Let us start with the astral forces corresponding to the three cosmic bodies nearest to the earth - Moon, Mercury, Venus. Their activity can be discerned, for example, by watching the successive stages of plant development - the formation of the sap-bearing parts; the flower-substance already partly transformed into aeriform condition; finally the propagating processes which belong essentially to the sphere of activity of the warmth-ether.6 In the human organism we find the same sequence in the step-by-step transformation of nutriment right up to the moment when earthly form passes into chaos, as we learnt previously. The so-called enzyme action, ascribed by physiology to the various digestive juices, is in reality the product of an activity of the lower part of man's astral organization, for which the relevant juices exercise the function of physical 'carriers'. In the field of macrotelluric phenomena, the metamorphosis of the atmospheric moisture extending beyond the different cloud-stages up to the stage of pure warmth is an example of the activity of the same forces.
Within all three-stage transitions of this kind, the astral forces connected with the Moon preponderate during the first stage, those connected with Mercury during the second, those connected with Venus during the third. We have already come across some examples of the outstanding share taken by the Moon in the events of the earth's watery sphere. To these phenomena, which show by their rhythm their connexion with the Moon, we may add the fertility rhythm in the female human organism which coincides, not in phase but in duration, with the rhythm set by the Moon's course in the heavens. If we consider that the formation of a new human body in the womb needs the play of formative forces from out of the whole world environment, and that for this purpose matter must be brought into a receptive condition for these forces, then we can better understand the preparatory part played by the Moon-forces. In order, however, that the substance of the female germ should reach that condition of chaos suitable for embryonic development, there is still necessary the influence of the supra-lunar astral forces. Entry for these is provided by the union of the germ-cell with the male sperm-cell.7
As the three sub-solar planetary spheres are responsible for events of a 'sulphurous' (radial) character, so are the three supra-solar spheres responsible for those of a 'saline' (spherical) character. For example, we meet with Saturn-activity in everything which radiates from the human head and brings about the hardening both of the head itself and of the entire skeleton. Observation has shown that, even if the human being, as usually happens, stops growing in the early twenties, so that the skeleton undergoes no further lengthening, it nevertheless reaches its final shape and its final hardening only between the twenty-eighth and thirtieth years. This is the time in man's life when Saturn returns for the first time to the position in which it stood relatively to the earth at his birth, or, more correctly, at his conception.
If the activity of the Saturn-force is most clearly manifest in the formation of the hard skull, that of Jupiter, the planet of 'Wisdom', is shown in the formation of the complicated structure of the brain, which enables it to co-ordinate the bodily and psychic functions of the entire man. In the realm of physical nature, man's brain is indeed the most perfect example of cosmic Intelligence at work in a manner resembling that activity of human intelligence which one usually understands by 'organizing'.
In order that Form should come about, the forces of Saturn are required; for the formative process to take place in Wisdom-filled order, Jupiter's forces are necessary. If form and order are to become manifest in the realm of earthly substance, both require the assistance of Mars. We can best form an idea of the part which Mars contributes to the coming into being of the world of Form in nature if we observe what takes place when we make use of speech as a medium for expressing our thoughts. In order to be able to shape a thought we have to participate in the formative force of Saturn. We depend upon Jupiter to bring about logical connexion between the single thoughts. To announce them to the world, we need the motive force of Mars, which enables us so to set external matter in motion that it becomes a carrier and relayer of our thoughts. (We here touch upon the field of the acoustic movements of the air which will occupy us more closely later on.)
Many examples of the activity of the force-spheres represented by the three exterior planets are to be found also in nature external to man. From the realm of plant life we may take the woody and bark-like formation of the trees as representing the operation of Saturn-forces. Similarly, all that goes on in the organizing of the single leaf, and particularly in the organization of the countless separate leaves which make up the foliage of a tree into a unified whole, the characteristic crown of a tree, is an example of the work of Jupiter. Both activities are assisted by the force of Mars, which directs them from the cosmic periphery toward the single physical object.
Between the two groups of astral force operating in this manner, the Sun acts as a mediating element through its double function of supporting the activity of the three lower planets by means of its heat and of conveying to the earth, through its light, the forces of the three higher planets. In the human microcosm the Sun-forces accomplish a corresponding task by means of the influences which radiate from the heart through the body along the paths taken by the blood.
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In what follows we shall point to a group of phenomena which show the astral interconnexion between earth and universe; we owe our knowledge of them to Rudolf Steiner. It is due to him, also, that experimental research into the relevant facts became possible. They concern the reflexion of the various planetary movements, observable in the sky, in the behaviour of certain mineral substances of the earth.
In connexion with our discussion of electricity (Chapter XIII) we spoke of the special function of the metals as bearers of the 'mercurial' quality (in the alchemical sense of the term). As one of the characteristics which reveal this function we mentioned the peculiar capacity of metals to behave as 'solid fluids'. This exceptional place among the mineral substances of the earth, the metals owe to their close association with the extra-terrestrial astral forces of the world. In this field, too, modern spiritual investigation has recovered something which was known to people of old - that among the metals there are seven which have a distinctive character, for each stands in a special relation to one of the seven planets (that is, the planetary force-spheres) of our cosmic system. This is shown in the following table: