Considering our light speed growing Planck scale universe, it seems possible to develop a practical model of Hubble-Hawking Universe by using which cosmic temperature and Hubble parameter can be correlated accurately. Without considering galactic dark matter, galactic flat rotation speeds can be addressed with ‘super gravity’ of galactic baryonic mass. In this context, (180 to 200) million solar masses can be considered as a characteristic upper mass limit of ordinary gravity. Considering the proposed current upper mass limit of ordinary gravity as a characteristic weak interaction mass unit, hypothecated galactic dark matter can be quantified. Clearly speaking, weak interaction boosts the gravity of galaxies in proportion to their virtual dark mass as (galactic baryonic mass)3/2 / (200 million solar masses)1/2. Based on cosmic recombination temperature and baryon acoustic bubble radius, upper mass limit of gravity can also be fitted. With further study, dark matter existence and physical properties can be explored.