Q: Measured changes in the CMB radiation?

[Joe Ciancimino]

The cosmic microwave background was a single event that happened literally everywhere in pretty much a single instance. That moment was in the past and is unchanging. What does change is the wavelength of the radiation as it travels through the expanding universe causing the wavelength to grow longer as it passes through expanding space.

My question is this. Can we measure any year to year change in the average wavelength of the CMB? My thinking being, the CMB is the same distance from the observer at any single point in the universe. If such a change could be measured, could that not be used as a Newtonian clock? That is to say, rather than using time as the primary unit of measurement for the age of the universe post CMB to instead use a measurement entropy which would not be effected Lorentz changes due to gravity? (Or at least marginally effected, to which the difference could be ignored in most cases.)

 

[Drakkith]

My question is this. Can we measure any year to year change in the average wavelength of the CMB?

I don't think so. Even a 1% change to the wavelength takes something on the order of a million of years if I remember correctly. I'm not sure our instruments are sensitive enough to detect a change so small.