The gravitational field as a preferred frame
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From: Surfer on 8 Jun 2010 02:04 http://en.wikipedia.org/wiki/Background-independent <Start extract> The resolution to the hole argument (mainly taken from Rovelli's book) is as follows. As GR does not determine the distance between spacetime points, how the gravitational and matter fields are located over spacetime, and so the values they take at spacetime points, can have no physical meaning. What GR does determine, however, are the mutual relations that exist between the gravitational field and the matter fields (i.e. the value the gravitational field takes where the matter field takes such and such value). From these mutual relations we can form a notion of matter being located with respect to the gravitational field and vice-versa, (see Rovelli's for exposition). What Einstein discovered was that physical entities are located with respect to one another only, independent of the spacetime manifold. This independence is background independence. Since the Hole Argument is a direct consequence of the general covariance of GR, this led Einstein to state: "That this requirement of general covariance, which takes away from space and time the last remnant of physical objectivity, is a natural one, ..."[3] <End extract> If one accepts the above statements, then motion cannot be relative to space or the spacetime manifold, as the latter were understood by Einstein. However, if we consider the phrase, "....From these mutual relations we can form a notion of matter being located with respect to the gravitational field and vice-versa..." then it is clear that matter can be in motion relative to the gravitational field, which if considered to be a preferred frame, would allow such motion to be considered absolute motion. Even more interesting however is that if Einstein's concept of space has had taken away from it "the last remnant of physical objectivity", how are we to explain the obvious fact that we move around in 3 dimensional space all the time? Isn't the fact that we can do so, sufficient evidence of the physical objectivity of 3-dimensional space? Putting two and two together, there seems only one way to reconcile these notions. If the space, time and spacetime manifold of GR lack physical objectivity, then the 3-dimensional space that we experience as physically objective, must be synonymous with the gravitational field. It then follows that absolute motion relative to the field is synonymous with absolute motion relative to this physically objective space. Surfer
From: Hayek on 8 Jun 2010 04:08 Surfer wrote: > http://en.wikipedia.org/wiki/Background-independent > > <Start extract> > > The resolution to the hole argument (mainly taken from Rovelli's book) > is as follows. As GR does not determine the distance between spacetime > points, how the gravitational and matter fields are located over > spacetime, and so the values they take at spacetime points, can have > no physical meaning. What GR does determine, however, are the mutual > relations that exist between the gravitational field and the matter > fields (i.e. the value the gravitational field takes where the matter > field takes such and such value). From these mutual relations we can > form a notion of matter being located with respect to the > gravitational field and vice-versa, (see Rovelli's for exposition). > What Einstein discovered was that physical entities are located with > respect to one another only, independent of the spacetime manifold. > This independence is background independence. > > Since the Hole Argument is a direct consequence of the general > covariance of GR, this led Einstein to state: > > "That this requirement of general covariance, which takes away from > space and time the last remnant of physical objectivity, is a natural > one, ..."[3] > > <End extract> > > If one accepts the above statements, then motion cannot be relative to > space or the spacetime manifold, as the latter were understood by > Einstein. > > However, if we consider the phrase, > > "....From these mutual relations we can form a notion of matter being > located with respect to the gravitational field and vice-versa..." > > then it is clear that matter can be in motion relative to the > gravitational field, which if considered to be a preferred frame, > would allow such motion to be considered absolute motion. > > Even more interesting however is that if Einstein's concept of space > has had taken away from it "the last remnant of physical objectivity", > how are we to explain the obvious fact that we move around in 3 > dimensional space all the time? > > Isn't the fact that we can do so, sufficient evidence of the physical > objectivity of 3-dimensional space? > > Putting two and two together, there seems only one way to reconcile > these notions. > > If the space, time and spacetime manifold of GR lack physical > objectivity, then the 3-dimensional space that we experience as > physically objective, must be synonymous with the gravitational field. > > It then follows that absolute motion relative to the field is > synonymous with absolute motion relative to this physically objective > space. > > > Surfer Some remarks : - reading "The End of Time" recently, I was surprised to learn that a contemporary Mathematician, Kretschmann, has argued in 1917, that general covariance has no physical content. see http://www.pitt.edu/~jdnorton/papers/decades_re-set.pdf - the way I see it, is that there is a preferred background, the average mass distribution of the universe, but that all attempts to measure it are doomed to fail because of the nature of the gamma factor, which has absolute and relative properties. That gamma factor is the measure of an inertial field strength, and a clock is an inertiameter. More on inertia : http://www.xs4all.nl/~notime/inert/gravp543.html Inertia is an "external parameter" that influences ALL of physics, so that it cannot be measured locally, hence the "laws of physics are the same for a local observer". Another observer has not the same inertial field strength and thus not the same clock rate, but the same laws of physics. HTH Uwe Hayek. -- We are fast approaching the stage of the ultimate inversion : the stage where the government is free to do anything it pleases, while the citizens may act only by permission; which is the stage of the darkest periods of human history. -- Ayn Rand I predict future happiness for Americans if they can prevent the government from wasting the labors of the people under the pretense of taking care of them. -- Thomas Jefferson. Socialism is a philosophy of failure, the creed of ignorance, and the gospel of envy, its inherent virtue is the equal sharing of misery. -- Winston Churchill.
From: harald on 8 Jun 2010 05:51 On Jun 8, 10:08 am, Hayek <haye...(a)nospam.xs4all.nl> wrote: > Surfer wrote: > >http://en.wikipedia.org/wiki/Background-independent > > > <Start extract> > > > The resolution to the hole argument (mainly taken from Rovelli's book) > > is as follows. As GR does not determine the distance between spacetime > > points, how the gravitational and matter fields are located over > > spacetime, and so the values they take at spacetime points, can have > > no physical meaning. What GR does determine, however, are the mutual > > relations that exist between the gravitational field and the matter > > fields (i.e. the value the gravitational field takes where the matter > > field takes such and such value). From these mutual relations we can > > form a notion of matter being located with respect to the > > gravitational field and vice-versa, (see Rovelli's for exposition). > > What Einstein discovered was that physical entities are located with > > respect to one another only, independent of the spacetime manifold. > > This independence is background independence. > > > Since the Hole Argument is a direct consequence of the general > > covariance of GR, this led Einstein to state: > > > "That this requirement of general covariance, which takes away from > > space and time the last remnant of physical objectivity, is a natural > > one, ..."[3] > > > <End extract> > > > If one accepts the above statements, then motion cannot be relative to > > space or the spacetime manifold, as the latter were understood by > > Einstein. > > > However, if we consider the phrase, > > > "....From these mutual relations we can form a notion of matter being > > located with respect to the gravitational field and vice-versa..." > > > then it is clear that matter can be in motion relative to the > > gravitational field, which if considered to be a preferred frame, > > would allow such motion to be considered absolute motion. > > > Even more interesting however is that if Einstein's concept of space > > has had taken away from it "the last remnant of physical objectivity", > > how are we to explain the obvious fact that we move around in 3 > > dimensional space all the time? > > > Isn't the fact that we can do so, sufficient evidence of the physical > > objectivity of 3-dimensional space? > > > Putting two and two together, there seems only one way to reconcile > > these notions. > > > If the space, time and spacetime manifold of GR lack physical > > objectivity, then the 3-dimensional space that we experience as > > physically objective, must be synonymous with the gravitational field. > > > It then follows that absolute motion relative to the field is > > synonymous with absolute motion relative to this physically objective > > space. > > > Surfer > > Some remarks : > > - reading "The End of Time" recently, I was surprised to > learn that a contemporary Mathematician, Kretschmann, > has argued in 1917, that general covariance has no > physical content. seehttp://www.pitt.edu/~jdnorton/papers/decades_re-set.pdf Interesting article! > - the way I see it, is that there is a preferred > background, the average mass distribution of the > universe, but that all attempts to measure it are doomed > to fail because of the nature of the gamma factor, which > has absolute and relative properties. In what way "preferred" if we don't need to prefer it? Probably you meant "absolute". Regards, Harald [..]
From: mpc755 on 8 Jun 2010 06:08 On Jun 8, 2:04 am, Surfer <n...(a)spam.net> wrote: > http://en.wikipedia.org/wiki/Background-independent > > <Start extract> > > The resolution to the hole argument (mainly taken from Rovelli's book) > is as follows. As GR does not determine the distance between spacetime > points, how the gravitational and matter fields are located over > spacetime, and so the values they take at spacetime points, can have > no physical meaning. What GR does determine, however, are the mutual > relations that exist between the gravitational field and the matter > fields (i.e. the value the gravitational field takes where the matter > field takes such and such value). From these mutual relations we can > form a notion of matter being located with respect to the > gravitational field and vice-versa, (see Rovelli's for exposition). > What Einstein discovered was that physical entities are located with > respect to one another only, independent of the spacetime manifold. > This independence is background independence. > > Since the Hole Argument is a direct consequence of the general > covariance of GR, this led Einstein to state: > > "That this requirement of general covariance, which takes away from > space and time the last remnant of physical objectivity, is a natural > one, ..."[3] > > <End extract> > > If one accepts the above statements, then motion cannot be relative to > space or the spacetime manifold, as the latter were understood by > Einstein. > > However, if we consider the phrase, > > "....From these mutual relations we can form a notion of matter being > located with respect to the gravitational field and vice-versa..." > > then it is clear that matter can be in motion relative to the > gravitational field, which if considered to be a preferred frame, > would allow such motion to be considered absolute motion. > > Even more interesting however is that if Einstein's concept of space > has had taken away from it "the last remnant of physical objectivity", > how are we to explain the obvious fact that we move around in 3 > dimensional space all the time? > > Isn't the fact that we can do so, sufficient evidence of the physical > objectivity of 3-dimensional space? > > Putting two and two together, there seems only one way to reconcile > these notions. > > If the space, time and spacetime manifold of GR lack physical > objectivity, then the 3-dimensional space that we experience as > physically objective, must be synonymous with the gravitational field. > > It then follows that absolute motion relative to the field is > synonymous with absolute motion relative to this physically objective > space. > > Surfer 'Ether and the Theory of Relativity by Albert Einstein' http://www-groups.dcs.st-and.ac.uk/~history/Extras/Einstein_ether.html "the state of the [ether] is at every place determined by connections with the matter and the state of the ether in neighbouring places, ... disregarding the causes which condition its state." The state of the aether as determined by its connections with the matter and the state of the aether in neighboring places is the aether's state of displacement. The aether is not at rest when displaced. The aether 'displaces back'. The 'displacing back' is the pressure exerted by the aether. Gravity is pressure exerted by displaced aether towards matter.
From: Hayek on 8 Jun 2010 06:48
harald wrote: > On Jun 8, 10:08 am, Hayek <haye...(a)nospam.xs4all.nl> wrote: >> Surfer wrote: >>> http://en.wikipedia.org/wiki/Background-independent >>> <Start extract> >>> The resolution to the hole argument (mainly taken from Rovelli's book) >>> is as follows. As GR does not determine the distance between spacetime >>> points, how the gravitational and matter fields are located over >>> spacetime, and so the values they take at spacetime points, can have >>> no physical meaning. What GR does determine, however, are the mutual >>> relations that exist between the gravitational field and the matter >>> fields (i.e. the value the gravitational field takes where the matter >>> field takes such and such value). From these mutual relations we can >>> form a notion of matter being located with respect to the >>> gravitational field and vice-versa, (see Rovelli's for exposition). >>> What Einstein discovered was that physical entities are located with >>> respect to one another only, independent of the spacetime manifold. >>> This independence is background independence. >>> Since the Hole Argument is a direct consequence of the general >>> covariance of GR, this led Einstein to state: >>> "That this requirement of general covariance, which takes away from >>> space and time the last remnant of physical objectivity, is a natural >>> one, ..."[3] >>> <End extract> >>> If one accepts the above statements, then motion cannot be relative to >>> space or the spacetime manifold, as the latter were understood by >>> Einstein. >>> However, if we consider the phrase, >>> "....From these mutual relations we can form a notion of matter being >>> located with respect to the gravitational field and vice-versa..." >>> then it is clear that matter can be in motion relative to the >>> gravitational field, which if considered to be a preferred frame, >>> would allow such motion to be considered absolute motion. >>> Even more interesting however is that if Einstein's concept of space >>> has had taken away from it "the last remnant of physical objectivity", >>> how are we to explain the obvious fact that we move around in 3 >>> dimensional space all the time? >>> Isn't the fact that we can do so, sufficient evidence of the physical >>> objectivity of 3-dimensional space? >>> Putting two and two together, there seems only one way to reconcile >>> these notions. >>> If the space, time and spacetime manifold of GR lack physical >>> objectivity, then the 3-dimensional space that we experience as >>> physically objective, must be synonymous with the gravitational field. >>> It then follows that absolute motion relative to the field is >>> synonymous with absolute motion relative to this physically objective >>> space. >>> Surfer >> Some remarks : >> >> - reading "The End of Time" recently, I was surprised to >> learn that a contemporary Mathematician, Kretschmann, >> has argued in 1917, that general covariance has no >> physical content. seehttp://www.pitt.edu/~jdnorton/papers/decades_re-set.pdf > > Interesting article! > >> - the way I see it, is that there is a preferred >> background, the average mass distribution of the >> universe, but that all attempts to measure it are doomed >> to fail because of the nature of the gamma factor, which >> has absolute and relative properties. > > In what way "preferred" if we don't need to prefer it? Probably you > meant "absolute". The preferred background is in these way preferred : - a clock at rest wrt it runs fastest - a rod at rest wrt it is longest. - it helps to understand how the mechanics of relativity work, also called "ontological purpose". - it solves the twin and barn&pole paradoxes. Uwe Hayek. > > Regards, > Harald > > [..] -- We are fast approaching the stage of the ultimate inversion : the stage where the government is free to do anything it pleases, while the citizens may act only by permission; which is the stage of the darkest periods of human history. -- Ayn Rand I predict future happiness for Americans if they can prevent the government from wasting the labors of the people under the pretense of taking care of them. -- Thomas Jefferson. Socialism is a philosophy of failure, the creed of ignorance, and the gospel of envy, its inherent virtue is the equal sharing of misery. -- Winston Churchill. |