Speed of Gravity?

tvanflandern
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20 years 4 months ago #10198 by tvanflandern

Replied by tvanflandern on topic Reply from Tom Van Flandern

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Thomas
 One does not really need observations to prove this because the concept of a force would be inconsistent if static forces do not act instantaneously.<hr height="1" noshade id="quote"></blockquote id="quote">This is untrue. The force produced by a wind is retarded by the wind speed. The force of solar radiation pressure is retarded by 8.3 minutes in traveling from Sun to Earth, and as a result, orbits of small particles are spirals.

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Just imagine that the sun is suddenly removed from the solar system. It is just inconceivable that the earth would continue in its orbit for another 8 min without any physical object present to provide the required gravitational attraction and hence force balance.<hr height="1" noshade id="quote"></blockquote id="quote">But the speed of gravitational force is billions of times faster than the speed of light, so we cannot yet measure any delay in gravity traveling from Sun to Earth.

Nonetheless, we may be certain that delay is finite. As Newton said: "It is inconceivable that inanimate gross matter, without the mediation of something immaterial, might affect some other matter with no mutual contact, as it should happen if gravitation (in the sense proposed by Epicurus) were essential and inherent to matter. This is one of the reasons why I do not wish innate gravity to be attributed to me. For me it is totally absurd that gravitation should be innate, inherent and essential to matter, so that a
body might act upon another body from a distance, through vacuum, without the mediation of something else, through which its action and force should be transported from one to the other; it is so absurd that I believe no man with philosophical questions in mind might believe it. Gravity must be caused by an agent constantly acting according to certain laws; but I should let my readers decide whether such agent is material or immaterial." (Newton Optics, edition of 1717, Foreword)

-|Tom|-

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Thomas
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20 years 4 months ago #10079 by Thomas

Replied by Thomas on topic Reply from Thomas Smid

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by tvanflandern
 <blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Thomas
 One does not really need observations to prove this because the concept of a force would be inconsistent if static forces do not act instantaneously.<hr height="1" noshade id="quote"></blockquote id="quote">This is untrue. The force produced by a wind is retarded by the wind speed. The force of solar radiation pressure is retarded by 8.3 minutes in traveling from Sun to Earth, and as a result, orbits of small particles are spirals.<hr height="1" noshade id="quote"></blockquote id="quote">Are you suggesting that gravity is produced by a kind of wind? Shouldn't one then have a repulsive rather than an attractive gravitational force?
The analogy with a wind is in fact inadequate here as the latter is not a fundamental physical force. It is a macroscopic force produced by the collision of atoms with an object. These atoms interact with the atoms of the object via their static Coulomb force field (which is the fundamental force at work here).
It is obviously a circular argument to suggest that a fundamental force is mediated by particles as one would need a further fundamental force for the latter to interact and hence excert any force. For the sake of logical consistency, a fundamental force therefore has to be of the 'action at a distance' type , i.e. the field has to be thought of as being fixed to the particle and instantaneously moving with it if the latter moves. This does not at all violate causality as the field as such is not observable but only its effect on other particles (which obviously take a finite time to develop because of the mass and inertia of particles).

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Just imagine that the sun is suddenly removed from the solar system. It is just inconceivable that the earth would continue in its orbit for another 8 min without any physical object present to provide the required gravitational attraction and hence force balance.<hr height="1" noshade id="quote"></blockquote id="quote"><blockquote id="quote">quote:<hr height="1" noshade id="quote">But the speed of gravitational force is billions of times faster than the speed of light, so we cannot yet measure any delay in gravity traveling from Sun to Earth.<hr height="1" noshade id="quote"></blockquote id="quote">It is irrelevant if the delay is 8min or a microsecond or whatever. In a closed system, the sum of the internal forces has to vanish at any instant and only a zero delay guarantees this.

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Nonetheless, we may be certain that delay is finite. As Newton said: "It is inconceivable that inanimate gross matter, without the mediation of something immaterial, might affect some other matter with no mutual contact, as it should happen if gravitation (in the sense proposed by Epicurus) were essential and inherent to matter. This is one of the reasons why I do not wish innate gravity to be attributed to me. For me it is totally absurd that gravitation should be innate, inherent and essential to matter, so that a
body might act upon another body from a distance, through vacuum, without the mediation of something else, through which its action and force should be transported from one to the other; it is so absurd that I believe no man with philosophical questions in mind might believe it. Gravity must be caused by an agent constantly acting according to certain laws; but I should let my readers decide whether such agent is material or immaterial." (Newton Optics, edition of 1717, Foreword)<hr height="1" noshade id="quote"></blockquote id="quote">It seems that Newton did himself not quite grasp the implications of his laws.

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Jan
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20 years 4 months ago #10080 by Jan

Replied by Jan on topic Reply from Jan Vink

<blockquote id="quote">quote:<hr height="1" noshade id="quote">The analogy with a wind is in fact inadequate here as the latter is not a fundamental physical force.<hr height="1" noshade id="quote"></blockquote id="quote">

We need to be careful what we call a "fundamental force". In what way fundamental? We, humans, perceive such foces on our scales of experiments and existence. Then, according to the MM, no scale can be called special, so there is no such thing as "fundamental".

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tvanflandern
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20 years 4 months ago #10199 by tvanflandern

Replied by tvanflandern on topic Reply from Tom Van Flandern

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Thomas
 Are you suggesting that gravity is produced by a kind of wind? Shouldn't one then have a repulsive rather than an attractive gravitational force?<hr height="1" noshade id="quote"></blockquote id="quote">The answer to both questions is "yes". I might add "of course". [

]

The latest and most complete gravity model is published in the 20-author book Pushing Gravity: New Perspectives on Le Sage's Theory of Gravitation, M. Edwards, ed., Apeiron Press, Montreal (2002). Much of the essence of these ideas may be found on the web site that hosts this message board. For example, one might start with "Possible new properties of gravity" at metaresearch.org/cosmology/gravity/gravity.asp

But whether all these details are correct or not, we can be certain of a few generalizations about nature. These are collectively called the "principles of physics", to be distinguished from the laws of physics. See "Physics has its principles" at metaresearch.org/cosmology/PhysicsHasItsPrinciples.asp

One corollary of these is that all forces are necessarily of the pushing variety because, at a fundamental level, the only way that any two physical entities can interact is by collision. So the apple falls from the tree because it is in an isotropic graviton wind balanced from all directions except below because the Earth blocks a small precentage of the gravitons that would otherwise strike the apple from below. The result gives the appearance of an attraction by Earth when it is really a repulsion by gravitons, some of which are screened by Earth.

<blockquote id="quote">quote:<hr height="1" noshade id="quote">It is obviously a circular argument to suggest that a fundamental force is mediated by particles as one would need a further fundamental force for the latter to interact and hence excert any force.<hr height="1" noshade id="quote"></blockquote id="quote">On the contrary. If something besides collision were operating for any force under any circumstances, nature would require a means of two physical entities interacting at a distance without intermediaries or contact, and the possibility of that is excluded by logic (as in my quote from Newton). Any such interaction without contact would be a violation of the causality principle, and as such a form of magic. While invoked often in math and philosophy, magic is forbidden as an explanation in physics. See the "principles" article, which explains why this is required.

<blockquote id="quote">quote:<hr height="1" noshade id="quote">For the sake of logical consistency, a fundamental force therefore has to be of the 'action at a distance' type , i.e. the field has to be thought of as being fixed to the particle and instantaneously moving with it if the latter moves. This does not at all violate causality as the field as such is not observable but only its effect on other particles (which obviously take a finite time to develop because of the mass and inertia of particles).<hr height="1" noshade id="quote"></blockquote id="quote">Physical entities are normally classified as either "particles" or "waves", the latter being a type of organized motion of the former. You seem here to be proposing some new form of physical existence for a thing called a "field" that is not composed of smaller entities. Although such thinking is widespread these days in QM, it has (unsuprisingly) led to contradictions within the field ("there is no deep reality" for one, Zeno's paradoxes for another).

By contrast, Meta Science gets back to physics that respects the principles, and therefore respects logic. The result is a new understanding of the fundamentals that works better than the old one, makes distinguishing predictions, and most importantly eliminates all internal contradictions, as logic demands. If you reach the point where you are curious about how to build a world model on the principles alone without assumptions, check out the "Dark Matter..." book available through our web site store.

<blockquote id="quote">quote:<hr height="1" noshade id="quote">In a closed system, the sum of the internal forces has to vanish at any instant and only a zero delay guarantees this.<hr height="1" noshade id="quote"></blockquote id="quote">That "force balancing" idea is widely misunderstood and misapplied. For example, if the centripetal force of the Sun on the Earth were balanced and canceled by Earth's centrifugal force, there would be no acceleration and no orbiting.

Concentrate on my example of solar radiation pressure -- the pressure of sunlight on small bodies orbiting the Sun. Photons have no coulomb forces (zero charge), gravity (no mass), or strong or weak nuclear forces (no nucleus). Yet they manage very nicely to produce a retarded pushing force that makes orbits spiral. This example alone should show that your present understanding of "fundamental forces" is, at the very least, incomplete.

<blockquote id="quote">quote:<hr height="1" noshade id="quote">It seems that Newton did himself not quite grasp the implications of his laws.<hr height="1" noshade id="quote"></blockquote id="quote">Or, it seems that Newton grasped the fundamentals better than many modern students of physics. Would you care to cite an objection to Newton's statement (or those in "Physics has its principles") on logical grounds, without invoking magic in some step? -|Tom|-

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Thomas
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20 years 4 months ago #10118 by Thomas

Replied by Thomas on topic Reply from Thomas Smid

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Jan
 <blockquote id="quote">quote:<hr height="1" noshade id="quote">The analogy with a wind is in fact inadequate here as the latter is not a fundamental physical force.<hr height="1" noshade id="quote"></blockquote id="quote">
We need to be careful what we call a "fundamental force". In what way fundamental? We, humans, perceive such foces on our scales of experiments and existence. Then, according to the MM, no scale can be called special, so there is no such thing as "fundamental".
<hr height="1" noshade id="quote"></blockquote id="quote">One obviously has to assume some fundamental (i.e. not further reducible) forces because otherwise one might as well stop doing physics altogether (all physical theories need some first principles to operate on). Of course this is subject to experiments and observation, but *if* you consider a force to be fundamental (and as far as my understanding goes, this holds presently for gravitation), this can only be an instantaneously acting force (as argued above).

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Thomas
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20 years 4 months ago #10315 by Thomas

Replied by Thomas on topic Reply from Thomas Smid

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by tvanflandern
One corollary of these is that all forces are necessarily of the pushing variety because, at a fundamental level, the only way that any two physical entities can interact is by collision. So the apple falls from the tree because it is in an isotropic graviton wind balanced from all directions except below because the Earth blocks a small precentage of the gravitons that would otherwise strike the apple from below. The result gives the appearance of an attraction by Earth when it is really a repulsion by gravitons, some of which are screened by Earth.<hr height="1" noshade id="quote"></blockquote id="quote">I have discussed this suggestion already on my own website ( www.physicsmyths.org.uk/discussions/grav.htm ) and replied as follows:
'in order to reproduce the known law for gravitational interaction, you need not only the 1/r^2 dependence (which you would obtain here) but also the proportionality between the masses m1 and m2. This would only be possible if the proposed 'wind' can penetrate the masses virtually with zero absorption or scattering (extremely optically thin condition), because otherwise the exponential absorption law would produce a significant deviation from the linear behavior.
Some kind of neutrino-like particle might be able to do this, yet as the absorption would have to be so small, the corresponding flux would have to be unrealistically isotropic and homogeneous (if the earth should be kept in its orbit around the sun with the presently known accuracy, the relative anisotropy would have to be many orders of magnitude smaller than a factor 10^-5 (the relative spatial angle of the sun as seen from the earth)). This is as good as impossible if this wind is associated with other physical processes in the universe because the latter is not sufficiently homogeneous.'

More importantly however: as already indicated above, a collision can only transfer momentum (and hence excert a force) if the colliding particles interact by means of some force field, i.e. you would again have to postulate a further 'wind' (on a smaller scale) that produces this force (and so on ad infinitum).

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Any such interaction without contact would be a violation of the causality principle, and as such a form of magic.<hr height="1" noshade id="quote"></blockquote id="quote">As mentioned above already, there is no problem with the causality principle for an 'action at a distance' type response of the field to any movement of the field source as the field as such is not observable but only its effect on other particles (which obviously take a finite time to develop because of the mass and inertia of particles).

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Concentrate on my example of solar radiation pressure -- the pressure of sunlight on small bodies orbiting the Sun. Photons have no coulomb forces (zero charge), gravity (no mass), or strong or weak nuclear forces (no nucleus). Yet they manage very nicely to produce a retarded pushing force that makes orbits spiral. This example alone should show that your present understanding of "fundamental forces" is, at the very least, incomplete.<hr height="1" noshade id="quote"></blockquote id="quote">How would the radiation then excert any force if not by means of a force field?
The classical derivation of radiation pressure is erroneous because the assumption that the velocity of the charged particle (induced by the electric field component) is always in phase with the oscillating magnetic field (and therefore the Lorentz force q/c*v×B always has the same sign) is simply wrong. It is obvious (and indeed easy to show by integration of the equation of motion) that v never changes sign as equal periods of acceleration and deceleration alternate.
With the particle picture of light on the other hand, one also runs into inconsistencies when assuming a photon momentum, not only for the reason mentioned above, but also because it contradicts experimental results (see my page www.physicsmyths.org.uk/photons.htm ).
The apparent 'radiation pressure' can only be due to secondary effects like vaporization of the objects' surface and the associated 'outgassing' of material (e.g. comets).

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Would you care to cite an objection to Newton's statement (or those in "Physics has its principles") on logical grounds, without invoking magic in some step?<hr height="1" noshade id="quote"></blockquote id="quote">The point is that Newton's argument is merely of a psychological rather than a logical nature. There is in fact no such thing as a 'contact' of objects. All interaction between particles takes place via their force field and separated by empty space (albeit this may be on a very small scale).

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