Again, in a limited way, one could reverse the direction of the gradient, but not what gravity is. True anti-gravity is a logical impossibility that would require negative existence (less than being non-existent).
And since mass accumulates in 3D spherical concentrations, the “reverse” direction for its gradient is that of being greater outside the spherical mass and less inside. One would have to arrange for the surrounding “space” of a particle to be the accumulation of affectance (the mass or solid) and the particle to be the lack of mass within that solid, exchanging space and mass. That would require that space (nothingness) automatically accumulated (hence having affect yet being nothing = no affect) and dispersed mass (somethingness = affect). And that would require that when two quantities of affect added, their sum was less that either of them (the reversal of absolute zero with absolute infinity, “2+2=0 and 2-2=4”). The result of that is that the distances would add to be less than the original distance.
Geometrically, it would mean that you have to have the outside of a box smaller than the inside of that box in order to reverse time, which is why they have that effect in the Dr Who TV time travel series.
But even with that magically arranged, the photon would still not follow a reversed course. If reflected exactly, the photon would leave the (formerly) massive object and bend upward into the (formerly) space vertically, not along the originally horizontal path. It would require the reversal of “A is A” including “vertical is horizontal” and “forward is backward”. But vertical and horizontal are not the only directions. With which do you reverse “far and near” (the Z-axis)?
Everything actually doesn’t have an opposite, despite popular propaganda. A truly negative universe cannot be arranged. Negative is opposite direction of positive, but not equally opposite affect. And the Higgs theory (of opposites) is a fallacious ontology.