In this paper, we investigate the effects of gravitational field on the dynamical behaviour of nonlinear atom–field interaction. We consider a moving tripod-type four-level atom interacting with a single mode field in the presence of a classical homogeneous gravitational field. The analytical solution of the model is calculated by using the Schr\"odinger equation for a coherent electromagnetic field and when the atom is in its excited state. The influence of the detuning parameter and the classical homogeneous gravitational field on the temporal behaviour of atomic inversion, Mandel Q-parameters, purity of the atomic system and concurrence is studied. Our proposal has many advantages over the previous optical schemes and can be realised in several multiple experiments, such as quantum gravity. The results show that the gravity parameter has an important effect on the properties of these phenomena. Finally, conclusions and some features and comments are given.