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I need to know about the data, which scientist have already received from JWST about the CMB.

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    $\begingroup$ JWST doesn't observe in the microwave range... $\endgroup$
    – Sten
    Commented Sep 25, 2023 at 6:39
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    $\begingroup$ @Sten But couldn’t this information be obtained indirectly using his measuring instruments? $\endgroup$
    – ayr
    Commented Sep 25, 2023 at 7:01
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    $\begingroup$ @dtn something like measuring heating of gas by the CMB? $\endgroup$
    – Sten
    Commented Sep 25, 2023 at 7:32
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    $\begingroup$ @Sten or something like a microwave radiometer with Horn antennas, like here. True, I don’t know if there is similar equipment at JWST. Or calculating microwave background parameters from other measured data using mathematical models. $\endgroup$
    – ayr
    Commented Sep 25, 2023 at 8:10
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    $\begingroup$ @dtn That's not really a discussion to have in the comments of somebody else's question, but if you want to post your own question, feel free. $\endgroup$ Commented Sep 25, 2023 at 13:03

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The James Webb Space Telescope is very specifically built to look at infrared light, not microwaves, so it hasn't collected information about the Cosmic Microwave Background directly. However, you might have recently heard about JWST and CMB in the same discussion because JWST has been observing Cepheid variable stars, which are related to CMB in an indirect sort of way.

The ongoing so-called "crisis in cosmology" is that there are two ways to measure the expansion of the universe: one by examining the CMB, and the other by observation of supernovas, using Cepheid variables to determine distance calibrations. The "crisis" is that the two measurements' error bars have shrunk to the point that they no longer overlap: there is no value that could fit both measurements. We have two ways to measure expansion, and they fundamentally disagree on the answer.

JWST recently did some work to see if the Cepheid distance values were being biased by other nearby stars interfering with our brightness measurements (which was one theory of why we might be seeing this divergence), but the result was that no, we actually had done a good job of adjusting for that and our distance measurements seem to be working correctly -- so the "crisis" continues.

Footnote: I dislike the term "crisis" because it implies that there's an emergency, that our whole understanding of the universe and physics itself is in danger of collapse -- which is of course absurd. As it's said, scientific progress very rarely sounds like "Eureka! I have found it!"; instead it usually sounds like "Huh. That's weird..." The fact that we have two measurements that disagree is not a terrible thing (however frustrating it might be for the theorists), because it's a signpost that shows us that there's something we should study right over there.

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