If the cosmic microwave background radiation (CMBR) is the remnant of the Big Bang’s fireball, we expect to see hot and cold regions in it. What are two causes of these wrinkles in the CMBR? Are the observed temperature variations greater or less than originally expected?

The CMBR (cosmic microwave background radiation) is the remnant of the big bang’s fireball. The old observation regarding temperature shows the uniform variation of the temperature but details and further studies show crack’s or wrinkles in the temperature variation.

Turbulence and quantum fluctuations, which form stars and galaxies over time, are the causes of wrinkles in CMBR. Because these phenomena occurred in the very early stages of our universe's development, it was expected that temperature variations would be prominent on a large scale due to the fact that the universe was expanding very rapidly, so every small-scale fluctuation at one moment would quickly blow up to a large-scale fluctuation at the next.

This was not found to be the case. The temperature variations were smaller than expected because the CMBR was very smooth and isotropic.