The Quantum World

The Nuclear (and Sub-Nuclear) World

Virtually all of the mass of an atom resides in its nucleus. This is centrally disposed and of diameter about 10^-14 meters (or 100 picometers). Small! At least 10,000 times smaller than nanotech and we can ignore this scale just as we can ignore G, the universal gravitational constant in nanotech.

One more thing: the nucleus contains elementary particles that are held together by energies measured in MeV (millions of eV). That’s inherently 1 million times more powerful (MeV) than moving electrons (eV) as in chemical reactions (remember it’s just electrons that move from higher level orbits to more stable ones when we denote a stick of dynamite – and even that can be quite powerful; now multiply by a million!).

If we break an atom of uranium, the re-arrangement of its elementary particles into stable subunits releases some of this energy as expressed by Einstein’s famous relationship, ΔE = Δm × c² (Δ means “difference in”). Hence 1 g of “fissioned” uranium will release 1 million watts of power for 24 hours. You can now see why Einstein wrote to President Roosevelt in 1939 warning of the effects of a possible atom bomb that could level a city with just a few kg of explosives!

The truly smallest scales we are aware of are from String theory. Dimensions may be as small as 10^-35 m. We have no interest here in them.