The Great American Total Solar Eclipse

An Awe-Inspiring and Historic Event Takes Place

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Get your protective eyewear ready and hope for clear skies on August 21, 2017, when the Great American Total Solar Eclipse takes place as the Earth, moon, and sun line up perfectly. The skies will darken, animals will suddenly change their behavior, and temperatures will rapidly drop all the way from Oregon to South Carolina, along a stretch of land about 70 miles wide. Due to the shadow of the moon moving from west to east, totality will occur later in the day the farther east you travel.

The moon’s dark shadow will sweep across the country starting around 9:05 AM PST in Lincoln Beach, Oregon and ending around 4:06 PM EST in Columbia, South Carolina, according to NASA. Observers outside the totality path will still see a partial solar eclipse where the moon covers part of the sun’s disk.

The last total solar eclipse to occur in the USA was on July 11, 1991, but was only viewable from parts of Hawaii. Before then, the February 26, 1979 eclipse could be seen in the Pacific Northwest, particularly in Washington, Oregon, Idaho, Montana, and North Dakota. The August 2017 eclipse will be the first with a path of totality crossing the USA’s Pacific and Atlantic coasts since 1918. Also, its path of totality makes landfall exclusively within the United States, making it the first such eclipse since our independence in 1776. (The path of totality of the eclipse of June 13, 1257 was the last to make landfall exclusively on lands currently part of the USA.)

During a total solar eclipse, the moon completely covers the sun and the sun’s outer atmosphere, its corona, can be seen, which is otherwise not viewable from Earth. Solar eclipses occur because the sun is just about the same apparent size as the moon from our perspective. The sun is about 400 times larger in diameter than the moon; the moon is about 400 times closer than the sun. Totality can last for no more than about seven and a half minutes but is usually less than three minutes long. Total solar eclipses are rare events because the moon’s orbit is tilted with respect to Earth’s orbit around the sun by about five degrees.

When the moon first formed around Earth over four billion years ago, it was much closer to Earth and appeared much larger in our sky. Over the eons, the moon has gradually receded from Earth due to the friction from the tides. At present, the distance from the Earth to the moon increases
by about an inch per year so in some distant future, the moon’s disk will become smaller enough that no more total solar eclipses will be visible from Earth.

The only safe way to look directly at the uneclipsed or partially eclipsed sun is through special-purpose solar filters, such as “eclipse glasses” or hand-held solar viewers. Homemade filters or ordinary sunglasses, even very dark ones, are not safe for looking at the sun and therefore, not recommended. Do not look at the uneclipsed or partially eclipsed sun through an unfiltered camera, telescope, binoculars, or other optical device. You never want to look directly at the sun without appropriate protection except during totality of a total solar eclipse otherwise you could seriously injure your eyes. If you are within the path of totality, you can remove your solar filter only when the moon completely covers the sun’s bright face and it suddenly gets quite dark. Experience totality, then, as soon as the bright sun begins to reappear, replace your solar viewer to glance at the remaining partial phases.

If you are not in the path of totality and don’t want to miss the experience of the total solar eclipse, NASA is hosting a live Eclipse Megacast for the four hours surrounding the event. The Megacast will be picked up by NASA TV as well as many other local and national TV stations.

Your next opportunity to experience a total solar eclipse over the continental United States will be on April 8, 2024.

The August 2017 total solar eclipse will be viewable from a band about 70 miles wide that stretches diagonally from north-west to south-east. Everyone in the contiguous united States will see at least a partial solar eclipse.