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What is a solar eclipse and why does it happen?

A solar eclipse occurs when the moon passes between the Earth and the Sun. In a total eclipse, the moon appears to block out the sun — except for a wispy ring of light called the corona — because from Earth, the apparent view of the Moon is almost as large as the apparent view of the Sun. Eclipses occur about every one to two years somewhere on Earth, but they are rare to see. When the Moon passes between the Earth and Sun, sometimes the shadow of the Moon falls above the Earth, and sometimes it falls below the Earth. That’s because the Moon wobbles on its axis. Any given spot on the planet is darkened by the moon's shadow once every 400 years or so. The last time the continental United States saw a total eclipse was in 1979. A total eclipse can only be seen from within the umbra: the darkest part of the Moon’s shadow where it falls on Earth. Viewers in the penumbra, the more diffuse part of the Moon’s shadow, in which the Sun is only partially blocked, will see a partial eclipse.

Where and when can I view the Great American Eclipse?

The Great American Eclipse will take place on August 21, 2017. The exact time of the eclipse depends on where in the country you are, but the eclipse will start around 10:15 am Pacific time on the West Coast and end around 2:45 pm Eastern time on the East Coast. "Totality" will last 2 minutes and 40 seconds at the most. However, only some people in the United States will be able to view a total eclipse. Those people will be within the “path of totality,” which forms an arc through the United States starting in Oregon and ending in South Carolina. You can see the path of totality on a map here. If you are outside the path of totality, you won’t see a total eclipse, but everyone in the US (plus people in parts of South America, Africa, and Europe) will see a partial eclipse. If you’d like to know exactly when the eclipse will start based on your geographic location, download our app and visit the Eclipse Center.

How can I view the solar eclipse safely?

It is always unsafe to look directly into the Sun except for a few brief moments during totality in which the Moon blocks out the majority of sunlight. If you are watching the entire progression of the total eclipse, or watching a partial eclipse, you must protect your eyes by looking through a special filter. The easiest solution is to obtain a pair of specialized eclipse glasses, which filter out harmful ultra-violet, infrared, and intense visible light. Ordinary sunglasses, no matter how dark, will not protect your eyes during an eclipse. Some telescopes also have specialized solar filters for viewing the sun, but do not look at the sun through unprotected telescopes, binoculars, or cameras. If you don’t have access to eclipse glasses or a filter, learn how to create a pinhole projector to project an image of the Sun. We will have more information on safely viewing the eclipse on our blog soon.


More Helpful Links

NASA Eclipse 2017 

American Astronomical Society

Eclipse MegaMovie Project

Radio Jove