6-15-CMB-fluctuations

When we see a hot spot, a cold spot, or a region of average temperature in the CMB, the temperature difference we see typically corresponds to an underdense, overdense, or average-density region at the time the CMB was emitted: just 380,000 years after the Big Bang. This is a consequence of the Sachs-Wolfe effect. However, other, later-time effects can also cause temperature fluctuations