Figure 25-13 of Universe, 11th ed., shows temperature variations in the cosmic microwave background. Dark areas in the image correspond to regions where the photons were gravitationally redshifted when they left the early universe. Suppose we point a telescope at one of these regions now. What would we expect to see?
A)nothing, because the early universe no longer exists
B)a fuzzy ball, because the primordial fireball is as far back as we can see
C)a red glow, because of the gravitational redshift
D)some structure, perhaps a cluster of galaxies, because such regions indicate clumps of larger density in the early universe

Question

Quizplus · Accepted Answer

Regions in the cosmic microwave background that are darker indicate areas of higher density in the early universe. These denser regions eventually led to the formation of structures such as galaxies and clusters of galaxies due to gravitational attraction. Thus, pointing a telescope at one of these regions today would likely reveal some form of cosmic structure, like a cluster of galaxies.

Figure 25-13 of Universe, 11th Ed