Question

At the time of recombination (z = 1100), the largest CMB temperature fluctuations (hot spots and cold spots) were 380,000 lightyears in size. What size (in Mpc) are these CMB fluctuations today (1 Mpc = 3.1 × 10⁶ lightyears)? Write two or three sentences about how this size compares to the sizes of galaxy clusters today (which are around 100-150 Mpc in size) and what the connection is between the CMB fluctuations and galaxy clusters.

Answer 1