A series of twenty non-fiction science readers which engages children in the world around them. What holds up skyscrapers? Why are sports domes curved? Why are triangles used in many bridges? You can find the answers to these and other questions about structures in Why Do Bridges Arch? What holds up skyscrapers? Why are sports domes curved? Why are triangles used in many bridges? You can find the answers to these and other questions about structures in Why Do Bridges Arch?