MOND GR: Bridging the Gap Between Newtonian and General Relativity?

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Discussion Overview

The discussion centers around the Modified Newtonian Dynamics (MOND) and its relationship with General Relativity (GR), particularly in the context of explaining phenomena such as the bullet cluster and other observational evidence. Participants explore the implications of MOND as a potential alternative to traditional gravitational theories, examining both theoretical predictions and experimental challenges.

Discussion Character

  • Debate/contested
  • Exploratory
  • Technical explanation

Main Points Raised

  • Some participants inquire about how MOND GR predictions compare with classical GR tests, such as light bending.
  • There is a question regarding MOND's ability to account for the bullet cluster, with some suggesting it poses a significant challenge.
  • References to Bekenstein's work on MOND GR are provided, indicating ongoing research and exploration in this area.
  • One participant expresses skepticism about the empirical MOND factor, noting its numerical coincidence with other physical constants.
  • Another participant prefers the standard model with dark matter adjustments over MOND, citing historical precedents in scientific discovery.
  • Concerns are raised about the complexity and potential counterexamples to MOND, with requests for additional experimental evidence.
  • Some participants discuss the implications of the curvature radius of a 4D de Sitter universe on galaxy energy distribution, suggesting a need for further explanation.
  • Links to various papers are shared, both supporting and challenging MOND, indicating a range of perspectives on its validity.

Areas of Agreement / Disagreement

Participants express a mix of support and skepticism regarding MOND, with no clear consensus on its efficacy compared to traditional gravitational models. Multiple competing views remain, particularly regarding the interpretation of observational data and the theoretical underpinnings of MOND.

Contextual Notes

Participants note the complexity of the situation surrounding MOND and its challenges, including unresolved questions about its predictions and the implications of various observational phenomena.

quasar987
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I heard a general theory of relativity was constructed based on MOND rather than on Newton's law of gravitation. How well do the predictions of the MOND GR compare with the classical tests of GR (such as light bending)?

Basically, is it in better or worse agreement with experiment than Newtonian GR?
 
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A related point is... can MOND adjust for the bullet cluster?
 
Awesome ccdantas :!)
 
MOND is not dead, but does appear injured. The bullet cluster does pose a difficult [albeit not insurmountable] problem for the model. The links provided by Christina provide a broad picture of current status.
 
Are there other experimental counterexamples (falsations) besides the Bullet cluster?
 
I am still inclined to believe that there must be something really profound behind the "empric" MOND factor a/(a^2 + a0^2)^1/2, especially taking into acount the "coincidence" that the best fit a0 (1.2*10-10 ms-2) is very close to c(lambda/3)^1/2

check :

"MOND as modified inertia" by Milgrom

http://arxiv.org/abs/astro-ph/0510117v1

really, really intriguing, don't you think so, another "numerical coincidence" ?
 
It sounds suspiciously numerological to me chrisina, but, that is strictly my personal perspective - more hunch than reason. The standard model with 'dark' tweaks remains more attractive to me. Remember the atom - it's existence was postulated many centuries before is was cornered in a laboratory.
 
I also prefer the "dark tweaks", (maybe I was influenced by Dark Vador too much when I was a kid... lol).
I am just very puzzled at how the curvature radius of a 4D de Sitter universe specified by the cosmological constant (3/lambda)^1/2 seems to play a very important role for the energy distribution profiles of the individual galaxies.
This requires an explanation.
 
  • #12
The situation seems to get more and more complicated and interesting. See here:

http://egregium.wordpress.com/2007/08/23/galaxies-and-dark-matter-apart/
 
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  • #14
jal said:
Does this fit in with weird and interesting.
from https://www.physicsforums.com/showthread.php?t=181546
"Gaping hole found in universe"
http://arxiv.org/abs/0704.0908

The MOND effect causes an increase in the gravitational strength at long distances. I suppose that an increase in the long distance gravitational strength could cause all matter to be concentrated in small regions. But I'm just guessing. This is way outside my realm of mediocrity.
 
  • #15
Garth is a very bright guy. He might be luring you into a serious discussion.
 

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