Is Gravity a Fundamental Force or an Emergent Effect?

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Discussion Overview

The discussion centers on the nature of gravity, questioning whether it is a fundamental force or an emergent effect. Participants explore concepts from general relativity (GR) and quantum theory (QT), considering implications for the understanding of gravity in both classical and quantum contexts.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants argue that GR eliminates the notion of gravity as a force, suggesting it is instead an effect of spacetime curvature.
  • Others propose that a quantum theory of gravity must exist, which would include a graviton as a force carrier, similar to other fundamental interactions.
  • One participant notes that current quantum theory (QT) is based on flat spacetime, but questions whether gravity can be treated as a force in a curved spacetime context.
  • Another participant counters that quantum field theory can indeed be applied in curved spacetime, citing Hawking radiation as an example.
  • There is a suggestion that gravity might be an effective description, akin to phonons in sound waves, depending on whether it is viewed as emergent or fundamental.

Areas of Agreement / Disagreement

Participants express differing views on the nature of gravity, with no consensus reached on whether it is a fundamental force or an emergent effect. The discussion remains unresolved, with multiple competing perspectives presented.

Contextual Notes

Some claims depend on specific interpretations of quantum theory and general relativity, and there are unresolved questions regarding the implications of treating gravity in curved versus flat spacetime.

nytmr24
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If what we perceive as the force of gravity is really just the effect of curvature of spacetime, why do theorists
hypothesize the graviton as the force carrier for gravity? I thought that GR does away with the notion that gravity is a "force." So, is gravity a force or is it merely an effect?
 
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nytmr24 said:
I thought that GR does away with the notion that gravity is a "force."

GR is a classical theory, not a quantum theory. Many physicists believe that a quantum theory of gravity must exist that underlies GR (i.e., for which GR is the classical limit), and in such a theory, there should be a level of description at which gravity works similarly to the other three known fundamental interactions, i.e., it should have a "force carrier" particle, which is called the graviton.
 
Current QT stands on flat space-time. Natural extension to gravity is force particle as we deal with Newton's gravitation force up to 19th century.
However, after thorough study of QT and GM fusion, in future as you say we may be able to build QT on curved space-time background where gravitation is not perceived as force.
 
sweet springs said:
Current QT stands on flat space-time.

Not necessarily. Quantum field theory can be done in a curved background spacetime; for example, this is how Hawking radiation has been treated pretty much since its discovery.

sweet springs said:
in future as you say we may be able to build QT on curved space-time background

This isn't "in future". It's been done for several decades now. See above.
 
Yes it was introduced by Hawking, but not thoroughly as I hope.
 
Last edited:
PeterDonis said:
GR is a classical theory, not a quantum theory. Many physicists believe that a quantum theory of gravity must exist that underlies GR (i.e., for which GR is the classical limit), and in such a theory, there should be a level of description at which gravity works similarly to the other three known fundamental interactions, i.e., it should have a "force carrier" particle, which is called the graviton.
It could be just an effective description, similar to how we use phonons to describe sound waves. It depends on the question whether gravity is an emergent phenomenon or fundamental.
 

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