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B Is Gravity a weak force?

  1. Jun 27, 2016 #1
    If gravity is a weak force , then
    How it holds planets , stars and galaxies together ?
    let me know if i am right..?
    Gravity only attracts there is no negative version of the force to push things apart and while gravity is powerful enough to hold galaxies together, it is so weak that you overcome it every day when pick up ball you are counteracting the force of gravity from all of earth.
  2. jcsd
  3. Jun 27, 2016 #2
    Answering the title: Yes.

    It's weak in the context of the four fundamental forces: gravity, electromagnetism, "strong nuclear, weak nuclear", the last two of which are just forces which keep atoms together.

    The key to understanding: Playing with magnets, you can easily see how electromagnetism can be stronger than gravity, while being 10000x smaller than the Earth. And of course, the nuclear forces are minuscule and of course resist gravity.

    (Look up videos of MRI machines or neodymium magnets, then imagine how strong a magnet the size of the Earth would be)
  4. Jun 28, 2016 #3
    means only gravity is responsible for the holding of stars planets together ?
  5. Jun 28, 2016 #4


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    Staff: Mentor

    The sum of many weak forces = a strong resultant force!
  6. Jun 28, 2016 #5
    They have a lot of mass so the force is large enough to hold them together.
  7. Jun 29, 2016 #6
    Thank you now its clear to me :smile:
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