World population grows exponentially. It means that for every marker generation, the previous one has less while the next has more for every count of human being living in it. In other words, if the marker generation starts out with one family then by inbreeding the next has more than one family. If this is true for every succeeding generation then after so many generations, the last generation has many, many more families than the first generation. Exponential growth can be used to model the cell growth of both bacteria and viruses. Although bacterial growth is modeled by doubling, viral growth is modeled by trebling, quadrupling, and multiplying, modeling the growth of malignant tumor. Similarly, exponential growth models chain reaction of nuclear fission. However, it is not effective or no effect at all to model nuclear fusion.

On the other hand, the ideal nuclear fusion is modeled by half reduction, since it takes two deuterons to make a Helium-4 nucleus. In other words, if at the outset there are 100 deuterons in the fusion chamber then after complete fusion there are only 50 Helium-4 nuclei and no further fusion can occur. Therefore, properly speaking, nuclear fusion cannot be called a chain reaction. It is an integer model of 2 in 1 out or 4 in 2 out or 6 in 3 out or 8 in 4 out, so on and so forth. However, since one deuteron is made of 1 proton and 1 neutron and one Helium-4 nucleus is made of 2 protons and 2 neutrons, clearly, the number of proton and neutron stays the same before and after the fusion reaction. But tremendous amount of energy is released. Nonetheless, the trick is how to make any of the first two deuterons to fuse. Using a principle of spatial control then microscopic funnel-shape volume contractors would force two deuterons to fuse wherever they move into an isolated spacetime region of much less controlled volume.