There will never be one. That's the trouble with facts: they can't be proved or disproved, they just are.
Anyhow, I prefer the word "model" instead of theory, since the Average Person can't distinguish between theory and guessing, and has even more trouble understanding that even with the best theories there is a "plus or minus X" built into the predictions made with them. In most cases, that +/-X is small enough to make no difference for practical purposes.
Gravity is a fact. That is, things fall down if not held up. Aristotle was the first to propose a theory to explain it. He posited "attractive properties", and theorised that light object had lower "attraction" than heavy ones. There is some dispute of exactly what he meant, BTW, so the above is my take on it.
Galileo developed a model that described how gravity works, (ie, how fast things fall in Earth's g-field could be calculated. This theory has not been falsified. Then Newton developed a model that applied Galileo's equations to the motions of planets. He universalised gravity theory. Later still, it was found that the theory worked only for low relative velocities, such as those that obtain when you fall to the ground. I believe Einstein had something to do with that.... ;-) Etc.
But none of these theories are powerful enough to predict the motion of three or more masses moving/orbiting relative to each other in a gravity field for more than a surprisingly low number of orbits. It appears that
3+ bodies in a gravity field move chaoticly, and chaos math must be used to build a model. That's not easy.If by "proving" gravity you mean some model that spits out gravity as a necessary consequence of solving the equations, no such model has as yet been successful, nor have any seemingly successful attempts produced results that could be translated into experiment. String theory looks promising, and, according to the people who build it, also has the requisite beauty. Certainly, without understanding the math involved, I think the concepts it uses are very cool.
There is a difference between predictive and explanatory theories. For your sakes, I've cut three paragraphs in which I enlarge on this theme. ;-)
cheers, wolf k.