The moon expresses to mankind the most inert, lifeless object in his entire experience. Perhaps ultimately from modern studies of the light reflected from the surface of the moon, changes in the moon's structure can be observed, but there is at present nothing observable by man more inert, more lifeless, or more changeless than the moon. Its temperature, due to different exposures to light from the sun, is the one known variable factor. To man changes alone are challenging. The earth's tides, clouds, and temperature changes, and above all the phenomena of life in its various phases are the very essentials of existence. These changes, so rapid, almost evanescent, are in striking contrast to cosmic changes. Galaxies, the universe, mountains, rocks are all undergoing changes, but these changes are usually immeasurably slow, and one does not think of them as having life. At times these changes represent disintegration processes which are sufficiently rapid to be observed by man, such as sedimentary deposits. The structural or developmental changes, such as continental movements, are very slow, but even these structural changes at times may be cataclysmic, as volcanic eruptions and geyser deposits. All changes, no matter where they occur or how rapidly or slowly, are accompanied by energy transformations the aggregate of which is of immense magnitude.
Life differs greatly from such geological changes, for with life changes are rapid. The energy transformations, though much less, are inevitably present, but with life the changes are unceasingly a procession of vital forces ebbing and flowing. These unceasing changes are such as to make almost unnecessary the question, "Is life ever static?". In form life is rarely static. During the phases of growth and decay changes are continually going on. Judged by geological time, life is anything but static, although according to the time measure of man's experience there are some changes in life processes that are quasi-static. They may be represented by certain plateaus in the stages of growth and development. These external appearances of a static state, however, are only one side of the picture, for in addition there is the inevitable accompaniment of energy changes, there being no life without energy. Geological and astronomical changes involve energy in tremendous quantities but they are, from the standpoint of man's lifetime, immeasurably slow. On the contrary, life is active, dynamic, measurable by the human sense of time. The changes are not from eon to eon but from minute to minute and, indeed, from second to second. Man is not given the opportunity in one lifetime or in one century, except rarely, to note precisely the changes in geological form save in the case of sudden disintegration processes, erosion, sedimentation, geyser deposits, or lava layers, but the changes in life processes are so rapid that man can study them repeatedly and ad infinitum.
Thus one may contrast the changes that deal with animal structure and the changes that deal with energy. Structural changes, as already stated, are relatively slow but of sufficient rapidity to form the basis of the entire . . .