History of CMB, prediction of 1 in 100,000?

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Discussion Overview

The discussion centers on the history and prediction of cosmic microwave background (CMB) temperature variations, specifically the measurement of anisotropies at a level of 1 part in 100,000. Participants explore the origins of these predictions, the contributions of various scientists, and the theoretical frameworks involved.

Discussion Character

  • Historical
  • Exploratory
  • Technical explanation

Main Points Raised

  • One participant notes that variations in the CMB were first measured by COBE and questions whether this value was predicted and what the estimates were prior to measurement.
  • Another participant discusses Robert Dicke's contributions to the prediction of the CMB while developing radar receivers, highlighting his encouragement of the Bell Labs team that first detected the CMB radiation.
  • It is mentioned that Dicke, along with Jim Peebles, re-derived the prediction of the CMB in the early 1960s, although he may have overlooked earlier predictions by George Gamow and others.
  • A participant references a paper by Steven Weinberg discussing expected thermal variations in the CMB based on Brans-Dicke theory, suggesting that Weinberg predicted anisotropies at the level of 10^-5, but seeks to confirm the relevant texts and publication dates.
  • Another participant shares a link to a paper discussing contributions by Sunyaev and Zel'dovich, and Peebles and Yu, from 1970, which may provide additional context.
  • There is mention of revisions to Weinberg's cosmology primer that include discussions on CMB anisotropies, but it is noted that these are not peer-reviewed publications specifically making predictive claims.
  • A later post references a specific paper by Weinberg that offers a method for calculating CMB anisotropies, but does not clarify whether it includes predictive elements.

Areas of Agreement / Disagreement

Participants express various viewpoints regarding the history and prediction of the CMB, with no clear consensus on the precedence of predictions or the specific contributions of different scientists. The discussion remains unresolved regarding the exact nature of the predictions and their historical context.

Contextual Notes

Some limitations include the potential for missing assumptions in the historical accounts, the dependence on specific definitions of predictions, and unresolved details regarding the publication dates of relevant works.

windy miller
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Variations in the tamperatureo of the CMB are 1 part in 100,00. My understanding is that this was first measured by COBE, But was this value predicted?
What were the ranges of estimates for its value before it was measured?
 
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Robert Dicke predicted the CMB while developing radar receivers beginning in the 1940s into 1960s. Dicke strongly encouraged the working group at Bell Labs who first detected the CMB radiation on the Homdel horn antenna. Dicke's Princeton research group verified the discovery and documented the second CMB detection using a super-cooled receiver of his design.

In the early 1960s, work on Brans–Dicke theory led Dicke to think about the early Universe, and with Jim Peebles he re-derived the prediction of a cosmic microwave background (having allegedly forgotten the earlier prediction of George Gamow and co-workers). Dicke, with David Todd Wilkinson and Peter G. Roll, immediately began building a Dicke radiometer to search for the radiation.

They were preceded by the accidental detection made by Arno Penzias and Robert Woodrow Wilson (also using a Dicke radiometer), who were working at Bell Labs near Princeton.[11][12] Nevertheless, Dicke's group made the second clean detection, and their theoretical interpretation of Penzias and Wilson's results showed that theories of the early universe had moved from pure speculation into well-tested physics.[13][14]

I read a paper by Steven Weinberg (IMS) describing expected thermal variations in CMBr based on Brans-Dicke theory confirmed by COBE measurements. I would like to say Weinberg predicted 10-5 anisotropies but need to locate the relevant texts and publication dates. George Gamov likely maintains precedence, as the above excerpt describes.
 
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Let me know if you find it thanks.
 
I found a paper (https://arxiv.org/abs/astro-ph/0501171) citing discussion by Sunyaev and Zel'dovich, and by Peebles and Yu, both in 1970. There are also review papers cited that may help.
 
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windy miller said:
Let me know if you find it thanks.
No, I did find revisions to his cosmology primer "First Three Minutes" that include CMBr (rev 3) and significance of anisotropies (rev 6 ), not a peer reviewed pub but in the OP period of interest.

Weinberg published numerous cosmology papers on the topic but not specifically "predictive".
From early this century:
astro-ph gr-qc hep-th
A No-Truncation Approach to Cosmic Microwave Background Anisotropies​
Authors: Steven Weinberg
Abstract: We offer a method of calculating the source term in the line-of-sight integral for cosmic microwave background anisotropies without using a truncated partial-wave expansion in the Boltzmann hierarchy.​
 

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