This is my summary of the work of other people, not my own beliefs. I happen to find these particular individuals extremely compelling and honest in intention.

First, I highly recommend the following:

Dark Matter, Missing Planets and New Comets by Tom van Flandern

Secrets of Antigravity Propulsion: Tesla, UFOs, and Classified Aerospace Technology by Paul A. LaViolette

Covert Wars and the Clash of Civilizations: UFOS, Oligarchs and Space Secrecy by Joseph P. Farrell

The latter is more speculative, and the first two are very technical, and extremely informative, about this entirely new approach to gravity.

This new approach can be (over) simplified in the following statement: Gravity is a push not a pull.

One of the first of the great 20th century scientists to figure this out was the enigmatic Thomas Townsend Brown, who in 1923 realized the following (and I quote from Covert Wars):

[Brown] began to cultivate the thesis that a radiation (other than light) prevailed in the Universe, independent of our Solar system. [He] felt that this radiation could be gravitation...that it exerted a pressure (however small) on all forms of matter. This gave rise to what could be considered as a new theory of gravitation.

Such a theory called for gravitation being a push and not a pull. This seemed logical in that Nature abhors a vacuum. A mechanism for the transmission of gravitation theoretically was needed.

Brown firmly believed in the interconnectedness and coupling effect between gravity and electromagnetism, and he spent his entire life experimenting in these fields, much of it deep in black ops because of the significance of his findings.

After holding some demonstrations, a story ran in 1924 in the Los Angeles Evening Express called "Claims Gravity is a Push, not a Pull." It read:

In plain words, his theory is this: That ether waves some outside space push from all directions against the earth, and against other objects and planets in space, forcing objects the way the wave extends instead of drawing them, according to the old Newton theory of gravitation.

By means of his equipment he conducts experiments with the X-ray, which is of the same family as light and the ether wave, and by means of which it is possible to test the theory. By means of this machine, he says, that since the X-ray is deflected, the gravity wave, being of the same family, also can be deflected.

If this theory is proved so thoroughly that it displaces the Newton theory, inventions of the future will revolutionize human industry. Be deflecting ether waves that are pushing against objects, man can control weight to such an extent that his deflecting machinery would enable him to lift a battleship out of the sea and set it on dry land.

Why stop with battleships?

By 1927, Brown had applied for his first patent for his "gravitators" or "gravitors," simple dielectric devices charged with high voltage that would then lift, and the return to their ground state in step-wise quantized fashion.

In 1928, Einstein was writing yet another unified field theory paper coupling gravitation and electromagnetism, and that same year Brown had received a British patent for a technology that demonstrated, and therefore, locally-engineered this coupling!

Quoting writers Joseph P. Farrell and Paul Schatzkin:

However, lest the reader object that this effect was simply "ionic wind" (this explanation was precisely used to discredit Brown), it is worth looking at the actual wording and claims of the patent:

The invention consists simply of surrounding or impregnating mass of any non-conducting material with an electro-static condition. This is accomplished by applying high-voltage but low-amperage current to opposite ends of material that does not transmit electric force (dielectric or insulator).

In other words Brown has sandwiched a layer of a material that does not conduct electricity between two layers of a material that does conduct electricity.

The material that does not conduct electricity is called a "dielectric" or "insulator" and the material that does conduct electricity is called an electrode.

Because the dielectric layer interrupts the flow of electrical energy in the apparatus, the circuit is not completed, and this is one reason why Brown and scientists called in by him to test his results (back in 1929) unite in saying the electrical energy present is not the cause of the force liberated.

When voltage was applied, the pendulum moved upward toward the positive pole, and then returned to its ground state in stepwise quantized releases of energy.

Why was Brown convinced there was an electro-gravitic coupling being demonstrated?

Because while conducting experiments with it, Brown noticed varying results depending upon planetary and stellar positioning relative to the galactic center.

When the Sun and Moon were aligned in the direction of the positive thrust of his gravitator, the displacement of the apparatus was greatest. In other words, the apparatus responded to conditions of local celestial space, and indeed was uniquely sensitive to them.

This is turn affected the quantized release of energy as the gravitator returned to its ground state. The quickest and greatest discharges of force and the quickest return to the ground state occurred, Brown noticed, when the Sun and Moon were on opposite horizons.

Brown began to call the concept "gravitational atoms". With it, Brown is suggesting that space-time is not a continuum, but like the implications of quantum mechanics, is a quantized phenomenon.

In the 1920's, Brown developed a device that, with the application of a minimal amount of electrical energy, appeared to release another form of energy that propelled the device.

In part because the movement of the device appeared to be influenced by the movement of the sun, moon, and other planet, he believed that the internal force was gravitational in nature, and was embodied within and released by the materials of the devices themselves.

IOW, Brown was saying that space itself was a dielectric, and the material universe was an asymetrical dipole in a state of non-equilibrium. His gravitators were not just idle curiosity and not "ion wind"...they were the "only way to go" if mankind ever hoped to venture to the stars.

Astronomer Tom Van Flandern has taken it further with his concept of "C-gravitons" which are thoroughly explained in the book I linked earlier.

Flandern is essentially saying that space is filled with both a light carrying medium (LCM) as well as an incredibly small and fast universal gravity medium (C-gravitons). These gravitons push celestial bodies together by bombarding them, rather than being drawn together.

Gravity acts by means of some sort of agents making contact with matter, despite the fact that no such agents are yet known to physicists. Conceptually, the only way that "agents" have to act on bodies is by means of collisions.

A sea of rapidly moving agents everywhere outside a body would tend to push down on the surface of the body, giving rise to an apparent force of attraction toward the center of the body.

Moreover, two bodies would shadow each other from some of the agents, giving rise to an apparent force of attraction between the bodies, since fewer agents would be available to "push" from the shadowed side than from the opposite side of the body.

Consider a spherical body of ponderable mass. Although the hypothetical agents are flying through it all the time, some of them are always colliding with the atomic particles making up the body, producing push-like forces.

When a collision occurs, the agent rebounds and therefore is not available to collide with other atomic particles deeper in the spherical body. This means that more agents strike every atom from above than from below, because of the shielding effect of the nearby matter.

The resultant of all such collisions must therefore be that every particle of the spherical body is "pushed" in the net direction toward the center of the mass, where the most shielding from push-collisions occurs.

I can't recommend van Flandern's book (and LaViolette's) enough if you want to understand why there's an entirety different perspective on gravity out there, and it has almost completely been swallowed up by the world of black ops and the Breakaway Civilization.

TLDR: Gravity is a push not a pull.