Hubbles vs. Dark Energy: Debunking the Mystery of Galaxy Expansion"

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Discussion Overview

The discussion revolves around the relationship between Hubble's observations of galaxy expansion and the concept of dark energy. Participants explore the implications of Hubble's findings in the context of an accelerating universe and the potential discrepancies between the two models.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants assert that Hubble's observations indicate that galaxies further away are moving faster, suggesting a linear expansion model.
  • Others argue that the dark energy model is more accurate, as it accounts for the accelerating expansion of the universe, which Hubble's data could not fully capture due to limitations in observational technology.
  • A participant questions whether the expansion rate might slow down at certain distances, proposing that Hubble's observations could reflect an increasing expansion rate only up to a point.
  • Another participant clarifies that the recession speed of galaxies is proportional to their distance, and that Hubble's Constant (H) is not truly constant but changes over time.
  • There is a suggestion that Hubble may not have detected changes in H due to the limitations of his observational range and the subtlety of the changes involved.

Areas of Agreement / Disagreement

Participants do not reach a consensus, as there are competing views regarding the accuracy of Hubble's model versus the dark energy framework. The discussion remains unresolved with ongoing questions about the implications of Hubble's findings.

Contextual Notes

Limitations include the dependence on observational data quality, the changing nature of Hubble's Constant, and the complexities of interpreting recession speeds over cosmological distances.

discord73
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So Hubbles observations showed that the further away a galaxy is the faster it is moving meaning that older galaxies are moving away faster from us than younger, closer ones. But dark energy says that the rate of expansion is increasing,meaning the closer, younger galaxies would be traveling faster than the farther, older ones. So. Which one is correct?
 
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The dark energy picture is more correct than hubble's simple linear expansion picture. Hubble simply didn't have the quality of data to detect the accelerating expansion, and indeed it's not until the late 90's that we finally did. I wouldn't really say Hubble was wrong though -- the situation is rather analogous to Newtonian and Einsteinian mechanics. Newton wasn't really wrong, the domain of applicability of his theory was just smaller than Einstein's.
 
So does that mean as we look farther away from our galaxy the expansion speeds up to a certain point of time/distance the expansion starts slowing down as we look further back? Meaning Hubble was right with his data, he could see the universe expansion increasing as he looked further out, he just couldn't see far enough to see where the universe started slowing down?
 
So Hubbles observations showed that the further away a galaxy is the faster it is moving meaning that older galaxies are moving away faster from us than younger, closer ones.
No.
1. At any given (cosmological) time, the so-called recession speed of a galaxy is exactly proportional to its distance. The proportionality factor is called H.
2. H is changing with time, getting less and less. "Accelerated expansion" means that H decrases slower than it would if all galaxies were freely floating.
3. Combine this with light travel time to get a recession speed - distance at emission chart. These are more complicated. Look athttp://www.astro.ucla.edu/~wright/cosmo_01.htm" .
 
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Ich said:
2. H is changing with time, getting less and less. "Accelerated expansion" means that H decreases slower than it would if all galaxies were freely floating.

Okay so Hubble's Constant isn't constant then? How did Hubble miss that? is the change in H as the farther you go away so slight that he was unable to look far enough away to see a change in H?
 
Okay so Hubble's Constant isn't constant then? How did Hubble miss that? is the change in H as the farther you go away so slight that he was unable to look far enough away to see a change in H?
You know, I gave you the link for a reason. Have a look at Hubble's data and decide for yourself.
Hint:1 Mpc~3Mly. Age of the universe ~13700 My.
 

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