Is gravity actually repulsive?

v. 6 n. 17

The title question appears absurd. Popularly, "It is obvious that gravity is attractive, otherwise we, and everything not nailed down, would just float upwards off the surface of the Earth; not only that but the Earth would never have formed in the first place."

While the title question is not a new topic it is so counterintuitive yet basic that it warrants further attention. (And negative condensed matter is not involved.)

The notion that gravity is attractive was formalized phenomenologically by Newton hundreds of years ago, and so entrenched that Einstein made sure general relativity reduced to it for small accelerations, but without realizing at the time that the Universe itself is accelerating. If this acceleration was known at the development of general relativity, it might have been incorporated then and made implicit. Instead, later it was tacked on to an incomplete theory to make it conform to observation, in the form of the cosmological constant, Lambda. There is preliminary evidence that Lambda itself is not constant, rather diminishing with time. [1]

It seems that general relativity should reduce to the acceleration of the Universe, not Newton's gravity. Then the cosmological constant would be implicit. This would be like calibrating general relativity to the Universe instead of to Newton, who only thought correctly in terms of the Solar system. All matter does not attract all other matter. Attraction and repulsion depend on scale, barring for the moment the various interpretations.

General relativity should be calibrated to the Universe instead of to Newton.

Newton's gravity begins to break down in comparison with general relativity in measurements of the Perihelion shift of planet Mercury for instance. Beyond the Solar system, at the galactic scale, Newton's gravity is in distinct error without the assumption of additional unknown matter or energy or corrected gravity theory. The situation deteriorates further as scale increases, until between the cluster of galaxies and galactic supercluster scales, the situation reverses and masses (clusters of galaxies) are repelled from one another.

Note that this slide into reversal is a steady deterioration of classical Newtonian gravity (without dark mass-energy) until the transition to repulsion. This repulsion is commonly said to be due to a new unknown actor, dark energy. Instead, the more logically consistent reason for the reversal should be gravitational because of the steady decline in accuracy of classical Newtonian gravity with increasing scale; recall, it is only marginally inaccurate at the Solar system scale with reference to general relativity.

At the galactic supercluster scale where repulsion begins, let's assume that gravity is the repulsive actor instead of dark energy. Dark energy is an unknown and there is no harm in assuming that Newtonian gravity is trending toward repulsion, which it indeed is, as mentioned, becoming less and less accurate as the scale increases (more and more dark mass-energy is required to maintain the classical Newtonian attractive viewpoint).

At the Solar system scale, the equivalence of Newton's gravitational and inertial forces is given by

Gmm'/r^2 = m'A

m/r^2 = A/G. ...................................................... (1)

HYPOTHESIS: Equation (1) holds at the galactic supercluster scale and above, where mass m is that of the sufficiently large expanding space encompassed by radius r. Mass m includes all the mass-energy within radius r to include visible matter, dark matter and dark energy.

It has been shown that

A ~ 10^-14 m/s^2

for the acceleration of the local galactic supercluster, which is representative of the acceleration of the Universe by and large (pending further DESI results). This should make Equation (1) scale invariant at and above galactic superclusters, so that the "cosmological constant" is implicit. [2][3]

Notably, the same classical mathematics in Equation (1) holds for the scale below that of the Solar system and above clusters of galaxies, when gravity is considered attractive in the former and repulsive in the latter. Since most of the volume of the Universe is in the large scale, repulsion is dominant, i.e. most of the mass-energy in the universe is dark and not visible matter; it is shown that dark matter could be dark energy at smaller scales. [2]

As to the fundamental means of gravity (attractive or repulsive, not both): regarding the cover image, in the upper situation gravitational attraction is assumed between two masses, where gravity is intrinsic to the particles in some unknown manner as Newton "made no hypothesis." In the lower situation gravity is fundamentally repulsive and the particles are pushed toward one another from outside the pair by accelerated expanding space, where there is less of this accelerated expanding space between than about the particles below galactic superclusters. We might be held to the Earth by a force pushing down from above rather than from a force pulling from below.

[1] Is "dark energy" the basis of gravity? | LinkedIn

[2] An explanation of dark matter and dark energy from unmodified Newtonian gravity* | LinkedIn

[3] Importance of a value for acceleration of the Universe | LinkedIn