Picturing the history of the world's expansion

In summary, the scale factor function (they write it R(t) or a(t)) gives the history of the expansion of the universe, as calculated from observational data. The slope at any moment is the expansion rate at that moment.

The universe's expansion curve is most like:

  • a straight-line ramp (steady expansion rate)

    Votes: 0 0.0%
  • an exponential growth curve (increasing rate)

    Votes: 2 66.7%
  • a convex ramp (decreasing slope)

    Votes: 0 0.0%
  • silhouette of a woman's breast down to the nipple

    Votes: 1 33.3%

  • Total voters
    3
  • #1
marcus
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The scale factor function (they write it R(t) or a(t)) gives the history of the expansion of the universe, as calculated from observational data. The slope at any moment is the expansion rate at that moment. Which of these best describes how you picture this curve?

1. straightline ramp (constant expansion rate)
2. exponential growth (increasing slope)
3. convex ramp (positive but decreasing slope)
4. silhouette of a woman's breast down to the nipple

http://nedwww.ipac.caltech.edu/level5/March03/Lineweaver/Figures/figure14.jpg

the solid dark line is the curve giving the best fit to current astronomical data
 
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  • #2
4. silhouette of a woman's breast down to the nipple

Oh, LOL!

And so, would it then be best to describe some of the slopes as "perkier" than the others? LOL! :0)
 
  • #3
Originally posted by Nacho
Oh, LOL!

And so, would it then be best to describe some of the slopes as "perkier" than the others? LOL! :0)

It was a conversation with you in "Newton's" cosmological constant thread that sparked the particular idea so I have to share credit with you on it, and this discussion of the shape of the scale-factor curve in general.
 
  • #4
Well?

Is everybody scared off by the anatomical comparison?

Would you rather the curve were described as a

"convex-then-concave ramp"?

afterthought: or maybe a "tilde ramp"?

the tilde symbol has the right kind of hump-then-dip, like a horizontal version of the ESS curve, so, if you make an upwards-sloping tilde, it looks about right.

the real curve starts out at time zero essentially vertical---infinite slope, and is convex and rounds off, then has an inflection point and becomes concave. being vertical at time zero (a time when expansion was very rapid) is essential to the shape
 
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  • #5
you only get one of these per 1,000 posts, marcus. :wink:
 
  • #6
Originally posted by Phobos
you only get one of these per 1,000 posts, marcus. :wink:

Yes, we have to keep it on the up and up!
I believe in fact that she is wearing a low-cut evening gown.
So everything is perfectly proper after all.

BTW Phobos, how about doing us a favor and responding to
Shadow's question in the Astronomy QA game. I believe Shadow
is a comparative newcomer and he just posted a nice one. I'm
refraining from answering because its time for some other people to get involved, with fresh interests.
 
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1. What is "Picturing the history of the world's expansion"?

"Picturing the history of the world's expansion" refers to the visualization and understanding of how the world has grown and changed over time, including the expansion of human civilizations, geographical changes, and evolutionary processes.

2. How is the history of the world's expansion studied?

The history of the world's expansion is studied through a multidisciplinary approach, combining research and data from fields such as archaeology, geology, paleontology, anthropology, and genetics. This allows scientists to gather a comprehensive understanding of how the world has evolved.

3. What tools and methods are used to visualize the world's expansion?

Scientists use a variety of tools and methods to visualize the world's expansion, including satellite imagery, digital mapping, 3D modeling, and data analysis. These technologies allow for a detailed and accurate representation of the world's history.

4. What are some key findings from studying the history of the world's expansion?

Some key findings from studying the history of the world's expansion include the development and spread of early human civilizations, the movement and adaptation of species, and the impact of natural events such as climate change and geological shifts.

5. How does understanding the history of the world's expansion inform our future?

By studying the history of the world's expansion, we can gain insights into how the world may continue to evolve and change in the future. This knowledge can help us make more informed decisions about environmental and societal issues, and guide our actions towards a sustainable future.

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