Jessie Peña caught video of a manhole cover in Phoenix, Arizona, the other day. Someone else saw a definite opportunity for a beat. What, exactly, is going on down there?
The storm drain system normally has a lot of air in it. When the system suddenly carries a lot of water, as it has during intense downpours in Arizona lately, the water pushes the air against the covers. That’s a lot of pressure, because those covers are heavy! -via reddit
(Image manipulation performed at Make Me Googly)
Why are manhole covers round? (hint: think applied geometry)