A Modified Gravity Phenomenology in Space and Time

Einstein's Theory of General Relativity allows us to distinguish between the repulsive pressure of Dark Energy and the apparently-waning gravitational attraction of light and Dark Matter. Dark Energy drives galaxies apart more forcefully than their intergalactic gravity can compete with, whilst Dark Matter constitutes the trellis that supports the large-scale distribution of galaxies. In this thesis, by contrasting the spatial arrangements of galaxies with the behaviour of their light beams across space and time, we investigate the prospects of extending or modifying Einstein’s Theory of Gravity to explain the sudden accelerated cosmic expansion observed by astronomers. We apply our methods to the leading current galaxy datasets, and discuss the farreaching scientific potential of upcoming observational advances.