Brownlee replicated the first experiment, but the column in Pascal-B was deeper at 500 feet. They also recorded the experiment with a camera that shot one frame per millisecond.
On August 27, 1957, the "manhole cover" cap flew off the column with the force of the nuclear explosion. The iron cover was only partially visible in one frame, Brownlee said.
When he used this information to find out how fast the cap was going, Brownlee calculated it was traveling at five times the escape velocity of the Earth — or about 125,000 miles per hour.
"The pressure at the top of that pipe was enormous," he told Insider in 2016. "The first thing that you get is a flash of light coming from the device at the bottom of the empty pipe, and that flash is tremendously hot. That flash that comes is more than 1 million times brighter than the sun. So for it to blow off was, if I may say so, inevitable."