Question about gravity
in [Physics]
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From: Huang on 15 Mar 2010 10:08 On Mar 15, 9:04 am, kenseto <kens...(a)erinet.com> wrote: > On Mar 15, 6:43 am, "Peter Webb" > > <webbfam...(a)DIESPAMDIEoptusnet.com.au> wrote: > > 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.. > > Wrong it provides no such physical mechanism. It merely assumes the > existence of a physical entity caLLED the fabric of spacetime for the > interacting object to follow. The problem with such assumption is: > What is the fabric of spacetime physically? This question is relevant > because SR/GR deny the existence of physical space. > > Ken Seto What ? ".... SR/GR deny the existence of physical space......" What the devil are you saying man ????? The theory of relativity says that gravity IS deformation of space. How can this same theory deny the existence of space ??? Better visit your optometrist really, really soon.
From: Yousuf Khan on 15 Mar 2010 10:14 MicroTech 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? The Einstein description of gravity is the only one that's been proven at some level. Not all aspects of Einstein's theory have been proven yet (e.g. gravity waves), but a large amount of it is has. So it is the only description of gravity that has passed beyond the stage of theory into a law of physics. The description of gravity as a force particle, the graviton, is part of a next generation theory of quantum mechanics known as Supersymmetry. Supersymmetry is part of a larger next generation framework theory called Superstring Theory, and now M-Theory. None of the aspects of these next-gen theories have been proven yet. We have not detected the graviton (or indeed any of the theorized Supersymmetrical particles) in any of the atom smasher experiments. So until we see it in an experiment, you can only call a graviton as theoretical particle. The entire impetus to look for the graviton is to reconcile the laws of Relativity with the laws of Quantum Mechanics. The graviton is supposed to be the bridge between them. It's supposed to be the description of gravity at the atomic scales. Meanwhile Relativity is the description of gravity at the grand scales. So until the graviton is actually found, only Einstein's Relativity is right. > 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 Yes. > 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? Yes, kind of. There is still a force here. Any change in direction requires a force. But it's just the force of spacetime itself. Maybe if the graviton is ever proven, we'll call that force of spacetime itself the graviton. But until then it's just the force of spacetime. Yousuf Khan
From: kenseto on 15 Mar 2010 10:16 On Mar 15, 9:16 am, Huang <huangxienc...(a)yahoo.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). > > Einstein is correct, that gravity can be regarded as curvature or > deformation of space. Other views are equivalent to this model, such > as the view that gravity is a force. These two approaches are > equivalent in my opinion. > > The pieces which are missing in this puzzle: > [a] Explaining strong force in terms of spacetime curvature, > [b] Explaining weak force in terms of spacetime curvature, > [c] Explaining electromagnetism in terms of spacetime curvature. > > When a,b,c have been explained in terms of spacetime deformation, and > are shown to be equivalent to the particle explanations of a,b,c, then > you will be very close to grand unification. a, b, c can be explained with a special aether called the E-Matrix in place of the none physical existence of spacetime in the following link: http://www.modelmechanics.org/2008irt.dtg.pdf
From: kenseto on 15 Mar 2010 10:30 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 A new theory of gravity called Doppler Theory of Gravity (DTG) is available in the following link: http://www.modelmechanics.org/2008irt.dtg.pdf DTG is based on the existence of a stationary, structured and elastic aether called the E-Matrix occupying all of space. Gravity between interacting objects is the result of the interacting objects follow the local curvature exists in the E-Matrix. The local curvature existing in the E-Matrix is the result of absolute motions of the interacting objects in the E-Matrix. Ken Seto
From: Uncle Al on 15 Mar 2010 10:34
MicroTech 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". Metric gravitation postulates the Equivalence Principle (local centers of mass in vacuum free fall pursue identical minmum action trajectories independent of all measurable properties) in which the effects of a massive body are geometrized as pseudo-Riemannian spacetime curvature and manifested by bodies pursuing minimum action geodesic paths (photons pursuing null geodesic paths). Teleparallel gravitation embedded in Weitzenb�ck spacetime has its massed body effects ignore the EP [5] and geodesic paths. Gravitation is analogous to electrodynamics' chiral Lorentz force with spacetime torsion. The two analyses give indistinguishable predictions except for angular momentum. Teleparalellism prdeicts EP violation by physical spin (gyroballs), quantum spin (nuclear, particle, orbital; classical and superconducting magnets), relativistic spin-orbit coupling. No sufficiently relativstic example exists to show measurable EP violations in physics, including PSR J1903+0327 and its unremarkable 1.05 solar-mass binary. From chemistry, opposite shoes (chemically and macroscopically identical, inverse geometric parity atomic mass distributions) in vacuum free fall should measurably violate the EP. Geometric parity divergence can be calculated but it cannot be measured. It requires a trivial experiment in existing apparatus using commercial materials. Somebody should look. http://www.mazepath.com/uncleal/erotor1.jpg http://www.mazepath.com/uncleal/qz4.htm String theory and all quantum gravitations assume the EP (through BRST invariance or direct postulate) and predict nothing. > 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). Fair enough. Find one that does not. > Adding to the confusion, Uncle Al smells bullshit. There is no "confusion." There is nothing worse than grantology. > some scientists use both concepts with no > apparent difficulty: String theory, quantum gravitations as a class, are mathematics not physics. They make no testable predictions, not a one. Classical physics works perfectly, but it won't quantize c=infinity G=G h=0 Newton c=c G=0 h=0 Special Relativity c=c G=G h=0 General Relativity c=infinity G=0 h=h quantum mechanics c=c G=0 h=h quantum field theory c=c G=G h=h quantum gravitation (utter failure) > 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. You can run the math either way to get classical gravitation. There is no evideence for the graviton existing. It is math not physics. > So what is gravity, "really"? Does anybody really know? Or do we just > know its effects? To criticize is to volunteer, 1) Build any working model you like. 2) Falsify by observation any model you dislike. Uncle Al tosses his hard hat into the ring, http://www.mazepath.com/uncleal/parity.pdf > 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? Newton was wrong but a good approximation. Metric and teleparallel gravitations are equivalent (less a disjoint sliver) and perfectly work within experimental error. Quantum gravitation is a non-predictive disaster. > At my current level of understanding, gravity should be one or the > other, and not both... To first order, Newton is good enough. Einstein appears to be perfect, but metric gravitation won't quantize. HOWEVER... Thermodynamics plus the Beckenstein bound give GR. Gravitation then *should* quantize. Nobody can imagine how to do it. As Euclid failed for his Fifth postulate, so we suspect the EP is not a strong postulate. It must be demonstrated to fail to make that stick. > If Einstein's concept of "curved spacetime" is "correct," where does > the (hypothetical?) "graviton" (and/or "gravitino") enter the picture? All the maths associated with quantum gravitation fail to be physical. > References to published papers (accessible online) would be much > appreciated! "Gravitation" by Misner, Thorne, Wheeler. It's old but it's good. -- Uncle Al http://www.mazepath.com/uncleal/ (Toxic URL! Unsafe for children and most mammals) http://www.mazepath.com/uncleal/qz4.htm |