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Thread: effects of moons gravity on the oceans

  1. #1 effects of moons gravity on the oceans 
    jlr
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    Hi new member here

    not sure it this should be in physics but here goes...

    If an object the size of the moon started moving slowly past the earth what affect would this have gravitationally on the oceans? would it be strong enough to suck the water into space or would it cause a bulge. also would satellites be drawn toward it?

    Many many thanks in advance.


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  3. #2 Re: effects of moons gravity on the oceans 
    Forum Professor sunshinewarrior's Avatar
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    Quote Originally Posted by jlr
    Hi new member here

    not sure it this should be in physics but here goes...

    If an object the size of the moon started moving slowly past the earth what affect would this have gravitationally on the oceans? would it be strong enough to suck the water into space or would it cause a bulge. also would satellites be drawn toward it?

    Many many thanks in advance.
    From how far away?

    The moon is currently about 320,000 kilometres away from the earth, and swings past it slowly and, guess what: it causes bulges in the oceans but doesn't suck the water into space!


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  4. #3  
    jlr
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    Thanks for the really quick reply. yep with tides but i'm thinking real close. kinda like a very near miss. would that increase the bulge or would it be powerful enough to do more?
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  5. #4  
    Administrator KALSTER's Avatar
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    Forget about the water, think about major earthquakes and volcanic eruptions!
    Disclaimer: I do not declare myself to be an expert on ANY subject. If I state something as fact that is obviously wrong, please don't hesitate to correct me. I welcome such corrections in an attempt to be as truthful and accurate as possible.

    "Gullibility kills" - Carl Sagan
    "All people know the same truth. Our lives consist of how we chose to distort it." - Harry Block
    "It is the mark of an educated mind to be able to entertain a thought without accepting it." - Aristotle
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  6. #5  
    jlr
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    thats really cool. would it be able to distort the entire surface? water is really interesting me still tho would it be powerful enough to suck the water and atmosphere away?
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  7. #6  
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    If some passing body could 'suck' up the ocean(s) it would also suck up the whole planet as the gravitational pull on both would be the same.
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  8. #7  
    Forum Professor sunshinewarrior's Avatar
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    Quote Originally Posted by jlr
    thats really cool. would it be able to distort the entire surface? water is really interesting me still tho would it be powerful enough to suck the water and atmosphere away?
    Nah. You need to start thinking about gravity and how it works in order to analyse even science fiction/fantasy secnarios.

    Which body has the greater gravity?
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  9. #8  
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    Don't worry about any object disrupting the Earth. the Moon does have a graviational force on the Earth but it is minimal. Think of oceans as an onion thin layer on a basketball. The oceans are about 1/2000th he mass of the Earth and the Moon has little impact on even a fraction of that 1/2000th via a hard-to-measure tug on the Earth. It would take a very large body much bigger than the Moon and much closer to the Earth to have much effect other than a bit of surface activity.
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  10. #9  
    Time Lord
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    The major problem with a near miss is the amount of time available vs. the amount of time needed for the water to make it into space.

    It would certainly cause world wide tsunamis, and as Kalster pointed out, the plates that make up the continents would shift causing volcanic eruptions and earth quakes world wide.

    As for water going into space, you have to remember the size of the Earth vs. the speed the water would be moving at. It could take hours for any of it to actually get into space, and how fast would this moon-sized object be moving past us? Also, most of it would evaporate when it hit the upper atmosphere due to the lower pressure, so in order to lose a lot of our water, we'd probably have to lose a lot of our atmosphere too.
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  11. #10  
    jlr
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    awesome stuff guys thank you all
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