• Question: How do you make satellites orbit earth? Is it the earths magnetic field that does all the work?

    Asked by Anakin to Eimear, James, Jonathan, Lána, Willi on 28 Feb 2018.
    • Photo: Lána Salmon

      Lána Salmon answered on 28 Feb 2018:

      Great question. Satellites, and other bodies, orbit earth due to earth’s gravitational field. Heavy bodies in the universe have a gravitational field which pulls smaller objects towards them. The larger the body, the larger the force. And the smaller the distance, the larger the force. So satellites are pretty small, but they’re also pretty close to earth, so they orbit around earth as the mass of earth pulls them around it.

      Earth’s magnetic field has a few cool applications for satellites. Willi can tell you more about this, but in short, we can move satellites if we put magnetic coils on them. The magnet in the satellite acts with (or against) the magnetic field of earth. It’s like a bar magnet repelling or attracting. This means you can control the way the satellite moves.

    • Photo: William O'Connor

      William O'Connor answered on 28 Feb 2018:

      Lana has given you a very good answer to a good question.
      Have you ever got a small bucket of water (like you might have on the beach) and swung it around and around with your arm, in a vertical circle, going above your head and around again?
      You can do it without spilling the water. The water stays inside even when the bucket is upside down over your head.
      It’s like a weight on a string: again you can spin it over your head and the string stays stretched even when it is upside down.
      That is because circular motion causes things to fly away from the centre, to feel a force pulling away. That’s why the water stays in the bucket, and the string stays tight.
      That “force” is called the “centrifugal force”, which is a big word for “flying away from the centre”.
      Well satellites are like that. They are going around the world so fast that there is a force causing them to try to fly away. But they are held back by the Earth’s gravity. When these two forces are equal and opposite they cancel, and the satellite stays in orbit, going round and round the Earth.

      The magnetic field is another story.