I’ve read that at the center of large celestial bodies there’s zero gravity (or close to). While confirmation would be nice, if true, I’m wondering how large that area can actually be and moreover, does it scale up with more mass and/or even size - that is, does the sun have a larger center area of low (zero?) gravity than the earth and so on with evermore mass. Or is that area the same regardless of mass’ size?

Thank you

  • FlowVoid@midwest.socialEnglish
    41·
    11 months ago

    Not quite. If by “edge” you mean the surface of the earth, then the force of gravity from the closer edge will always exactly offset the gravity from the farther edge. So if the earth were hollow, then you would experience zero gravity at any point in the hollow portion.

    Of course, the earth is not hollow. And any mass under you (i.e. closer to the center than you are) will not be offset, and all of it will pull you towards the center. As you move further away from the center, more of the earth’s mass will be closer to the center than you and therefore the force of gravity will increase.

    • jet@hackertalks.comEnglish
      31·
      11 months ago

      Excellent point, well made!

      So if the original poster wanted to have a 10km sphere in the center of the earth of zero gravity (earth gravity at least), then all they have to do is hollow out 10km and they are good to go?

    • awwwyissss@lemm.eeEnglish
      15·
      11 months ago

      Nah, there’s only one exact center of gravity for a given body of mass. You can’t just make a vacuum and have gravity equalizer throughout it.

      • FlowVoid@midwest.socialEnglish
        3·
        11 months ago

        Yes you can, as long as you are inside a perfectly spherical shell.

        The net gravitational force on a point mass inside a spherical shell of mass is identically zero! Physically, this is a very important result because any spherically symmetric mass distribution outside the position of the test mass m can be build up as a series of such shells. This proves that the force from any spherically symmetric mass distribution on a mass inside its radius is zero.

        From: http://hyperphysics.phy-astr.gsu.edu/hbase/Mechanics/sphshell2.html#wtls