| Substance | ρ in kg/m3 | g in m/s2 | Light Speed c in m/s |
| AIR | 1225 | 3.42 × 10−10 R | 3 × 108 = c |
| WATER | 1000 | 2.79 × 10−7 R | 2.25 × 108 = 0.75c |
| GLASS | 2500 | 6.98 × 10−7 R | 2 × 108 = 0.67c |
| DIAMOND | 3500 | 9.77 × 10−7 R | 1.25 × 108 = 0.42c |