• Question: How does gravity even keep us on the ground?#

    Asked by agatha window to Angela, Claire, Ian, Robert, Sarah on 17 Nov 2014.
    • Photo: Angela Stokes

      Angela Stokes answered on 17 Nov 2014:

      Hi lily
      Gravity is a force of attraction. It’s like the Earth pulling on you and keeping you on the ground. That pull is gravity at work.

      Every object in the universe that has mass exerts a force, on every other mass – the size of the force depends on the mass of the objects. Really large masses, like the Earth and Moon have very large pulls and he gravitational force between the Earth and the molecules of gas in the atmosphere is strong enough to hold the atmosphere close to our surface.

    • Photo: Ian Cade

      Ian Cade answered on 17 Nov 2014:

      Gravity is just one of the forces of nature and it acts to cause an attraction between masses. The other forces are ‘electromagnetic’ (associated with light, electricity and magnetism), ‘weak’ and ‘strong’ (both associated with the nuclei of atoms and not something that people experience directly).

      The force of gravity is always (as far as we know) attractive, and diminishes the further the two masses are from each other (diminishing with the square of the distance: Gravitational force is proportional to 1/r^2)

      One of the odd things about gravity is it is extremely weak compared to the other forces (electromagnetism is 10^36 times (a lot!) more powerful than gravity). This might seem fairly strange, after all gravity ‘seems’ strong, it stops you floating away!…

      But on the other hand, you can use the electromagnetic force (the force that holds all your molecules together and stops you being a gas) to pick things up. Indeed if you are able to pick something up you are actually able to pull it up more strongly than the entire Earth is pulling it down.

Comments