The Pre-Stellar Era: A Glimpse into the Cosmic Darkness

The cosmic dark ages were a period in the early Universe when neutral atoms formed and photons stopped scattering off of free electrons. This marked the time when radiation began to travel in a straight line. The temperature of the photon bath during this period was around 2970.8 K. Overdense regions, with more matter, had stronger gravity and emitted colder photons, while underdense regions emitted hotter photons. Gravity and radiation pressure played crucial roles in the growth of matter clumps, but it took around 50 to 100 million years for the first star to form. The formation of neutral atoms and the subsequent emission of 21 cm light from hydrogen atoms were important milestones before the formation of stars.