The flash of a camera is bright enough to cause a reflection off the human retina -- the red we see in these photos comes from the blood vessels in the eye. Learn more about red eyes and cameras in this HowStuffWorks podcast.
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BrainStuff Classics: Why Are Some Americans Cancelling Columbus Day?
07:16

American Versus British English: What Are Biscuits, Muffins, and Pudding?
09:51

How Do Sunspots Work?
14:22