The experimental investigation of Newton's law of universal gravitation requires expensive and sensitive equipment. Therefore, it is often not possible to conduct such an experiment within a typical physics class. An alternative is to investigate the universal gravitation law by using simulations. In this paper, we are presenting such an augmented reality simulation (GravityAR). The simulation has been developed for mobile devices and runs on an Android operating system, making it very accessible for students and teachers at all educational levels. It allows the user to investigate how the gravitational force between two spherical bodies depends on their masses and mutual distance. Additionally, the simulation can be used to determine the value of the gravitational constant (G).