Is It Possible to Integrate General Relativity and Quantum Mechanics?

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Discussion Overview

The discussion revolves around the potential integration of General Relativity (GR) and Quantum Mechanics (QM), exploring theoretical frameworks, implications of gravity, and the nature of spacetime. Participants examine the relationship between these two fundamental theories, their limitations, and the challenges in unifying them at the quantum level.

Discussion Character

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

Main Points Raised

  • One participant suggests that both gravity and velocity affect spacetime, proposing that a formula incorporating both could exist.
  • Another participant states that Special Relativity (SR) is a special case of General Relativity (GR), applicable when gravitational effects are negligible.
  • A question is raised about the exclusion of gravity in Quantum Mechanics, with a participant wondering why gravity is not included if it is considered too weak.
  • It is noted that in small regions of space, spacetime can be approximated as flat, allowing GR to reduce to SR, which is valid locally but not globally due to varying gravitational effects.
  • One participant clarifies that GR encompasses SR, but expresses interest in a formula that combines both theories at the quantum level.
  • Another participant mentions that while SR and QM are successfully combined in quantum electrodynamics (QED), a unified theory of GR and QM remains an open area of research, with various approaches being explored but lacking experimental validation.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between GR and QM, with some proposing that a unifying formula could exist while others acknowledge the ongoing challenges in integrating the two theories. The discussion remains unresolved regarding how GR and QM can be combined.

Contextual Notes

Participants highlight limitations in current understanding, particularly regarding the integration of gravity into quantum frameworks and the conditions under which GR reduces to SR. There is an acknowledgment of the lack of experimental tests for proposed theories that aim to unify GR and QM.

Who May Find This Useful

This discussion may be of interest to those studying theoretical physics, particularly in the fields of general relativity, quantum mechanics, and attempts at unification of these theories.

GoodPR
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Gravity seems to squish space time, velocity seems to also.
It seems that through each's affect on distance, a formula containing both could possibly exist.

Also, if we stopped and considered GR a law instead of a theory for a moment, then we conclude singularities must not exist.
And QM must be slightly flawed if GR can not apply.
One reason for this is I think is that QM relies on a static field and that field is time, I don't understand why time was used since we know both gravity and velocity affect time.

Any ideas?
 
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SR is a special case of GR. If the effects of gravity are weak or can be ignored, then GR reduces to SR.
 
"SR is a special case of GR" could you explain what you mean by that, without explaining too much, I do understand them in general, but I don't know what you mean by that exactly.

"If the effects of gravity are weak or can be ignored, then GR reduces to SR"

So are you saying in QM they just don't include gravity because its too weak to care about?
If that's true why would they want to have it in their model anyways? Also if its true why can't they add it in their model.
 
If we consider a small enough region of space then we can make the approximation that the space-time in this small region is flat. This means that any curvature effects can be ignored and GR is reduced to SR. It allows us to deal with uniform gravitational fields and hence frames in uniform relative motion.

An example would be the surface of the Earth. Look out a window and the world seems very flat and it's a good approximation on such a small scale that the world is flat. If we then consider the Earth as a whole it is certainly not flat and the gravitational field is not uniform. For example someone on one side of the Earth would feel a vector acceleration towards the center of the Earth and any person on the other side of the Earth would experience a vector acceleration towards the Earth such that the vectors would be anti-parallel (they both point towards the center of the Earth but from opposite sides).

This would mean that, because they experience gravity acting in 'different directions', it would not be possible to construct a global inertial frames. Hence SR would fail globally but be valid locally.

Think it would be better for someone more knowledgeable to answer the question on quantum gravity, sorry.
 
GoodPR said:
dx: "SR is a special case of GR"
could you explain what you mean by that,
It means that GR contains SR.
GoodPR said:
a formula containing both could possibly exist.
Yes, that "formula" is called General Relativity.
 
Ok, that answers mostly
A.T.
I meant a formula containing both at the quantum level.
 
SR and QM work together, and the result is called quantum electrodynamics (QED) for electromagnetic interactions.

We don't know yet how GR and QM can be combined. It's a big area of theoretical research, and people are trying various approaches: string theory, quantum gravity, etc. But so far we don't have anything that we can test experimentally, as far as I know.
 

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