It might be useful as a theoretical model to consider the universe contracting to the size of a single atom, Not a singularity, Since

 

Esmating total mass,

 

 

density

4.5 × 10^-30 and 1.8 × 10^-29 grams per cubic centimeter

 

Radius

3 × 10²⁶ meters

1.8 * (10^(-29)) (grams per cc) = 1.8 × 10^-23 grams per (cubic meter)

 

total mass= D * 4/3(PI)R^3=  2.035752e+103 or

 

 (2 * 10^100 kg, nice even number, low end est.)

 

 

  could see that during the early moments the expansion  particle number quickly increases as force decreases. The expansion initially accelertes based on star lifespns and later contrancts due to stars dimming essentially. Photonsmight evolve into atoms based on frequencies. That mass could also give a direct ene estimate based on e=mc^2+ momenum term.