A new gauge-theory description of gravity is presented, employing gauge fields in a flat background spacetime. These fields ensure that all physical relations are independent of the position and orientation of the matter fields in this background. The language of ‘geometric algebra’ best expresses the physical and mathematical content of the theory and is employed throughout. A method of working directly with the physical fields is developed and applied to the case of a radially-symmetric time-varying perfect fluid. A gauge is found in which the physics reduces to a set of Newtonian equations. The insistence on finding global solutions alters the physical picture of the horizon around a black hole, and enables one to discuss the properties of field lines inside the horizon created by a point charge held at rest outside it. Some applications to cosmology are discussed, and a study of the Dirac equation in a cosmological background reveals that the only models consistent with homogeneity are spatially flat.

A. N. Lasenby, C. J. L. Doran and S. F. Gull, **Astrophysical and Cosmological Consequences of a Gauge Theory of Gravity, **In N. Sanchez and A. Zichichi, eds. *Advances in Astrofundamental Physics. Erice 1994* (World Scientific Publishing Co., 1995), p. 359-401