Galaxies strung like necklace beads

Some of the confusion might arise from the difference between gravity WAVES, assuming such a thing exists which is a gigantic assumption, and the force of gravity itself.

Gravity WAVES, again assuming they exist, would certainly propagate at C.

Nonetheless the fact that the basic force of gravity is instantaneous to within our ability to measure it, has been known for centuries. Our own solar system would fly apart pretty quicklyif there were any noticable delay in the force of gravity acting on each of the planets from the sun and that's been known at least since LaPlace.

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gungasnake wrote:

Some of the confusion might arise from the difference between gravity WAVES, assuming such a thing exists which is a gigantic assumption, and the force of gravity itself.

Gravity WAVES, again assuming they exist, would certainly propagate at C.

Nonetheless the fact that the basic force of gravity is instantaneous to within our ability to measure it, has been known for centuries. Our own solar system would fly apart pretty quicklyif there were any noticable delay in the force of gravity acting on each of the planets from the sun and that's been known at least since LaPlace.

The force of gravity propagates at the speed of light. LaPlace died in the early 1800s, long before the Theory of Relativity, so obviously, he'd be unaware of the speed of light limit. I urge you not to proffer expert opinions on things that you don't know about.

By the way, if the sun disappeared this instant, the earth would go flying off in space at the same time the sky went dark (about 8 and a half minutes).

Rap

2. Gravity and light do not act in parallel directions

There is no cause to doubt that photons arriving now from the Sun left 8.3 minutes ago, and arrive at Earth from the direction against the sky that the Sun occupied that long ago. But the analogous situation for gravity is less obvious, and we must always be careful not to mix in the consequences of light propagation delays. Another way (besides aberration) to represent what gravity is doing is to measure the acceleration vector for the Earth’s motion, and ask if it is parallel to the direction of the arriving photons. If it is, that would argue that gravity propagated to Earth with the same speed as light; and conversely.

Such measurements of Earth’s acceleration through space are now easy to make using precise timing data from stable pulsars in various directions on the sky. Any movement of the Earth in any direction is immediately reflected in a decreased delay in the time of arrival of pulses toward that direction, and an increased delay toward the opposite direction. In principle, Earth’s orbit could be determined from pulsar timings alone. In practice, the orbit determined from planetary radar ranging data is checked with pulsar timing data and found consistent with it to very high precision.

How then does the direction of Earth’s acceleration compare with the direction of the visible Sun? By direct calculation from geometric ephemerides fitted to such observations, such as those published by the U.S. Naval Observatory or the Development Ephemerides of the Jet Propulsion Laboratory, the Earth accelerates toward a point 20 arc seconds in front of the visible Sun, where the Sun will appear to be in 8.3 minutes. In other words, the acceleration now is toward the true, instantaneous direction of the Sun now, and is not parallel to the direction of the arriving solar photons now. This is additional evidence that forces from electromagnetic radiation pressure and from gravity do not have the same propagation speed.

NO it wouldn't. It would go flying off immediately.

The first principle is that you must not fool yourself - and you are the easiest person to fool.
Richard Feynman, Caltech commencement address, 1974

If gravity travels as light does is it distorted by gravity as light is.

I think gravity is instantaneous but I know no arguments to support the contention. The intensity of light falls off with distance and physical objects impede it.

Do physical objects impede gravity.

I read somewhere that a photon collector at the bottom of a deep mine occasionally registered a hit.

Gravity creates a geodesic in the geometry.

Rap

In a non-Euclidian (in this case hyperbolic) universe that geodesic is not quite straight as predicted by general relativity and confirmed by observing normally occluded quasars during solar ellipses.

Brandon9000 wrote:

gungasnake wrote:

Some of the confusion might arise from the difference between gravity WAVES, assuming such a thing exists which is a gigantic assumption, and the force of gravity itself.

Gravity WAVES, again assuming they exist, would certainly propagate at C.

Nonetheless the fact that the basic force of gravity is instantaneous to within our ability to measure it, has been known for centuries. Our own solar system would fly apart pretty quicklyif there were any noticable delay in the force of gravity acting on each of the planets from the sun and that's been known at least since LaPlace.

The force of gravity propagates at the speed of light. LaPlace died in the early 1800s, long before the Theory of Relativity, so obviously, he'd be unaware of the speed of light limit. I urge you not to proffer expert opinions on things that you don't know about.

LaPlace was well aware that light speed wasn't infinite. Observations by Romer and Huygens a century before demonstrated that light speed was in the region of 250,000 Km/s (c is about 3X10^10 cm/s). What LaPlace did not know was that the universe wasn't Euclidean, that space was warped by gravity into a nonEuclidian geometry. Moreover, at the time of LaPlace there was a great discussion among pure mathematicians on the necessity of Euclids fifth postulate to create geometry. The great Gauss in the late 18th and early 19th century considered this premise, but withheld publication leaving the nonEuclidian geometry claim to Rieman and Lobachesky (sp). Their geometries were developed by taking the fifth postulate in different directions (something that Gauss had already done, but never published).

As an aside light (electromagnetic radiation) travels in waves and at the time of LaPlace that was not known, as the accepted theory of the time was Newton's idea that light was corpuscular.

By the way, if the sun disappeared this instant, the earth would go flying off in space at the same time the sky went dark (about 8 and a half minutes).

Rap

....The fact that gravity (and magnetic force for that matter) are typically described as "fields" is due to the instantaneous rate of propagation....

That fellow Einstein suits his convenience. Every year he retracts what he wrote the year before.

Mea culpa roz. Simon Pierre Laplace predated Michelson-Morley so he couldn't have known that c was independent of the observers velocity. But he was aware that light had a velocity. He did; however, live in interesting times both politically and scientifically and will be remembered for nothing less than stable solutions to the three body problem (L1, L2, L3, L4, & L5).

An interesting missive on General Relativity exists at the St andrews math site. The missive indicates that Einstein wasn't in a vacuum, nor was he certain as reflected in his own quote about himself in 1915

Quote:

That fellow Einstein suits his convenience. Every year he retracts what he wrote the year before.

.

BTW Einstein recognized help on the development of the general relativity to pretty much every mathematician and mathematical physicist in Gottengen from 1911 to 1919---and Hilbert too.

Rap

Science 17 January 2003:
Vol. 299. no. 5605, pp. 323 - 324
DOI: 10.1126/science.299.5605.323a

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News of the Week
PHYSICS:
Confirmation of Gravity's Speed? Not So Fast
Robert Irion

SEATTLE--Last week, the media were awash with reports that astronomers had confirmed Einstein's prediction that gravity crosses space at the speed of light. Not necessarily, say some physicists. The work described at the annual meeting of the American Astronomical Society here, they warn, may have been nothing more than a test of the speed of light itself.

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