Read section 8.12 and answer question 22.
Below is an image from the Wilkinson Microwave Anisotropy Probe (WMAP) team has made the first detailed full-sky map of the oldest light in the universe. This full-sky temperature map of the cosmic microwave background shows a red band in the foreground that corresponds to the signal from our galaxy. The galactic foreground signal is strongest in 23 gigahertz. Combining the data from all the frequencies and removing the Milky Way signal allows the generation of a map (Figure 8.23: The Microwave Sky) that eliminates most of the signal from our Galaxy, revealing the light coming from much farther away.
Figure 8.23: The Microwave Sky
The first detailed, all-sky picture of the infant universe released in February 2003. The WMAP image reveals 13 billion+ year old temperature fluctuations (shown as color differences) that correspond to the seeds that grew to become the galaxies and clusters of galaxies. Encoded in the patterns are the answers to many age-old questions, such as the precise age and geometry of the Universe.