1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Confusion over gravity and tides

  1. Dec 9, 2008 #1
    I am having trouble rationalising the fact that the moons gravity is a fraction of the earths and is far out in space, but still manages to out pull the earths gravity albeit a tiny amount and create tides?
  2. jcsd
  3. Dec 9, 2008 #2


    User Avatar
    Science Advisor
    Homework Helper

  4. Dec 9, 2008 #3


    User Avatar
    Science Advisor

    One thing that might help is to recall that the tides are caused only by the difference between forces. It's true that the Earth's gravitational field has much more pull on the seas than the Moon's. But, the Earth's pull on the sea is pretty much the same all over. So, the oceans all over the Earth "feel" the Earth's gravitational pull about equally; like a perfectly ballanced system. The tiny influence of the Moon is then enough to upset that ballance.
  5. Dec 9, 2008 #4
    Thanks guys, is the assumption that gravity travels in waves and if so is there evidence of reinforcement or canellation. Hence my original question should the opposing gravity waves result in the Moons being totaly cancelled out before reaching Earth.
  6. Dec 9, 2008 #5


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    The force of gravity is not carried by waves. There are gravity waves, but they have the same relationship to the pull of gravity as light has to the pull of a magnet.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook