SP-345 Evolution of the Solar
27. CONCLUDING REMARKS
 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
(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
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  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
- (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
(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
Following the actualistic principle (2), (d)
is analyzed in Part A; (c), in Part B; (b), in Part C; and (a), in
The general conclusion is that with the
empirical material now available it is
already possible to reconstruct the basic events leading to
the  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.