[501] Having completed our analysis of the origin and evolution of the solar system, we can summarize the general results as follows:

Our analysis is based on the following principles:

(1) We aim at a general theory of the formation of secondary bodies around a primary body. This hetegonic theory should be equally applicable to the formation of planets around the Sun and the formation of satellites around a planet.

The results confirm that this approach is sensible. In fact it is shown that the properties of a system of secondary bodies is a unique function of the mass (sec. 21) and the spin (sec. 23) of the central body. No special assumption needs to be introduced concerning the Sun.

(2) To avoid the uncertainty concerning the state of the primeval Sun and its environment, the analysis should start from the present state of the solar system and systematically reconstruct increasingly older states. Hence, part A is a critical review of those initial facts which are considered to be relevant for a reconstruction of the origin and evolution of the system.

(3) Before an analysis of the evolution of the solar system can be made, it is essential to clarify what physical laws govern its evolution. A lack of clarity in this respect has been disastrous to many other attempts at such analysis. More specifically the following mistakes have been made:

(a) Based on the prehydromagnetic Laplacian concepts, the importance of electromagnetic effects has been neglected. Studies have been [502] made without any knowledge at all of plasma physics or with erroneous concepts of its laws ("frozen-in" field lines, etc.) (ch. 15).

 

(b) Reliance upon such Laplacian concepts has also led to pictures of the solar nebula as a vapor disc containing all the present matter now in the solar system (or more) together with a complement of light gases, all of which condense in a short time. This has given rise to very high estimates of the instantaneous gas density in the system. unreasonable both in terms of the length of the formation interval and the conditions for angular momentum transfer.

 

(c) Condensation of solids has been thought to occur in a state of temperature equilibrium between grains and gas, and it has not been realized that in space the solid grain temperature normally is an order of magnitude lower than the plasma or gas temperature under such conditions where condensation can take place during cooling of the medium. This has lead to chemical interpretations which are clearly unrealistic.

 

(d) The nature of collisions between grains has not been understood. It has been assumed that these result only in fragmentation, and the accretional processes which necessarily are more important have been neglected. Studies of electrostatic attraction and of collision involving fluffy aggregates are essential.

 

(e) The orbital evolution of a population of grains, although of obvious importance, has not been properly considered. It is necessary to introduce the concept of jet streams as an intermediate stage in the accretional process.

(4) It seems that the origin and evolution of the solar system can be reconstructed as a result of the following processes:

(a) Emplacement of plasma in specific regions around the central bodies. The critical-velocity phenomenon is essential for this process. The exulting chemical differentiation produces substantial differences in the composition of the bodies (chs. 20-21).

 

(b) The transfer of angular momentum from the central body to the surrounding plasma: A partial corotation is established as demonstrated by the structure of the Saturnian rings and the asteroid belt (ch. 18).

 

(c) The condensation from this state results in populations of grains which are focused into jet streams in which the accretion of planets or satellites takes place (ch. 9).

 

(d) Whereas all these processes took place during a period of some hundred million years, there was a slow evolution during 4-5 Gyr to attain he present state.

Following the actualistic principle (2), (d) is analyzed in Part A; (c), in Part B; (b), in Part C; and (a), in Part D.

The general conclusion is that with the empirical material now available it is already possible to reconstruct the basic events leading to the [503] present structure of the solar system. With the expected flow of data from space research the evolution of the solar system may eventually be described with a confidence and accuracy comparable to that of the geological evolution of the Earth.

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