Looking for a good analogy of the shape of the expanding universe

[Andrew Bone]

I have heard people say there is no center to the expansion of the universe. I have also heard the expansion described as an ever expanding balloon with all galaxies as dots on the surface. These to statements seem contradictorily to me.

If the expansion of the universe was like the above balloon example wouldn’t all galaxies be close to the edge or event horizon with a huge volume of empty space in the middle of which we could easily locate or at least mathematically define the center (e.g. we can determine the center of a balloon if we understand its size and dimensions).

I get that my lack of understand likely stems from the shortfall of the metaphor but I was hoping someone could explain the expansion in terms that make sense to a non-physicist.

 

[A.T.]

The 2D balloon surface represents the universe. The 2D balloon surface doesn't have an intrinsic center that lies within the surface. The universe doesn't have an intrinsic center that lies within the universe. Whether the universe is actually embedded in a higher dimensional space, like the balloon surface, is speculation and not relevant to the intrinsic geometry.

 

[Chronos]

We have good observational evidence the universe either does not have a center, is unfathomably enormous, or, we ARE the center of the universe. Were this not true we would see fewer galaxies in the direction opposite the 'center'.

 

[Velikovsky]

I have heard people say there is no center to the expansion of the universe. I have also heard the expansion described as an ever expanding balloon with all galaxies as dots on the surface. These to statements seem contradictorily to me.

If the expansion of the universe was like the above balloon example wouldn’t all galaxies be close to the edge or event horizon with a huge volume of empty space in the middle of which we could easily locate or at least mathematically define the center (e.g. we can determine the center of a balloon if we understand its size and dimensions).

I get that my lack of understand likely stems from the shortfall of the metaphor but I was hoping someone could explain the expansion in terms that make sense to a non-physicist.

The balloon analogy gives the impression of an ever expanding mass where all the bodies within that mass move further away from each other. It's a rather bleak prospect for astronomers in the future were the heavens grow increasingly dim. I like to envision a series of balloons expanding within one another. If we occupy a balloon in the middle and look to an inward expanding balloon we see a dense mass of galactic and intergalactic material expanding rapidly towards us. They however see a slightly less densely populated universe expanding at a slower velocity away from them. If we in turn look outwards we see what they see. If there is a centre to the universe, I am always perplexed as to what it,s motivative force is? Or that other old nut; " into what are we expanding?". Expansion is another concept that may be misleading, are we "the universe" being "pushed" deeper into the void? or are we being "pulled" into it?
Sorry for the comment, but as always with concepts of universal expansion; we re left with more questions and paradoxes and little in absolute certainty.

 

[pmacias]

I can understand your confusion about the expanding universe and its shape. The balloon analogy is often used to help visualize the expansion of the universe, but it is important to understand that it is just an analogy and not a perfect representation of the actual phenomenon.

In reality, the universe is expanding in all directions simultaneously, much like the surface of a balloon expanding as it is inflated. However, unlike a balloon, the universe has no center or edge. This means that all galaxies are moving away from each other, and there is no central point from which this expansion originates.

To understand this better, we can think of the universe as a three-dimensional grid, with galaxies evenly distributed throughout. As the universe expands, the grid itself expands, with each point moving away from its neighboring points. This means that there is no point that can be considered the center of the expansion, as all points are moving away from each other.

It is also important to note that the expansion of the universe is not happening within a fixed space, like the surface of a balloon. Instead, the very fabric of space itself is expanding. This means that there is no empty space in the middle of the expanding universe, as every point in space is being stretched and expanded.

I hope this helps to clarify the concept of the expanding universe for you. It is a complex and fascinating phenomenon, and while analogies can be helpful, they should always be taken with a grain of salt and not be seen as a perfect representation of the actual science.