Wednesday, May 16, 2012

time-variation of the CMB

does the pattern of hot and cold patches of the CMB change in time? if yes, on what time scale?

bonus question: which parts of the CMB spectrum will gain in amplitude and which effects will loose in their importance?


  1. Yes, the CMB will change, with a time scale of 1/Ho

  2. I basically agree. But, well, 1/Ho holds for the largest scales of the fluctuations only. The most prominent scale of the fluctuations is around 2 degrees apparently, which corresponds to something like 300 Mpc linearly. Light takes only 1 billion years to traverse that, not 13 billion years. That is, after 1 billion years the patter will have changed drastically. And after a few hndred years, a VERY sensitive measurement (10-6) could already detect the change.
    Uli Bastian
    (the above I learned about two years ago from Bjoern Schafer)