Using gravity to explain gravity

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Discussion Overview

The discussion revolves around the explanation of gravity, particularly the conventional relativistic model that uses the analogy of a rubber sheet to illustrate the curvature of space-time. Participants explore the implications and limitations of this analogy, questioning whether it adequately explains the nature of gravity without presuming the existence of an attractive force.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • Some participants express confusion about the rubber sheet analogy, suggesting it may rely on an intuitive understanding of gravity rather than providing a true explanation.
  • Others argue that the analogy serves as a useful tool for conceptualizing complex ideas, despite its limitations.
  • A participant emphasizes that the rubber sheet is not an explanation but rather an analogy, pointing out that gravity results from bodies following the straightest possible lines in curved space-time.
  • There is a question about whether the principle of bodies following straight lines is axiomatic or if there are deeper explanations for it.
  • One participant introduces a thought experiment involving ants on a sphere to illustrate how following geodesics can lead to apparent attraction, likening this to gravitational effects.
  • Another participant challenges the significance of the ant analogy, questioning why space-time must be considered curved and suggesting that a straight line could simply be defined as the shortest distance between two points.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the adequacy of the rubber sheet analogy or the nature of gravity. Multiple competing views are presented, with some defending the analogy while others critique its effectiveness in explaining gravitational phenomena.

Contextual Notes

Participants highlight limitations in the analogy, such as its reliance on intuitive concepts and the distinction between spatial and space-time curvature. There are unresolved questions regarding the foundational principles of gravity and the nature of straight lines in curved space-time.

  • #31
pmb wrote:
That is not an explanation. That is a description.
By my understanding this is true for most of the threats I have read here. And it is of no surprise. Einstein himself has only given descriptions and no explanations regarding relativity.

Einstein's space-time is a typical example of a so called "geometrized theory". It is an elegant mathematical presentation but hides the view to the physics behind.

Roman Sexl has once given the direction for a physical explanation of gravity: We know very precisely that the speed of light is reduced in a gravitational potential. If this is applied to a photon which passes the sun (e.g. the sun eclipse observation of 1922 which made Einstein famous), then the photon is subject to a classical refraction in the gravitational field. If this is computed, the result is exactly the one which was observed. There is absolutely no need to use space-time curvature to explain this.

If this refraction process is applied to the internal oscillations within an elementary particle, the particle's acceleration towards the source of gravity is also exactly what we observe. With conventional space-time. It also covers the relativistic aspects of it (like the perihelion shift of the planets.)

For details refer to http://www.ag-physics.org/gravity
 
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