SELF

O. N. Karavashkina and S. B. Karavashkin.

22

Some aspects of the Earth evolution

In 1755 I. Kant [17] published his hypothesis of cold dust cloud; from it, by way of accretion (gravitational capture of the substance) the scorching clot of Sun has produced. P. Laplace [18] correctly indicated that a cold and initially immovable cloud will not have the energy enough for such heating. He suggested the model of hot rotating gas nebula with the central clot of substance - the Sun. Cooling down, the system becomes more compact and accelerates its rotation. When at the nebula periphery the centrifugal and centripetal forces reach the equilibrium, a ring separates from the cloud, and in it due to the accretion the planets and satellites origin. The rest of nebula, after Laplace, having lost a part of its mass, accelerates again, which causes it separating a new ring. Of course, then the structures like annular planetary nebulas (see Fig. 1.3) were yet unknown, but the Saturnian ring (Fig. 1.4) undoubtedly pointed, this is a fragment of general regularity, and the calculation showed it too.

a)                                                                                  b)

Fig. 1.3. The planetary nebulas: a - in the Lira constellation [19, p. 43, Fig. 2], and b - NGC 7293 [19, p. 44, Fig. 3].

Fig. 1.4. The Saturnian ring [20, p. 3 of the cover].

This hypothesis is seemingly more logic, but also has a basic discrepancy: every system is known tending to its balance and, having reached it, tends remaining in it, but never splashes the substance out. Furthermore, it is unclear, if he considers some rotating nebula, what makes it stripping off just a ring? And how this ring appears disconnected from the main body of nebula, due to which this last gains an acceleration? Becker [21] comments both basic hypotheses so:

"The same as Kant, Laplace infers the common origin of the bodies of Sun system from the similarity of their motion, from small value of inclination and orbit eccentricities of both planets and satellites. Only a liquid (fluid) scattered over the entire space which the system occupies could cause such unity. He concludes that the Sun atmosphere, due to its extremely high temperature, has originally extended for the confines of contemporary Sun system and then gradually narrowed to its today size. That nebula had the angular momentum which Kant thought to be yield from collisions. The planets have originated in the areas filled with the gaseous products, by way of clustering of broken rings… Kant proceeds from the idea of cold immovable nebula which then heats because of compression, and its first transformations start, since the rotation accumulated. Laplace begins with the heated rotating nebula, giving no explanation to its high temperature. Kant suggests the annular laws of freely rotating nebular matter which accumulates into clods due to the attraction, whereas the entire nebula contracts. Laplace suggests the rings emanated by the nebula when it cools off and then thicken, just like Kant suggested. They both give the Saturnian rings as an example illustrating their hypotheses, but none of them explains, why the planet rings were not so stable as Saturnian rings. They both state that the positive rotation of planets is an inevitable consequence of their thickening, but no one gives quite clear explanation. The satellites formation seems to each author to be a small-scale repetition of the entire planet system formation…" [22]. In other words, if we consider the rotation of some nebula, what makes it to separate just a ring? And how even a separated ring (within a nebula) appears already disconnected from the body of nebula, due to which it gains an acceleration?