Question

1. why is the cmb considered the \afterglow\ of the big bang?
2. on the cosmic calendar, when did humans appear? what does that suggest about our place in cosmic history?

Explanation:

1. The CMB is considered the "afterglow" of the Big Bang because it is the residual radiation left over from the early - hot, dense state of the universe. After the Big Bang, the universe was filled with hot plasma. As it expanded and cooled, the radiation decoupled from matter and has been traveling freely since then, now detected as a nearly uniform microwave radiation across the sky.
2. On the Cosmic Calendar (where the entire history of the universe is compressed into one year), humans appear just a few seconds before midnight on December 31st. This suggests that in the vast scale of cosmic history, the existence of humans is a very recent and relatively tiny part of the overall timeline.

Answer:

1. It is residual radiation from the early universe after the Big Bang.
2. Humans appear just a few seconds before midnight on December 31st on the Cosmic Calendar. It suggests humans are a very recent part of cosmic history.