• Question: How do we measure the gravitational pull of planets and objects

    Asked by anon-150745 to Maggie, Ry, Scott on 16 Nov 2017.
    • Photo: Ry Cutter

      Ry Cutter answered on 16 Nov 2017:

      We have to see how other things move around them.
      A great example is Jupiter and it’s moons. It was one of the first tests for gravity!
      By looking at the orbits of the moons we can find the gravitational pull of the planet.
      For black holes it can be a bit trickier. A really fun way is to use a star! If a black hole sucks up a star a disk is formed, the brightness of the disk is determined by how strong the gravity is!
      This means we can use the brightness of the disk to find the gravity of the black hole, which means we can find out how heavy the blackhole is!
      Great Question,
      Ryan

    • Photo: Maggie Lieu

      Maggie Lieu answered on 16 Nov 2017:

      To measure the gravitational pull of planets all you need to do is put the planet on a scale to see how much mass it has… oh wait there aren’t scales that big? Okay so the other way to do it is to measure the speed the planet is travelling around the sun and the distance it travels. If we also know the Sun’s mass then we can use some equations called Keplar’s laws to calculate the mass of the planet. The heavier the mass the more the gravity!

      For Earth’s gravity there is a very simple experiment you can do I. Let me show you:

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