Universe AgeSize with respect to DM?

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Discussion Overview

The discussion revolves around the relationship between the age and size of the universe and the content of dark matter. Participants explore whether the percentage of dark matter influences these cosmic parameters, particularly in the context of the universe's expansion and historical evolution since the Big Bang.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant questions the prospects of aging the universe based on dark matter content and its implications for the universe's size.
  • Another participant asserts that while the total mass of dark matter remains constant, its density relative to critical density changes over time, affecting the universe's flatness.
  • There is a claim that the current percentage of dark matter relative to critical density is about 23%, countering an earlier assertion of 95%.
  • Participants discuss the impact of dark matter and dark energy contributions on the universe's size and expansion rate, noting that baryonic matter's contribution does not affect these parameters.
  • Questions arise regarding the nature of the universe's early state, specifically whether it originated from a proton-sized entity and the role of dark matter at that time.
  • There is uncertainty about whether the ratio of dark matter to baryonic matter has remained constant since the Big Bang, with suggestions that this is a topic for particle physicists to explore.
  • One participant expresses confusion regarding the presence of dark matter within protons today, indicating a need for clarification on this point.

Areas of Agreement / Disagreement

Participants express differing views on the percentage of dark matter and its implications for the universe's age and size. There is no consensus on the historical ratios of dark matter or its form in the early universe, leaving several questions unresolved.

Contextual Notes

Participants reference the "lambda transition" and the evolving contributions of dark matter and dark energy, but the discussion lacks clarity on specific definitions and assumptions regarding dark matter's historical ratios and its relationship to baryonic matter.

Spin_Network
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What are the prospects of Aging the Universe with respect to the Dark Matter Content of our perceived Universe?..and can we gauge the size of the Universe with respect to the percentage of Dark Matter?..ie..DM amounts to about 95%,,does this have a baring on the Universe age and size?
 
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The total mass in dark matter should not change with time, but its density relative to the critical density will. In other words, its relative contribution to the flatness of the universe changes with time. Before the "lambda transition" where the dark energy became the dominant contribution to the flatness, dark matter's contribution had been increasing with time. Now, we think that its contribution is decreasing.

I'm not sure where your "95%" number came from. The current percentage of the critical density that's dark matter is about 23%.

Oh, and yes, the relative contributions of dark matter and dark energy do make a difference for the size and expansion rate of the universe. The relative contributions of baryonic and dark matter to the total matter budget don't impact the expansion rate or size, however.
 
SpaceTiger said:
The total mass in dark matter should not change with time, but its density relative to the critical density will. In other words, its relative contribution to the flatness of the universe changes with time. Before the "lambda transition" where the dark energy became the dominant contribution to the flatness, dark matter's contribution had been increasing with time. Now, we think that its contribution is decreasing.

I'm not sure where your "95%" number came from. The current percentage of the critical density that's dark matter is about 23%.

Oh, and yes, the relative contributions of dark matter and dark energy do make a difference for the size and expansion rate of the universe. The relative contributions of baryonic and dark matter to the total matter budget don't impact the expansion rate or size, however.

I see, can you point me to a source that explains the Big-Bang evolved from a Proton Sized entity..and is this Proton sized 'object', Dark Matter free?

A simpler question is:Was the Dark Matter 'percentage' always the same ratio( 75% *) at the Big-Bang?..and would there be a small 'fraction' still evident within ..say a Proton today?

Thanks for the correction, I was incorrect in my original ratio.
 
Spin_Network said:
I see, can you point me to a source that explains the Big-Bang evolved from a Proton Sized entity..and is this Proton sized 'object', Dark Matter free?

I don't think we have a strong enough grasp of physics to confidently extrapolate that far back (if it even goes that far), but whatever the dark matter is, it would be in an entirely different form at that point.


A simpler question is:Was the Dark Matter 'percentage' always the same ratio( 75% *) at the Big-Bang?

The ratio of non-baryonic matter to baryonic matter has been the same for most of the history of the universe. Whether it has always been the same is an issue for particle physicists to address (i.e. whether baryon number is always conserved). Dark matter, however, can include some baryonic matter (like planets). Thus, the ratio of dark matter to luminous matter will change with time.


..and would there be a small 'fraction' still evident within ..say a Proton today?

I'm not sure what you mean by that.
 

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