equivalent size to the sun to cover the sun’s disk in completion. However, moon is not larger enough to cover the entire atmosphere of the sun and the corona. While viewing from earth, we can witness the sight of moon coming between earth and sun as a complete solar eclipse, which is the one occurs during the <a href="https://www.solar-eclipse-august-21-2017.com/">great American solar eclipse</a> in August 2017.

The history and future of eclipses

Total solar eclipses could have been so different at different times. It is also said that total eclipses may not last in this way for long. Moon was formed about four billion years back. During that time, the location of the moon was far closer to earth. So, it used to appear so larger on the sky.

However, now it found that moon is slowly receding farther from earth due to tidal friction. It is estimated that the distance between moon and earth is increasing at a rate of 1 inch each year. So, in distant future, moon’s disc may become will be visibly much smaller on the sky and will not be able to cover the entire solar disk during an eclipse, and total solar eclipses may not be visible from earth.

Umbra and penumbra

If you start to read more about solar eclipses, you may come across the terms
• Umbra, and
• Penumbra

These are basically two distinct types of shadows created by the moon. The inner shadow is called Umbra and Penumbra is the outer shadow. If you are located somewhere inside the path of umbra, you may witness the sun getting completely blocked during the time of eclipse. If you away from the umbra path, you can only see a partial eclipse.

Types of solar eclipses

• Annular solar eclipse

Even though sun and moon has the same visible size on the sky, that itself may slightly as the moon is a little elliptical on its orbit and our earth too revolves around the sun in an elliptical orbit. This variation may reflect during an eclipse as the moon's disk not fully covering the sun. These are called annular solar eclipses. Such an eclipse occurred in the United States last on May 20, 2012. There will be another annular solar eclipse to be witnessed in the country on October 14, 2023.

• Partial solar eclipse

If the shadow of the moon is centered away from earth, there are more frequent common type of solar eclipses occur, called a partial solar eclipse. In partial solar eclipses, umbra misses the earth and only partial coverage of the sun’s disk is visible. We are not supposed to view the partial solar eclipse with naked eyes. One should use approved and quality solar filters or pinhole projection to view partial eclipse. Last partial eclipse occurred in the United States on October 23, 2014.

Total solar eclipse

This is the one we are going to experience on August 21, 2017 in which the moon’s orbit may exactly be within the same plane of earth’s orbit. It will cover the sun’s disk fully and darken the earth by just leaving a twilight at mid-day. The total great American solar eclipse of this year will last for about 2 minutes 45 seconds maximum.

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