Final answer:
The cosmic microwave background (CMB) shows slight temperature variations due to Earth's motion and initial density fluctuations in the universe; these 'wrinkles' are captured by spacecraft like WMAP and are key to understanding the formation of galaxies.
Step-by-step explanation:
The cosmic microwave background (CMB) appears to be slightly warmer in one direction and cooler in the opposite due to our motion relative to the CMB itself. When we measure the CMB, we observe very uniform temperatures across the sky due to the incredibly smooth nature of the universe after the Big Bang. However, the slight temperature variations we do observe in the CMB are due to the Doppler effect as a result of Earth's motion and are also related to the tiny fluctuations in density that existed when the CMB light was first released. These tiny fluctuations, also referred to as 'wrinkles,' are highlighted in data from the WMAP spacecraft, where red spots show slightly higher temperatures and densities, and blue spots represent cooler, less dense areas. The temperature fluctuations are incredibly small, less than one part in 1000, and they are important because they are thought to be the seeds of the eventual formation of galaxies.
Moreover, another cause for the uniform temperature despite regions being beyond each other's horizon at the time of the CMB's emission is addressed by the Inflationary Hypothesis, proposing that the universe went through a period of rapid expansion, which smoothed out any irregularities.