TL;DR basically just don’t do it.
The total solar eclipse on August 21, 2017 is kind of a big deal.
On August 21, 2017, for the first time in 99 years, a coast-to-coast solar eclipse will be visible across the continental US. This means that just about anyone in those 48 states will be within a day's drive of seeing a total solar eclipse. In other words, if you will be in the US on August 21, this is pretty much the total solar eclipse of a lifetime.
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Depending on where you are in the US, you'll see either a partial or total eclipse.
"The moon will totally block the sun for up to two minutes and 40 seconds, as seen from within a roughly 70-mile-wide path stretching from the Oregon coast to the South Carolina coast," Rick Fienberg, astronomer and press officer for the American Astronomical Society (AAS), writes in an email to BuzzFeed Health. This 70-mile swath is called the "path of totality" — where you'll see the sun totally blocked by the moon. And if you're there, says Fienberg, "you will see the most spectacularly beautiful sight you have ever seen in nature."
Outside the path of totality, you'll get to see a partial solar eclipse, "in which the moon glides across the sun, blocking part of it but never covering it fully," Fienberg says.
Other than the brief moment when the moon completely blocks the sun (if you're in the path of totality), the eclipse must be viewed with special solar filters that are certified to meet international safety standards, says Fienberg. (More on those and eclipse-viewing safety shortly.)
So, what exactly happens when you look at the sun? Turns out that although you probably won't go totally blind, you can get super serious, permanent eye damage in less than 30 seconds. Yikes.
Let's start with a quick primer on how the eye works.
The different parts of the eye work together to create vision. The iris, the colored band around your pupil, opens and closes your pupil to control how much light enters the eye. The cornea is the front of the eye; it bends the incoming light. The lens is behind the pupil, and it focuses light onto the retina, a delicate tissue that's located in the back of the eye. There are light-sensitive cells on the retina that detect light coming from the lens, and process it into information that then gets sent to the brain via the optic nerve. From there, the brain decides what to make of this information.
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