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Thread: Einstein's general theory of relativity

  1. #21
    Join Date
    Aug 2001
    Just something I thought... If gravity moves instantly, why does gravity "fade out" the further away it get's. I mean Jupiter pulls on us, if I jump Jupiter pulls me up or down or whatever, but because it's so far away and our own earth so close, we will not feel it, if it's even there. If it traveled instantly it has to have resistance in some way.

    Also if you pull a rope two ways, and you release one end it won't instantly move sideways. The rope has a mass wich has to gain some speed first wich needs a force (you) and energy. It takes time for the rope to actually start moving.

    Another thing, Einstein and a lot of other people based these theories on their experience, thoughts and test. They're still theories though. Something is true if it's not not true and you never know that for sure. It also could just be a big mess of nonsence. Who made the idea of a forth, fifth etc. dimension. Who says that even exists. Do we have prove that we live in a three dimensional world anyway. If time is a forth dimension something and we experience it in this dimension, then mass has to be in higher dimensions to. If you think about it a bit it's almost stupid to call length or hight a dimension. Of course there have been many test and experiments. Somehow people got some effect in the 9th dimension or something.
    Maybe it's just a weird idea of humans. Also if you make a list of dimensions like this :
    dimension 1
    dimension 2
    dimension 3
    what would be here:
    dimension 1,1 dimension 1,2 dimension 1,3
    dimension 2,1
    dimension 3,1
    or even in a "third" dimension etc. etc.

    Just some thoughts of me... hope it made some sence

    Double Dutch

  2. #22
    Join Date
    Oct 2002
    Hrm everyohne is saying the results of gravity are instantaneous...but is that with the light we already have here. or do we have to wait for the light to come from the object that causes the gravitational pull to see the affects?

  3. #23
    "Put your hand on a hot stove for a minute, and it seems like an hour. Sit with a pretty girl for an hour, and it seems like a minute. That's relativity."

    -Albert Einstein-

    It's not all that relavent to this discussion, but I thought I'd share it anyways. Such a splended little quote.

    Take care,


  4. #24
    "Put your hand on a hot stove for a minute, and it seems like an hour. Sit with a pretty girl for an hour, and it seems like a minute. That's relativity."

    -Albert Einstein-

    It's not all that relavent to this discussion, but I thought I'd share it anyways. Such a splended little quote.

    Take care,


  5. #25
    Junior Member
    Join Date
    Jul 2002
    The Gravitational force is the weakest of the four fundamental forces, but the one with the longest range. Scientiest theorize that each of our thoughts, with electrical impulses and chemical reactions, cause a small gravitational shift that has a ripple effect on the universe. Of course this effect in impossible small, but if we could build a device capable of detecting these tiny changes, perhaps a mind-reading machine could be built... weird stuff.
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  6. #26
    Senior Member
    Join Date
    Sep 2001
    Alright. A few words on Gravity.

    First, to address a few questions in Neel's post.

    Gravity does not 'fade out', per se.

    Gravity is the force of attraction between two masses. It is proportional to the mass of each of the bodies, and to the distance between them. It's expressed by the following formula: F == ((G*m*n) / r^2 )

    Where F is the force, G is the Gravitational Constant, m and n are the associated masses, and r is the distance between them.

    G == 6.67259*10^-11 N*m^2/kg^2, assuming the Kilogram-Meter-Second system of measurements.

    The reason for the lessening effects of gravity over a distance can be visualized if you think of gravity as operating as lines of force. The closer to the body that the lines are, the denser they are. As they travel outward, they spread apart, and anything that they act upon will be acted on by fewer of the lines, as it were, than a closer body.

    With the tug on the rope--you're confusing gravity and inertia. In order for the metaphor to hold, you have to use an imaginary sort of rope--one with no mass, and no tendency to stretch. A better example might be a metal rod that you're only allowed to pull. The free end of the rod will move instantly with any force on the other end, as the two ends are connected ridgidly. Being massless, there's no inertia to worry about.

    Now, I'm fairly sure that the concept of the speed of propogation of the gravitational force is pretty much meaningless. After all, according to the law of conservation of matter and energy, the total amount in the universe must remain constant. Believe it or not, energy also affects gravity. If you were to turn a pound of bananas into energy, a pure conversion, and contain this energy, it would still have the same 'mass' as the bananas did.

    Thus, in order to measure such a propogation, would one not have to create some sort of mass, and then measure it's effects on the rest of the universe? It's not terribly likely that that's going to happen, assuming that the laws of physics stay constant.

    What they could be measuring, instead, is the propogation of gravity waves. These are fluctuations in the gravitational field, brought on by moving masses. Think of it like a couple of ducks swimming in a pond. The wakes that they leave will collide, and cause all manner of interesting patterns.
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  7. #27
    Senior Member
    Join Date
    Aug 2001
    For those who are interested, the results are in.

    Einstein was correct - gravity does travel at the same speed as light.
    It is definitely not an instantaneous force, so his General theory of relativity still holds good.

    There are reports in the scientific newsletters, but a brief summary can be found at http://newsvote.bbc.co.uk/1/hi/sci/tech/2639043.stm ,which also has the links to the other journals.

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