Gravity force: Isn't it just the shape of space?

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Discussion Overview

The discussion centers on the nature of gravity, specifically whether it is fundamentally a result of the shape of space (or spacetime) influenced by mass, or if it should be understood through the lens of theoretical force particles known as "gravitons." The conversation explores both classical and quantum perspectives on gravity, touching on concepts from general relativity and quantum field theory.

Discussion Character

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

Main Points Raised

  • Some participants propose that gravity is a geometric result of masses bending the shape of space, aligning with the classical view of general relativity.
  • Others argue that the existence of gravitons is necessary from a quantum field theory perspective, suggesting a different framework for understanding gravitational interactions.
  • A participant mentions the need to compare experimental predictions of geometric theories with those of quantum gravity theories, indicating uncertainty about their equivalence.
  • There is a suggestion to remain open-minded and not become too entrenched in one viewpoint, emphasizing the importance of observational confirmation for any theory.
  • References to Kaluza-Klein theories are made, which attempt to connect spacetime geometry with gauge symmetries, proposing a higher-dimensional framework for understanding gravity and electromagnetism.

Areas of Agreement / Disagreement

Participants express differing views on whether gravity should be understood primarily as a geometric phenomenon or through the existence of force particles. No consensus is reached, and multiple competing perspectives remain in the discussion.

Contextual Notes

Participants acknowledge the limitations of their understanding and the need for further exploration of the predictions made by different theories of gravity. There is an emphasis on the role of experimental validation in determining the validity of these theories.

chris4642
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Isn't the force of gravity just a result of the shape of space as it is affected by masses within it? Why is it believed that it is a force associated with theoretical force particles "gravitons"? I can understand that the electric or magnetic force is a product of particles with fundamental interactions, but isn't gravity different? I always imagined gravitational force being more a geometric result of masses bending the shape of space. I am only in Physics 2, undergraduate level, but this is a question I have been thinking about for months now. Should I be thinking about this in a different paradigm?
 
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Yes the gravity has to do with the geometry of spacetime. However QFT doesn't work like that, and so that's why you need to ask for a graviton to exist. And in the standard model you don't only have force mediator for the EM interactions (photon), you do have for the weak and strong interactions too (W's, Z and gluons).
Also there are people trying to connect the spacetime geometry to the gauge symmetries ones. For an example one could have a look at Kaluza Klein theories, trying to get a 5D spacetime and compactify the 5th dimension to a perfect circle- the result is to get gravity to the 4D and electromagnetism from the compactification (together with an extra scalar field).
 
chris4642 said:
Isn't the force of gravity just a result of the shape of space as it is affected by masses within it?

If you replace space with space-time, the above is the classical view of general relativity. It's a good place to start learning GR.

Why is it believed that it is a force associated with theoretical force particles "gravitons"?

That comes from a non-classical view of quantum gravity. What we need to ask here is "are the experimental predictions of this theory any different" from the former theory. I'm afraid I don't know the answer for sure.

I can understand that the electric or magnetic force is a product of particles with fundamental interactions, but isn't gravity different? I always imagined gravitational force being more a geometric result of masses bending the shape of space. I am only in Physics 2, undergraduate level, but this is a question I have been thinking about for months now. Should I be thinking about this in a different paradigm?

I would suggest sticking with your current belief as representing the prevailing picture of gravity in the textbooks and literature at the current time, but keep in mind the fundamental principle that it should be observation that ultimately decides the issue, and that no theory, however elegant, can stand unless it's confirmed by experiment.

To make a decision between the two theories, it becomes necessary to understand what the two theories (the geometric theory and the spin 2 theory) actually predict. I'm reasonably familiar with what the curved space-time theory predicts, but not so familiar as to what the spin-2 theories predict.

Two widely respected papers with somewhat different views on the topic of whether the spin-2 theory has equivalent predictions to GR:

http://arxiv.org/abs/astro-ph/0006423
http://xxx.lanl.gov/abs/gr-qc/0409089

The bottom line - I would personally recommend that you keep on as you have been, but try to keep an open mind and not get totally "locked into" one viewpoint as much as you can.
 

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