Since 1957 human beings have launched thousands of satellites and other spacecraft. Most of the spacecraft launched successfully achieve orbit. Those that explode after attaining orbit altitude and those that fail after achieving orbit become space debris (also known as orbital debris or space junk). Anything that reaches orbit altitude—about 300 kilometers (186 miles) above Earth’s surface—becomes a satellite. Once in orbit, objects are constantly under the pull of Earth’s gravity,... więcej

Salem Press Encyclopedia, 2020. 3p.