It is essential to realize that all fields dealt with by physical science, the gravitational, electric, magnetic - however much they differ otherwise - have this one characteristic in common, that they have a centre where the field is at its highest intensity, diminishing as the distance from the centre increases. Motion in such a field naturally takes place from regions of lower to those of higher intensity - in other words, it follows the rising potential of the field. This accounts for the tendency of physical masses to arrive at the shortest possible distance between them.
It was natural for the modern mind to picture a dynamic condition of the kind just described, that is, one in which the centre and source, as it were, is a point round which the dynamic condition spreads with steadily diminishing strength as the distance from the point grows. For such is the condition of man's head-bound consciousness. The locus from which modern man watches the world is a point within the field of this consciousness, and the intensity with which the world acts on it diminishes with increasing spatial distance from this point. This is the reason why levity was banished from scientific inquiry, and why, when the field-concept was created by the genius of Faraday, it did not occur to anyone that with it the way was opened to comprehend field-types other than the centric one characteristic of gravity and kindred forces. To make use of the field-concept in this other way is one of the tasks we have to undertake if we are to overcome the impasse in which present-day scientific cognition finds itself.
To develop a picture of the type of field represented by levity, let us recall certain results from the observations of the last chapter.
There the volcanic phenomenon, when taken in its wider implications, made us realize that the upward movement of physical masses, in itself part of the total phenomenon, is due to a dynamic cause which we had to describe, in contrast to centripetally working pressure, as peripherally working suction. Of this concept of suction we must now observe that we may apply it with justification only if we realize that suction can be caused in two different ways. In the sense in which we are wont to use the term, suction is the result of a difference of pressure in adjacent parts of space, the action taking place in the direction of the minor pressure. Apart from this, however, suction can occur also as a result of the outward-bound increase of the strength of a levity-field.
It is in this sense that we may speak of the seismic movements of the earth as being caused by suction acting from without. In the same sense we may say that the upward movement of the saps in the plant (to which Ruskin pointed as being responsible for the apple appearing at the top of the tree) and with it the entire growth-phenomenon in the plant world, is due to peripheral suction.
Considerations of this kind lead one to a picture in which the earth is seen to be surrounded and penetrated by a field of force which is in every respect the polar opposite of the earth's gravitational field. As the latter has its greatest intensity at its centre, which is identical with the centre of the earth's globe, so has the levitational field its greatest intensity at its circumference which is somewhere in the width of the universe. (Later considerations will enable us to locate its position more precisely.)
As the gravity-field decreases in strength with increasing distance from the centre of the field, that is, in the outward direction, so does the levity-field decrease in strength with increasing distance from its periphery, or in the inward direction. In both fields the direction of movement is from regions of lower to those of higher intensity. This is why things 'fall' under the influence of gravity and 'rise' under the influence of levity.4
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How does thermal expansion read as a letter in nature's script when seen in the light of the two contrasting field-concepts?
Let us, for simplicity's sake, imagine a spherically shaped metallic body, say, a ball of copper, which we expose to the influence of heat. As we have seen, it is the centrically orientated gravity-field which gives the ball its permanency of shape. Consequently, the dynamic orientation of the material constituting its body is directed towards the interior of the body itself.