Universe Expansion: Understanding the Concept

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SUMMARY

The discussion centers on the concept of universe expansion, clarifying that while the universe is expanding, individual stars and galaxies maintain their velocities and do not move beyond their coordinates. The balloon analogy is highlighted as an effective way to visualize this expansion, where the space between points (representing stars and galaxies) expands without altering their positions. It is emphasized that gravitational forces can overpower this expansion in gravitationally bound regions, such as galaxy clusters. The conversation also touches on the relationship between expansion, density, and the potential for new matter creation.

PREREQUISITES
  • Understanding of cosmic expansion concepts
  • Familiarity with gravitational forces and their effects on celestial bodies
  • Basic knowledge of astrophysics terminology
  • Awareness of the balloon analogy for visualizing expansion
NEXT STEPS
  • Explore the balloon analogy in detail at www.phinds.com/balloonanalogy
  • Study the FAQ subforum on Physics Forums for foundational concepts in cosmology
  • Read the tutorial on cosmic expansion at http://www.astro.ucla.edu/~wright/cosmo_01.htm
  • Investigate the recent thread on Physics Forums related to universe expansion for additional insights
USEFUL FOR

Astronomy enthusiasts, astrophysics students, and anyone interested in understanding the dynamics of universe expansion and gravitational interactions among celestial bodies.

Abscissas
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Hey i am new to the forum but i have done some studying and I am trying to wrap my head around something but I am not sure if I am quite getting it i was hoping if someone could direct me to some reading or books, and so here it is, i was recently explained to that as the universe is expanding everything in it expands with it like a graph being stretched but for example the stars are on the points in the graph now, but does that mean that the stars and galaxies don't move beyond these points but i know that's not true is it? or is it moving in sync with the points on the graph, or am i just looking at this the wrong way?
 
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Abscissas said:
Hey i am new to the forum but i have done some studying and I am trying to wrap my head around something but I am not sure if I am quite getting it i was hoping if someone could direct me to some reading or books, and so here it is, i was recently explained to that as the universe is expanding everything in it expands with it like a graph being stretched but for example the stars are on the points in the graph now, but does that mean that the stars and galaxies don't move beyond these points but i know that's not true is it? or is it moving in sync with the points on the graph, or am i just looking at this the wrong way?

Perhaps this will help:

www.phinds.com/balloonanalogy
 
Phinds balloon analogy is a good one.
On the descriptive you gave above. I would like to clarify you graph analogy. Think of those points on the graph as coordinates. The coordinates do not change. The space between coordinates expand evenly in all directions. Expansion does not provide inertia or motion to those coordinates Individual stars and galaxies maintain their normal velocities. That graph example only represents expansion which has nothing to do with inertia.
One other note expansion is easily overpowered by gravity. Such as galaxy clusters. So we usually state that expansion does not occur in gravitationally bound regions.
 
Thank you for your response and the great read so let's say the pennies are expanding on the surface of the balloon they don't change mass or velocity am i correct? but now this leads me to ask how do the galaxies move? is it from the momentum of each others gravity?
 
Mordred said:
The coordinates do not change. The space between coordinates expand evenly in all directions.
This is where i become less read but I am going to try to use common sense, if the universe is expanding then the volume in it must be decreasing unless new matter is being created.Is there a particular reason why the universe is expanding? at this point i feel like i can find the answer somewhere in the forums, rendering this post useless i suppose my question is why is the universe expanding and would there be a way to ride the expansion sort of like an ocean wave or to accelerate it?
 
FAQs is a good place to start.
The FAQ subforum has some good articles.

Also this site has a decent tutorial as well

http://www.astro.ucla.edu/~wright/cosmo_01.htm

In your questions above switch
volume with density. The link I provided along with the PF FAQ subforum will provide those answers.
 
Thank you
 
Thank you man your a very helpful person it is greatly appreciated
 

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