In 1957, the Nevada Test Site saw a series of nuclear explosions that, according to legend, launched a manhole cover into space. Except it probably didn’t. Here’s where the story came from—and why the inadvertent source of the story has been trying to stop its spread for years.

Operation Plumbbob was a series of 29 explosions meant to study various aspects of nuclear bombs—including how to contain the fall-out from an underground explosion. To test this, the military set off several explosions at the bottom of long “wells,” covered with metal caps. In the Pascal B test, when the cap was welded to the top of the well, the blast hit the cap so hard that, according to analyst Robert Brownlee, it reached six times escape velocity. That 900 kilogram cap, according to legend, became the first object launched into space.

It has since become clear that Dr. Brownlee hates the legend. In an essay from 2002, he explained how the story had originated in the first place.

Brownlee’s problem was that, at the time, he had little information. He had, for example, very few equations describing the materials that he would be working with—instead of an equation of state for the dirt around the nuclear test, he had to use the equation for aluminum, since that was all he had and the ground had traced of aluminum in it.

Given that he had no access to anything we would consider a decent computer, he wasn’t doing any more calculations than necessary. For the Pascal B test, he was asked to calculate information about the shock wave hitting the cap, and no more. He did so, and he and deputy division leader Bill Ogle had a quick conversation about what would happen then.

Ogle: “What time does the shock arrive at the top of the pipe?”

RRB: “Thirty one milliseconds.”

Ogle: “And what happens?”

RRB: “The shock reflects back down the hole, but the pressures and temperatures are such that the welded cap is bound to come off the hole.”

Ogle: “How fast does it go?”

RRB: “My calculations are irrelevant on this point. They are only valid in speaking of the shock reflection.”

Ogle: “How fast did it go?”

RRB: “Those numbers are meaningless. I have only a vacuum above the cap. No air, no gravity, no real material strengths in the iron cap. Effectively the cap is just loose, traveling through meaningless space.”

Ogle: And how fast is it going?”

This last question was more of a shout. Bill liked to have a direct answer to each one of his questions.

RRB: “Six times the escape velocity from the earth.”

It’s clear they weren’t on the same page. Brownlee wasn’t interested in what happened to the cap, and so pretended that the atmosphere didn’t exist. When the cap wasn’t found, he put it out of his head, figuring it had vaporized in the atmosphere. It was only later, when he both got credit for the world’s first space launch and criticism for not taking the atmosphere into account when he calculated the velocity of the cap, that he realized the legend of the cap that got launched at “six times the escape velocity from earth,” had taken on a life of its own.