Parabolas in the Physical World

The parabola does not appear only when you throw a ball. Satellite dishes are paraboloids — 3D parabolas — because they reflect parallel rays to a single focal point, so every incoming signal lands on the receiver.

Car headlights reverse the trick. A bulb at the focal point sends light outward, and the parabolic reflector turns it into a parallel beam. Suspension bridges like the Golden Gate hang their cables in a parabolic curve when evenly loaded — distributed weight produces the quadratic shape on its own.