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In a , a group of skydivers flash each other quick thumbs-up before leaping from the hatch of their plane. The patchwork of fields outside of Kristianstad, Sweden, viewed from jumper Tobias Persson’s GoPro camera, stretches out below them as the group hurtles toward the ground. At roughly 1:30 into the video, the GoPro starts spinning madly, creating a hypnotizing swirl of green and brown. It’s broken free of Persson’s helmet. A minute and a half and almost 10,000 feet later, the camera smacks into the grass—and keeps filming.

POV footage shot on a GoPro and captured everywhere from the summit of Everest down to almost 1,000 feet underwater is now ubiquitous. With the abuse their owners put them through in pursuit of action shots, the cameras and their casings have to be well nigh indestructible. When Persson’s camera hit the ground, it was smashed up, but the memory card was intact. That left us asking: How did the thing survive?

The short answer: really, really smart engineering that makes the cameras practically bombproof. GoPro cameras and their housings are made out of polycarbonate, the same impact- and temperature-resistant, electrically insulated material used in cellphones. Todd Gotham, senior director of product design at , says that the company uses an iterative design process. This means they determine how much of a beating they want the camera to take, then put it through enough tests until it meets those standards. 

“We usually drop it from two meters [about 6.5 feet] up,” Gotham says. They also subject the devices to humidity, temperature fluctuations, and intense vibrations (the kind that come from racecars). When he spoke with �����ԹϺ���, Gotham was at the Thunderhill racetrack in Willows, California, putting some cameras through their paces by strapping GoPros to the cars to get readings on the vibrations.

The physics at work during the camera's 10,000-foot fall are basic. Shortly after it flew off Persson’s helmet, the GoPro would have accelerated downward at a speed of 9.8 meters per second squared. (Gravity pulls all falling objects toward earth at the same speed, regardless of weight or mass.) Given its dimensions, the camera hit a terminal velocity of about 67 mph in three seconds, according to Carl Wieman, physics professor at Stanford University. The GoPro took about 94 seconds to hit the ground, striking with 36 Newtons of force. “That’s roughly the force you would feel if you were in a two mph car accident with your seatbelt on,” Becky Thompson, head of public outreach for the American Physical Society, says. 

The fact that the GoPro landed on a relatively soft surface definitely helped, as it did when someone tossed one out of an airplane . “If it’d landed on wood or concrete, it would’ve exploded,” Gotham says. “It’s definitely surprising to me that it survived. As the designer, I should be saying I’m not surprised, but falling out of an airplane is pretty extreme. It never occurred to us that someone would toss their GoPro out of a plane.”

In the case of the GoPro , it was the 2.3-millimeter-thick walls and silicon sealing of the waterproof housing that saved it. The housing can withstand the 70-psi pressure at a depth of 130 feet, and silicon is used to make submarine windows. “Silicon doesn’t degrade,” Gotham says. “Technically our housing is going to stay waterproof through the whole life of the camera. Once you seal this baby in, you can hold it underwater for as long as you want to.”

Or at least until you need to recharge the battery.