The gravitational constant G and the speed of light c are usually treated as independent universal constants. This paper shows that both emerge from the same geometric calibration  of Earth’s rotation and that their product Gc has a simple rational meaning in meters: Gc ≈ 0.02 m. This relation reveals that c defines the right angle (90◦ ) and G defines the density of space as a function of the angle between spatial axes. The equation 10^2 · Gc = 2 connects the decimal volume calibration (1 kg = 1 dm^3) with the geometric definition of space. In the Panvitalistic Theory (PVT), space is 6D (3 lengths + 3 angles), not 3D isotropic. This resolves why massless particles (photons) have zero rest mass: at 90◦ the density of space is minimal.