• Question: Why does gravity only pull?

    Asked by 232grak26 to Daniel, Hannah, Maggie, Ry, Scott on 14 Nov 2017.
    • Photo: Maggie Lieu

      Maggie Lieu answered on 14 Nov 2017:

      Gravity is the force between any 2 masses, and the object with the most mass will pull the other mass towards it. It can push but only if you have negative mass

    • Photo: Ry Cutter

      Ry Cutter answered on 14 Nov 2017:

      Exactly what Maggie said, we often use magnets as a comparison. With + (North) magnets being positive mass and – (South) magnets being negative mass. It’s very strange how similar magnets and gravity are.
      The only problem is that we don’t know if we can even make negative mass… some people think that is what dark energy is!
      Brilliant Question,
      Ryan

    • Photo: Scott Melville

      Scott Melville answered on 14 Nov 2017:

      As usual, Maggie and Ryan have given wonderful clear answers (much faster than me 😉 ).
      But I’ll add that negative mass has all kinds of weird properties – if we ever found some, we could use it to build time machines and wormholes and travel faster than light 😛 So a lot of people think that it doesn’t exist.
      Dark energy is a funny one, it’s like a fluid with negative pressure, so it ‘pushes’ out the Universe and makes it expand faster and faster – it’s not quite the same as having negative mass though.

    • Photo: Hannah Middleton

      Hannah Middleton answered on 17 Nov 2017:

      We don’t really know why! It’s always hard in physics to work out why something is as it is. The main thing we can do is make experiments or observations to try and understand how something works and match up those observations with our theories. So far we haven’t seen any evidence for a gravitational push!

Comments