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Why there are gravitation at all

  1. Oct 6, 2007 #1
    Hi I like to know,
    Why there are gravitation at all which make every matter in our daily life can attract each other? such as earth with moon, sun with earth, earth with human, and so on. I've searched in many source even e-source(internet source), many physic books, professor in universities. but its cannot explain to me so clearly, many source just told me “Gravitation is a natural Phenomenon by which all objects with mass attract each other “ . So many theories still cannot make me to understand this thing. The point is there are'nt any further explanation about Gravitation.

    Many Thanks to your explanations
  2. jcsd
  3. Oct 6, 2007 #2


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    The ultimate answer in physics happens to be: "That's just the way it is, dear".

    Whether "gravitation" is derivable from more basic properties, or must be regarded as an unavoidable existing premise that cannot be deduced from anything else is still a matter of research.
  4. Oct 6, 2007 #3


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    As Arildno says, it is a property of matter that we simply do not understand yet.
  5. Oct 6, 2007 #4


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    Even if gravity is made up of more basic elements you can always ask "why are they like that". The answer to all these questions is that physics trys to find the laws that determine the forces of nature behave - not why there're forces to begin with.
  6. Oct 6, 2007 #5
    It was explained to me like this once. I don't know if it is correct, but certainly food for thought. This is mostly in relation to the "ether".

    All mass displaces spacetime. If all things exist within spacetime, think of spacetime as a giant bucket of "anti-water".

    If we drop a sponge into water, it will displace a certain amount of it around the sponge. Then if the sponge were uniform, a certain amount of water density would exist inside the sponge.

    If it were a steel ball, it would fully displace all water in the volume it occupies. The difference between water and spacetime is that spacetime compresses, and instead of diplacing outward like water, it displaces inward. This creates a curvature which results in a sort of vacuum. So in the regard of compression, it's more like air, but opposite.

    The steel ball would be a black hole in relation to spacetime, and the sponge would be a massive object. It is just a simple law of general relativity that spacetime compresses and curves around a massive object, and all massive objects are drawn to more concentrated areas of spacetime.

    It actually seems to be the opposite of what occurs naturally in chaos and entropy, in which all things tend toward disorder and tend to spread out. With gravitation, all things tend to attract each other, and that is the very basic reason why we are having difficulty unifying gravitation into "the theory of everything".

    It has it's own unique nature. It involves no charges, and no real "source" that we can measure. It is only mass displacement and a resultant curve in the ether. For this reason, I personally feel that it doesn't qualify as a "force" at all, but simply a passive "slope" in spacetime, much like falling down down a hill with nothing propelling you.
    Last edited: Oct 6, 2007
  7. Oct 6, 2007 #6


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    Without going into the detail of you water analogy, you say the following towards the middle:
    "It is just a simple law of general relativity that spacetime compresses and curves around a massive object, and all massive objects are drawn to more concentrated areas of spacetime."
    What's the fundamental difference between saying this and saying:
    "It is just a simple law of nature that massive objects are attracted"?
    But anyway, this thread seems more directed towards philosophy than physics.
  8. Oct 6, 2007 #7


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    I agreed.

    for example if you believe in the so-called scientific theory called "intelligent design", you will find that this is the kind of issue they are trying to "explain".

    the study of physics, put it simply, is a study of symmetry or pattern. when you see like charges repel time and time again, you tend to think that there may be some fundamental laws behind that phenomenon. you may continue to pursuit that idea down to the Quantum Field Theory level and find that the effective action (a technical term) pick up a -ve or +ve sign depending on whether the force is attractive or repulsive. But then you can ask something more fundamental such as what make an object +ve or -ve charge? Or why the Quantum field theory picture should be regarded as the final picture when it has problem dealing with the non-renomalisable (technical term) interaction such as gravity?

    so the moral of the story is "we don't truly understand these stuffs yet" perhaps in 50 yrs time, we will know a bit more, and so on... ultimately though you can't explain everything.

    "what I'm really intersted in is whether God could have made the world in a different way; that is, whether the necessity of logical simplicity leaves any freedom at all.
    -- Albert Einstein
  9. Oct 6, 2007 #8
    Perhaps the question is: "What if there were no gravitation at all"?

    Otherwise, to keep everything from flying away?
  10. Jan 4, 2010 #9
    Quite confusing, to comply with so many rules in life. When i am old, one day i woke up i may forget, how much energy to use to step down the stairs, or how much energy to walk my body up a slope. If i fly between moon and earth to work, via a spacecraft, it's worse, the gravity is different and my mind cannot cope with the physics pattern, mass 1kg = 10 x 1 newton, or mass = ? x 1 newton ??
  11. Jan 5, 2010 #10
    Of all the four forces, gravity is the one that we know the least about, and the one that gives us the most trouble.
  12. Jan 5, 2010 #11
    if you blame gravity on the compression that the vacuum of space emits, you might as well change the original question to "why does space compress matter?"
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