Question about gravity
in [Physics]
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From: MicroTech on 15 Mar 2010 02:42 Can someone in this forum please help me sort out a confusing issue? Many scientists (including Einstein) claim that gravity is not a force, but the effect of mass on the "fabric of spacetime". Many other scientists refer to gravity as one of the four fundamental interactions (three, if one considers the unification of the weak and electromagnetic interactions, the "electroweak" force). Adding to the confusion, some scientists use both concepts with no apparent difficulty: Stephen Hawking (in his "A Brief History Of Time") first says that gravity is not a force, but "simply" the effect of mass on the "spacetime fabric" (making it "curve"). However, later in the book, he refers to gravity as a fundamental force, carried by the graviton. So what is gravity, "really"? Does anybody really know? Or do we just know its effects? Is it an attractive force "mutually pulling" the Earth towards the Sun (and vice versa), "causing" the Earth to "fall" towards the Sun? And due to the "forward motion" of the Earth, exactly matching the "gravitational pull", it stays in orbit (just like any other satellite, man-made or not); OR Is it the mass of the Sun that "curves spacetime", so no force is interacting with the Earth, it is just moving in a "straight line" along a "curved spacetime" geodesic? At my current level of understanding, gravity should be one or the other, and not both... If Einstein's concept of "curved spacetime" is "correct," where does the (hypothetical?) "graviton" (and/or "gravitino") enter the picture? References to published papers (accessible online) would be much appreciated! Henry Norman
From: Androcles on 15 Mar 2010 02:58 "MicroTech" <henry.ko.norman(a)gmail.com> wrote in message news:3a9b00f7-065e-42a2-b6f2-769bb9d63582(a)s36g2000prh.googlegroups.com... > Can someone in this forum please help me sort out a confusing issue? > > Many scientists (including Einstein) claim that gravity is not a > force, but the effect of mass on the "fabric of spacetime". Many idiots (including Einstein) aren't scientists no matter what they call themselves. All murderers are innocent, just ask one. > Many other > scientists refer to gravity as one of the four fundamental > interactions (three, if one considers the unification of the weak and > electromagnetic interactions, the "electroweak" force). > Many other idiots aren't scientists no matter what they call themselves. All thieves are innocent, just ask one. > Adding to the confusion, some scientists use both concepts with no > apparent difficulty: Why do you keep referring to scientists? > Stephen Hawking (in his "A Brief History Of Time") first says that > gravity is not a force, but "simply" the effect of mass on the > "spacetime fabric" (making it "curve"). Hawking is an idiot. > However, later in the book, he > refers to gravity as a fundamental force, carried by the graviton. > That proves Hawking is an idiot. > So what is gravity, "really"? Does anybody really know? Or do we just > know its effects? > Gravity is a force. > Is it an attractive force "mutually pulling" the Earth towards the Sun > (and vice versa), "causing" the Earth to "fall" towards the Sun? And > due to the "forward motion" of the Earth, exactly matching the > "gravitational pull", it stays in orbit (just like any other > satellite, man-made or not); OR > > Is it the mass of the Sun that "curves spacetime", so no force is > interacting with the Earth, it is just moving in a "straight line" > along a "curved spacetime" geodesic? So what is spacetime, "really"? Does anybody really know? Or do we just know its effects? > > At my current level of understanding, gravity should be one or the > other, and not both... > > If Einstein's concept of "curved spacetime" is "correct," where does > the (hypothetical?) "graviton" (and/or "gravitino") enter the picture? > So what is a picture, "really"? Does anybody really know? Or do we just know its effects? > References to published papers (accessible online) would be much > appreciated! http://www.guardian.co.uk/education/2010/mar/14/university-heads-vice-chancellor-salaries
From: Inertial on 15 Mar 2010 03:05 "MicroTech" <henry.ko.norman(a)gmail.com> wrote in message news:3a9b00f7-065e-42a2-b6f2-769bb9d63582(a)s36g2000prh.googlegroups.com... > Can someone in this forum please help me sort out a confusing issue? > > Many scientists (including Einstein) claim that gravity is not a > force, Its a "fictional" force according to GR > but the effect of mass on the "fabric of spacetime". Yeup > Many other > scientists refer to gravity as one of the four fundamental > interactions (three, if one considers the unification of the weak and > electromagnetic interactions, the "electroweak" force). Yeup > Adding to the confusion, some scientists use both concepts with no > apparent difficulty: Not at the same time (or when it matters) > Stephen Hawking (in his "A Brief History Of Time") first says that > gravity is not a force, but "simply" the effect of mass on the > "spacetime fabric" (making it "curve"). However, later in the book, he > refers to gravity as a fundamental force, carried by the graviton. There are different theories which are stil to be reconciled regarding gravity. Hawking is quite free to talk about either or both theories. > So what is gravity, "really"? Does anybody really know? Or do we just > know its effects? It is an area of research still ..in particular in the areas of 'quantum' gravity. So its a 'we don't really know how the theories work together' yet > Is it an attractive force "mutually pulling" the Earth towards the Sun > (and vice versa), "causing" the Earth to "fall" towards the Sun? Something is making the Earth appear to do that. > And > due to the "forward motion" of the Earth, exactly matching the > "gravitational pull", it stays in orbit (just like any other > satellite, man-made or not); OR > > Is it the mass of the Sun that "curves spacetime", so no force is > interacting with the Earth, it is just moving in a "straight line" > along a "curved spacetime" geodesic? That's the most likely > At my current level of understanding, gravity should be one or the > other, and not both... When physics comes up with a good answer that explains gravity at both the marcoscopic and qunatum levels, then we will. ATM we don't really know. Physics isn't all finished now and something you can just learn as one complete work. It is stil levolving .. physicists still have jobs to do :):) > If Einstein's concept of "curved spacetime" is "correct," where does > the (hypothetical?) "graviton" (and/or "gravitino") enter the picture? That is what is being worked out. > References to published papers (accessible online) would be much > appreciated! > > Henry Norman
From: mpc755 on 15 Mar 2010 03:13 On Mar 15, 2:42 am, MicroTech <henry.ko.nor...(a)gmail.com> wrote: > Can someone in this forum please help me sort out a confusing issue? > > Many scientists (including Einstein) claim that gravity is not a > force, but the effect of mass on the "fabric of spacetime". Many other > scientists refer to gravity as one of the four fundamental > interactions (three, if one considers the unification of the weak and > electromagnetic interactions, the "electroweak" force). > > Adding to the confusion, some scientists use both concepts with no > apparent difficulty: > Stephen Hawking (in his "A Brief History Of Time") first says that > gravity is not a force, but "simply" the effect of mass on the > "spacetime fabric" (making it "curve"). However, later in the book, he > refers to gravity as a fundamental force, carried by the graviton. > > So what is gravity, "really"? Does anybody really know? Or do we just > know its effects? > > Is it an attractive force "mutually pulling" the Earth towards the Sun > (and vice versa), "causing" the Earth to "fall" towards the Sun? And > due to the "forward motion" of the Earth, exactly matching the > "gravitational pull", it stays in orbit (just like any other > satellite, man-made or not); OR > > Is it the mass of the Sun that "curves spacetime", so no force is > interacting with the Earth, it is just moving in a "straight line" > along a "curved spacetime" geodesic? > > At my current level of understanding, gravity should be one or the > other, and not both... > > If Einstein's concept of "curved spacetime" is "correct," where does > the (hypothetical?) "graviton" (and/or "gravitino") enter the picture? > > References to published papers (accessible online) would be much > appreciated! > > Henry Norman In Aether Displacement, my theory, matter and aether are different states of the same material. I named this material mather. Matter is compressed mather and aether is uncompressed mather. Matter and aether have mass. Matter displaces aether. The aether is not at rest when displaced and 'displaces back'. This 'displacing back' is the pressure the aether exerts towards the matter. How do we know aether exerts pressure towards the matter? Because light from distant stars reaches from where Jupiter was in its orbit (i.e. Jupiter does not leave a void in its wake). Think of the aether as a frictionless superfluid or supersolid. 'Frictionless supersolid a step closer' http://www.physorg.com/news185201084.html "Superfluidity and superconductivity cause particles to move without friction. Koos Gubbels investigated under what conditions such particles keep moving endlessly without losing energy, like a swimmer who takes one mighty stroke and then keeps gliding forever along the swimming pool." The 'water' applies pressure towards the 'swimmer' but there is no loss of energy between the interaction of the 'water' and the 'swimmer'. If you take the 'swimmer' out of the 'water' a void does not remain in the 'water'. The 'water' fills-in where the 'swimmer' was. The 'water' applies pressure towards the 'swimmer'. The difference between water and a swimmer and aether and a body is the body consists of nuclei which are surrounded by aether. The aether permeates the body. 'On the super-fluid property of the relativistic physical vacuum medium and the inertial motion of particles' http://arxiv.org/ftp/gr-qc/papers/0701/0701155.pdf "Abstract: The similarity between the energy spectra of relativistic particles and that of quasi-particles in super-conductivity BCS theory makes us conjecture that the relativistic physical vacuum medium as the ground state of the background field is a super fluid medium, and the rest mass of a relativistic particle is like the energy gap of a quasi-particle. This conjecture is strongly supported by the results of our following investigation: a particle moving through the vacuum medium at a speed less than the speed of light in vacuum, though interacting with the vacuum medium, never feels friction force and thus undergoes a frictionless and inertial motion." There still exists pressure associated with the super fluid medium towards the particle. The pressure associated with the aether displaced by massive objects is gravity.
From: Peter Webb on 15 Mar 2010 06:43
Not a whole lot to add to what Inertial in particular said. In GR, gravity is a virtual force in a similar way to centrifugal force in Newton. In both cases its really an acceleration, and the force is just the product (literally) of this acceleration and the mass of the object. Einstein in GR gave a geometric interpretation of what gravity is. This is very appealing, because it provides a mechanism for force at a distance. I might point out that the central concept of Newton and all other models of gravity is really acceleration not force, and acceleration is the second derivative of position, so this suggests a self-contained geometric interpretation. GR AFAIK gives no explanation for EM action at a distance. I'm not very knowledgeable about QM, but as I understand it the mechanisms for force exchange are different, specifically the exchange of virtual particles for which their are real equivalents. Charged particles repel/attract through the exchange of virtual photons. This actually produces the same results - you can consider charge to be fundamental and photons the derived concept, or have photons as fundamental and derive charge. This model works also for the weak and strong forces. So by analogy if QM is to explain gravity, it must do so through the exchange of particles, hence gravitons. "MicroTech" <henry.ko.norman(a)gmail.com> wrote in message news:3a9b00f7-065e-42a2-b6f2-769bb9d63582(a)s36g2000prh.googlegroups.com... > Can someone in this forum please help me sort out a confusing issue? > > Many scientists (including Einstein) claim that gravity is not a > force, but the effect of mass on the "fabric of spacetime". Many other > scientists refer to gravity as one of the four fundamental > interactions (three, if one considers the unification of the weak and > electromagnetic interactions, the "electroweak" force). > > Adding to the confusion, some scientists use both concepts with no > apparent difficulty: > Stephen Hawking (in his "A Brief History Of Time") first says that > gravity is not a force, but "simply" the effect of mass on the > "spacetime fabric" (making it "curve"). However, later in the book, he > refers to gravity as a fundamental force, carried by the graviton. > > So what is gravity, "really"? Does anybody really know? Or do we just > know its effects? > > Is it an attractive force "mutually pulling" the Earth towards the Sun > (and vice versa), "causing" the Earth to "fall" towards the Sun? And > due to the "forward motion" of the Earth, exactly matching the > "gravitational pull", it stays in orbit (just like any other > satellite, man-made or not); OR > > Is it the mass of the Sun that "curves spacetime", so no force is > interacting with the Earth, it is just moving in a "straight line" > along a "curved spacetime" geodesic? > > At my current level of understanding, gravity should be one or the > other, and not both... > > If Einstein's concept of "curved spacetime" is "correct," where does > the (hypothetical?) "graviton" (and/or "gravitino") enter the picture? > > References to published papers (accessible online) would be much > appreciated! > > Henry Norman |