Measurment that proves that the universe is flat

In summary, this blog post discusses how temperature fluctuations in the universe can be used to determine the curvature of the universe. The blog post mentions that the curvature must be zero in order to use this measurement and that a proof in physics is something that is not possible because you can never be sure that something will not be false in the future. Two other blog posts on the same topic mention the same thing.
  • #1
alkmini
28
0
hello
I have a question:
i am trying to understand how we find out that the curvature of the universe is zero using the angular size of the hot spots of the d microwave background radiation.
http://scienceblogs.com/startswithab...tire-universe/
there is a picture in this blog showing the light rays from the opposite sides of the hot spots.
My question is: doesn't the proof that the curvature is zero require that the rays are parallel to each other? If they are parallel in a positively curved universe they converge. But in a flat one they should remain parallel and in a negatively curved they should diverge. Then, in the last two cases, how do they meet in the eye?
 
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  • #2
The universe may be flat, but locally there will be gravitational effects which curve light rays.
 
  • #3
thank you for your reply mathman
when we measure the apparent size of temperature fluctuations, in order to determine the curvature of the universe, is the measurement local or global ?
 
  • #4
Your link is broken.

My question is: doesn't the proof that the curvature is zero require that the rays are parallel to each other?
You can use non-parallel rays and see how the angle between them evolves. In a flat universe, it does not change, in a universe with curvature it does.

No visible curvature is not a proof that the universe is flat - that is impossible. But it set an upper limit on the curvature (at least in that direction of space).
 
  • #6
i don't understand why the angular size of temperature fluctuations should be 1 degree to prove that it is flat
 
  • #8
alkmini said:
the foolowing are 2 other links that say the same thing .
http://www.einstein-online.info/spotlights/cosmic_sound/?searchterm=angular size



i don't understand why it is a proof and i don't understand why it is not a proof either


Proofs are for math, not physics. NOTHING in physics is considered proven because you can never show that there will not some day be an example of it being false. The best you can do is show that a theory fits the evidence extremely well and better than anything else.
 
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  • #9
well, maby it is not a proof, but this in not what i am looking for. I am just trying to understand the thought, the logic, behind what may , or may not be a proof. the insight is interesting
 

Related to Measurment that proves that the universe is flat

1. How is the universe's flatness determined through measurement?

The flatness of the universe is determined through various astronomical measurements, such as the cosmic microwave background radiation and the large-scale distribution of galaxies. These measurements are used to calculate the curvature of space and determine if it is flat or curved.

2. What is the significance of a flat universe?

A flat universe has significant implications for the future of our universe. It suggests that the expansion of the universe will continue forever, as opposed to a closed universe where the expansion eventually stops and reverses. A flat universe also supports the theory of cosmic inflation, which explains the uniformity of the universe on a large scale.

3. How do scientists measure the curvature of space?

The curvature of space is measured by looking at the geometry of the universe on a large scale. This can be done through observations of the cosmic microwave background radiation, which is the leftover radiation from the Big Bang, or by studying the distribution of galaxies and their redshifts.

4. Can the flatness of the universe change over time?

According to current theories and measurements, the flatness of the universe is a fundamental property that does not change over time. However, the expansion of the universe may cause the curvature of space to deviate from perfect flatness, but it would still be considered a flat universe.

5. 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 has been found to be extremely uniform and consistent with a flat geometry. Additionally, studies of the large-scale structure of the universe and the behavior of light from distant objects also support the idea of a flat universe.

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