We show mass and energy being equivalent, and the same for space and time.

We can break it down even further and find dualities and symmetries all over the place: electricity/magnetism; matter/antimatter; wave/particles; position/momentum; etc.

But we not only suspect, yet have astoundingly strong evidence to believe all manifestations of nature, along with our mathematical descriptions of it, can be (and actually once was) unified.

Matter attracts matter by a function of what we observe and describe as gravity. At the same time, space is becoming ever more evident that there’s just as much something in the fabric we call the vacuum as there is typical matter within it* — virtually sizzling with energy/particles popping in and out of existence — as it’s not only expanding, but accelerating as far as we can tell. Is there any reason to not look at space-time as a true opposite of mass-energy?

If positive mass attracts to itself, and negative mass would repel itself, does it make sense to look at space-time as “negative mass”? Could gravity be less a “force” as it appears to be, and more of a consequence of what we perceive as “tangible” mass-energy, and “intangible” space-time interacting with each other if seen as being opposites of the same thing?

Or have I flown completely off my ontological rocker again?

Actually, it’s my understanding that positive matter attracts everything, and negative mass repels everything.

And I understand that the expansion of space can be looked at as possessing negative mass/energy; I recall reading of theories that used that as an explanation for the origin of matter. The idea being that the rapid expansion of space counting as negative energy, and the appearance of positive mass/energy cancel it out so the universe has net zero energy. I’m not a physicist, so I’m probably butchering the explanation though.

Not exactly… but there is evidence for the idea that the Graviational Constant on our brane is particularly weak and ‘should’ be equal to Coloumb’s Constant. There’re suggestions, however, that gravity can somehow ‘cross branes’ and serve as a means of communication between universes in the multiverse.

No. The gravitational field has stress-energy (and is thus a source of the gravitational field) just like the other forces do. And the expansion of space is due to it having a positive energy density (via the cosmological constant), leading to a negative pressure.

It depends on what you mean by ‘interpretation’.
That we live in a multiverse is rock solid, as the mathematics behind the Inflation (think big bang) show that it wasn’t an isolated event.
That various 'verses are essentially holographs on branes, that’s much more conjecture.
And that gravitation can ‘leak’ between branes, of course, relies on branes being real in the first place, and then that hypothesis being falsifiable.

Nah, inflation is perfectly consistent with there just being one universe. The multiverse gets started with eternal inflation/bubble universe model, which is much less well supported observationally (certainly far from ‘rock solid’).

It could still be held together by electromagnetic forces much like positive matter, although the details would be different since it would react in an opposite fashion to electrical charge (like charges would attract, opposite charges repel). And for that matter in an opposite fashion to force; pushing negative matter away would make it move towards you, while pulling on it would make it move away from you. There’s a Wikipedia article or two about it.

Actually, this idea is what inspired the OP. I know it’s been around for a while, I just was curious if thinking about space-time as “anti-mass”, in the same vein as anti-matter or electrical charge, was accurate.

Upon further thought, I suppose I’d like to argue here (my admittedly half-baked proposition) that space-time is “anti mass-energy” (or the equivalence that mass-energy is “anti space-time”).

Where mass-energy gives rise to matter, space-time gives rise to the vacuum; at the smallest scales, matter and the vacuum are a stochastic, quantum fluctuation between space-time and mass-energy.

But, on the largest scales, matter and the vacuum likewise clump and diffuse, respectively. From this perspective, I see “gravity” arising from mass-energy, and the “vacuum” expanding from space-time (assuming it being “anti mass-energy”).

From here, looking at something like a singularity where the “pull” of mass-energy, and the “push” of space-time cancel each other out, yet the equal and opposite signs of positive mass and negative mass would still favor an acceleration toward the positive mass, forming an unintuitively enigmatic region of space-time that now “pulls”, and the converse of mass-energy which now “pushes.”

Momentum and energy would remain conserved, but the resultant black hole could be seen as a physical manifest of the reversal of attraction/repulsion of matter-energy/space-time respectively.

Gravity then is a consequence of the interaction of +/- mass as they interact with each other; a dance of mass-energy informing space-time how to curve and space-time informing mass-energy how to move.