What is the shape of the universe?

In summary: We're still working on it. However, Ralph Rotten did a pretty good job summarizing the current thinking on the shape of the universe without getting too bogged down in the details. In summary, the shape of the universe is unknown, but we can make some guesses based on observed structures.
  • #1
bwana
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is the cmb radiation redshifted the same amount in ALL directions? as i understand the data, redshift is a function of distance between 2 points only(scalar quantity). is there a an angular component as well (vector quantity?)

does the fact that there is a 'dipole' mean that the universe is expanding more along a particular axis? in other words, the universe is shaped like a weiner (would Einstein laugh?) The ends of the weiner are further apart so light coming from the ends would be redshifted more than light from any other direction.
 
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  • #2
bwana said:
is the cmb radiation redshifted the same amount in ALL directions?
yes

What is the shape of the universe?
unknown

does the fact that there is a 'dipole' mean that the universe is expanding more along a particular axis?
it is not; it is expanding the same everywhere except inside bound objects (galactic clusters and smaller) where it is not expanding at all.

All of this is cosmology 101 (or earlier)
 
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Thread closed temporarily for cleanup...

Thread re-opened.
 
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  • #5
Ralph Rotten said:
Again, (as in the posts that have been deleted), you are talking about the structures in the universe, which is very interesting stuff but has nothing to do with the OP's question which is what is the shape of the universe. Do you understand the difference?
 
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Well, we can't verify the shape of our universe, but we can make good guesses. And in Ralph Rotten's defense, looking at structures inside the universe does gives us some clues to the shape of a larger system, with limitations ofc.

For example, from looking at our solar system and planets within it, we observed the interaction between gravity and angular momentum, or spin. From these observations and calculated approximations of mass and density of our galaxy both towards the galaxy center and away, we made a good guess of the shape of the Milky Way. We've never seen the entirety of our galaxy ever, but we can be pretty confident about our guess when there is a plethora of other galaxies to verify our models against and everything operates in 4 neat dimensions.

That being said, the Universe may or may not operate on the same principles as the things within it. For example, if the Cosmological Principle holds true and we use the same logic as before, we should be able to say that the universe is relatively close in size in each of its 3 spatial dimensions and that the Universe is not spinning, because matter is relatively distributed and it should not be the case if the Universe is spinning.
But if you think about it for another few minutes, you would realize this idea breaks in quite a few places. I'll leave finding those places to you as I found it quite fun to think about.

However, there are still pieces we can gleam from our observations that are likely to be useful.
What our current theories on the shape of the universe stem from stuff in Einstein's GR, the space-time curvature models portion of it to be more precise.
This link pretty much tries to answer-but-not-answer your exact same question:
https://starchild.gsfc.nasa.gov/docs/StarChild/questions/question35.html
The overall answer is contingent on us getting a bunch of other things about our universe right, such as dimensionality, rate of change in the rate of expansion, etc.
 

1. What is the shape of the universe?

The shape of the universe is a complex and debated topic in astronomy and cosmology. It refers to the overall geometry of the universe, which can be described using mathematical models and observations of the universe's structure and expansion. Currently, scientists believe that the universe is flat, meaning that it has zero curvature, and is infinite in size.

2. How do scientists determine the shape of the universe?

Scientists use various methods to determine the shape of the universe, including observations of the cosmic microwave background radiation, the large-scale distribution of galaxies, and the expansion rate of the universe. By analyzing these data, scientists can calculate the overall geometry of the universe and determine its shape.

3. What are the different proposed shapes of the universe?

There are three main proposed shapes of the universe: flat, open, and closed. A flat universe has zero curvature and is infinite in size, while an open universe has negative curvature and is also infinite in size. A closed universe has positive curvature and is finite in size, meaning it would eventually loop back on itself.

4. What evidence supports the idea of a flat universe?

The strongest evidence for a flat universe comes from observations of the cosmic microwave background radiation, which is the leftover heat from the Big Bang. This radiation is incredibly uniform and shows no signs of curvature, supporting the idea that the universe is flat. Additionally, measurements of the expansion rate of the universe also suggest a flat shape.

5. Could the shape of the universe change over time?

The shape of the universe is believed to be constant and unchanging. However, some theories suggest that the shape of the universe could have changed in the very early stages of its existence, shortly after the Big Bang. But currently, there is no evidence to support the idea that the shape of the universe is changing or will change in the future.

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