What is a satellite?
When you hear the word satellite what normally comes to your mind? Is it the image below that comes to your mind?
If this is what comes to your mind then you are not entirely correct. The image above is a "satellite dish". This not a "satellite". A satellite dish is basically an antenna that send and/or receive signals from communications satellites.
So what is a satellite then?
A satellite is an object that orbits (goes around) a planet. There are two types of satellites. These are natural satellites and artificial satellites. There are several hundred natural satellites, in our Solar System. Thousands of artificial (human-made) satellites have also been launched since 1957.
A natural satellite is any celestial body in space that orbits around a larger body. Moons are called natural satellites because they orbit planets. The animation above shows the moon (natural satellite) orbiting the Earth.
Planets, asteroids and comets orbit around stars such as our Sun and so can also be thought of as natural satellites. Our Solar System has eight official planets as well as millions of minor planets, asteroids, comets and other objects orbiting around the Sun. All of these can be thought of as natural satellites.
Would consider the Earth to be a satellite? Why?
In this lesson, we will focus mostly on artificial (made-man) satellites. An artificial satellite is an object that people have made and launched into orbit using rockets.
The world's first artificial satellite, the Sputnik 1, was launched by the Soviet Union on October 4, 1957. This surprised the world, and the United States quickly worked to launch their own satellite, starting the space race. Sputnik 2 was launched on November 3, 1957 and carried the first living passenger into orbit, a dog named Laika. The United States launched their first satellite, called Explorer 1 on January 31, 1958. The UK launched its first satellite in 1962.
Sputnik was very simple satellite --a small aluminium ball, about the size of a beach ball, with four long antennas, and was powered by batteries.
Picture of Sputnik
Why are satellites able to orbit the Earth?
Most satellites are launched into space on rockets.
Satellites are able to orbit around the planet because they are locked into speeds that are fast enough to defeat the downward pull of gravity. Satellites are sent into space by a rocket launched from the ground with enough energy (at least 25,039 mph!) to get outside our atmosphere
Why don't fall
Satellites don't fall from the sky because they are orbiting Earth. 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.
A satellite orbits Earth when its speed is balanced by the pull of Earth's gravity. Without this balance, the satellite would fly in a straight line off into space or fall back to Earth.
Uses of Satellites of artificial satellites Watch the video to learn about the uses of artificial satellites.
Satellites have many different uses. These including taking pictures of the Sun, Earth, and other planets, and looking deep into space at black holes, and distant stars and galaxies. There are also communications satellites, weather satellites, and the International Space Station.
How communication satellites work
Video lesson on satellites in space
Click here to take a quiz on this topic.
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