"The "hole" that Dirac describes is the vacuous force of the expansion stroke of the universal pump. This force is correctly described as negative electricity, negative discharge, radiation, radio-activity or by any other name which results in the disappearance of mass into its surrounding tenuous field." [Russell to NYT - 1930 November 2]
See Also
center of repulsion
expansion of the field
expansion pressure
expansion pressure force
Hole
Space
universal pump
Vacuity
Vacuum