Matter Density of The Universe

[gianeshwar]

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.

 

[Dr. Courtney]

http://www2.lbl.gov/Science-Articles/Archive/SNAP-3.html

https://en.wikipedia.org/wiki/Shape_of_the_universe

 

[anorlunda]

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.

 

[mfb]

4. Is idea of Dark matter caused only by such background researches.

No, there are direct observations of its gravitational influence.

 

[gianeshwar]

Thank you Dr Courtney,Anorlunda and mfb! May come back with further doubts after more studies.

 

[Chronos]

Calculating the critical matter density is fairly trivial, measuring it is not. For discussion see http://www.astro.ucla.edu/~wright/density.html

 

[phinds]

... 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

 

[gianeshwar]

Thanks chronos for the link! I will take time to study it.Can ask further questions after that.
Thanks phinds for language guidance!

 

[Luminescent]

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.

 

[gianeshwar]

Thanks Luminescent!Will respond soon!