What spatial scales does dark matter become significant?

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Discussion Overview

The discussion revolves around the spatial scales at which dark matter becomes significant and its effects on general relativity (GR). Participants explore the volume or mass of space necessary to observe these effects, particularly in relation to smaller structures than galaxies.

Discussion Character

  • Exploratory, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant questions the critical volume of space needed to observe dark matter effects and whether these effects can manifest in scales smaller than galaxies.
  • Another participant asserts that small galaxies and similar structures may show dark matter effects, while star clusters are generally too small, although exceptions exist.
  • A different viewpoint suggests that if dark matter exists, GR does not break down; rather, it implies additional mass must be accounted for in measurements.
  • It is proposed that the significance of dark matter depends on the accuracy of measuring the motions of bodies in space, with larger sections of galaxies being more relevant for dark matter studies.
  • A participant acknowledges a misunderstanding regarding the breakdown of GR, indicating a need for clarification on the topic.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between dark matter and general relativity, with some asserting that GR remains intact while others question the conditions under which dark matter effects become observable. The discussion does not reach a consensus on the specific spatial scales involved.

Contextual Notes

There are unresolved aspects regarding the precise measurements and definitions of spatial scales relevant to dark matter effects, as well as the conditions under which general relativity is considered to apply.

Albertgauss
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Hello,

How much volume or mass of space does one need to see appreciable effects of dark matter where general relatively seems to break down? What is the critical volume of space at this time where people can see the effects of dark matter and where they cannot? Is there a spatial scale smaller than galaxies--or even sub-sections of galaxies--where the effects of dark matter first manifest themselves as departures from general relativity?
 
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Albertgauss said:
How much volume or mass of space does one need to see appreciable effects of dark matter
Small galaxies and similar structures. Star clusters are usually too small, but there are exceptions.
Albertgauss said:
where general relatively seems to break down?
It doesn't.
 
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Albertgauss said:
How much volume or mass of space does one need to see appreciable effects of dark matter where general relatively seems to break down?
If dark matter exists then GR is not breaking down. There is just extra mass that needs to be taken into account.
Albertgauss said:
What is the critical volume of space at this time where people can see the effects of dark matter and where they cannot?
I think that would technically depend on how accurately you can measure the motions of bodies in space. Dark matter is often considered important when studying large sections of galaxies and anything larger. I am not aware of any precise number for the scales at which dark matter should be considered.
 
Okay, sounds good. I just wanted to get a basic idea. Yes, yes about GR not breaking down, I realize I worded that wrong.
 

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