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Author | Topic: What Creates Gravity? | |||||||||||||||||||||||||||||||||||||||
Dr Adequate Member (Idle past 306 days) Posts: 16113 Joined: |
Well, when you drop something, the force of gravity accelerates it downwards: this has the effect of turning its potential energy into knetic energy (which is dispersed as heat (also energy) and sound (more energy) when the object hits the ground).
The gravitational force doesn't make energy: energy is conserved. The action of gravity turns one sort of energy into another. I hope this answers your question: I wasn't quite sure what you were asking.
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zcoder Member (Idle past 6230 days) Posts: 66 Joined: |
yeah, I think that explains it.
anyways I was reading a article about dark matter expelling energy though out the universe and is lost. something like that, anyway I took it that space is someday going to cool down and then, well no one knows what will happen then. But the article was not very clear as to how the energy in the universe wasbeing spent. Zcoder....
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fallacycop Member (Idle past 5542 days) Posts: 692 From: Fortaleza-CE Brazil Joined: |
Umm, I am confused.
Most sensible thing you've said so far
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zcoder Member (Idle past 6230 days) Posts: 66 Joined: |
is it a felony to be confused?
Umm double confused Zcoder....
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CosmicChimp Member Posts: 311 From: Muenchen Bayern Deutschland Joined: |
You mention that space is expanding. The universe is expanding. Do you mean to say that the universe is expanding away from the ball?
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Taz Member (Idle past 3313 days) Posts: 5069 From: Zerus Joined: |
What ball?
We are BOG. Resistance is voltage over current. Disclaimer: Occasionally, owing to the deficiency of the English language, I have used he/him/his meaning he or she/him or her/his or her in order to avoid awkwardness of style. He, him, and his are not intended as exclusively masculine pronouns. They may refer to either sex or to both sexes!
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RAZD Member (Idle past 1427 days) Posts: 20714 From: the other end of the sidewalk Joined:
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is it a felony to be confused? No but it is a misdemeanor to stay confused. Get thee to a One I have read and enjoyed was The Dancing Wu Li Masters: An Overview of the New Physics by Gary Zukav - Bantam ; Reissue edition (September 1, 1984). There is also The Tao of Physics by Fritjof Capra and
The Fabric of the Cosmos: Space, Time, and the Texture of Reality and The Elegant Universe, by Brian Greene It will lead to more questions than answers, but it also leads out of your current state of confusion. Questions lead to more refined search for answers. Enjoy. compare Fiocruz Genome and fight Muscular Dystrophy with Team EvC! (click) we are limited in our ability to understand by our ability to understand RebelAAmericanOZen[Deist ... to learn ... to think ... to live ... to laugh ... to share.
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anglagard Member (Idle past 858 days) Posts: 2339 From: Socorro, New Mexico USA Joined: |
Zukav and Capra, good Lord!
The next time any Lophophora williamsii goes missing around here, I say check the nearest physics department.
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Rahvin Member Posts: 4039 Joined: Member Rating: 8.2 |
yeah, thats right, but if that force has already pushed things down to the surface of an object, then was it not used as energy? expelled as work? No. The work was raising the object in the first place. When the object falls, it is simply returning to a lower level of potential energy, increasing entropy. Gravity cannot be "used up," any more than magnetism or the Strong/Weak atomic forces. It's a basic property or matter - as has been said, it's existence is part of matter's definition. And if you recall the rest of the Law of Thermodynamics, you'll rememeber that matter cannot be created or destroyed. Every time a fundy breaks the laws of thermodynamics, Schroedinger probably kills his cat.
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dkv Member (Idle past 5754 days) Posts: 38 Joined: |
Gravity is sometimes understood as geometry of space time.
General theory of relativity says that the space time wraps due to the presence of mass. There is no force just a geometry. However I have my doubts. General theory of relativity is based on the principle of equivalence. Which in my opinion is fundamentally flawed. "The principle of equivalence: There is no experiment observers can perform to distinguish whether an acceleration arises because of a gravitational force or because their reference frame is accelerating - Douglas C. Giancoli Physics for Scientists and Engineers with Modern Physics, p. 155" However note that GMm/r^2=ma ; a= GM/r^2 (acceleration is independent of mass but not independent of the distance from the source of gravity)therefore as the distance between gravitational center and the center of frame decreases the acceleration increases ... this can be used to distinguish between gravitational and non-gravitational frames. Experiment :A body falls freely towards Earth because the force is inversely propotional to distance between earth and object ,as it falls it will experience an increase in acceleration due decrease in the distance(g=9.8m/s^2 is only an approximation because change in R is small). Therefore if a sufficiently sensitive instrument is available then it should be possible to detect the increase in acceleration thus violating the equivalence principle. Moreover spatially distributed point masses experiences different accelerations. It is in principle possible to differentiate between a accelerating frame and gravitationally accelerating frame.
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Syamsu  Suspended Member (Idle past 5612 days) Posts: 1914 From: amsterdam Joined: |
"The Newton law of gravitation is based on an instantaneous propagation of gravity, and the Newtonian equations for the solar system, for example, work rather well, except for the anomalous perihelion of the planet Mercury. General relativity explains this aberration. In taking into account the retarded gravitational potential in the Newtonian equation, the equation of general relativity is obtained in introducing anticipative propagation of the gravitational field. "
http://www.mindspring.com/~cerebroscopic/Dubois.html So what this means basically, is that general relativity is derived from Newtonian gravity, and that in an information view of things, objects are computing their next state with the equations of gravity itself. So to say, the objects consist of the equations of gravity, and the particular values they have for the variables, past, present and future. The objects are information computing units. Now what is the origin of the particular values of the variables? Note how anticipation is a time principle, it is instantaneous. The origin of the values come from a decision for every step in time, which freedom still obeys the conservation of properties.
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cavediver Member (Idle past 3665 days) Posts: 4129 From: UK Joined: |
General theory of relativity is based on the principle of equivalence. No - the principle of equivalence helped lead Einstein to the General Theory, but the EP is a *prediction* of GR as we formulate it.
Which in my opinion is fundamentally flawed. First check - if you think your simple hunch is going to overturn 100 years of physics and the thinking of the greatest physicists of recent times such as Einstein, Hawking, Feynman, Dirac, Pauli, Cavediver (I wish) - then you should probably doubt your hunch first. Trust me - been there, done that.
"The principle of equivalence: There is no experiment observers can perform to distinguish whether an acceleration arises because of a gravitational force or because their reference frame is accelerating Unfortuanetly, either you or Prof Giancoli is missing an exteremly important word - LOCAL. This should read:
"The principle of equivalence: There is no LOCAL experiment observers can perform to distinguish whether an acceleration arises because of a gravitational force or because their reference frame is accelerating" And sadly the rest of your argument now falls apart. Of course we can distinguish the acceleration if we can look sufficiently far around us to notice the tidal effects of the gravitational field. But this is irrelevant for the equivalence principle.
A body falls freely towards Earth because the force is inversely propotional to distance between earth and object ,as it falls it will experience an increase in acceleration due decrease in the distance(g=9.8m/s^2 is only an approximation because change in R is small). Therefore if a sufficiently sensitive instrument is available then it should be possible to detect the increase in acceleration thus violating the equivalence principle. No - you cannot detect any acceleration if you are freely falling! What you could detect with your sensitive instrument, is the difference between what is happening at the top of your frame and what is happening at the bottom of the frame. This is where the differential gravitational field will be noticed. A partcile at the top of your frame will be moving away from a particle at the bottom of your frame. Two partciles on either side of your frame will actually be moving towards each other. But again, these ar not LOCAL experiments as you are comparing partciles at different points. All you are doing is discovering that your lcoal space-time curvature is changing as you move through space-time - nothing unusual there... That all said - it is quite possible that the equivalence principle is not infallible, but it will not be because of a failure of GR, but because of corrections to GR resulting from quantum gravity.
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Dr Adequate Member (Idle past 306 days) Posts: 16113 Joined: |
That was ... very odd.
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dkv Member (Idle past 5754 days) Posts: 38 Joined: |
EQuivalence Principle is a principle because it is one of the basic postulates of General relativity. Experiments have supported it.(no amount of experiment can prove a theory... one single experiment can disprove a theory...observations can only "support" a theory)
There is Weak Equivalence principle and there is strong equivalence priciple using which a theory was proposed and the predictions were made. Therefore IMO it is wrong to say that EP is a prediction of the theory. Why do we suspend our skeptisim when discussing Einstein's theory? Was einstein right ? Had he had the last say on nature of universe ? No. Einstein's GR totally fails are microscopic levels...
No - you cannot detect any acceleration if you are freely falling! What you could detect with your sensitive instrument, is the difference between what is happening at the top of your frame and what is happening at the bottom of the frame. This is where the differential gravitational field will be noticed. A partcile at the top of your frame will be moving away from a particle at the bottom of your frame. Two partciles on either side of your frame will actually be moving towards each other. But again, these ar not LOCAL experiments as you are comparing partciles at different points. All you are doing is discovering that your lcoal space-time curvature is changing as you move through space-time - nothing unusual there... That all said - it is quite possible that the equivalence principle is not infallible, but it will not be because of a failure of GR, but because of corrections to GR resulting from quantum gravity.
Local Frame from my point of view is made up of finite volume.. Which when subjected to a gravitational force experiences a non-uniform stress.i.e the acceleration at the top and bottom of the frame is not the same. Gravitation is Forcibly assumed UNIFORM in this local metric. Which is not the case in reality.
"The principle of equivalence: There is no LOCAL experiment observers can perform to distinguish whether an acceleration arises because of a gravitational force or because their reference frame is accelerating"
Observers can not perform ANY experiment in the LOCAL frame as defined by GR.Let us ask is it really a Local reference frame? All experiments return a ratio between observed and the standard. In a local frame we must be able to keep a standard measurement. In the LOCAL defined by GR can we keep a standard to measure? for example in order to measure time we need a atomic clock.. is it possible to keep a atomic clock in such a infinitely small metric. It is obvious that we can not keep local standard measurements to define the local reference frame. (rocket or train compartment is valid a reference frame because the local standards can be kept there.. note that everything is relative therefore it should always be possible to define the local measurements.) Local frame as defined by GR can not be defined at all because in such case the local measurements can not be made. Therefore IMO the EP is conceptually incorrect and therefore the GR is also incorrect.
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Dr Adequate Member (Idle past 306 days) Posts: 16113 Joined: |
Therefore IMO the EP is conceptually incorrect and therefore the GR is also incorrect. You should write to physicists about that. Make sure that you write your letters in purple ink, to let them know you're serious.
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