How is Dark Matter distributed around our galaxy?

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Discussion Overview

The discussion revolves around the distribution of dark matter in our galaxy, exploring various models and theories, including the LCDM model and MOND. Participants raise questions about the nature, shape, and implications of dark matter's distribution, as well as its relationship with baryonic matter and gravitational theories.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants inquire about the laws or equations governing dark matter distribution and whether it can be described as a halo, noting confusion between common and astronomical definitions of "halo."
  • There are questions regarding whether dark matter repels itself, if baryonic matter can concentrate dark matter, and the reasons for its distribution around the galaxy.
  • One participant suggests that MOND could provide a simpler explanation for dark matter phenomena, while another argues that both dark matter and MOND could potentially describe different aspects of the same phenomena.
  • Concerns are raised about the elegance of having two theories to explain a single phenomenon, with a preference expressed for dark matter over MOND.
  • Participants discuss the historical context of dark matter's role in the formation of galaxies and large-scale structures shortly after the Big Bang, as well as the need for a theory of quantum gravity.
  • There is a correction regarding the terminology used, with emphasis on the proper term "dark matter" instead of "black matter."

Areas of Agreement / Disagreement

Participants express differing views on whether dark matter and MOND are mutually exclusive theories, with some suggesting that both could hold some truth. The discussion remains unresolved regarding the relationship between these theories and the implications for understanding dark matter.

Contextual Notes

Participants highlight the need for further research and clarification on the definitions and implications of dark matter distribution, as well as the potential limitations of existing theories.

KurtLudwig
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Wikipedia describes the distribution of Dark Matter as a halo around our galaxy. Are there any laws or equations on the distribution of dark matter?
From what I have read, dark matter does not clump into stars, since it cannot radiate energy. It cannot be seen or directly observed. Does it repel itself? Does baryonic matter concentrate dark matter? Is its shape and distribution fixed relative to itself? Why would it distribute itself on the peripheries of our galaxy? It did not distribute itself to uphold Newton's Law of Universal Gravitation, yet it seems that it is used as such in arguments in some articles and books which I have read on the structures of galaxies.
For our galaxy, is MOND a simpler explanation? Can there be two models? (Similar to, light is both a particle and a wave.)
According to the LCDM Model, which most physicists support, an existing structure of dark matter was needed at our 380,000 year-old universe to accelerate the formation of large structures and galaxies. We know that dark matter must exist to explain the large scale structures in our universe.
 
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Many of your questions are quite basic and wold be resolved by a very modest amount of research. How about you do that and then you'll have fewer and better targeted questions
 
KurtLudwig said:
Wikipedia describes the distribution of Dark Matter as a halo around our galaxy. Are there any laws or equations on the distribution of dark matter?
From what I have read, dark matter does not clump into stars, since it cannot radiate energy. It cannot be seen or directly observed. Does it repel itself? Does baryonic matter concentrate dark matter? Is its shape and distribution fixed relative to itself? Why would it distribute itself on the peripheries of our galaxy?
The problem here is that you are confusing the common usage idea of the word "halo" with its meaning in astronomy.
In common usage, the word "halo" brings up the image of a ring or torus shape*. In astronomy it represents a spherical volume. (So no, the DM halo is not confined to the peripheries of the galaxy.)

*And even this is a corruption of its original usage. In many older pieces of artwork showing religious figures with halos, that "ring" or circle around their head is meant to symbolize an overall aura or glow surrounding the figure's head and not an actual ring of light.
 
I have re-read the whole article on dark matter in Wikipedia.
Now, I do understand that dark matter is distributed in a spherical shape in our galaxy.
Is there a field equation for the distribution of black matter which predicts the acceleration gradient due to black matter?
Are the hypothesis of Black Matter and MOND mutually exclusive? Why is there a reluctance to allow both to describe different phenomena?
Do you have a better source of information on black matter, such as a physics paper on arXiv or a textbook.
 
KurtLudwig said:
Are the hypothesis of Black Matter and MOND mutually exclusive?
Probably but since we don't have a settled theory, it's impossible to say that there isn't some truth to both. I think the smart mony is on dark matter (NOT "black" matter) and not MOND.

Why is there a reluctance to allow both to describe different phenomena?
Elegance is admired in physics. If TWO theories are required to describe what appears to be a single phenomenon, that would not be elegant.
 
(Sorry for the slip on dark matter, I wrote black matter for the second time.)
There must be at least two theories involved:
1. It makes sense to assume that at the beginning, 380,000 years after the big bang, gravity wells of dark matter were required to initiate and accelerated the formation of galaxies and large scale structures from the uniform gas of baryonic matter. These structures could not have formed in the time of 13.8 billion years.
2. It is reasonable to assume that there is quantum gravity. All textbooks write about the need for a theory of quantum gravity. But we do not need to have a theory of quantum gravity to observe its effects. Newton stated his laws of universal gravity, force and inertia while wondering about "action at a distance." It is more than a coincidence that modified Newtonian dynamics and TeVeS accurately describe the motion of stars in extremely weak gravitational fields. There quantum gravity shows its secrets, if only we are willing to take its hints.
 
KurtLudwig said:
There must be at least two theories involved:
That is your opinion and not physics.
 
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