How Does Dark Matter Influence Gravity in Galaxies?

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Discussion Overview

The discussion revolves around the influence of dark matter on gravity within galaxies, specifically addressing its distribution and effects on galactic structure. Participants explore theoretical implications and gravitational dynamics related to dark matter's presence in the outer regions of galaxies.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • Some participants suggest that if dark matter is primarily located in the outer portions of galaxies, it could lead to a tendency for galaxies to be pulled apart due to gravitational forces.
  • Others argue that the center of mass remains within the galaxy, which may counteract the potential for galaxies to be pulled apart.
  • A later reply reiterates the idea that the net gravitational force on the inside of a shell of matter is zero, regardless of the density distribution of dark matter.

Areas of Agreement / Disagreement

Participants express differing views on the implications of dark matter's distribution for galactic stability, indicating that multiple competing perspectives remain without a clear consensus.

keepitmoving
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I've heard that most of dark matter is located in the outer portions of galaxies. If that is so, wouldn't the gravity from the dark matter tend to pull the galaxies apart?
 
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The center of mass is still within the galaxy.
 
many thanks Chronos
 
keepitmoving said:
I've heard that most of dark matter is located in the outer portions of galaxies. If that is so, wouldn't the gravity from the dark matter tend to pull the galaxies apart?
Even if the dark matter wasn't more dense towards the center of the galaxy, the net gravitational force on the inside of a shell of matter is identically zero.
 

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