When the moon passes in front of the sun on August 21, it will be the first total solar eclipse visible in the continental U.S. since 1979. There was a total solar eclipse last year too, but it was visible mainly in the Eastern Pacific ocean, a place you likely weren’t, so this is the best chance you’ll have to witness the natural spectacle in nearly 40 years.
The umbra, or the shadow that the moon will cast, will pass over the U.S. from about central Oregon, through the plains states, before dipping southward in Missouri and passing through South Carolina and out through the Atlantic. The umbral shadow will average about 70 miles from north to south along the arc the eclipse traces through the country. If you’re not within that shadow, you’ll still see a partial eclipse, with the moon looking like it’s chomping a big hunk out of the sun’s disk.
Eclipses are complicated. Basically, the moon’s shadow is projected into space in the shape of a massive cone, over 235,000 miles long. But since the moon is typically in orbit at about 239,000 miles from Earth, total eclipses only occur when the moon’s (wandering) orbit is unusually close to us. This dictates the size and location of the umbral shadow.
Because the shadow is a cone, the Earth and the moon are spheres, and because the Earth spins on its axis, there are tons of variables that dictate how long the eclipse will appear to the ground-based observer. For people in the sweet spot, the maximum duration will be between two minutes and about two minutes and forty seconds, depending where in the country they’re positioned. The longest-lasting view of the eclipse will be in Kentucky, which is where the moon’s shadow will be moving the slowest.
It’s been a century since a total eclipse passed across the continental U.S. from the Pacific to the Atlantic. Needless to say, people weren’t armed with smartphones and obsessed with documenting every single cool thing they witnessed back then. And, as you’ve been told a zillion times, looking directly at a solar eclipse is very bad (unless you’re smack in the middle of the umbra and the moment the moon completely obscures the sun) whether you’re looking at it through sunglasses or a camera.
Unless you’ve got certified solar glasses (yes, this is a thing), taking two pieces of paper and making a pinhole projection to view the eclipse is a good call. Take a piece of white paper, poke a tiny hole in it, turn your back to the sun, hold up the pierced paper, and use a second piece of paper as a screen. The eclipse’s image will project through the pinhole onto the screen paper.
NASA has a webpage devoted to helping you watch the eclipse without burning the eyes from your skull.
If you’ve been considering a big road trip, here’s your chance. Natural phenomena like this aren’t to be missed.
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