How can we accurately determine the expansion rate of the Universe?

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Discussion Overview

The discussion revolves around the expansion rate of the Universe, exploring concepts such as dark energy, dark matter, cosmic inflation, and the implications of observational data on these topics. Participants engage in theoretical and conceptual inquiries regarding the nature of the Universe's expansion and its initial conditions.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • Some participants question whether the Universe is expanding or accelerating, and whether it is contracting or decelerating, suggesting that observations and scientific papers provide insights into these questions.
  • There is a contention regarding the interpretation of dark energy, with some arguing that existing models do not adequately describe its properties or implications.
  • Participants discuss the distinction between dark energy and dark matter, raising questions about their definitions and contexts.
  • One participant references the Bullet Cluster as evidence that dark matter behaves differently than normal matter during collisions, suggesting that dark energy is not expected to be associated with normal matter.
  • Questions are raised about the forces driving the expansion of the Universe and the nature of cosmic inflation, with some noting that the specifics of cosmic inflation remain uncertain.
  • Another participant challenges the idea of a singular starting point for the Universe, suggesting that while our region may have had a beginning, the entirety of the Universe's origins are unknown.
  • The concept of Jeans' Length is introduced to explain how local density can counteract the overall expansion of the Universe, leading to clustering phenomena observed in cosmic structures.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the nature of dark energy and dark matter, the expansion of the Universe, and the implications of observational data. The discussion remains unresolved with no consensus reached on these topics.

Contextual Notes

Participants highlight limitations in current models and observations, including the need for more precise definitions and the impact of systematic uncertainties on data interpretation. The discussion also reflects the complexity of cosmic phenomena and the challenges in understanding them fully.

  • #91
Hello

The observable universe does not show expansion or acceleration one way or another.

It does show a clustering affect.

The clustering produces areas of high density such as large galaxies and centres of clusters of galaxies that produce extremely large jets and Star that produce extremely small jets. This process of ejecting matter and reforming star and galaxies is a main player in the universe.


A Jet is a Jet, Big or Small: Scale Invariance of Black Hole Jets
http://www.mpa-garching.mpg.de/HIGHLIGHT/2003/highlight0308_e.html


The blowtorch jet in the radio galaxy NGC 6251
http://www.astr.ua.edu/keel/agn/ngc6251.html

One important lesson from radio galaxies is that the central engine continues to eject material in nearly the same direction for at least several million years, based on the fact that the tiny parsec-scale jets in the core regions point in the same direction as the very extended radio structure which may stretch several million light-years (and thus took at least that many years to form).

Photo Release - heic0804: Gargantuan galaxy NGC 1132 - a cosmic fossil?
http://www.spacetelescope.org/news/html/heic0804.html

The Origin of the Brightest Cluster Galaxies
http://www.cita.utoronto.ca/~dubinski/bcg/

Giant Galaxy's Violent Past Comes Into Focus
http://chandra.harvard.edu/press/04_releases/press_051004.html

and

Spectacular X-ray Jet Points Toward Cosmic Energy Booster
http://chandra.harvard.edu/press/00_releases/press_060600pic.html

M87:
Chandra Reviews Black Hole Musical: Epic But Off-Key
http://chandra.harvard.edu/photo/2006/m87/

The processes show a two part one part contracting pulling in star matter into dense regions and the other part ejecting the matter back into space reforming not just star areas but galaxies afar.
 
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  • #92
Sundance said:
Hello

The observable universe does not show expansion or acceleration one way or another.

It does show a clustering affect.
And your evidence for this is? Because nothing you posted after this has any relevance whatsoever to any of these claims you have made.
 
  • #93
  • #94
Sundance said:
G'day Chalnoth

I have given you information and you come back with such a statement.

The question is do you want to understand what's happening?

If you do than start reading

This topic, it has the key to many issues.


Magnetic Reconnection
http://arxiv.org/find/all/1/all:+AND+Magnetic+Reconnection/0/1/0/all/0/1

If you do not read it so be it.
I suspect I understand the issues at hand much better than you do. It is not enough to simply throw a few papers out there and claim that they support your case. Make your case, and I will respond.
 
  • #95
Hello Chalnoth

You said

I suspect I understand the issues at hand much better than you do. It is not enough to simply throw a few papers out there and claim that they support your case. Make your case, and I will respond.

Its OK, do not worry about. You know all.
 
  • #96
Sundance said:
Its OK, do not worry about. You know all.
No, I don't. I'm just saying I am likely aware of a fair fraction of the evidence you are presenting. At least as it relates to cosmology. So make your case already. Why, specifically, does this evidence endorse your view?
 
  • #97
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  • #98
Sundance said:
Hello Chalnoth

My view is not that important. It's what science can prove and give us some understanding of the working parts of the universe.
Okay...

Sundance said:
I keep on reading knowing that I know very little and yet what I know tells me that you lack understanding of critical issues.
But you keep throwing out stuff about the astrophysics of particular objects in the universe. The astrophysics of these objects has no direct bearing upon cosmology. So why do you think these are 'key' issues? What makes them key? Why are they important?

Because as far as I'm concerned, I'm really only interested in understanding astrophysics so far as it helps me to understand cosmology. Cosmology is what interests me the most. And you haven't even attempted to draw a logical line between the astrophysics of these particular objects and cosmology. So what are you trying to say?
 
  • #99
G'day Chalnoth

Those topics are Key topics. I think you missed the boat in understanding astrophysics and cosmology.

Understanding the parts that make up the larger parts is quite important.

What triggers a Supernova?

What triggers a Jet small or large?

What evolution path do galaxies take?

How do galaxies form small or large?

Since you find no value in those topics so be it.
 
  • #100
Sundance said:
G'day Chalnoth

Those topics are Key topics. I think you missed the boat in understanding astrophysics and cosmology.

Understanding the parts that make up the larger parts is quite important.

What triggers a Supernova?

What triggers a Jet small or large?

What evolution path do galaxies take?

How do galaxies form small or large?

Since you find no value in those topics so be it.
There is value in these topics, to be sure, but they're not things I personally find interesting.

Except perhaps for the supernova part. At least for Type IA supernova, the supernova occurs when a white dwarf that is accreting matter exceeds the Chandrasekhar limit. I like to have at least some understanding of these as they directly impact cosmology (as they're used as distance measures).

The other points you bring up are, as yet, very poorly-understood. Many astrophysicists are extremely interested in those questions. I am not. I'm interested in the large-scale behavior of the universe, not the details of objects within it. And none of these topics are key topics for understanding the large-scale behavior.
 
  • #101
G'day from the land of ozzzzzz

At the door step we have our Sun with quite important activities that we can study and learn how the parts of the universe work.

Magnetic reconnection is a most important process that allows matter to be broken up into Neutrons and compacted if the evironment allows for the confinement.

The following images show the Sun and the magnetic reconnection causing jet streams.

http://74.125.153.132/custom?q=cach...n+spots&cd=7&hl=en&ct=clnk&client=google-coop


http://74.125.153.132/custom?q=cach...n+spots&cd=3&hl=en&ct=clnk&client=google-coop
 
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  • #102
Too many unclear facts concerning expanding Univerce, what force and conditions...doubtedly...
 

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