Universal things on Instagram: "This high-power hobby rocket just reached Mach 2, which means it flew at twice the speed of sound - over 1,500 miles per hour. Mach numbers are a simple way to compare an object’s speed to how quickly sound travels in air. Mach 1 is matching the speed of sound, about 760 mph at sea level. Mach 2 is doubling that. At 25,000 feet up, higher than most clouds, the air is thinner, but the rocket was still moving faster than a bullet leaves a handgun. Going this fast, t