A question relating to expansion rate of the Universe

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The discussion centers on the expansion rate of the Universe and its relationship with dark matter, energy, and the formation of galaxies. It is established that the conversion of mass into energy by stars has a negligible effect on the expansion rate. The cosmological constant is confirmed to be consistent across voids, with gravitational attraction dominating in locally bound regions. Dark matter, estimated to be 5.5 times the mass of ordinary matter, plays a crucial role in gravitational dynamics and is accounted for in the expansion rate calculations. The changing percentages of dark matter and ordinary matter over time are attributed to the cooling of the Universe and the dynamics of cosmic expansion.

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  • Understanding of cosmological constants and their implications
  • Familiarity with dark matter and its role in the Universe
  • Knowledge of the expansion of the Universe and its historical phases
  • Basic principles of energy-matter conversion in astrophysics
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  • Research the implications of the cosmological constant on cosmic expansion
  • Study the role of dark matter in galaxy formation and structure
  • Explore the historical phases of the Universe's expansion: radiation-dominated, matter-dominated, and lambda-dominated eras
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Astronomers, astrophysicists, cosmologists, and anyone interested in the dynamics of the Universe's expansion and the role of dark matter in cosmic structure.

  • #31
Answer is still the same as when posted in #25.

edit; Maybe I should say that's about as much as we think we know...
there seems to be a lot more we don't know than we know..."Do you have a good link for this description of DM?"

not so much...search these forums, and Wikipedia has a good outline under DARK MATTER...

and I think also discusses MACHOS and WIMPS...

and I see Drakkith has posted links to hot,warm, cold dark matter...

lots of candidates, lots of questions, not so many detailed answers yet.
 
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  • #32
Tanelorn said:
What stops DM from accumulating inside the rims and possibly near the centers of galaxies or is this unknown?

The issue is that DM can't interact through anything other than gravity. What happens is that DM follows an orbit around our galaxy just like everything else. In order for it to fall in towards the center of our galaxy and stay it must give up energy, otherwise it just swings back around all the way out to the halo region again. (or doesn't fall in at all)

When you have a dust cloud that is collapsing under its own gravity, the particles get rid of energy by colliding with each other and giving off EM radiation. This allows it to collapse into dense regions and eventually form stars, planets, etc.

But dark matter can't do this. It simply passes through itself without absorbing or giving off any energy. So it can't collapse into dense regions very easily, if at all.
 

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