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My views on Cosmology and Physics

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Books by David Michalets

Mass and Gravity

2 Newton's Force Between Masses

This is section 2 of 11 in the web-book.

The force of gravity is defined by Newton's Law of Universal Gravitation.

F = G * (m1 * m2) / r^2

where F is the gravitational force acting between two objects, m1 and m2 are the masses of the objects, r is the distance between the centers of their masses, and G is the gravitational constant.

The measured value of the gravitational constant is approximately 6.674×10^-11 x m^3x  kg^-1  x s^?2 6.674×10-11 m^3xkg-1 x s^-2


One might notice the mix of units in the force equation. There are seconds in the units of its constant, but there is no time variable in the factor that it multiplies, which has only these units:  kg^2 / m^2

The units of force are kg x m / s^2 or a Newton.

Wikipedia has a topic Cavendish Experiment describing how G was initially calculated using the oscillation of a torsion bar in an experiment taking 20 minutes.


Its current accepted value is by measurement, so it is not from a calculation using defined "free space" parameters, or using parameters enabling an introduction of parameters based on the medium.

I assume the units of ke are just a remnant from measurements during experiments.
Dropping the s^-2 units from the constant (again, there is no time value in the equation) leaves only:

 m^3 /kg

This ratio of units looks like inverse density, as a ratio between:

a)  a volume (from m^3) and

b) an amount of mass (from kg)..

This factor is essentially a ratio of a volume to mass.

The multiplication results in less force per kg, because the G value is much < 1

Instead of "Gravitational constant" this factor could be named "Gravitational Gradient" because the force reduces over volume, based on the medium, though the underlying parameters are not identified as Maxwell did for an electromagnetic constant.

This ratio might be considered a "free space" behavior for a gravity field.

Electric and magnetic fields required individual free space parameters. A gravity field apparently requires its own free space parameter.

Unfortunately, the value of G is measured by experiment, not calculated based on the medium.

Go to Table of Contents, to read a specific section.

last change 03/21/2022