Is Dark Matter Only Present on a Galactic Scale?

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Discussion Overview

The discussion centers on the influence of dark matter on the movement of bodies within the solar system compared to its effects on galaxies. Participants explore whether dark matter's gravitational effects are significant at smaller scales, such as those of solar systems, and consider the implications of its density and distribution.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants question why dark matter does not appear to affect the movement of solar system bodies as it does with galaxies and stars.
  • Concerns are raised about the precision of measurements of solar system orbits and whether this precision can detect dark matter's influence.
  • There is a suggestion that dark matter may only be relevant at galactic scales, potentially due to the heliosphere's interference.
  • Participants discuss the need to determine the density of dark matter required to have an observable effect on solar system scales.
  • One participant notes that the estimated amount of dark matter in the solar system is very small, about 10^20 kg, which is significantly less than the mass of the asteroid Ceres.
  • Another participant mentions that dark matter is likely not evenly distributed within galaxies, which could explain discrepancies in expected rotational behavior.
  • There is a consideration of how the expansion of the universe operates on large scales and does not affect smaller scales like the solar system.
  • Some participants express that the gravitational effect of dark matter within the solar system is negligible due to its sparse distribution.

Areas of Agreement / Disagreement

Participants express differing views on the relevance and influence of dark matter at solar system scales, with no consensus reached on whether dark matter significantly affects solar system bodies.

Contextual Notes

Limitations include the dependence on the assumptions regarding dark matter density and distribution, as well as the unresolved nature of how these factors might influence gravitational effects at smaller scales.

alvarogz
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Why doesn't dark matter affect the movement of solar system bodies as it does with the galaxies and stars movement?. Is it possible that dark matter affects only at galaxies scales or that the heliosphere interferes with the interaction of dark matter at solar systems scales (I say this because the measurements of the orbits of solar system bodies are very precise)?.

I was watching BBC.Horizon.2006.Most.of.Our.Universe.is.Missing when the question came up. Thanks.
 
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alvarogz said:
I say this because the measurements of the orbits of solar system bodies are very precise
How precise?
 
enough precise to calculate the orbit of planets, moons, comets, asteroids, etc. That's why we have artificial satellites orbiting the Earth and other planets... What I'm trying to say is if the influence of dark matter is applicable to the orbit of solar system bodies or not. If the answer is NO, I'm wondering why? if this dark matter is a kind halo that sorrounds the galaxy and gives it the rest of the mass that explains its movement.
 
alvarogz said:
enough precise to calculate the orbit of planets, moons, comets, asteroids, etc. That's why we have artificial satellites orbiting the Earth and other planets... What I'm trying to say is if the influence of dark matter is applicable to the orbit of solar system bodies or not. If the answer is NO, I'm wondering why? if this dark matter is a kind halo that sorrounds the galaxy and gives it the rest of the mass that explains its movement.

You'd need to determine how dense the dark matter would need to be to show the effects it is showing on the galaxies. Then you'd need to show whether that density would have any effect on such as small scale as the solar system.

And I do believe the the dark matter is not evenly distributed throughout a galaxy. That's why it's not rotating as expected.


Here's an unrelated effect to chew on when thinking about scaling forces: expansion of the universe happens on a very large scale - it happens between galaxies and galaxy clusters. We do not see its effect within galaxies and certainly not within our solar sytem. It is simply far too small to overcome the effects of gravity.
 
DaveC426913 said:
You'd need to determine how dense the dark matter would need to be to show the effects it is showing on the galaxies. Thne you'd need to show wherher that density would have any effect on such as small scale as the solar system.

And I do believe the the dark matter is not evenly distributed throughout a galaxy. That's why it's not rotating as expected.

I thought about density of the dark matter as way to explain its possible marginal gravitational effect over a solar system, considering its little size, compared to the vast dimension of the interstellar space and the whole galaxy. Probably at minor scales the effect is less than in bigger scales.
 
alvarogz said:
enough precise to calculate the orbit of planets, moons, comets, asteroids, etc. That's why we have artificial satellites orbiting the Earth and other planets... What I'm trying to say is if the influence of dark matter is applicable to the orbit of solar system bodies or not. If the answer is NO, I'm wondering why? if this dark matter is a kind halo that sorrounds the galaxy and gives it the rest of the mass that explains its movement.

The amount of dark matter estimated in the entire Solar system is only estimated to be about 10^20 kg or about 1/9 the mass of the asteroid Ceres.
 
very interesting information. if that data is correct we can assume that dark matter and, off course, its gravity, governs at bigger scales.
You mean Ceres, the dwarf planet...? So, its a very little amount of dark matter that is interacting at our solar system.
 
alvarogz said:
very interesting information. if that data is correct we can assume that dark matter and, off course, its gravity, governs at bigger scales.
You mean Ceres, the dwarf planet...? So, its a very little amount of dark matter that is interacting at our solar system.
Also the dark matter is pretty evenly spread out within the solar system, so its gravitational effect would be extremely negligible.
 
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