How does curved spacetime result in an effective gravitational force?

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Discussion Overview

The discussion centers on the relationship between curved spacetime and gravitational force, exploring concepts from general relativity (GR) and the implications of mass warping spacetime. Participants examine analogies, the nature of gravitational force, and the potential existence of gravitons, as well as the limitations of current theories.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants express confusion about how curved spacetime leads to an effective gravitational force, questioning the adequacy of analogies like the bowling ball on a trampoline.
  • One participant argues that in GR, there is no gravitational force, as free-falling objects move along straight paths in curved spacetime.
  • Another participant uses the analogy of airplanes flying along longitude lines on a spherical Earth to illustrate how paths can converge without a force acting on them.
  • Some participants suggest that the existence of a graviton would not disprove GR, as they represent different frameworks (quantum mechanics vs. classical physics) for understanding gravity.
  • There are mentions of alternative explanations for gravity, such as the Higgs field or string theory, and the idea that gravity might arise from acceleration or other fundamental processes.
  • One participant describes a conceptual model involving water pressure in a sealed box to illustrate how spacetime might exert pressure on objects in space.
  • Another participant references Einstein's work, discussing how light is influenced by both mass and spacetime curvature, but there is contention over whether these are distinct effects or two descriptions of the same phenomenon.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the nature of gravitational force in relation to curved spacetime, with multiple competing views and ongoing debates about the adequacy of analogies, the implications of GR, and the potential existence of gravitons.

Contextual Notes

Some participants note that the understanding of gravity remains incomplete, with unresolved questions about the fundamental nature of mass, energy, space, and time. There are also references to the limitations of GR in extreme conditions, suggesting that it may not provide a complete explanation of gravitational phenomena.

  • #31
[/QUOTE] From A.T. Nothing is stationary or at rest in spacetime. Everything moves trough space or time or both.[/QUOTE]

Getting your head around the time part of space-time was the biggest hurdle for me. Remember, the only way to not be moving in time (not including black hole event horizons) is to be moving at the speed of light.
 
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  • #32
exactly Pete62 , not only at the speed of light but also at the 'speed' of 'stationary dimension' . By this i mean that if we consider the 'parallel worlds' which have been mentioned so many times in 'quantum physics' , we even would not need any 'speed' , you can 'move' or 'enter' easily to lot of other 'worlds, and why not to 'other' planets or galaxies , without spending energy to produce 'speed' . In my opinion the theory of einstein about the 'curved ' space-time , has stopped all sort of 'different considereations' of space-time concept and has made the physics to remain at a stagnation point. Since then we don't search elswhere to find some other sort of explanations of the 'physics' , 'quantum physics or rather the 'metaphysics' and why not the 'metarealism'
 
  • #33
I think the original question has been answered but I thought I'd add my own analogy in case it helps the poster more.

The geometric aspect of acceleration/force in GR is explained more or less by our inability to "see" the "temporal dimension". By this I mean the object may appear to be taking a linear path to us only because we cannot see its path "in time".

As always, let's consider Flatland. There's two stick figure Flatlanders here. There is a big depression in Flatland and one of the sticks is down in the depression, moving out. The other stick is in a flat region watching the other stick coming toward him. These Flatlanders cannot perceive nor conceive of the "up" direction, however the stick at the bottom of the depression is doing most of his motion "upward". The observing stick, then, sees the traveler moving very slowly at first, then faster and faster as the traveler moves out of the depression. The up component of the traveler's velocity is decreasing as its rightward velocity component is increasing. The whole time the magnitude of the traveler's velocity was actually constant, but it appeared to change to the observer because s/he could not see the decreasing velocity in the "up" direction, but only the increasing velocity in the "rightward" direction.

Does that make sense?
 

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