- #1
alw34
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This is a kind of cooperative problem solving post. But don't be too terribly 'focused' because likely I have missed important issues. I had not seen a dynamic illustration like this before: maybe I am over impressed, weak-kneed, like seeing Kate Hudson the first time??
In Wikipedia at
https://en.wikipedia.org/wiki/Comoving_distance#Uses_of_the_proper_distance
is a dynamic illustration of some cosmological limits. Clicking on the Wikipedia illustration activates the dynamic rendering, and an observer ascends vertically along the black line in time as the yellow light cone for the observer does also and approaches the dark red event horizon. No explanation of what's happening given in Wikipedia. So sad.
Given all the attention that has been justly paid to the balloon analogy [say by phinds and in Brian Powell's new "Inflationary Misconceptions and the Basics of Cosmological Horizons"
Reference https://www.physicsforums.com/insights/inflationary-misconceptions-basics-cosmological-horizons/]
is it worthwhile to focus attention on the attributes and weakness of this illustration?
Does it complement the balloon analogy in enough worthwhile respects to warrant attention? Interesting/Insightful enough for a FAQ?
Some thoughts:
I like how the particle horizon is inside the event horizon early in the universe, and then passes outside as expansion slows. Doesn't that illustrate "faster than light" expansion? When did that end? Maybe be nice to label that event with values using the Jorrie Calculator.
Maybe label a few other events? Which ones? Like the Hubble radius value today. Maybe when the Hubble radius hits 99% of the event horizon?? [light blue Hubble curve gets lost in the vertical red even horizon]
Also, obvious that the thin black horizontal line is today at about 13.8B yrs of age, and the vertically ascending event horizon is approaching the 17.3B LY that Powell mentions. How to best take advantage of the time dimension in the illustration despite being limited to only one space dimension in explanations? Can we pick out anything valuable about a[t] and H[t]?? I can't. Lastly, how does the comoving dynamic view complement this one?
In Wikipedia at
https://en.wikipedia.org/wiki/Comoving_distance#Uses_of_the_proper_distance
is a dynamic illustration of some cosmological limits. Clicking on the Wikipedia illustration activates the dynamic rendering, and an observer ascends vertically along the black line in time as the yellow light cone for the observer does also and approaches the dark red event horizon. No explanation of what's happening given in Wikipedia. So sad.
Given all the attention that has been justly paid to the balloon analogy [say by phinds and in Brian Powell's new "Inflationary Misconceptions and the Basics of Cosmological Horizons"
Reference https://www.physicsforums.com/insights/inflationary-misconceptions-basics-cosmological-horizons/]
is it worthwhile to focus attention on the attributes and weakness of this illustration?
Does it complement the balloon analogy in enough worthwhile respects to warrant attention? Interesting/Insightful enough for a FAQ?
Some thoughts:
I like how the particle horizon is inside the event horizon early in the universe, and then passes outside as expansion slows. Doesn't that illustrate "faster than light" expansion? When did that end? Maybe be nice to label that event with values using the Jorrie Calculator.
Maybe label a few other events? Which ones? Like the Hubble radius value today. Maybe when the Hubble radius hits 99% of the event horizon?? [light blue Hubble curve gets lost in the vertical red even horizon]
Also, obvious that the thin black horizontal line is today at about 13.8B yrs of age, and the vertically ascending event horizon is approaching the 17.3B LY that Powell mentions. How to best take advantage of the time dimension in the illustration despite being limited to only one space dimension in explanations? Can we pick out anything valuable about a[t] and H[t]?? I can't. Lastly, how does the comoving dynamic view complement this one?
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