Mass of the Universe: What's the Real Number?

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Discussion Overview

The discussion revolves around the mass of the universe, specifically focusing on the observable universe, the role of dark matter and dark energy, and the challenges in measuring cosmic mass density. Participants explore various theories and perspectives on these topics without reaching a consensus.

Discussion Character

  • Debate/contested
  • Exploratory
  • Technical explanation

Main Points Raised

  • Some participants question the terminology used when referring to "the universe," suggesting that it is ambiguous and may refer to the observable universe.
  • There is a discussion about whether dark matter and dark energy should be included in the margin of error for mass estimates, with some arguing they are not part of the margin despite uncertainties surrounding their nature.
  • One participant mentions a "fudge factor" in mass estimates to account for dark energy, while another argues that precise measurements of density parameters for dark matter and dark energy exist.
  • Concerns are raised about the accuracy of measuring the mass of interstellar gas and its contribution to galaxy mass, with some suggesting that existing models may not account for all forms of matter.
  • Participants discuss the difficulties in measuring the actual mass of the observable universe, noting that cosmologists often focus on global mass density instead.
  • Speculative ideas are presented, including the possibility that the observable universe could be contained within its Schwarzschild radius and the notion that the universe's mass could theoretically be zero due to a balance of positive and negative contributions.
  • One participant expresses a belief in the infinite nature of the universe, adding to the complexity of the discussion.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the mass of the universe, the role of dark matter and dark energy, and the implications of these factors on measurements. The discussion remains unresolved, with no consensus reached on key points.

Contextual Notes

Participants highlight limitations in current understanding and measurement techniques, including the challenges of defining the universe's boundaries and the accuracy of various observational methods.

  • #31
An actual number for the mass of the observable U

Just to put a cit-able number on the OP's question:

I called up http://www.wolframalpha.com in a browser window.

in the _search term_ box I entered the following: What is the mass of the observable universe

Wolframalpha's response, cited as 'calculated by Wolfram Mathematics' was as follows:

~~ 3.4×10^54 kg (kilograms)

~~ ( 2×10^(-6) ~~ 1/600000 ) × high end for estimated mass of the universe (~~ 2×10^60 kg )

~~ 10000 × low end for estimated mass of the universe (~~ 3×10^50 kg )

-----------------------

I make no representations about the validity of the above information except that it is accurately transcribed and is from a publicly accessible source.

diogenesNY
 
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  • #32
We've even calculated the number of atoms, even Planck areas, in the observable universe. Those are some big numbers. All such calculations require debatable assumptions.
 
  • #33
Chronos said:
Dark matter is virtually collisionless, even with itself, hence it does not clump in stars, or pretty much anything else. It tends to be most abundant in halos because it continuously yo-yo's in and out of the galaxy, and that is where it's velocity is minimal.

Been out of the loop for a while but on this issue, obviously any dark matter outside a formed star would simply fall in, gain speed and then re-escape. But this would be less the case when a gas cloud was coallescing into a star.

I remain open on dark matter but I also remain convinced that a lot more of the unaccounted for mass is baryonic. Correct me if I am wrong but as I understand it, LSB galaxies appear to be some 20 times as massive as their luminoscity would suggest rather than 5 or 6 times for a typical galaxy. Yet why would there be any dramatic difference in the ratio of dark matter to baryonic matter in the original gas clouds?

I know we can see hydrogen gas thanks to the 21cm line but how much of it can we see? I am having a lot of difficulty finding descriptions of how to calculate the output at 21cm per Kg of hydrogen, under typical interstella conditions. On top of this are our estimates of the metalicity of interstella gas wrong?

I shall leave with a question that is related to this issue. I was told once by a lecturer, that the different elements were assumed to be evenly distributed throughout a star - rather than have the heavier elements sink to the center. Is this still thought to be the case?
 

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