The speed of gravity revisited (nueva revisión de la velocidad de la gravedad)
Posted by Albert Zotkin en abril 10, 2013
Una breve presentación de estos cuatro relevantes comentaristas científicos:
1. Tom Van Flandern, era un prestigioso astrónomo americano especializado en mecánica celeste, y entre otras muchas cosas, contribuyó notablemente a mejorar el GPS.
2. Steve Carlip es un prestigiso profesor de física en la Universidad de California, Davis. Son destacables sus papers en gravedad cuántica (2+1) dimensional, fundamentos gravitacionales cuánticos de la termodinámica de los agujeros negros, o en triangulaciones dinámicas causales.
3. Tom Roberts, PhD en fisica, prolífico comentarista en usenet, y acérrimo defensor de la relativdad Einsteniana, trabaja en Fermilab, es autor, entre otros trabajos, de “What is the experimental basis of Special Relativity?”
4. Juan R. González-Álvarez. Cientifico español, con una sólida base académica. Estudió físca y quimica en la Universidad de Vigo. Trabajó en temas científicos en el Ilustre Colegio de Químicos de Galicia y fue investigador asistente de bioquímica de las Rias en el CSIC, participó en varios simposios, conferencias e informes. Puedes encontrar algunos de sus papers en FQXi Community, por ejemplo este.
|1. Albertito:||6 mar 2008, 22:41|
There are evidences showing that in Solar system, the speed of gravity is many orders of magnitude higher than the speed of light. But, what must we understand by speed of gravity?. Aetherists often claim that gravity are longitudinal waves, whereas light are transverse waves through the aether. We know that in any medium longitudinal waves travel faster than transverse waves. We can find that longitudinal speed, cL, and transverse cS, in a medium, with Young’s modules E, Poison’s ratio v and mass density d0, are
We also know there exists a relation between those elastic constants, as
where G is shear modulus and K is bulk modulus. So, we have
Therefore, for a Poison’s ratio of v=1/2, it would result an infinite longitudinal speed. In general we have
This quadratic relation suggests it is a universal constant for vacuum. This suggests
where R is a scale parameter and tp is Planck time, or
where lp is Planck length
So, for a speed of light being cS=c, it would yield
which is roughly
if R is meaningfully larger than lp.
If we define R = R_h (Hubble radius), then the speed of gravity, there where the local speed of light is c, would be
it is saying it would be a very superluminal speed (i.e. infinite velocity, for practical purposes).
|2. Tom Roberts:||7 mar 2008, 17:44|
> There are evidences showing that in Solar system,
> the speed of gravity is many orders of magnitude higher
> than the speed of light.
Sure. But this is MODEL DEPENDENT. In the model of Newtonian
|3. Juan R. González-Álvarez:||7 mar 2008, 20:17|
Tom Roberts wrote on Fri, 07 Mar 2008 15:44:38 +0000:
> Albertito wrote:
>> There are evidences showing that in Solar system, the speed of gravity
>> is many orders of magnitude higher than the speed of light.
> Sure. But this is MODEL DEPENDENT. In the model of Newtonian
> gravitation, gravity propagates INSTANTLY (i.e. with infinite speed).
Being a AAAD theory, nothing propagates in Newtonian gravitation.
Gravitational waves travel at c like changes in spacetime geometry do.
GR gives better results (i would not say “MUCH”) for purely relativistic
|4. Tom Roberts:||8 mar 2008, 04:11|
Juan R. González-Álvarez wrote:
> Tom Roberts wrote on Fri, 07 Mar 2008 15:44:38 +0000:
>> In the model of Newtonian
>> gravitation, gravity propagates INSTANTLY (i.e. with infinite speed).
> Being a AAAD theory, nothing propagates in Newtonian gravitation.
> speaking about infinite speed is misleading also. Infinite speed of what?
Infinite speed of gravity, of course. You are just saying the same thing
Of course — gravitational waves _ARE_ changes in spacetime geometry.
Hmmm. If you mean NG is accurate in the non-relativistic regime, then
Where “correct” means within the appropriate experimental resolution.
If this is not a typo it makes no sense. If it is a typo, writing “NG”
Some of those “difficulties” are merely complications that are
|5. Juan R. González-Álvarez:||8 mar 2008, 14:51|
Tom Roberts wrote on Sat, 08 Mar 2008 02:11:31 +0000:
> Juan R. González-Álvarez wrote:
>> Tom Roberts wrote on Fri, 07 Mar 2008 15:44:38 +0000:
>>> In the model of Newtonian
>>> gravitation, gravity propagates INSTANTLY (i.e. with infinite speed).
>> Being a AAAD theory, nothing propagates in Newtonian gravitation.
>> speaking about infinite speed is misleading also. Infinite speed of
> Infinite speed of gravity, of course.
Gravity in AAAD has not a property called “speed”, of course.
No, i am just saying the contrary: in AAAD nothing propagates including
Of course “like… do” could be emphasized as “_LIKE_… _DO_”.
Hmmm. Crizing a non-relativistic theory because fails on relativistic
Sure perihelions for Mercury, the Shapiro time delay, bending of EM
As explained before NG does not exactly fail to explain relativistic
This table has been clearly done to confound readers.
Only a genious could see it is a typo, thanks by kindly correction!
You are wrong. The NG limit does not exist and the several Newtonian-like
They they are “inescapable” when you decide to introduces it on physics,
Those problems are well-known and studied on literature. Several
But NG can be quantized without the further problems of GR!
|6. Tom Roberts:||8 mar 2008, 22:26|
Juan R. González-Álvarez wrote:
> Tom Roberts wrote on Sat, 08 Mar 2008 02:11:31 +0000:
> Hmmm. Crizing a non-relativistic theory because fails on relativistic
> regimes is very old relativistic tactic but is clearly unfair.
Criticizing a non-relativistic theory for disagreeing with experiments
Hmm. The usual meaning of “relativistic effects” is that they are
There is no “relativistic phenomena” involved in ANY of the experiments
Ok. I’m not the one pushing NG, you are. Note its “range of validity”
The “confounding” is all yours.
That is a very silly way to do this. And your denominator is outrageous
I merely remark that neither Uncle Al nor you have ever responded to my
Whyever would that matter? — who cares about a demonstrably incorrect
|7. Juan R. González-Álvarez:||9 mar 2008, 18:13|
Tom Roberts wrote on Sat, 08 Mar 2008 20:26:21 +0000:
> Juan R. González-Álvarez wrote:
>> Tom Roberts wrote on Sat, 08 Mar 2008 02:11:31 +0000: Hmmm. Crizing a
>> non-relativistic theory because fails on relativistic regimes is very
>> old relativistic tactic but is clearly unfair.
> Criticizing a non-relativistic theory for disagreeing with experiments
> is not “unfair” at all.
English may be not your natural language.
Completely wrong. E.g. anomaly Mercury perihelion is explained by two
One of your usual FALSE accusations tactics. Read i exactly said.
No SERIOUS scientist would apply a theory outside its range of
In the physics community it is rather common to provide detailed replies
“Yours is a statement of profound ignorance in all of its parts.”
|8. Tom Van Flandern:||1 abr 2008, 19:17|
Tom Roberts” <tjroberts…@sbcglobal.net> writes:
> [Roberts]: In the model of GR, gravity does not propagate at all, but
> changes in gravity propagate with speed c.
That is directly in contradiction to experiment and observations. Binary
True but irrelevant because GR is a field theory and describes only the
The "speed of gravity" is not a model-dependent concept except at the
Quit making up nonsense. The published papers are in references (A),
The comparison of theory with observations is not relevant? How absurd!