Equivalence principle + light speed postulate =

Click For Summary

Discussion Overview

The discussion revolves around the relationship between Einstein's equivalence principle and the constancy of the speed of light, particularly in the context of gravitational propagation. Participants explore whether these concepts imply a constant speed of gravitational propagation in a vacuum, examining both theoretical implications and mathematical formulations.

Discussion Character

  • Exploratory
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants suggest that combining the equivalence of gravitational and non-gravitational acceleration with the constancy of light speed should imply a constant speed of gravitational propagation.
  • Others argue that it is unnecessary to invoke the constant velocity of light or relativity to derive gravitational acceleration, relying instead on Newton's law of gravitation and the equality of inertial and gravitational mass.
  • A participant questions how the previous claims demonstrate that the velocity of gravitational propagation is constant.
  • Some participants propose that any constant, such as gravitational acceleration (g), can be used in the mathematical framework, suggesting that the conclusions remain consistent regardless of the constant chosen.
  • There is a challenge regarding the absence of a defined constant of velocity in Hall's equations, indicating a need for clarification on this point.
  • One participant hypothesizes that the combination of the equivalence principle and light speed constancy should yield a constant gravitational propagation speed, reiterating the need for a clear definition of propagation speed.

Areas of Agreement / Disagreement

Participants express differing views on the necessity of light speed in deriving gravitational propagation speed, leading to an unresolved debate regarding the implications of the equivalence principle and the constancy of light speed.

Contextual Notes

Participants highlight the dependence on definitions of constants and the mathematical relationships involved, with some unresolved questions about the propagation speed of gravity and its representation in existing equations.

Loren Booda
Messages
3,115
Reaction score
4
It seems to me that Einstein's equivalence of gravitational acceleration and non-gravitational acceleration, when combined with his constancy of light speed in vacuuo, should yield a constancy of gravitational speed in vacuuo.
 
Physics news on Phys.org
It's not necessary to appeal to the constant velocity of light or relativity in general.

F= G(gravitational mass A)(gravitational mass B)/r2

(inertial mass A)(acceleration of A)= F so as long as inertial mass= gravitational mass:

acceleration of a= G(gravitational mass B)/r2, a constant.
 
Last edited by a moderator:
How does this show that the velocity of gravitational propagation is constant?
 
pick a constant, any constant. if you don't like c, take g. the math still works out to the same conclusion.
 
So where is the constant of velocity in Hall's equations?
 
Chronos said:
pick a constant, any constant. if you don't like c, take g. the math still works out to the same conclusion.
All you have proven is that the acceleration due to gravity is dependent only upon the object causing the accelerationa and not the accelerated object. Loren's question has to do with the propagation speed of gravity. Perhaps Loren could explain more clearly what is meant by this.
 
The speed of light propagation is c. Propagation speed in general may be finite or infinite. Simply put, propagation speed is distance per the time that particle action takes to travel over that distance.

Here I hypothesize that
Einstein's equivalence of gravitational acceleration and non-gravitational [inertial] acceleration, when combined with his constancy of light [propagation] speed in vacuuo, should yield a constancy of gravitational [propagation] speed in vacuuo.
 

Similar threads

Undergrad Constancy of Speed of Light: Postulate or Assumption?
  • · Replies 78 ·
3
Replies
78
Views
7K
Undergrad Speed of light one more time
  • · Replies 5 ·
Replies
5
Views
2K
High School Speed of Light in Free Space - Einstein's Second Principle
  • · Replies 8 ·
Replies
8
Views
3K
Graduate Is the constancy of c a postulate or a derivable theorem?
  • · Replies 13 ·
Replies
13
Views
1K
Undergrad How to rule out that the speed of light was different in the past?
  • · Replies 76 ·
3
Replies
76
Views
7K
Undergrad Bending of Light Along the Sun: Explaining Half w/ Equivalence Principle
  • · Replies 15 ·
Replies
15
Views
3K
Undergrad The Einstein Clock aka Light Clock
  • · Replies 34 ·
2
Replies
34
Views
5K
Undergrad SR flat Lorentzian manifold and Anderson simultaneity convention
  • · Replies 16 ·
Replies
16
Views
2K
Undergrad The Equivalence Principle as a Starting point of GR
  • · Replies 44 ·
2
Replies
44
Views
7K
Graduate Why is the Principle of Equivalence Necessary for GTR?
  • · Replies 9 ·
Replies
9
Views
2K