• Question: Why is the gravity In earth different to the gravity in space

    Asked by shanley to Angela, Gabriele, Karen, Maria, Shane on 11 Nov 2013.
    • Photo: Karen McCarthy

      Karen McCarthy answered on 11 Nov 2013:

      Gravity seems different in space vs Earth, because of the Earth. On Earth, when you throw or drop something, Earth’s gravity will pull the object down to the floor, which is steady. But in space, because a spaceshuttle or astronaut is working around Earth’s gravity or orbit, it is in a constant state of falling, so if you throw/drop an object, it it floats because the floor is also falling too.

      This video from NASA explains alot better (although it is pretty old!)


    • Photo: Shane Mc Guinness

      Shane Mc Guinness answered on 11 Nov 2013:

      Good answer Karen. But what is also cool about gravity is that everything has it! If a thing has any weight at all, it has a gravitational field! Pretty cool eh!? Even your pencil has gravity and it is pulling the earth closer to it by just a tiny amount. If it were floating in space though, it would very slowly float toward something else close to it. So the strength of gravity depends on how heavy a thing is and how close it is to another thing! So when you’re standing on the earth’s surface the earth gravity is quite strong because you’re very close to the centre of that big huge heavy thing we call earth. If you’re far away from it though, like in space, it’s much weaker. And the even cooler thing is that it doesn’t matter how big something is, but how heavy it is! Take black holes, which aren’t really that big but because they were formed by an INCREDIBLY heavy star, their gravity is so strong it even sucks in light itself!

    • Photo: Gabriele De Chiara

      Gabriele De Chiara answered on 11 Nov 2013:

      in principle there is no difference between gravity in space and on the earth. On the earth, each body is attracted to the centre of the earth by a force mg where m is the mass of the body and g=9.8m/s^2 is the local gravity acceleration. g depends on the inverse of the distance from the centre of the earth. So in space the local constant g will be reduced by the total distance. But for example if you consider the international space station, this is at about 370 km from the earth and the local g would be only 10% smaller.However this is different than asking for the feeling of weight: on the ground we fill the resistance of the floor to our weight. In space, astronauts are constantly falling because they are freely orbiting around the earth. So there is no force opposing their weights and therefore they float as if their weight were zero.

    • Photo: Angela Stevenson

      Angela Stevenson answered on 12 Nov 2013:

      Ahhh another great question 🙂 And you guys have already done a great job at answering this question! Soooo here’s a fun fact about gravity instead, Mars is smaller and has less mass than Earth, so from what you ve learned already you know that it has less gravity, which means that if you weigh 100 pounds on Earth, then you ll weigh 38 pounds on Mars! That’s cool hey. And since I m a marine biologist I ll sneak in a cool fact about gravity and the ocean 😉 did you know that the ocean’s tides are caused by the gravity of the moon? Hope we answered your question. Thanks for asking 🙂