What Are Satellites and How Do They Stay up While Orbiting the Earth?
Satellites are any objects that revolve around (orbit) another object in space. Some satellites are natural, while others are artificial (man-made). The moon is an example of a natural satellite that orbits the Earth. Artificial satellites are machines that humans launch into orbit, usually around the Earth. Artificial satellites can be sent to orbit other planets, too. For example, there are currently satellites orbiting the Moon, the Sun, and several other planets, including Mercury, Venus, Mars, and Saturn.
The Soviet Union launched the first artificial satellite — Sputnik 1 — on October 4, 1957. The United States launched its first artificial satellite — Explorer 1 — about four months later. Since that time, over 2,500 satellites have been launched into space. Most artificial satellites orbit within 500 miles of Earth or what scientists call low-Earth orbit. These satellites have to travel very fast — about 17,000 miles per hour — to avoid being sucked back into Earth’s atmosphere.
Satellites don’t fall from the sky because they are orbiting Earth because of the force of gravity. Even when satellites are thousands of miles away, Earth’s gravity still tugs on them. Gravity–combined with the satellite’s momentum from its launch into space–cause the satellite go into orbit above Earth, instead of falling back down to the ground.
Sooner or later, though, the force of gravity will pull all objects, including artificial satellites, back to Earth. When satellites quit working, they become orbiting “space junk” until gravity pulls them back to Earth. Although at least one piece of space junk returns to Earth every day, it’s rare that anyone ever notices.
What in the world do they do up there? Why do we need so many of them? Artificial satellites are used for all sorts of purposes. Satellites like the Hubble Space Telescope, the International Space Station, and the Russian Mir space station help scientists explore space in new and exciting ways. Communications satellites help us communicate with people all over the world.
Weather satellites help us observe the Earth from space to help predict weather patterns. Radio and television satellites beam our favorite songs, movies, and television shows to Earth for us to enjoy. There’s even a group of 27 satellites that make up the Global Positioning System (GPS). Without these satellites, we couldn’t use GPS devices to find our way while traveling.