The Scale-Symmetric Theory (SST) shows that the gravitational constant depends on properties of the two-component spacetime i.e. on properties of the superluminal non-gravitating Higgs field and the luminal gravitating Einstein spacetime. More precisely, the gravitational constant depends on internal structure of neutrinos, inertial-mass density of the Higgs field and on dynamic viscosity and the infinitesimal spin of the tachyons the Higgs field consists of. According to SST, gravitational masses produce gradients in the Higgs field so value of inertial-mass density of the Higgs field inside the neutrino-antineutrino pairs the Einstein spacetime consists of, depends on steepness of gravitational gradients. It leads to conclusion that in experiments with steeper gravitational gradients, the gravitational constant should be lower. But such changes in gravitational constant are too low to be measured. SST shows that in expanding spacetime, value of the gravitational constant must decrease. The invariance of gravitational constant suggests that our Cosmos has boundary nontransparent for the superluminal non-gravitating Higgs field - it is consistent with SST.