Automatic Doors

In the 1st century A.D., Greek mathematician Heron of Alexandria invented the first known automatic door. He described two different automatic door applications. The first application was used to open temple doors. The device used heat from a fire lit by the city's temple priest. After a few hours, atmospheric pressure built up in a brass vessel caused it to pump water into adjacent containers. These containers acted as weights that, through a series of ropes and pulleys, would open the temple's doors at about the time people were to arrive for prayer. Heron used a similar application to open the gates to the city.