FIG. 4: Shrinking of a volume containing mass M is limited by gravitational collapse to a black hole in the top figure, and by the creation of particle anti-particle pairs in the lower figure. FIG. 5: A region of space of size l to be measured in time l/c . As the size approaches the Planck length there can occur wild variations in the geometry, including such things as black holes and wormholes. FIG. 6: Potential energy of many small dM elements reappears as energy density ρ$_{g}$ of the gravi- tational field. 22