Gravitational Time Dilation and the Galaxy Rotation Curve

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Discussion Overview

The discussion explores the potential relationship between gravitational time dilation and the galaxy rotation curve problem, particularly focusing on whether the mass concentration at galaxy centers could influence time dilation effects that might account for observed discrepancies in rotational velocities.

Discussion Character

  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant proposes that the high concentration of mass at galaxy centers, including supermassive black holes, could cause significant time dilation affecting the rotational curve.
  • Another participant counters that the central black hole accounts for a small fraction of the galaxy's total mass and that its influence on time dilation is negligible compared to the overall mass distribution.
  • A further reply emphasizes that the mass in the center includes more than just the central black hole, suggesting that the overall mass distribution should be considered in the context of time dilation effects.
  • Another participant asserts that the mass of a galaxy is well-distributed throughout its disk, challenging the notion that the center contains the majority of stellar mass.
  • One participant introduces the concept of gravitational lensing as evidence for unseen dark mass, noting the uncertainty surrounding the composition of the universe.

Areas of Agreement / Disagreement

Participants express disagreement regarding the significance of mass concentration at galaxy centers in relation to time dilation and the rotation curve problem. Multiple competing views remain, with no consensus reached.

Contextual Notes

Participants highlight limitations in understanding the distribution of mass within galaxies and the implications for gravitational effects, including time dilation. The discussion reflects ongoing uncertainty about the nature of dark mass and its role in cosmological observations.

dewclaw
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Is it possible that the very high concentration of mass at the centers of galaxies is causing a significant enough time dilation to explain a non-negligible part of the rotational curve problem? i.e. time is traveling more slowly in the super-massive, black hole rich cores of galaxies and faster in the relatively diffuse extremities.
 
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No .
 
No. The central black hole usually accounts for less than 2% of the galaxy mass, and the region where its gravity causes any significant time dilation is, liberally, one cubic parsec out of 10^12 of them in the galaxy. Most stars in the galaxy don't even know it exists.
 
There is much more mass in the center of a galaxy than just the central black hole though. There are other black holes and a vast majority of the stellar mass. And its not just the very center that would need to be considered right? Its the huge discrepancy between the amount of matter near the core and the amount on the fringes.
 
dewclaw said:
There is much more mass in the center of a galaxy than just the central black hole though. There are other black holes and a vast majority of the stellar mass.

No. The center of the galaxy does not contain "the vast majority of the stellar mass." The mass of a galaxy is very well distributed throughout the disk.
 
OK. Thanks for commenting.
 
Gravitational lensing beyond that attritubtable to visible mass also seems to support the existence of additional unseen dark mass over vast cosmological distances. It's embarassing, but little is known about 96% of the "stuff" in the universe...
 

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