• Question: does the strength of gravity vary

    Asked by shep97 to Antonia, Douglas, Hugh, Matt, Tom on 20 Jun 2010 in Categories: .
    • Photo: Matthew Hurley

      Matthew Hurley answered on 15 Jun 2010:

      It does on different planets, but I think its constant on earth – (or at least averaged) to be 9.81m/s.

    • Photo: Hugh Roderick

      Hugh Roderick answered on 15 Jun 2010:

      I don’t think the absolute strength of gravity changes just the size of the object that is causing gravity – but it’s a little outside of my area!

    • Photo: Tom Hardy

      Tom Hardy answered on 15 Jun 2010:

      Yes. The Earth’s gravity field strength varies depending on geographical location. What we kow as standard gravity is measured at the surface of the Earth. Think about astronauts, they go so far away from Earth that they are not affected by the gravitational pull of the Earth so that is why they flot in space shuttles.

    • Photo: Douglas Blane

      Douglas Blane answered on 20 Jun 2010:

      Yes, gravity varies very slightly all over the Earth. That means your weight is different, depending on where you are.

      The higher you go the smaller the force of gravity. So at the top of Mount Everest a 70 kilogram man (me for instance) would weigh 69.8 kg

      Not a big difference but easily measured.

      If you go higher still the force of gravity gets less and less. It never actually disappears – Earth’s gravity even has a small effect on Pluto. But it gets very, very small

      Astronauts in orbit around the Earth seem to have no weight. But that’s not because they’re too high for gravity. (My 70 kg would be down to 63 kg at the height of the International Space Station.)

      The astronauts seem weightless because they’re in free-fall, just like a skydiver. Only difference is the ISS is flying so fast parallel to the Earth’s surface that it never actually hits it.

      It’s falling towards the Earth all right. But it just keeps missing it.

      Another thing that produces a slightly different gravity force around the world is how dense the rocks are under the surface. So in Helsinki the force of gravity is 0.4% more than it is in Mexico City.

      So I could gain 0.2kg by flying from Mexico to Finland, without eating a thing.

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