People usually think of satellites floating through space while the actual situation reveals that satellites continuously move toward Earth. Satellites stay in orbit because gravity creates an equilibrium with their velocity.
How Satellites Stay in Orbit
The two fundamental forces which maintain satellites in space can be explained as follows:
- Gravity Pulls Satellites Toward Earth
The gravitational force of Earth pulls every object towards its centre just like apples fall from trees and satellites also experience this attraction. Forward motion operates on satellites while they orbit because they do not fall in a straight vertical path like apples.
- High Speed Prevents Falling to the Ground
Satellites maintain their position in space through their high orbital speed which reaches 28,000 km/h (17,500 mph) at low Earth orbit altitudes. The Earth’s surface moves away from the descending satellite because of its high speed. A satellite remains in perpetual descent while escaping ground contact because of this gravitational effect.
The perfect state of balance which satellites maintain is known as orbital motion and Isaac Newton originally explained it through his cannonball thought experiment.
Newton’s Cannonball Thought Experiment
According to Isaac Newton’s imagination a cannon situated on top of a mountain would fire horizontally to observe the following motion:
The cannonball would strike the ground if the firing velocity was insufficient.
The object would descend towards Earth at the precise velocity where Earth’s surface would move away at an equal rate preventing it from hitting the ground.
The cannonball would completely break free from Earth’s gravitational pull if launched at an excessive speed.
Satellites work the same way! The satellites achieve their orbit by receiving the precise launch velocity which allows them to circle Earth without hitting the surface.
The scientific explanation behind why satellites stay aloft despite gravitational attraction is explained in this text.
People usually think of satellites drifting through space while the actual situation reveals that satellites continuously move toward Earth. The satellites stay in orbit because gravity creates an equilibrium with their velocity.
Types of Orbits and Speeds
Satellites orbit at different distances from Earth, each requiring a specific speed:
- Low Earth Orbit (LEO) (~300–2,000 km) -> 28,000 km/h (17,500 mph) -> Used for the ISS, Earth observation satellites.
- Medium Earth Orbit (MEO) (~2,000–35,000 km) -> 12,000 km/h (7,500 mph) -> Used for GPS satellites.
- Geostationary Orbit (GEO) (~35,786 km) -> 11,000 km/h (6,800 mph) -> Used for communication and weather satellites.
- Escape Velocity (~40,270 km/h) -> The speed needed to leave Earth’s gravity completely.
Why Don’t Satellites Stay in Orbit Forever?
Even though satellites seem stable, they eventually fall back to Earth due to:
- Atmospheric Drag: In low Earth orbit, tiny air particles slow down satellites over time. If they lose enough speed, they descend and burn up in the atmosphere.
- Gravitational Perturbations: The Moon, Sun, and other planets exert slight gravitational forces that can alter satellite orbits.
- Aging and Malfunctions: Over time, satellites lose energy and control, leading to orbital decay.
To keep satellites in orbit longer, engineers use small thrusters to adjust their position and speed when necessary.
Conclusion
Satellites don’t float in space, they fall continuously while moving fast enough to never hit the ground! This delicate balance of gravity and motion is the key to how everything from GPS systems to the International Space Station stays in orbit.
Next time you see a satellite passing overhead, remember: t’s not just flying; it’s falling… and missing Earth every second!