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B How do you know the size/maximum area of a gravity field

  1. Mar 20, 2017 #1
    The title said it, how do you know the size or maximum area of a planet's gravity field can cover. The reason i asked this question because from the gravity equation the r is the radius from Mplanet and Mobject. So, that doesn't explain how big is the gravity field. Is it when the gravity force become 0?
     
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  3. Mar 20, 2017 #2

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    There is no maximum. The gravitational effects go forever. They may become negligible, since it decreases proportional to 1/r2, but it never completely disappears. As object A gets farther from one other object B and closer to a third object, C, the gravitational effect of C may become greater than that of B, but the effect of B is still there.
     
  4. Mar 20, 2017 #3
    Thanks for the answer, i still have one more question that i forgot to ask, why does gravitational force weakens as it get farther from a planet. I'm really confused. I also don't understand why when you get near fire it's hot and when you get away from it, you don't get any heat. thanks for answering!
     
  5. Mar 20, 2017 #4

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    For heat from a fire, the energy of a source gets spread out, so less of it hits another object of a fixed size as it gets farther away.
    For gravity, the true answer is beyond my expertise on the subject. A mass distorts space-time in a certain way that is the subject of General Relativity.
     
  6. Mar 20, 2017 #5
    Okay, that really helped me to where i should find my answer, thanks for answering :)
     
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