As the light propagated it behaved in the same way that it does when deflected by huge masses. To do so they captured light in a small area close to the surface of a specially made object and forced it to follow the course of the surface. The researchers examined the effects of this intrinsic curvature of space on the propagation of light in their experiment. The curvature of the surface of a sphere is an intrinsic property that can't be changed and has an effect on geometry and physics inside this two-dimensional surface.' 'A well known example of this is world maps that always show the surface in a distorted way. 'For example, while you can easily unfold a cylinder or a cone into a flat sheet of paper, it is impossible to lay the surface of a sphere out flat on a table without tearing or at least distorting it,' says Vincent Schultheiß, a doctoral candidate at FAU and lead author of the study. However, not all curved surfaces are the same. Instead of changing all four dimensions of spacetime, they reduced the problem to two dimensions and studied the propagation of light along curved surfaces.
Ulf Peschel from Friedrich Schiller University Jena used a special trick to examine the propagation of light in such curved spaces in the laboratory. In this curved space, celestial bodies and light move along geodesics, the shortest paths between two points, which often look anything but straight when viewed from the outside. According to Einstein's general theory of relativity, gravity can be described as the curvature of four-dimensional spacetime.