Galaxies on the Edge: Understanding the Expansion of the Universe

  • Thread starter Thread starter jimjohnson
  • Start date Start date
  • Tags Tags
    Expansion
AI Thread Summary
The discussion explores the analogy of the universe's expansion using raisins in a loaf of bread, illustrating how galaxies move away from each other. A key question raised is how outer galaxies can exist on the surface while all appear to be in the middle, leading to confusion about their perspective. The analogy is clarified by comparing it to spots on a balloon's surface, emphasizing that no raisin sees an asymmetric universe due to the lack of boundaries. The conversation also touches on the concept of our 3D universe being curved in 4D, which helps explain the expansion without a definitive edge. This model provides a logical framework for understanding the universe's expansion despite its complexity.
jimjohnson
Messages
83
Reaction score
0
The analogy for the expansion of the universe is explained as raisins (mass, or galaxies) expanding inside an expanding loaf of bread (bread being space), everything is moving away from everything else. This may be a simplistic question, but when the expansion started some raisins were on the outside of others. Where are the raisins on the outer surface, how can all raisins be in the middle? These galaxies would look opposite the expansion and "see" nothing. What am I missing?
 
Physics news on Phys.org
The analogy is from the SURFACE of the loaf to the VOLUME of space.
 
Sorry, do not understand response, the surface would be 2 dimensions. tks
 
What Mathman is saying is that the analogy is an analogy. The analogy is a 2D example of what could happen in 3D.
 
I think jim asked a very fair question, which is a long way short of an answer.

Jim's pudding analogy is of an expanding euclidian 3D object, not a map from a 2D one to a 3D one.

This issue of the edge galaxies can be addressed in two ways?

How do we know (what evidence is there) that the inhabitants don't see an asymmetric universe?

The second is the current explanation which is by no means proven.

The thinking runs as follows.

Instead of the raisins being distributed throughout your pudding, imagine they are just popped onto the outer surface, as if they were spots painted on a balloon. So the zone of raisins or spots really is a 2D surface in a 3D world. In this model or analogy no raisin sees an asymmetric view as there is no boundary in the 2D of the durface.

Now let the dough rise so the pudding expand. The outer surface gets bigger and all the raisins move farther away from each other. There is stil no boundary so the raisins maintain their viewpoint.

Translating this model to our 3D universe, The most widely accepted explanation of theory and observable facts in modern physics is that our 3D space is 'curved' in 4D, just as the 2D surface of the pudding is curved in 3D.
 
This is hard to visualize but a logical explanation which I have not read before. Thanks for response.
 

Thread 'Need help understanding particle physics and quantum physics'

So I know that electrons are fundamental, there's no 'material' that makes them up, it's like talking about a colour itself rather than a car or a flower. Now protons and neutrons and quarks and whatever other stuff is there fundamentally, I want someone to kind of teach me these, I have a lot of questions that books might not give the answer in the way I understand. Thanks
View full post »

Thread 'Raman Spectroscopy help'

I am attempting to use a Raman TruScan with a 785 nm laser to read a material for identification purposes. The material causes too much fluorescence and doesn’t not produce a good signal. However another lab is able to produce a good signal consistently using the same Raman model and sample material. What would be the reason for the different results between instruments?
View full post »

Similar threads

I Perceived vs. Actual Velocity in an Expanding Universe
Replies
2
Views
2K
I Is the expansion of the universe affecting time or just space?
Replies
22
Views
3K
I How fast were distant galaxies moving?
Replies
7
Views
2K
I How do you get to the conclusion that there is accelerating expansion?
Replies
23
Views
2K
Explanation of expanding universe
Replies
2
Views
2K
I Expansion of Space: Questions on How the Universe Works
Replies
1
Views
1K
B Can the "creation" of space in the Universe affect the speed of light?
Replies
7
Views
3K
I How Does Space Expansion Affect the Velocity of Galaxies?
2
Replies
65
Views
6K
I Expansion-Collapse cycle in cosmological structures?
Replies
1
Views
2K
I The Universe is expanding with acceleration
Replies
5
Views
3K

Hot Threads

Recent Insights

Back
Top