What is a satellite?
Right now, thousands of machines are racing around our planet, faster than any jet, helping you find directions, check the weather, watch videos, and talk to people far away. They are called satellites. Here is how they work and why they matter.
The big idea
A satellite is any object that orbits, or travels in a path around, a bigger object in space. The Moon is a natural satellite of Earth. But when most people say "satellite," they mean an artificial satellite, a machine that people built and launched into space on a rocket.
Here is the part that surprises a lot of people: a satellite is actually falling toward Earth all the time. So why does it not crash? Because it is also moving sideways incredibly fast, about 17,000 miles per hour in low orbit. By the time gravity pulls it down a little, the satellite has zipped so far sideways that the ground has curved away beneath it. It keeps "falling around" the planet instead of into it. That is what an orbit really is.
Try this thought experiment
Imagine throwing a ball. Throw it harder, and it lands farther away. Now imagine throwing it so hard that the Earth curves away as fast as the ball drops. The ball would never land, it would circle the whole planet. That is exactly the trick a rocket uses to put a satellite into orbit.
A short history
The space age is younger than you might think. It started less than 70 years ago, and your grandparents were alive for the very first satellite.
Sputnik 1, launched by the Soviet Union, becomes the first artificial satellite. It was a metal ball about the size of a beach ball that beeped radio signals as it circled the Earth. People around the world looked up to watch it.
The United States launches Explorer 1, which discovers belts of radiation around the Earth. The space race is on.
Telstar relays the first live television pictures across the Atlantic Ocean, showing that satellites could connect the whole world.
The first GPS satellites go up. Decades later, this is the system in your phone that knows exactly where you are standing.
The Hubble Space Telescope is launched. Floating above the blurry atmosphere, it sends back the clearest pictures of distant galaxies humans had ever seen.
Construction begins on the International Space Station, a giant satellite where astronauts live and do science. You can spot it from your backyard.
Thousands of small satellites, like the Starlink internet fleet, now orbit together in huge groups called constellations. There are more satellites in space now than ever before.
What do satellites do?
Satellites are not all the same. Different ones have very different jobs. Here are the main ones you use, probably without even noticing.
Communication
They bounce TV, phone calls, and internet signals between faraway places, even ships in the middle of the ocean.
Navigation
GPS satellites send out time signals. Your phone listens to several at once to figure out exactly where you are.
Weather
Weather satellites photograph storms and clouds from above, which is how forecasters know a hurricane is coming.
Earth observation
They watch forests, ice, farms, and oceans over time, helping scientists understand how our planet is changing.
Science
Space telescopes look outward at stars and galaxies without the atmosphere getting in the way.
Exploration
The Space Station and crew vehicles are satellites too, carrying people to live and work in orbit.
Where do satellites orbit?
Satellites do not all fly at the same height. The distance from Earth changes how fast they move and what they are good for. These are the three main neighborhoods.
Low Earth Orbit
About 100 to 1,200 miles up. The closest and fastest, circling Earth in about 90 minutes. Home to the Space Station and Starlink.
Medium Earth Orbit
Around 12,000 miles up. This is where GPS and other navigation satellites live, taking several hours per lap.
Geostationary Orbit
About 22,000 miles up. At this exact height a satellite circles in 24 hours, so it appears to hover over one spot. Great for TV and weather.
See it for yourself. Open the live visualizer to watch real satellites orbiting Earth right now. Try the GPS group to spot the medium orbit, or speed up time to watch the Space Station race around the planet.
Open the live visualizer