Legendary test pilot Chuck Yeager—the first man to break the sound barrier and live to tell the tale—died on Monday in Los Angeles. The retired Air Force brigadier general was 97.

On October 14, 1947, Yeager clambered inside the neon orange Bell X-1 with the help of a 10-inch broomstick. The pilot, already legendary after a series of World War II dogfighting heroics, had broken a few ribs the night before on a post-saloon horse ride with his wife—he needed the stick to the close the door of the cockpit behind him.

At 23,000 feet, the bullet-shaped experimental aircraft, powered by a four-chamber rocket engine, dropped out of the bomb bay of a B-29 Superfortress. Yeager had been flying the X-1 for a few months by then, in an attempt to push flight to greater speeds. But a new innovation, courtesy of the US Air Force, gave him renewed confidence that it was time to push his luck again. A horizontal all-flying tail, also called a stabilator, allowed the pilot to control the airplane’s pitch. This could be the day.

OK, quick pause for science. In the years following World War II, pilots the world over were desperate to break the sound barrier, the speed close to the speed of sound during which aerodynamics go topsy-turvy. (Hitting speeds between 660 and 760 mph will break the sound barrier, depending on atmospheric conditions.) It was hard. When something moves through the air at slower speeds, air molecules have time to “dodge” the object. But speed up the thing—say, an aircraft—and the air molecules move closer together, compressing and increasing the air density at the aircraft’s nose. This is when things get slightly spooky. Shock waves form and move rearwards, creating a pressure differential that lifts up the back of the wing. The result: epic destabilization.

Before Yeager—and the Air Force’s stabilator, which you can still spot on superfast fighter jets—pilots would lose control of their aircraft. Some fell apart in the air. Some, including decorated British test pilot Geoffrey de Havilland Jr., died in the effort. “We weren’t getting free houses or notoriety,” Yeager later told WIRED of the Air Force’s efforts. “We were working our tails off for $250 a month. Many of us were dying in the process.”

But on that day in 1947, as Yeager cruised above California’s Mojave Desert, he fired the last two chambers of his rocket engine. The needle on the X-1’s machmeter, which indicated the ratio between the aircraft’s speed and the speed of sound, hit 1.0—its maximum. (In truth, Yeager hit Mach 1.06.) Later, the pilot described the experience of breaking the sound barrier as “smooth as a baby’s bottom.”

As the writer Tom Wolfe noted in The Right Stuff, his 1973 book documenting the triumphs and travails of the daring American test pilots who powered the country’s postwar forays into rocket tech, Yeager’s feats were so celebrated that his “West Virginia poker-hollow drawl” become the intercom template for pilots everywhere. Yeager later served as a technical adviser for the film version of the book; he also made a cameo as a bartender.

Below Yeager, staff who were gathered at Muroc Air Base (now known as Edwards Air Force Base) heard the sound of distant thunder. OK, another science pause: As the X-1, or anything traveling superfast, begins to move at speeds near sound, sound waves begin to pile up in front of it. When the object finally outruns the sound waves and all the pressure that has built up around it, those disturbance waves make their way down to the ground. They are loud. Perhaps you’ve heard of a sonic boom.