-13. In this final picture we see the nucleus of the sodium atom. We cannot even guess how the 12 protons and 11 neutrons in it are placed. This nucleus is not painted an even grey; its edge is of a somewhat lighter tone which gradually merges into the darker hue in the center. The meaning of this difference of tone is again different from that in drawings -7 to -11. Here a darker grey denotes greater density of electric charge. As a new element there is a gamma ray, full of astonishingly penetrating power, coming in from the left. Its wave length is only a millionth of an angstrom unit, which itself is a hundred millionth of a centimeter! Looking back on the whole series of 40 pictures we find that in only 10 of them (3 to -6) is life known to exist. In other scales there may, however, be forms of life we do not yet know.
1 cm. in picture = 10-13 cm. = 0.00001 A.
Scale = 10 million million:1 = 1013