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The moon is going to completely eclipse the sun on Monday in the first coast-to-coast solar eclipse in 99 years.

People across the U.S. will be able to watch — but can watching the eclipse without any eye protection hurt your eyes? When you look at something bright, your pupils naturally get a little bit smaller to let in less light and protect your eyes. But when you look at something super bright, such as a solar eclipse, your eyes can’t keep up.

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Staring at just a sliver of the sun can damage the retina, leading to vision problems. To shield your eyes during the solar eclipse, experts urge viewers to sport glasses or use filters specially designed for looking at the sun.

We investigate the science of what happens to your eyes when you look at a solar eclipse in our new video.

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