How is the value of gravity 9.81?

How is the value of gravity 9.81?

Putting mice and men in the proper perspective

A physicist is concerned with causes and mechanisms. A physicist works on trying to elucidate the invisible physical nature behind the phenomenon of gravity and not on the precise value of the acceleration of gravity.

It is as a result of being distracted by measurement accuracy and precision that non-physicists keep making the most embarrassing blunders in their equations. They later obtain careers as professors and bequeath these misconceptions to the next generation at the universities.

You can recognize a non-physicist in at least five ways. A non-physicist will:

  1. use the little letter ‘r’ (for radius) and talk about radius instead of using ‘d’ (for distance) in his calculations
  2. confuse the distance-traveled of Newton’s 2nd ‘law’ (F = ma) with the static distance embodied in Newton’s gravitational equation (F = G m1 m2/ d^2)
  3. never explain what the complex unit of the gravitational constant G (kg m^3 / kg^2 s^2) means or stands for in physical terms
  4. use the gravitational constant G in relativistic (cosmic) equations when the value is determined empirically here on Earth using Cavendish’s torsion balance experiment in a local scenario where cosmic relativity does not apply
  5. place the constant speed of light ‘c’ (300,000 km/s) in his equations despite that he theorizes that the photon bead is deflected by the Sun’s curved gravity well

The little letter ‘r’

The Earth is not a perfect sphere. It is flattened at the poles. Therefore, the acceleration of gravity changes at different locations on the surface of our planet, especially when comparing North-South versus East-West. If you are standing on the North Pole, you will weigh more than if you measure your weight at the equator. You are not only closer to the center of mass at the North Pole, but you are also spun radially (centrifugally, outwards) with greater force at the equator. If the Moon orbited the Earth around the poles rather than near the equator, the calculation of its gravitational interaction with the earth would be a bit different. Non-physicists never realized this and still continue to place the cute little ‘r’adius in their equations.

Distance vs distance-traveled

To a non-physicist, it makes no difference whether he talks about length or distance. As far as he’s concerned, these words are synonyms. He has to unroll the end of the measuring tape whether he measures the length of a turtle or the distance between two elephants. A non-physicist is unperturbed about qualitative matters and, as a result, he typically arrives at fantastic supernatural conclusions (black holes, dark matter, particles of mass dubbed ‘Higgs’, many copies of you in different universes, etc.) It is thus that he defines the word length in terms of distance and the word distance in terms of length

length: “a measure of distance… the word length is synonymous with distance” (Wikipedia)

length: the straight line distance (Wolfram Physics)

distance: a physical length… the length of the shortest possible path through space (Wikipedia)

distance: The length of the line segment joining two points (Mathematics Encyclopedia)

In other words, a non-physicist pays little attention and a lot of lip service to rigorous definitions. He ends up chasing his tail around by introducing synonyms in lieu of definitions.

It turns out that what the non-physicist did was measure neither length nor distance. What he measured is distance-traveled: the distance the end of his measuring tape traveled from A to B (…or the number of predetermined tiles he placed between A and B, or the number of pre-established seconds his clock clocked between departure and arrival of the end of the tape). A non-physicist incongruously uses the words of Physics length and distance to refer to a measurement of distance-traveled.

In contrast, a physicist recognizes lengthdistance, and distance-traveled as three irreconcilable concepts:

length: continuous matter between the borders of an object

distance: separation between two objects

distance-traveled: movement of an object from one location to another; trajectory, itinerary.

In Physics, lengthdistance, and distance-traveled are qualitative parameters. They are not specified in terms of pre-established units. The purpose of lengthdistance, and distance-traveled (displacement, itinerary) is not to describe mathematically, but to explain the mechanism of a phenomenon.

The mysterious units of the gravitational constant G

A non-physicist robotically places in his equations the value followed by the enigmatic and complex units of the gravitational constant G: (kg m^3 / kg^2 s^2). He has no idea what this constant stands for because he is not thinking in physical terms (…or thinking at all for that matter)! He just memorizes the value for the test and parrots it verbatim like a mantra for the rest of his life.

In Physics, it’s a different matter altogether. In order to understand the physical significance of units of Big G, the first step is to factor out the mass of the hydrogen atom and the second step is to factor out the square of the speed of light. This enables the physicist to peer into the invisible nature of gravity: All hydrogen atoms are physically interconnected. In this model, light propagates along an extended physical mediator to all others and from all others back to the target atom. Light is a two-way mechanism: from one atom to all others and back: c^2!

Nevertheless, it goes without saying that the only way to explain any action-at-a-distance phenomenon, whether entanglement, gravity, or something as plain as how to pull on a donkey, is by introducing an elongated mediator between the two objects in question. Otherwise, the non-physicist is in effect forcing spirits at gunpoint into that same intervening space!

The gravitational constant G has not been justified for cosmic phenomena

Perhaps the gravitational constant G does indeed apply to cosmic phenomena. The argument is that this ‘tradition’ has never been justified. The gravitational constant G is determined empirically through the torsion balance experiment first devised by John Michel and later carried out by Henry Cavendish after Michel died.

Under the Rope Model of light, the gravitational constant G is definitely a universal constant because there is an underlying physical cause for it.

Curving little ‘c’

Non-physicists propose that the Sun weighs down an unimaginable 4-dimensional mathematical concept they call ‘spacetime’ and that curvature in this amusing 3-dimensional ‘fishnet’ – typically illustrated as a 2-dimensional projection – compels the Earth to roll around our star. But it gets more comical when these misguided fellows claim that spacetime curvature bends light. It is amusing first of all because the absent-minded abstracist claims that light is comprised of discrete beads he calls ‘photons’. Therefore, what he is actually trying to say in his contorted, unscientific way is that the photon marbles are deflected by the warped walls that form the cosmic fishnet.

But then, if the distorted canvas deflects the photon ball, it no longer travels rectilinearly. And if the photon doesn’t travel rectilinearly, it no longer travels at the magical constant velocity of 300,000 km/s. Yet, the non-physicist mechanically plugs this value (little ‘c’) into his field equations as a constant and ‘bumbles’ and ‘bungles’ on as if nothing…


The 9.81 m/s^2 is an average value of the acceleration of gravity here on Earth. It was determined empirically.

  • This value should first be calculated using distance and not radius. A fellow falling from an airplane without a parachute has no radius with respect to the center of mass of the Earth. That bit of separation is known in Science as distance.
  • The dynamic distance-traveled of Newton’s F=ma equation is not the same static chasm of Physics known as distance embodied in his universal ‘law’ (m1m2/d^2).
  • The weight of a free-falling individual is calculated for any given distance from the center of mass of the Earth. If he falls another inch, his weight changes because distance has now changed.
  • Spiritualists and other abstracists would like you to believe the contrary. The non-physicist theorizes that it would take 8 minutes for the Sun to telegraph the message to you that it has disappeared. Meanwhile, the Earth would, in this Ptolemaic view, be orbiting around nothing. The comical ‘logic’ of the non-physicist is that it takes an eternity for the message to reach the mountain climber that his rope has been cut. And perhaps if the non-physicist factors relativity’s time dilation and that the climber was climbing into a black hole, he might even live another 50 years up there near the dark summit while his twin ages in the cosmic valley.
  • The gravitational constant G has physical significance. Spiritualists, abstracists, and other non-physicists have yet to come to grips with its meaning. Big G embodies two factors: the mass of the H atom and the constant speed of light in two opposite directions. Torsion propagates at a constant speed along the EM rope binding any two atoms. Refractive index is a Ptolemaic explanation where the speed of light varies from medium to medium.

So rather than focusing on the precise value of the acceleration of gravity, it is more profitable for the intelligent mind to focus on the cause of gravity. That’s where grey matter really accelerates.

Author: billg