Constraints on the Singularity: Resolving the Initial Conditions of the Hot Big Bang Model

 This paper examines the theoretical framework of the initial singularity in the standard Hot Big Bang model. While the model successfully predicts the cosmic microwave background (CMB) radiation and the abundance of light elements, the singularity itself represents a breakdown of classical general relativity. We review the physical conditions at Planck time (10⁻⁴³ seconds) and discuss why extrapolation back to t=0 leads to infinite density and temperature. Using a combination of quantum gravity considerations and loop quantum cosmology, we propose that the singularity may be replaced by a "quantum bounce," offering a finite, non-singular starting point for cosmic expansion. Observational windows, such as the large-scale homogeneity of the CMB and the lack of certain gravitational wave signatures, are presented as indirect constraints on pre-Big Bang physics.