Cosmologists say that when the universe was very young it underwent a period of extremely rapid expansion known as inflation.About 380,000 years after the Big Bang, the CMB came into being.Physicists had expected the temperature of the CMB to be the same everywhere but for 10 years,CMB has grown.It's clear that the temperature fluctuations in the two hemispheres of the sky are different.This means that the density of matter and energy seems more strongly on one side of the sky than on the other.