Signals, noise, and the discovery of CBR

I’m reading with interest, not knowing enough to post, but I was thinking when Patrick mentioned CBR and the “noise” that, truly, what is “signal” and what is “noise” in that case, at least, was of paramount importance. The noise ended up to be the signal, right?

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Yes, but only after a change of viewpoint.

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Right! I was intending to agree with you!


well in the CBR case, the signal that Penzias and Wilson were looking for was a signal coming from the center of the Milky way galaxy. What they measured was a homogeneous noise coming from everywhere (isotropic). This noise was also adiabatic and Gaussian. A noise at 2.7 degrees K coming from everywhere, very uniform, very Guassian, a nearly prefect blackbody radiation. Penzias and Willson had no idea what it was but it was everywhere, day and night, summer and winter, unvarying, homogenious, isotropic noise.

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I remember reading about that! I think that they first thought it was bird poop on the satellite mesh… Didn’t they even tell people to pressure wash it before they discovered it was the CBR causing the “noise”??

We must be reading the same ID books.

At first they thought it was radio interference from New York City. Then the Sun, then the center of the Milky Way Galaxy. They thought it was nonlinear reflections from the metal rivets inside the antenna and had them filed down flat. The pigeon nesting was a clean up problem. Here is there entire paper that won them the Nobel Prize. It is only a page long and starts at the bottom of page 419.


As an old radio guy (amateur radio) with an interest in radio astronomy, I enjoyed reading the description above of the testing they did. They went through every mundane possible cause of the problem, but then didn’t stop there.

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