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Thread: A question about gravity

  1. #1 A question about gravity 
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    I'm not a physicist, so don't make fun of me if this question betrays my ignorance, but I was thinking about the cause of gravity. Now from what I understand, no one claims to know what causes gravity in any ultimate sense. Regardless, I was pondering on about the effects of putting a bowling ball on a trampoline. When you do that, it pushes the material of the trampoline down, and if you then put a marble on the trampoline, you can make it "orbit" the bowling ball for a while. I was wondering if objects in space might do a similar thing to the space around them, except in 3 dimensions.

    *edit

    Maybe gravity is space trying to close back in on itself after having been displaced by an object, like water around a submarine.


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  3. #2  
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    I was pondering on about the effects of putting a bowling ball on a trampoline. When you do that, it pushes the material of the trampoline down, and if you then put a marble on the trampoline, you can make it "orbit" the bowling ball for a while. I was wondering if objects in space might do a similar thing to the space around them, except in 3 dimensions.
    That is pretty close to how Einstein saw gravity, i.e. a geometric phenomenon of space-time. Well done. :wink:

    Maybe gravity is space trying to close back in on itself after having been displaced by an object, like water around a submarine.
    Wouldn't this work in both directions though (gravity is only attractive)?


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  4. #3 Re: A question about gravity 
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    Quote Originally Posted by delsydebothom
    I'm not a physicist, so don't make fun of me if this question betrays my ignorance, but I was thinking about the cause of gravity. Now from what I understand, no one claims to know what causes gravity in any ultimate sense. Regardless, I was pondering on about the effects of putting a bowling ball on a trampoline. When you do that, it pushes the material of the trampoline down, and if you then put a marble on the trampoline, you can make it "orbit" the bowling ball for a while. I was wondering if objects in space might do a similar thing to the space around them, except in 3 dimensions.

    *edit

    Maybe gravity is space trying to close back in on itself after having been displaced by an object, like water around a submarine.
    You have been watching too many "Disney movies" or reading too many popularizations of general relativity.

    The trampoline analogy is very misleading. Bodies DO NOT follow a geodesic in space, even curved space, they follow a geodesic in spacetime, and that is quite a different thing.

    One other problem with the trampoline analogy, if you think about it, is that it requires gravity in orde to produce its "explanation" of gravity.

    Unfortunately there is no simple explanation of the notion of curcature as used in general relativity nor a simple explanation of how the theory really works.
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  5. #4 Re: A question about gravity 
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    Quote Originally Posted by DrRocket
    You have been watching too many "Disney movies" or reading too many popularizations of general relativity.
    But you have to start somewhere (though maybe not with Disney movies. [As a Scot I could say 'that disney make any sense'.])

    Could you suggest some reading that might help delsydebottom get a better grasp of the principles?
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  6. #5  
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    im not a physicist myself, (though i am intending to become one)
    try to watch Leornard Susskind's lecture on Einstein's theory of general relativity. it explains about gravity and all its mathematical concepts of curvature of space-time. Though you wont get everything he talks about(you might, not sure), you will still get some idea on what gravity, and what actually causes these mysterious forces to act upon our 3 dimensional world.
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  7. #6  
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    Quote Originally Posted by Heinsbergrelatz
    im not a physicist myself, (though i am intending to become one)
    try to watch Leornard Susskind's lecture on Einstein's theory of general relativity. it explains about gravity and all its mathematical concepts of curvature of space-time. Though you wont get everything he talks about(you might, not sure), you will still get some idea on what gravity, and what actually causes these mysterious forces to act upon our 3 dimensional world.
    Susskind's GR lectures are pretty good.

    If one would rather read then Essential Relativity, Special, General and Cosmological by Rindler would also be good. The best GR book is probably Gravitation by Misner, Thorne and Wheeler, but it is also pretty hard core.
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  8. #7 Re: A question about gravity 
    Geo
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    Quote Originally Posted by delsydebothom
    no one claims to know what causes gravity in any ultimate sense. .
    Mass is what causes gravity.

    Matter has mass and takes up space.
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  9. #8 Re: A question about gravity 
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    Quote Originally Posted by Geo
    Quote Originally Posted by delsydebothom
    no one claims to know what causes gravity in any ultimate sense. .
    Mass is what causes gravity.

    Matter has mass and takes up space.
    This s not the content of the best available physical theories.
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  10. #9 Re: A question about gravity 
    Geo
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    Quote Originally Posted by DrRocket
    Quote Originally Posted by Geo
    Quote Originally Posted by delsydebothom
    no one claims to know what causes gravity in any ultimate sense. .
    Mass is what causes gravity.

    Matter has mass and takes up space.
    This s not the content of the best available physical theories.
    Your right, it underpins all physical science.
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  11. #10  
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    If one would rather read then Essential Relativity, Special, General and Cosmological by Rindler would also be good. The best GR book is probably Gravitation by Misner, Thorne and Wheeler, but it is also pretty hard core.
    i just cant get a hold of these books, here where i live... and ordering them is such a pain. :?
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  12. #11 Re: A question about gravity 
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    Quote Originally Posted by Geo
    [Your right, it underpins all physical science.
    I don't think you understood what I said.

    I'll put it more simply. Your statements are wrong.
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  13. #12 Re: A question about gravity 
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    Quote Originally Posted by DrRocket
    Quote Originally Posted by Geo
    [Your right, it underpins all physical science.
    I don't think you understood what I said.

    I'll put it more simply. Your statements are wrong.
    I don't think you understood what he said. He doesn't believe you. :wink:
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  14. #13 Re: A question about gravity 
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    Quote Originally Posted by Ophiolite
    Quote Originally Posted by DrRocket
    Quote Originally Posted by Geo
    [Your right, it underpins all physical science.
    I don't think you understood what I said.

    I'll put it more simply. Your statements are wrong.
    I don't think you understood what he said. He doesn't believe you. :wink:
    That is OK.

    Apparently he doesn't believe Einstein, Feynman, Weinberg, Schrodinger, Pauli, or Heisenberg either.
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  15. #14  
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    DrRocket you strike me as a bit of a flame merchant. I dont see what your exchange with Geo has got to do with anything except to flex your ego, which i think has enough mass to "cause" all gravity. 8)
    'Aint no thing like a chicken wing'
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  16. #15  
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    Harvestein,
    I think you need to get a grip on reality. .... Rapidly.

    Geo posted these comments:
    Mass is what causes gravity.
    Matter has mass and takes up space.


    Dr. Rocket, who actually has some knowledge in this area, gently corrected Geo with this post.
    This s not the content of the best available physical theories.

    Geo either totally misunderstood this correction (in which case he isn't very bright), or chose to completely disagree with it (in which case he isn't very bright), by posting this.
    Your right, it underpins all physical science.

    Dr. Rocket, maintaining a polite and objective demeanour then posts as follows:
    I don't think you understood what I said.

    I'll put it more simply. Your statements are wrong.


    This is not flaming. This is Dr. Rocket using his expertise in this area to try to educate another forum user.

    Flaming is what I am doing to you in this post. Do you see the difference?
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  17. #16 Re: A question about gravity 
    Geo
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    Quote Originally Posted by DrRocket
    Quote Originally Posted by Ophiolite
    Quote Originally Posted by DrRocket
    Quote Originally Posted by Geo
    [Your right, it underpins all physical science.
    I don't think you understood what I said.

    I'll put it more simply. Your statements are wrong.
    I don't think you understood what he said. He doesn't believe you. :wink:
    That is OK.

    Apparently he doesn't believe Einstein, Feynman, Weinberg, Schrodinger, Pauli, or Heisenberg either.
    How are these statements wrong?
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  18. #17 Re: A question about gravity 
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    Quote Originally Posted by Geo
    Quote Originally Posted by delsydebothom
    no one claims to know what causes gravity in any ultimate sense. .
    Mass is what causes gravity.

    Matter has mass and takes up space.
    You have it backwards...

    Space, even seemingly empty black space of nothingness holds a tiny amount of energy and mass nomatter how extremely small. Light passing through space gives it volume even though its so small it not even measurable right?

    So what happens when you have a QUADRIZILLION Trillions of trillions of trillions of it (as vast as space is)? The effect is then not so small anymore.

    If you put a man in 10 000 meters deep water he isnt crushed from the pressure because he attracts the ocean around him, the ocean of water is crushing him trying to get back to its space.

    You cannot prove in anyway that mass causes gravity. Gravity is most likely according to logic the pressure of space geometry moving within time in a limited space.

    I just posted a similar thread here without knowing this one existed, so guess ill be posting here instead since this discussion is allready on the move :wink:
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  19. #18 Re: A question about gravity 
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    Quote Originally Posted by Raziell
    Quote Originally Posted by Geo
    Quote Originally Posted by delsydebothom
    no one claims to know what causes gravity in any ultimate sense. .
    Mass is what causes gravity.

    Matter has mass and takes up space.
    You have it backwards...

    Space, even seemingly empty black space of nothingness holds a tiny amount of energy and mass nomatter how extremely small. Light passing through space gives it volume even though its so small it not even measurable right?

    So what happens when you have a QUADRIZILLION Trillions of trillions of trillions of it (as vast as space is)? The effect is then not so small anymore.

    If you put a man in 10 000 meters deep water he isnt crushed from the pressure because he attracts the ocean around him, the ocean of water is crushing him trying to get back to its space.

    You cannot prove in anyway that mass causes gravity. Gravity is most likely according to logic the pressure of space geometry moving within time in a limited space.

    I just posted a similar thread here without knowing this one existed, so guess ill be posting here instead since this discussion is allready on the move :wink:
    may I ask what your source is?

    space (debated if it is a vacuum or not) might be more difficult to define.......true void to my logic can only be infinite and equal at all points - quite a paradox!
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  20. #19 Re: A question about gravity 
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    Quote Originally Posted by fatman57
    may I ask what your source is?
    I think it may be this.
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  21. #20 Re: A question about gravity 
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    Quote Originally Posted by Ophiolite
    Quote Originally Posted by fatman57
    may I ask what your source is?
    I think it may be this.
    Knew i shouldve gotten one of these instead.
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