Catenary Arch

Catenary Curves at the Exploratorium. 
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Paul Hewitt wonderfully describes the physics of the catenary. 

Catenary Arch @exploratorium : when an arch is built in the shape of this special mathematical curve (even with slippery blocks) the compression forces between each block are always parallel to the curve- the stack is stable with no tendency to buckle. The catenary is the exact shape of a chain hanging by its ends, also known as the hyperbolic cosine. Famously used in architecture, from the buttresses of Notre Dame to the Gateway Arch. ?With special thanks to the Exploratorium!