Comments on the Cosmological Horizon Problem

Current attempts to find a solution to the problem of the cosmological particle horizon are reviewed with reference to two general approaches. The first approach involves modifications to the standard theory in the very early Universe, close to the Planck time, whereas the second approach tries to exploit new developments in elementary particle physics in such a way as to eliminate the problem at much later times. The relative merits and demerits of the two approaches are examined and it is suggested that the resolution of the cosmological horizon problem be sought in processes occuring at or near the Planck epoch.