What provides evidence for the early moments of the Universe's existence as per the Big Bang theory?

The Cosmic Background Radiation, often referred to as the Cosmic Microwave Background (CMB), serves as a critical piece of evidence for the early moments of the Universe following the Big Bang. This radiation is a remnant from when the Universe was approximately 380,000 years old, a time when it had cooled enough for protons and electrons to combine and form neutral hydrogen atoms. This transition allowed photons to travel freely through space, creating a uniform background radiation that fills the Universe.

When we observe the CMB today, we see it as a nearly perfect black body spectrum at a temperature of about 2.7 Kelvin. The uniformity of this radiation across all directions in space supports the theory that the Universe was once in a hot, dense state and has been expanding ever since. Variations in the CMB are also critical for understanding the large-scale structure of the Universe and the distribution of matter, providing insights into the seeds of cosmic structure formation.

Other options, such as stellar parallax, dark matter, and galactic clusters, while important topics in astrophysics, do not specifically provide evidence for the early moments of the Universe. Stellar parallax is a method of measuring distances to nearby stars, dark matter is an unseen component that affects galactic