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Why Are Manhole Covers Round?

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They're an easily overlooked feature of urban life: the manhole covers that dot a city's streetscape. But why are manhole covers round?

Because there are no angles for alignment, the round shape makes these heavy covers easier to put back on once they're taken off. Round covers are also easier to manufacture.

But the main reason manhole covers are round is so they won't accidentally fall into the manhole itself. With a round cover, no matter how you hold it, you can't shove it in. It just won't go. If it were square, a prankster could hold the cover diagonally over the hole and drop it in, to be followed by who knows how many scooters and pedestrians. 

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Sara Goudarzi
Sara Goudarzi is a Brooklyn writer and poet and covers all that piques her curiosity, from cosmology to climate change to the intersection of art and science. Sara holds an M.A. from New York University, Arthur L. Carter Journalism Institute, and an M.S. from Rutgers University. She teaches writing at NYU and is at work on a first novel in which literature is garnished with science.