This theory assumes an INNER and OUTER universe. What we currently term as ‘the universe’ is the Inner-verse, and it is contained within a boundary which is within the Outer-verse.

Please note: in the following thought experiment, all the Einstein Field Equations at the heart of his General Theory of Relativity would equally apply.
Gravity is not a force. It is an inert ‘substance’ which is set to a very specific low pressure and it pervades every part of our Inner-verse. The level of this pressure is created by the volume of gravity in relation to the overall area of our Inner-verse. However, as our Inner-verse is expanding in order to experience TIME, the infusion of gravity from the Outer-verse has to be regulated so as to fill the created space and yet maintain the same overall state of pressure. If this was not the case, we would perceive that matter would fluctuate in weight in ways that we could not explain.
One way (very metaphorically speaking!) to think about gravity is as if it is water in a completely still pond and in which the volume of water relative to the size of the pond never fluctuates. The water pressure is created by the boundaries of the pond and this pressure never changes
The ‘force’ that we detect from gravity, therefore, is actually increased pressure resulting from the fact that lumps of matter are preventing gravity from being uniformly distributed across our Inner-verse. As gravity ‘tries’ to move to an evenly spread low pressure state, pressure is created. So when we refer to gravity, we are referring to detectable gravity, i.e. gravity which is exerting pressure on whatever is preventing its even distribution across the Inner-verse.
It may be that gravity is a substance, the mass of which is 0. That is why it is not apparent that it has a mass. Gravity exerts a pressure on matter because matter interrupts its completeness. Gravity cannot exert a pressure on itself. So if gravity has undetectable mass which fills the entire Inner-verse, then that would be an enormous volume of undetectable mass. Could gravity itself be the elusive ‘dark’ matter?
But if gravity has mass of a kind, then why does the movement of planets through gravity not create detectable ripples? Presumably the answer is because its mass is so infinitesimally small that only enormous cosmic events can create a gravity wave. Would such an event enable us to calculate the mass of gravity then? And would such a calculation accord with the predicted mass of ‘dark’ matter?
The neutron star collision in 2017 was an event enormous enough to create waves in gravity. The gravity waves detected in the above event do not prove that gravity is a force. But they may demonstrate that gravity is an inert entity of incredibly insignificant mass which had been disturbed by the tremendous force of the collision.
Also, could it be the case that gravity is also responsible for our Inner-universe’s rate of expansion, i.e. gravity is also ‘dark’ energy? As the flow of gravity from the Outer-verse increases in proportion to the increase of area in the rapidly expanding Inner-verse, perhaps the expansion of the ever-increasing volume of gravity actually inflates the membrane bounding the Inner-verse whilst the membrane simultaneously maintains the fixed level of gravitational pressure? It would be possible for this simultaneous function to happen if the Inner-verse was expanding at the speed of light and the ‘membrane’ was actually the extreme outer edge of the Inner-verse’s expansion. As nothing can exceed the speed of light, gravity would not be able to leak out beyond this extreme outer limit and so could form an expandable seal.
As this rate of expansion, and increase in gravitational volume, progresses, more space is created between galaxies, making it appear as if they are flying, rather than being carried, apart. Gravity cannot attempt to close the hole in its own universal completeness by consolidating the galaxies into one overall mass because of the ever-expanding area of space. However, at the localised level of each galaxy, gravity is still attempting to close the hole in itself created by the massive lumps of mass in its proximity. At this localised level, gravity is acting as ‘dark’ matter and so holding the galaxies together. One of the consequences of this is the likelihood of there being a black hole in the centre of every galaxy.
Under this definition of gravity, weight is created whenever one lump of matter is squeezed against another by gravity’s attempt to close the hole in its own completeness. Prior to this event, the weight of an object will be zero. Gravity will not only press all around each individual lump of matter as it tries to close the hole, but it will also press both lumps together, again trying to close the hole. The less atomically dense lump will be pushed towards the more atomically dense lump. Once they touch, weight has been created. This will then result in a positive gravitational pressure reading on the less atomically dense lump, i.e. weight. This weight is potential kinetic energy.
Objects of a similar size occupying a similar volume of space will feel different degrees of gravitational pressure depending upon their atomic mass. This suggests that gravity suffuses everything, including matter. More atomically dense objects will have less ‘internal’ gravity because of the structure of the atoms. Hence, the external gravitational pressure on them is greater as there is less ‘internal’ gravity to resist the external pressure. The balance between the internal and external force of gravity on matter has been mistaken as two separate fundamental forces, i.e. the ‘strong’ and ‘weak’ nuclear forces.
In effect, the universe consists of electromagnetism, gravity and space to expand – the 3D dimensions of observable space and the unobservable 4th dimensional space we call TIME – plus the ever-flowing kinetic energy derived from the Big Bang which, quite literally, sets things in motion.
TIME
Without the expansion of our Inner-universe (which expands into the Outer-verse) TIME would not be possible within the Inner-verse. TIME, in effect, is the extent to which the Inner-verse has expanded at any given point in the 4D space of TIME. So if you were to measure a line drawn from any point on the outer boundary of the Inner-verse back to the Big Bang at any given point in time, and then take the same measurement a day later, the additional length of this line would indicate the volume of TIME (and 4D space) that would have been experienced during that twenty-four hour period.
Presumably the infusion of gravity is from the centre of the Inner-verse because the Inner-verse is expanding in all directions. As it is from the centre, and as the rate of flow is precisely calibrated to ensure the integrity of the low pressure environment, the absolute stillness of the overall volume of gravity would be never be disturbed –and galaxies would be floated apart without the need for any additional ‘dark’ force. This rate of expansion would speed up as the volume of the Inner-verse increased, thus making the galaxies ‘fly’ apart at an exponential rate, but the rate of expansion from the perimeter of the Inner-verse back to the origin in 4D space-time, i.e. the Big Bang, would remain constant at the speed of TIME, i.e. the speed of light.