Geometric circles of unit radius are called hoops. Using the Axiom of Choice, J.H. Conway and H.T. Croft showed that it is nevertheless possible to discontinuously fill three-space using disjoint hoops. However, Daniel Asimov has shown that using continuous families of disjoint hoops, it is not possible to fill a region of infinite volume.
This article describes research results of Daniel Asimov, of NASA Ames Research Center in Mountain View, California. It gives an example of an open region in three-space continuously filled with hoops. It then explains the higher dimensional generalizations of continuous families of hoops.