Gravitation Speed/Acceleration/Velocity

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    Gravitation
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Discussion Overview

The discussion revolves around the speed of gravitational signals, comparing it to the speed of light, and exploring the nature of gravity in a vacuum. Participants examine theoretical implications, potential experiments, and the propagation of gravitational waves in various contexts.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant questions how long it takes for a gravitational signal to travel from the Sun to Earth, contrasting it with the time light takes.
  • Another participant asserts that the speed of gravity is the same as the speed of light and that disturbances like gravity have a velocity, while space itself does not.
  • Some participants reference General Relativity (GR) and its experimental success, suggesting it supports the idea that gravity propagates at the speed of light.
  • There is a discussion about the implications of the Sun suddenly disappearing, with one participant noting that such a scenario violates conservation laws, while another suggests a hypothetical explosion of the Sun would allow gravity changes to propagate at light speed.
  • One participant introduces the concept of gravitational waves, likening them to wave-like disturbances in spacetime that propagate at the speed of light.
  • Another participant expresses a view that gravitational waves could be understood as fixed standing waves of a 'Pure Fluid', raising questions about how this perspective could lead to experimental tests of gravity's speed.
  • There is a challenge regarding the definition of empty space and the nature of gravitational communication in the absence of matter, questioning what can be observed in such conditions.

Areas of Agreement / Disagreement

Participants express differing views on the nature of gravitational signals and their propagation. While some agree on the speed of gravity being equal to the speed of light, others raise questions about the implications of gravity in a vacuum and the conditions under which gravitational communication occurs. The discussion remains unresolved with multiple competing perspectives.

Contextual Notes

Participants highlight the need for careful phrasing when discussing the speed of gravity and the conditions under which it operates. There are unresolved questions about the nature of empty space and gravitational signals in the absence of matter.

Olias
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Light leaves the Sun, it takes *8 minutes to reach earth, how long does a Gravitational Signal take to get from the Sun to Earth?

Does Space have a Velocity?..what is the derived speed of Gravity through a near Vacuum, one that has no Matter , actually does gravity signals become null?
 
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The speed of gravity is the same as the speed of light, and likewise is constant. Space doesn't have a velocity, disturbances such as gravity have a velocity. Should the sun suddenly disappear from the sky, we would see it and feel it happen at exactly the same time.
 
That's according to GR, which has met all experimental/observational tests so far with flying colours.

Olias, can you think of an experiment which, in principle, could test whether the speed of gravity is c or not?
 
Gravity has no more problem propagating through empty space than light does.

As far as the speed of gravity goes, one has to be careful how one asks the question. One might ask "what would happen if the sun would suddenly disappear". The answer is that "The sun can't suddenly disappear"! (It violates some important conservation laws).

But one can sensibly ask "what would happen if I blew up the sun". The answer is that the change in gravity would propagate outwards at the speed of light.

There are other questions one could ask as well, but this is probably a long enough response for now.
 
That propagation being the essence of gravity waves. Imagine a binary pulsar system. The motion of two massive bodies around each other would mean that the strength of the gravitational field is changing in a given direction. In GR terms, this means that that the amount of curvature of spacetime is changing. As you can visualize these wave-like disturbances radiating outward, it's easy to make the comparison with light and see why gravity should travel at the finite speed of c. (btw, that wasn't directed at you pervect, just an addendum on my previous post for Olias)
 
Nereid said:
That's according to GR, which has met all experimental/observational tests so far with flying colours.

Olias, can you think of an experiment which, in principle, could test whether the speed of gravity is c or not?

Yes, I actually am leaning towards Gravitational Waves being the fixed standing waves of a 'Pure Fluid', which are Low-Energy, obviously the Lowest Energy Possible, Absolute.
 
Olias said:
Yes, I actually am leaning towards Gravitational Waves being the fixed standing waves of a 'Pure Fluid', which are Low-Energy, obviously the Lowest Energy Possible, Absolute.
How do these concepts help you devise an experiment from which you can determine the 'speed of gravity'?
 
pervect said:
Gravity has no more problem propagating through empty space than light does.

Lets define empty space?..whats Gravititating?..if there is "nothing" there to communicate, what do we look for..is there a transformation of Gravitational Signals, ie without, er... 'Matter Content'?

should ask if Photon goes from one atom to another, then this is a 3-D spacetime (two-body-communication)..what about a single photon without any atoms in near vicinity to communicate, won't the photon get confused!
 
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