3.3. The relation between gravitational constant G
        and speed of light

The gravitational constant G originally determined by Henry Cavendish in 1798, differs from currently accepted value by less than 0.5%.
Already Einstein, and then other scientists tied the gravitation to a relation between speed of light and distribution of masses in the universe. The idea appeared that G constant may depend on a speed of light.
The author of this book has noticed quite surprising relation:
,   where  c - speed of light
The G constant derived from this equation corresponds to the constant determined by Cavendish. We need to clarify however, which speed of light should be used – the one in a vacuum which applies in universe, or the one in the environment in which the gravitational constant was determined. Thus, while determining gravitational constant,
the speed of light in the same environment should be determined with adequate accuracy.
The “same environment” means the same conditions of measurements. If measurement of gravitational constant is performed on planet Earth, the measurement of speed of light, i.e. whole distance traveled by light should be also in Earth surroundings. When speed of light is determined for distances in universe, measurement of gravitational constant should be also performed remotely from Earth and other significant masses. In the relation presented above, some people may point out incompatibility of units. However, they are forgetting that gravitational constant G by itself causes relevant unit conversion in Newton’s formula. To complete formal unit accordance in the presented relation, the value of “one” in a numerator can be treated as a coefficient of units’ conversion, so we can present this relation as:
.
The above relation should be considered for now as “guessed” although we cannot exclude an idea that a scientific justification will be found someday. Nevertheless, it presents a challenge for more inquisitive minds – is this a coincidence that there is a numerical equivalence in the relation:
.