Towards a Unified Cosmology
by Reginald O. Kapp
17. Forces in Extragalactic Space
The technique of inference that has been discussed in the preceding chapter calls for a survey of all the forces that could conceivably have an influence on the course of events. The following list seems to be exhaustive: gravitational forces, centrifugal forces, forces of impact, pressure of radiation, electrostatic forces, magnetic forces. But a moment's thought shows that some of these cannot materially influence the shape or behaviour of an extragalactic cloud.
Electrostatic and magnetic forces, for instance, can have a big influence on small-scale events. They can cause turbulence in a gas. There is little doubt that they play a large part in terrestrial and solar phenomena of various kinds. But the known processes by which such forces are produced set a limit to the distance over which they act.
An electrostatic force occurs only when electric charges have been separated, and the region within which the force acts is the region between the places to which the charges have been removed. If an electrostatic field is to cause hydrogen to move through a great distance, the field must extend over at least the same distance. For this to happen, charges must have been torn asunder and removed to the extremities of the field. This must have been done against the force of their mutual attraction. So the charges must have been subjected for a long period of time to a unidirectional force before the field could be produced. In the process, vast quantities of energy must have been employed. Now from established knowledge, and without the help of some quite fantastic ad hoc hypothesis, it is not possible to infer a process that would separate charges by the requisite distance.
It is by the same reasoning that one is obliged to dismiss magnetic forces from the list of those that could cause the unidirectional movement of matter over any distance that was an appreciable fraction of the diameter of a galaxy. I am aware that at the time when this is being written, the hypothesis that large-scale movements within galaxies are controlled by magnetic forces has considerable backing. It cannot be proved that they are not, but I should be more inclined to accept this hypothesis if its authors showed more awareness of the difficulty there is in finding a cause of the hypothetical magnetic forces. Magnetic forces are known only as the result of the movement of electric charges. They operate only over such distances as may form the limits of an electrostatic field. It is not so difficult to believe that electric charges must circle the earth and cause opposite places on it to have, respectively, north and south polarity. But one would have to go a very long way in search of an hypothesis by which charges would encircle a noticeable part of a galaxy and give it a particular magnetic polarity.
That external pressure of radiation has to be ruled out has been explained already in Chapter 11. Such pressure, it will be remembered, must operate generally in the same direction as gravitation and diminish according to the same inverse square law; but its intensity must everywhere be negligibly small in comparison with the intensity of the gravitational field.
Internal pressure of radiation must, however, have a significant effect on any body hot enough to generate much radiant energy in its interior. It is known to be so for the stars and must also be so for the hot central core of a spiral nebula. However, we are now considering the early cloud and we have not discovered any reason why this should be hot. When a cloud begins to form on an astronomical summit, its component molecules can be moving only under the influence of the faint gravitational fields in which they find themselves. In the very early stage, their velocity must be so slow that the cloud must be quite near the absolute zero of temperature. It should not be overlooked, however, that internal pressure of radiation on the very large core of the cloud may have a significant effect at some later stage.
Thus inference (as distinct from speculation) permits only three kinds of force for the construction of a cosmological model based on Symmetrical Impermanence. They are: gravitational forces, forces of impact, and centrifugal forces. If these alone do not serve for inferring a model that resembles actuality, Symmetrical Impermanence will have to be replaced by some other basic hypothesis.