Dark Energy, Distance to Galaxies and Distance in time.

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Discussion Overview

The discussion revolves around the concept of dark energy and its role in explaining the observed acceleration of galaxies moving away from us. Participants explore the implications of distance and time on the recession rates of galaxies, as well as the observational evidence that led to the formulation of the dark energy hypothesis.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant questions whether the age difference between galaxies affects their recession rates, suggesting that older galaxies should be receding faster due to the expansion of the universe being more rapid in the past.
  • Another participant notes that the redshift of galaxies is typically used to determine their recession rates and provides a resource for calculating these rates based on redshift values.
  • Some participants argue that dark energy was not simply invented but was necessary to explain certain observational evidence, describing it as a fragile hypothesis that could be challenged by new observations.
  • There is mention of the possibility that modified gravity could explain the accelerated expansion, although this is considered less likely by some participants.

Areas of Agreement / Disagreement

Participants express differing views on the nature of dark energy, its necessity, and the implications of galaxy distances on recession rates. There is no consensus on the explanations for the observed phenomena, and multiple competing views remain.

Contextual Notes

Participants reference the need for observational evidence to support claims about dark energy and its implications. There is an acknowledgment of the fragility of the dark energy hypothesis and the ongoing investigations into its nature.

discord73
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I've read that Dark Energy was invented to explain why galaxies really far away are moving away from us faster than ones closer to us. Now I'm sure they did this, but did they take into account that if they look at 2 galaxies A and B. Galaxy A is 500 million ly away and B is 5billion ly away, so, galaxy B would also be 4.5 billion ly older than galaxy A and therefore receding from us at a faster rate since according to bing bang the galaxy was expanding faster 4.5 billion years ago than it was 500 mililon years ago? or do they take this into account and still find that the universe is accelerating?

Also. is there a website I can go to to find the reletive speeds of galaxies that have been observed and measured and what not?
 
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discord73 said:
Also. is there a website I can go to to find the reletive speeds of galaxies that have been observed and measured and what not?

What is ordinarily listed is a galaxy's redshift.

You should learn how to calculate the recession rate (the rate the distance is increasing) from the redshift. There is a calculator for that. the URL is in small print in my signature.
Or google "cosmos calculator". Morgan's calculator will be the first hit.

We observe galaxies with a big range of redshifts from low numbers like 0.5 to 1.0 to 1.5, to 2 to 3 up to 6.5 or 7.

The redshift of the microwave background is 1090, larger than that of any galaxy.

Why don't you try Morgan's calculator and see if you can get it to work.
If you have any questions, ask!

When you first open the calculator you need to type in three numbers, over on the left:
From the top down, the three numbers are .27, .73, and 71
These are the parameters of the standard model.
Then all you do is type in some redshift like, say, 5, or 6. and press calculate.

If it doesn't respond when you put in a new redshift and press calculate again, please let me know. I will back up your calculation and make sure it's giving the right answer.
http://www.uni.edu/morgans/ajjar/Cosmology/cosmos.html
 
Dark energy was not 'invented', it was necessary to explain observational evidence. No scientist desired this solution, it was an evil they could not refute. The DE hypothesis is very fragile. Almost any stray observation could kick the stool out from under it, but, it still stands.
 
Last edited:
Chronos said:
Dark energy was not 'invented', it was necessary to explain observational evidence. No scientist desired this solution, it was an evil they could not refute. The DE hypothesis is very fragile. Almost any stray observation could kick the stool out from under it, but, it still stands.
Bear in mind that there still remains the possibility that it's explained by modified gravity, but for theoretical reasons this seems rather less likely. Investigations are underway...hopefully we'll understand something about the cause of the accelerated expansion within a decade or so.
 

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