What Determines the Fate of Our Universe?

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Discussion Overview

The discussion revolves around the fate of the universe, specifically focusing on concepts such as critical density, the implications of an open or closed universe, and the roles of dark matter and dark energy. Participants explore theoretical implications, observational challenges, and the influence of inflationary cosmology.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants propose that if the average matter density of the universe is below a critical value, the universe will expand indefinitely, leading to a "cold and lonely death." Conversely, if the density is above the critical value, the universe may eventually collapse in a "big crunch."
  • Others argue that the question of the universe's fate is complicated by the observation that the expansion of the universe is accelerating, which has led to the introduction of dark energy as a necessary concept.
  • There is a suggestion that the understanding of dark matter is influenced by research into the universe's density and structure, although some participants note that dark matter has direct observational evidence of its gravitational effects.
  • One participant highlights that while calculating critical matter density is straightforward, measuring it poses significant challenges.
  • Another participant engages in a linguistic clarification regarding the use of "doubts" versus "questions," emphasizing the distinction between uncertainty and inquiry.

Areas of Agreement / Disagreement

Participants express differing views on the implications of matter density for the universe's fate, with some emphasizing the role of dark energy and others focusing on traditional density models. The discussion remains unresolved regarding the definitive fate of the universe and the roles of dark matter and dark energy.

Contextual Notes

Limitations include the dependence on current observational data and theoretical models, as well as the unresolved nature of dark energy and its implications for cosmology.

gianeshwar
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Dear Friends!
Probably more than a decade back understanding tells us : If the average matter density of the universe happens to be smaller than a critical value,then the galaxies will never come to a halt and turn back(Open Universe).Which will imply cold and lonely death.
If on the other hand average density is larger than the critical density ,then Universe will turn back and end in a big crunch(Close Universe I understand).
My questions are:
1. Do we now know our fate?
2.What role has inflationary cosmology played in determining critical density.
3. Has the matter remained strictly matter after relativity(affecting these questions)
4. Is idea of Dark matter caused only by such background researches.
 
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The question is somewhat moot. No matter what the density, (above, below or at the critical value) the expansion of the universe should be decellerating. But observations in the 20th century show that expansion is actually accelerating. Scientists had to invent the concept of dark energy to explain that.

Dark energy is yet to be fully understood or proven. But the idea that our fate is determined only by the matter density can be said to be moot.
 
gianeshwar said:
4. Is idea of Dark matter caused only by such background researches.
No, there are direct observations of its gravitational influence.
 
Thank you Dr Courtney,Anorlunda and mfb! May come back with further doubts after more studies.
 
gianeshwar said:
... May come back with further doubts ...

I think you mean questions. To have a question means you do not understand something and would like information.

To have a doubt about something means you think it might be wrong. You are not ASKING anything at all, you are stating a fact; the fact that you think something might be wrong.

https://www.physicsforums.com/showthread.php?t=607274
 
Thanks chronos for the link! I will take time to study it.Can ask further questions after that.
Thanks phinds for language guidance!
 
gianeshwar said:
Thank you Dr Courtney,Anorlunda and mfb! May come back with further doubts after more studies.

What exactly do you doubt about the existing mechanics of our currently observed matter density formulation? Can you please be more specific within regards to your question.
 
  • #10
Thanks Luminescent!Will respond soon!
 

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