Space-Time gravitational field problem

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Discussion Overview

The discussion centers on the nature of gravitational fields in relation to space-time curvature and the resulting orbits of celestial bodies. Participants explore why planetary orbits are elliptical rather than circular, considering implications from general relativity, the cosmological constant, and dark matter. The conversation includes theoretical and conceptual aspects of gravity and space-time, as well as interpretations of general relativity.

Discussion Character

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

Main Points Raised

  • One participant suggests that space-time is deformed into a curvature that should lead to circular orbits, questioning why orbits are elliptical instead.
  • Another participant argues that orbits do not have to be circular, challenging the initial premise and suggesting confusion between simplified models and modern understanding.
  • There is a proposal that elliptical orbits could be influenced by the interaction of multiple celestial bodies or could indicate the presence of dark matter or a cosmological constant.
  • One participant asserts that elliptical and precessing orbits naturally emerge from general relativity, countering the claim that this was overlooked in the theory.
  • Another participant emphasizes that objects move as straight as possible through curved space-time, which contradicts the idea of following circular gravitational field lines.
  • A later reply points out potential contradictions in the initial statements regarding the nature of flat space, uniform gravitational fields, and curved space-time.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between gravitational curvature and orbital shapes, with no consensus reached on the reasons for elliptical orbits or the implications of general relativity.

Contextual Notes

Participants reference various models of gravity and space-time, indicating potential limitations in understanding the implications of general relativity and the nature of gravitational fields. There are unresolved assumptions regarding the definitions of curvature and the effects of multiple celestial bodies.

Foxdove
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Space-Time is deformed from a uniform gravitation field to one that is compressed inward so as to form a curvature. That curvature is uniform and can be understood as a series of decreasing diameters of circular field lines. If that is the case, then why are the planet's orbits elliptical and not circular? They follow the curvature of the gravitational field lines, which are circular. Are the orbits elliptical due to a composite interaction of an infinite number of celestial bodies in the universe? Are the elliptical orbits a sign of the cosmological constant or perhaps if not taken into consideration the illusion of the mysterious dark matter, yet undetected? If the elliptical orbits are a result of the motion of the celestial bodies, then why was this overlooked or skirted around (no pun) in the General Theory of Relativity?
 
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Foxdove said:
can be understood as a series of decreasing diameters of circular field lines. If that is the case
That is not the case; perhaps your questions are based in confusion between modern knowledge and oversimplified cartoons of modern knowledge. Nothing in GR nor Newtonian gravity would say that orbits have to be circular in the first place.
 
Foxdove said:
Space-Time is deformed from a uniform gravitation field to one that is compressed inward so as to form a curvature. That curvature is uniform and can be understood as a series of decreasing diameters of circular field lines. If that is the case, then why are the planet's orbits elliptical and not circular? They follow the curvature of the gravitational field lines, which are circular. Are the orbits elliptical due to a composite interaction of an infinite number of celestial bodies in the universe? Are the elliptical orbits a sign of the cosmological constant or perhaps if not taken into consideration the illusion of the mysterious dark matter, yet undetected? If the elliptical orbits are a result of the motion of the celestial bodies, then why was this overlooked or skirted around (no pun) in the General Theory of Relativity?

You're using a model where gravity is the curvature of space as you move through it. This isn't right; most of the visible effect of gravity is due to an acceleration which is experienced even for slow-moving or static objects, and can be considered as being due to the curvature of paths in space with respect to time. For a spherically symmetrical situation, the curvature of space is of the same magnitude, but the rate at which something moves through space is typically tiny (as a fraction of c) compared with the rate at which it moves through time, so the dominant effect is the curvature with respect to time.
 
Are the elliptical orbits a sign of the cosmological constant or perhaps if not taken into consideration the illusion of the mysterious dark matter, yet undetected? If the elliptical orbits are a result of the motion of the celestial bodies, then why was this overlooked or skirted around (no pun) in the General Theory of Relativity?
Elliptical, and precessing orbits emerge naturally in GR. You have been misinformed.
 
Last edited by a moderator:
Space-Time is deformed from a uniform gravitation field to one that is compressed inward so as to form a curvature.

This statement seems self contradicting... there is flat space (without gravity, as in special relativity), a uniform gravitational field (as in the equivalence principle, from an infinite plane of mass) and then typical curved spacetime when gravity from finite sized masses is present.
 
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