Undergrad CMBR and the expansion history of the Universe

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The Cosmic Microwave Background Radiation (CMBR) provides a snapshot of the universe at the time of last scattering, reflecting its state then rather than the entire expansion history. While the redshift of the CMBR indicates the total amount of expansion since that time, it does not reveal the specifics of how that expansion occurred. This concept parallels the observation of redshifted galaxies, where the image reflects the state at emission, altered by subsequent expansion. The Planck Survey's findings on the flatness of space pertain to the universe's condition at last scattering, not its current state. Thus, while the CMBR contains valuable information, it cannot independently detail the full history of cosmic expansion.
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Does the CMBR contain the imprint of the entire expansion history of the universe or only of the last scattering ?
 
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It's a snapshot of the state of the universe at last scattering. Its redshift contains information about the total amount of expansion over the remaining history of the universe, but not the details of how that expansion has happened.
The two can be combined into a model that tracks the entire expansion history, but that information isn't there in the light itself.
This is similar to observing a particular redshifted galaxy - the image is of the state at emission, modified (redshifted) by the amount of expansion undergone until reception.
 
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Bandersnatch said:
It's a snapshot of the state of the universe at last scattering. Its redshift contains information about the total amount of expansion over the remaining history of the universe, but not the details of how that expansion has happened.
The two can be combined into a model that tracks the entire expansion history, but that information isn't there in the light itself.
This is similar to observing a particular redshifted galaxy - the image is of the state at emission, modified (redshifted) by the amount of expansion undergone until reception.
So when the Planck Survey of CMBR observed that space is flat, is that a measure of flatness of the present universe or during last scattering?
 

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