Beginning with a gravity gedanken experiment; this paper predicts a null result for CERN 31’s upcoming antimatter free-fall gravity experiment. That prediction that antihydrogen will neither fall up nor down in Earth’s gravitational field; builds out into a Toy Gravity Universe which has subtle repulsive gravitational force and leads to the definition of the quantum graviton. After 100 years, there is no agreed upon merger of gravity and the quanta. Something obvious has been missed. There is no such thing as an obvious gravity experiment. Yet views such Dragan Slavkov Hajdukovic32 are common, “An amusing (while non-scientific) question is why so many great experimentalists waste significant time on experiments whose outcomes are known in advance (according to the nearly unanimous prediction of theorists, antimatter must fall in the same way as matter).” That certainty needs to be loosened. A minority of theorists believe that antimatter falls up. Virtually none support my view that antimatter falls neither up nor down in Earth’s gravitational field. In my mind a null result holds the key to defining the quantum graviton as this Toy Gravity Universe will do. This Toy Gravity Universe is built without changing standard equations physics, the constants of nature, or disagreeing with the physical evidence. With these constraints, building a Toy Gravity Universe is achieved by reinterpreting concepts, theories and equations with reason applied to physical evidence and insight. This Toy Gravity Universe is composed of subUniverseR (i.e. our visible universe) and subUniverseI, which has imaginary number dimensions and is CPT symmetric to subUniverseR. These two subUniverses are large enough, finite, non-inflating 3-spheres related mathematically by T-duality and physically connected by gravity. Quantum mechanics and the gravity of Newton and Einstein give essential clues in the development of this Toy Gravity Universe. New CPT particles and CPT antiparticles will necessarily be added to the Standard Model of Elementary Particles; these are not supersymmetry particles. The Concordance Model of Cosmology’s interpretations of cosmic redshift evidence and CMB evidence will be replaced with Toy Gravity Universe interpretations that don’t require inflation. Finally, if CERN 31’s upcoming antimatter free fall gravity experiment shows that antihydrogen falls up or down in Earth’s gravitational field (rather than give a null result); then the predictions and interpretations of this Toy Gravity Universe collapse like a house of cards.