What Is a Partial Solar Eclipse?

What Is a Partial Solar Eclipse?

Steve Russell via Getty ImagesThe Aug. 21, 2017 partial solar eclipse at it maximum as viewed in Toronto.

The eclipse will cross the continental United States, from OR to SC, over a span of nearly two hours.

This is the first eclipse to pass over the United States in the 21st century. The last one was in 1979, and that swept only a handful of northwestern states.

Today's solar eclipse is a uniquely American phenomenon.

You don't actually need special glasses to view the eclipse, you just need them to look directly at the sun.

Total solar eclipses happen because the Sun's diameter is 400 times wider than the Moon's, but it is also 400 times farther away. These total eclipses happen every 12 to 18 months somewhere in the world, often over the open ocean since most of the Earth is covered by water.

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"Cross the outstretched, slightly open fingers of one hand over the outstretched, slightly open fingers of the other, creating a waffle pattern; with your back to the sun, look at your hands' shadow on the ground...the little spaces between your fingers will project a grid of small images on the ground, showing the sun as a crescent during the partial phases of the eclipse", NASA wrote on its website. Where and when can I see this "Great American Eclipse?".

"Totality" - the term for when the Moon completely blocks out light from the Sun - begins near Lincoln Beach, Oregon, at 10:16 am Pacific time (1:16 pm Eastern, or 1716 GMT).

Nasa reported 4.4 million people were watching its TV coverage midway through the eclipse, the biggest livestream event in the space agency's history. "The safest and most low-priced method of viewing an eclipse is by projection, in which a pinhole or small opening is used to cast the image of the sun on a screen placed a half-meter or more beyond the opening", NASA says, according to the Atlanta Journal Constitution. We wanted to cover the total eclipse in person, but we didn't want to drive.

The last coast-to-coast total solar eclipse to grace the United States was 99 years ago, in 1918, in the final days of WW1.

As for the next eclipse to travel over North America, we will have to wait until 2024!

Understanding more about how the Sun works, and how solar flares emerge, can help protect astronauts in space as well as electrical grids on Earth. -AFP People make pinhole eclipse viewers in the Smithsonian's Air and Space Museum on the National Mall before an eclipse August 21, 2017 in Washington, DC.