Using the CMB to verify the universe is flat

In summary, the video claims that if you use the Earth as the apex of a triangle, then you can measure the angles of the triangle and use this information to determine the size and shape of the universe. The video also claims that you can measure the distance to the last scattering surface using the acoustic oscillation of the cosmic microwave background.
  • #1
robertjford80
388
0
There is a video on youtube called how do we know the universe is flat. (put those keyword in youtube and you should find it, I can't post links to videos until I have 10 posts) It has something to do with using the Earth as an apex of a triangle then measuring two points on the cosmic microwave background. I'm assuming they then add the angles of the triangle up to 180 degrees. Well, how do you know what the angles of your triangle are? I've seen three tries at attempting to explain this. No one succeeds. There is also something about going around the Earth in a balloon in Antartica and I don't see why that is necessary.
 
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  • #2
There is a very special length scale for the perturbations in the cosmic microwave background. This scale is defined by speed of sound in the initial soup of hot plasma, and basically it's the distance across which sounds waves had time to travel before CMB decoupled from the plasma. We can determine this distance theoretically (given a certain cosmological model).

When you measure CMB today, you can see this length scale very clearly in the data: it corresponds to the highest peak in http://lambda.gsfc.nasa.gov/product...nyear/powspectra/images/med/dl7_f01_PPT_M.png. The position of the peak tells us what is the angle that this length is seen in the sky; it's about 1 square degree. We can also determine the angular diameter distance to the last scattering surface (again given a cosmological model, so the possible curvature enters the calculation here). Then we can compare to observations via
[tex] d_A = \frac{x}{\theta}, [/tex]
where dA is the angular diameter distance, x is the actual size of these sound waves and [itex] \theta [/itex] is the angle we observe in the sky.
 
  • #3
Already been done, its called the baryonic acoustic oscillation of the cmb.
 

1. What is the CMB and how is it used to verify the flatness of the universe?

The Cosmic Microwave Background (CMB) is the leftover radiation from the early universe, which is now observed as low-energy microwaves. By analyzing the pattern and intensity of this radiation, scientists can determine the curvature of the universe and verify its flatness.

2. How does the CMB support the theory of a flat universe?

The CMB is considered to be the most direct evidence for the flatness of the universe. According to the theory of inflation, the universe underwent a rapid expansion in the early stages, resulting in a flat geometry. This is consistent with the uniform distribution of the CMB across the sky, which would not be observed if the universe had a curved geometry.

3. What other evidence supports the flatness of the universe?

In addition to the CMB, other observations such as the large-scale structure of the universe, the cosmic microwave background lensing, and measurements of the cosmic microwave background temperature all support the theory of a flat universe. These observations are consistent with a flat geometry and would not be possible if the universe had a significant curvature.

4. Are there any competing theories to the flat universe model?

While the flat universe model is currently the most widely accepted, there are some competing theories, such as the closed universe model and the open universe model. These models propose different geometries for the universe, but currently, there is no conclusive evidence to support them over the flat universe model.

5. How does the flatness of the universe impact our understanding of the cosmos?

The flatness of the universe has significant implications for our understanding of the cosmos. It suggests that the universe is infinite and has no boundaries, and that it will continue to expand forever. It also supports the theory of inflation and helps to explain the large-scale structure of the universe. Additionally, the flatness of the universe has implications for the study of dark energy and the ultimate fate of the universe.

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