Satellites are objects that orbit, or travel around, a larger body in space. While natural satellites like the Moon orbit Earth, artificial satellites are human-made machines launched into space for various purposes. These satellites help us with communication, weather forecasting, navigation, and scientific research. But how do they stay in orbit without falling back to Earth or flying off into space? The answer lies in a careful balance between two forces: gravity and inertia. Gravity pulls the satellite toward Earth, while inertia keeps it moving forward. When a satellite is launched at just the right speed and height, it falls around Earth instead of crashing into it.
To understand orbits, imagine throwing a ball horizontally. The ball will travel forward but eventually curve downward and hit the ground because of gravity. If you throw it faster, it travels farther before hitting the ground. Now imagine throwing it so fast that the curve of its fall matches the curve of Earth's surface. The ball would keep falling but never hit the ground—it would be in orbit. This is exactly what happens with satellites. They are launched with powerful rockets to reach speeds of about 28,000 kilometres per hour, known as orbital velocity.
At this speed, the satellite's forward motion balances Earth's gravitational pull, creating a stable orbit. Satellites orbit at different heights depending on their purpose. Low Earth orbit (LEO) is from about 200 to 2,000 kilometres above Earth. Satellites here, like the International Space Station, orbit quickly—about every 90 minutes. They are used for Earth observation, spying, and some communications. Medium Earth orbit (MEO) ranges from 2,000 to 35,786 kilometres. GPS satellites often orbit here, taking about 12 hours to circle Earth. Geostationary orbit (GEO) is at 35,786 kilometres.
They are launched with powerful rockets to reach speeds of about 28,000 kilometres per hour, known as orbital velocity.
Satellites here match Earth's rotation, so they appear fixed over one spot. This is ideal for weather satellites and TV broadcasts, as they can constantly monitor the same area. Keeping a satellite in orbit requires more than just the right speed. Over time, tiny amounts of atmospheric drag—even in the thin upper atmosphere—slow a satellite down, causing its orbit to decay. To stay in orbit, satellites must occasionally fire small thrusters to boost their speed. Also, the gravitational pull of the Moon and Sun can gradually alter a satellite's orbit.
Engineers plan for these changes by calculating fuel needed for adjustments. When a satellite runs out of fuel, it can no longer maintain its orbit and eventually falls back to Earth, burning up in the atmosphere or crashing into the ocean. Satellites are launched using multi-stage rockets. The rocket lifts off, burning fuel to overcome Earth's gravity. As it climbs, stages separate and fall away, making the rocket lighter. The final stage places the satellite into its intended orbit. Sometimes, satellites are released from the Space Shuttle or from the International Space Station.
Once in orbit, solar panels unfold to provide power, and antennas deploy to communicate with Earth. Ground stations track the satellite's position and send commands to ensure it functions correctly. The entire process requires precise calculations and timing. Satellites have become essential to modern life. They enable global communication, from phone calls to internet connections. They provide accurate weather forecasts by monitoring clouds, storms, and ocean temperatures. Navigation systems like GPS rely on a network of satellites to pinpoint locations anywhere on Earth. Scientists use satellites to study climate change, map forests, and observe natural disasters. Without satellites, many everyday activities—like using a smartphone map or watching live television from another continent—would be impossible. Understanding how satellites orbit Earth helps us appreciate the technology that keeps our world connected.