Question about gravity
in [Physics]
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From: "Juan R." González-Álvarez on 16 Mar 2010 07:39 Bill Hobba wrote on Tue, 16 Mar 2010 12:23:21 +1000: > On 15/03/2010 4:42 PM, 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). > > It is just terminology to say it is a fundamental force. That's how it > shows its effects but as far as we can tell today it is really > space-time curvature. No. The concept of force is not mere terminology, a force has associated properties. Those properties are missed in GR and this is why we say that gravity is not a force in GR. Your statement that gravity is spacetime curvature is also wrong. There exist theories where gravity is spacetime torsion, theories where gravity is a force carried by gravitons and theories where gravity is an AAAD force. All them verified in experiments with at least the same precision than GR. We also know that the metric model of GR cannot explain all the observations and aspects of gravitation and improved models have been proposed. See the thread for references. >> 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? > > As far as we can tell today it is space-time curvature. Corrected above. > >> 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? > > Actually it is a bit more complicated than either view. In a rather > interesting addition to general relativity Einstein did with some other > coworkers whose names escape me off the top of my head he showed it is > actually only space-time curvature - that's all that is really required. > The equations that govern that fully determine an objects motion. The > idea particles follow 'straight lines' is not required. That they do is > an excellent approximation to what really happens but evidently > exceptions do exist. An intreresting consequence of this is that > particles follow 'straight lines' in curved space time is really a > generalization of the principle of inertia that particles left to > themselves either remain at rest of move at constant velocity. So > space-time curvature with nothing else added explains inertia - neat > hey? > > >> 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? > > It comes when you try to combine gravity and quantum mechanics. No one > has been able to do it successfully valid to all energy levels. Nope. Nobody has been abel to provide an unification of general relativity with quantum mechanics, but the other theories are combined with quantum mechanics without the problems specific of GR (such as the problem of energy, the problem of time, renormalization...). > However > if you impose a cutoff of energy at about the plank scale (a very very > large amount of energy well beyond anything we can even get close to > toady) then its actually a pretty good theory. Check out: > http://arxiv.org/abs/grqc/9512024 Where the author repeats the confusion (already noticed by the OP) between a true field theory of gravity based in gravitoins and a metric theory of gravity as GR Field Theory of Gravitation: Desire and Reality 1999: arXiv:gr-qc/9912003v1. Baryshev, Yurij, V. "From Gravitons to Gravity: Myths and Reality." http://www.worldscinet.com/ijmpd/17/1703n04/S0218271808012085.html The difference between metric and field theories is analized in the section 14 of the next report http://www.canonicalscience.org/publications/canonicalsciencereports/20092.html > Actually all our most powerful quantum theories such as QED only really > make sense if we impose some kind of cutoff to avoid infinities. Even imposing some ad hoc cuttof, the theory is still flawed because is given in terms of bare (unphysical) quantities instead of dressed real quantities. It is needed a process for which all bare particles are substituted by physical particles. This process only works at the S-matrix level. (...) >> References to published papers (accessible online) would be much >> appreciated! >> >> Henry Norman > > If you want to delve into the technicalities check out: > http://preposterousuniverse.com/grnotes/ Those are Sean Caroll notes on general relativity. They are not error free but good in average. However, the problem is that they do not address the OP question about the difference between a field theory (where gravity is due to exchange of gravitons) and a metric theory as GR (where gravity is due to spacetime curvature). -- http://www.canonicalscience.org/ BLOG: http://www.canonicalscience.org/publications/canonicalsciencetoday/canonicalsciencetoday.html
From: mathematician on 16 Mar 2010 07:40 On 15 maalis, 08:42, 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 I have thought one possibility that origin of gravitational interaction could be "oscillation of size of neutrino´s signal periphery" What you think about this possibility? (Neutrinos are described as colored black holes in this H-M´s picture.) Best Regards, Hannu Poropudas
From: "Juan R." González-Álvarez on 16 Mar 2010 07:57 Bill Hobba wrote on Tue, 16 Mar 2010 12:43:20 +1000: > That the field equations all by themselves imply how particles move is a > very startling characteristic of General Relativity. Normally field > theories have equations that govern how fields behave and how objects > respond to those fields. That GR is not like that is rather > interesting. This is not a surprise but a consequence that GR is not a field theory but a metric theory. For the field theory of gravity the equations of motion are obtained in the usual form, for instance the Lagrangian formalism (as happen also in the field theory of electrodynamics) Field Theory of Gravitation: Desire and Reality 1999: arXiv:gr-qc/9912003v1. Baryshev, Yurij, V. Also section 6 in http://www.canonicalscience.org/publications/canonicalsciencereports/20092.html > Because of that I thought I would dig up a bit more about > it. Check out: > http://www.mathpages.com/rr/s5-08/5-08.htm 'Once the field equations > have been solved and the metric coefficients have been determined, we > then compute the paths of objects by means of the equations of motion. > It was originally taken as an axiom that the equations of motion are the > geodesic equations of the manifold, but in a series of papers from 1927 > to 1949 Einstein and others showed that if particles are treated as > singularities in the field, then they must propagate along geodesic > paths. Therefore, it is not necessary to make an independent assumption > about the equations of motion. This is one of the most remarkable > features of Einstein's field equations, and is only possible because of > the non-linear nature of the equations. Of course, the hypothesis that > particles can be treated as field singularities may seem no more > intuitively obvious than the geodesic hypothesis itself. Indeed Einstein > himself was usually very opposed to admitting any singularities, so it > is somewhat ironic that he took this approach to deriving the equations > of motion. On the other hand, in 1939 Fock showed that the field > equations imply geodesic paths for any sufficiently small bodies with > negligible self-gravity, not treating them as singularities in the > field. This approach also suggests that more massive bodies would > deviate from geodesics, and it relies on representing matter by the > stress-energy tensor, which Einstein always viewed with suspicion.' Being a metric theory, the Hilbert-Einstein metric equations G_ab = T_ab (incorrectly named field equations in any textbook I know and confused with the field equations of field theory of gravity, see reference above) give the (metric) structure of spacetime. The geometrical identity D^bG_ab = 0 implies D^bT_ab = 0. Since geodesics may check this conditions for the EMT, it follows that one can obtain the geodesic equation of motion instead postulating it separatedly. However, the problem is that the condition D^bT_ab = 0 only fixes the equations of motion for systems with less than four degrees of freedom. For physical systems with more degrees of freedom (e.g. a 3-body system) the equations of motion cannot be obtained in this form. This is the well-known problem of the systems of reference of GR. There is a beatiful discussion about this problem of GR in the textbook Gravitación 2005: Editorial URSS. Ivanenko, Dmitri Dmítrievich; Sardanashvili, Guenadi Alexándrovich. where authors also explain the metohds used by astronomers/astrophysist to postulate equations of motion and check for those systems. In other theories of gravity the equations of motion are perfectly determined for systems with arbitrary degrees of freedom. -- http://www.canonicalscience.org/ BLOG: http://www.canonicalscience.org/publications/canonicalsciencetoday/canonicalsciencetoday.html
From: PD on 16 Mar 2010 09:23 On Mar 16, 1:06 am, mpc755 <mpc...(a)gmail.com> wrote: > On Mar 16, 1:55 am, Sam Wormley <sworml...(a)gmail.com> wrote: > > > > > On 3/16/10 12:49 AM, mpc755 wrote: > > > > On Mar 16, 1:31 am, Sam Wormley<sworml...(a)gmail.com> wrote: > > >> On 3/15/10 2:13 AM, mpc755 wrote: > > > >>> In Aether Displacement, my theory, matter and aether are different > > >>> states of the same material. > > > >> If your Aether existed, one would be able to detect it > > >> and measure measure its properties. > > > > It is detectable. It is measurable. Every time a double slit > > > experiment is performed the C-60 molecule enters and exits a single > > > slit. It is the displacement wave in the aether the moving C-60 > > > molecule makes in the aether which enters and exits the available > > > slits and creates interference upon exit the slits. This alters the > > > direction the C-60 molecule travels. > > > What are some of its measured properties and how were the > > measurements made. Cite publications and/or governing equations. > > Yes, the old I wish to remain ignorant so anything that has already > been calculated is correct no matter how nonsensical it is. I don't believe he said that. He asked you a question: What are some of the aether's measured properties and how were the measurements made? Do you have an answer to a direct question? > The > delusional denial defense. Even though it is physically impossible for > a C-60 molecule to enter, travel through, and exit multiple slits > simultaneously without requiring energy, releasing energy, or having a > change in momentum, that is not what is important. What is important > is the mathematics of QM are able to determine the type of > interference pattern the C-60 molecule creates. > > Never mind what QM requires of the C-60 molecule is physically > impossible in nature. No, that is not what is important. For in QM, we > make stuff up like 'wave function probabilities' are physical. No > matter the fact that a wave function probability is a mathematical > construct. That is not what is important. What is important is the > ability to remain in a state of delusional denial. > > Do you want to play the 'future determines the past' and other > nonsensical answers from the delusional denial QM club? And here we > go... > > Detectors are placed at the exits to the slits while the C-60 molecule > is in the slits. If the detectors are left at the exits the C-60 > molecule is always detected exiting a single slit. If the detectors > are placed and then removed from the exits to the slits while the C-60 > molecule is in the slits the C-60 molecule creates and interference > pattern. > > How is this possible? > > Only one of your delusional denial club members has even offered up an > answer and the answer by your club member was the future determines > the past. You read that right. The C-60 molecule will enter one or > multiple slits depending upon there being, or not being, detectors at > the exits to the slits when it gets there in the future. > > In AD, the C-60 molecule always enters a single slit and the > displacement wave the C-60 molecule creates in the aether enters and > exits multiple slits. Detectors at the exits to the slits causes > decoherence of the associated aether displacement wave (i.e. turns the > wave into chop) and there is no interference. When the detectors are > removed prior to the C-60 molecule exiting the slit the displacement > wave exits the slits and creates interfere which alters the direction > the C-60 molecule travels. > > Your answer?
From: PD on 16 Mar 2010 09:23
On Mar 16, 1:28 am, mpc755 <mpc...(a)gmail.com> wrote: > On Mar 16, 2:21 am, Sam Wormley <sworml...(a)gmail.com> wrote: > > > > > On 3/16/10 1:06 AM, mpc755 wrote: > > > > On Mar 16, 1:55 am, Sam Wormley<sworml...(a)gmail.com> wrote: > > >> On 3/16/10 12:49 AM, mpc755 wrote: > > > >>> On Mar 16, 1:31 am, Sam Wormley<sworml...(a)gmail.com> wrote: > > >>>> On 3/15/10 2:13 AM, mpc755 wrote: > > > >>>>> In Aether Displacement, my theory, matter and aether are different > > >>>>> states of the same material. > > > >>>> If your Aether existed, one would be able to detect it > > >>>> and measure measure its properties. > > > >>> It is detectable. It is measurable. Every time a double slit > > >>> experiment is performed the C-60 molecule enters and exits a single > > >>> slit. It is the displacement wave in the aether the moving C-60 > > >>> molecule makes in the aether which enters and exits the available > > >>> slits and creates interference upon exit the slits. This alters the > > >>> direction the C-60 molecule travels. > > > >> What are some of its measured properties and how were the > > >> measurements made. Cite publications and/or governing equations. > > > > Yes, the old I wish to remain ignorant so anything that has already > > > been calculated is correct no matter how nonsensical it is. The > > > delusional denial defense. Even though it is physically impossible for > > > a C-60 molecule to enter, travel through, and exit multiple slits > > > simultaneously without requiring energy, releasing energy, or having a > > > change in momentum, that is not what is important. What is important > > > is the mathematics of QM are able to determine the type of > > > interference pattern the C-60 molecule creates. > > > > Never mind what QM requires of the C-60 molecule is physically > > > impossible in nature. No, that is not what is important. For in QM, we > > > make stuff up like 'wave function probabilities' are physical. No > > > matter the fact that a wave function probability is a mathematical > > > construct. That is not what is important. What is important is the > > > ability to remain in a state of delusional denial. > > > > Do you want to play the 'future determines the past' and other > > > nonsensical answers from the delusional denial QM club? And here we > > > go... > > > > Detectors are placed at the exits to the slits while the C-60 molecule > > > is in the slits. If the detectors are left at the exits the C-60 > > > molecule is always detected exiting a single slit. If the detectors > > > are placed and then removed from the exits to the slits while the C-60 > > > molecule is in the slits the C-60 molecule creates and interference > > > pattern. > > > > How is this possible? > > > > Only one of your delusional denial club members has even offered up an > > > answer and the answer by your club member was the future determines > > > the past. You read that right. The C-60 molecule will enter one or > > > multiple slits depending upon there being, or not being, detectors at > > > the exits to the slits when it gets there in the future. > > > > In AD, the C-60 molecule always enters a single slit and the > > > displacement wave the C-60 molecule creates in the aether enters and > > > exits multiple slits. Detectors at the exits to the slits causes > > > decoherence of the associated aether displacement wave (i.e. turns the > > > wave into chop) and there is no interference. When the detectors are > > > removed prior to the C-60 molecule exiting the slit the displacement > > > wave exits the slits and creates interfere which alters the direction > > > the C-60 molecule travels. > > > > Your answer? > > > I want to know some of your aether's measured properties and how > > were the measurements made. Cite publications and/or governing > > equations. > > Another member of the delusional denial club, So asking questions about your aether is a sign of delusion? > sponsored by QM and > brought to you by ignorance brought on by a refusal to understand > aether is a material. > > 'Interpretation of quantum mechanics > by the double solution theory > Louis de BROGLIE'http://www.ensmp.fr/aflb/AFLB-classiques/aflb124p001.pdf > > 'LOUIS DE BROGLIE > The wave nature of the electron > Nobel Lecture, December 12, 1929'http://nobelprize.org/nobel_prizes/physics/laureates//1929/broglie-le... > > In AD, de Broglie's statement of a moving particle has an associated > wave is stated as a moving particle has an associated aether wave and > a moving particle of matter has an associated aether displacement > wave. |