1. Nebular hypotheses
All the cosmogonical hypotheses can be divided into several groups: nebular hypotheses (of Kant, Laplace and others, among them – the hypothesis of O.Yu.Schmidt); hypotheses of capture, ejection, etc. The nebular hypotheses being the most numerous can, in their turn, be divided into two sub-groups. According to the first of them, the Sun and all the bodies of the Solar System: planets, satellites, asteroids, comets and meteoric bodies – had been generated from the single gas-dust or dust cloud. According to the second group of hypotheses, the Sun and its family are of different origins; at that, the Sun had been formed from one gas-dust cloud (nebula, globule), while the other celestial bodies of the Solar System – from another cloud being captured by the Sun in some, not quite understandable way into its orbit and then being separated (by some still less comprehensible way) into a number of various bodies (planets, their satellites, asteroids, comets and meteoric bodies) having various characteristics: mass, density, eccentricity of orbit, direction of orbital circulation and axial rotation, orbit inclination to the plane of Solar equator (or obliquity to the ecliptic), as well as slope of the equator plane to the orbit plane.
Since our reader is most of all familiar with the hypothesis of O.Yu.Schmidt, we will dwell upon it in more detail. As the celestial mechnicians assert, nebular hypotheses of Kant, Laplace, etc. have, among others, the following shortcoming: they cannot explain why the momentum (angular momentum) of the Solar System is so non-uniformly distributed between the Sun and planets – about 2% of angular momentum falls to the share of the Sun, while nearly 98% falls to the share of planets, although the aggregate mass of all the planets is 750 times less than that of the Sun.
Apparently, to avoid this contradiction, Schmidt proceeds from the assumption of different origin of the Sun and planets. However, to be perfectly consecutive, one should suppose that not only the Sun and all the planets, but also different planets are of different origin, because they have different specific angular momentums, i.e. momentums per unit mass. If the specific angular momentum of Earth is equal to 1, then the planets of Solar System would have the following specific angular momentums:
(B.S.Levin. Origin of Earth and planets. M. 1964, p. 14).
All the parts of proto-planet gas-dust cloud, that once supposedly met the Sun and had been captured by the latter to its orbit, should have absolutely equal specific angular momentums, as before the capture they moved in one direction and had the same speed. We assume that this cloud did not rotate, since in such a case it apparently should be dispersed in interstellar space under the influence of centrifugal force long before encounter with the Sun. The planets should also have equal specific angular momentums, if we assume their origin according to the hypothesis of O.Yu.Schmidt. Meanwhile, they are very different. Why is it so? How could Mercury “transfer” its surplus of momentum to Pluto, while Venus, Earth and Mars – to Neptune or Uranus, etc? The hypothesis of Schmidt does not answer this question.
The question of regularity of interplanetary distances is also explained unconvincingly in the hypothesis of Schmidt. According to Schmidt, these distances rise in arithmetical progression (why?), but the terrestrial planets have the difference of 0.20, while the distant planets have another difference – 1.00. The hypothesis does not explain why there appeared a gap between Mars and Jupiter, in which, instead of the notorious planet Phaeton, there is a number of asteroids circling the Sun. The hypothesis does not explain why Pluto is so “close” to Neptune that sometimes it crosses the orbit of the latter..
Schmidt tries to explain the interplanetary distances by means of specific angular momentum of planets; the latter is in need of its own explanation, however.
A weak spot in Schmidt’s hypothesis is the explanation of distribution of the mass of substance of proto-planetary cloud between planets. Indeed, the most part of mass of the cloud circling the Sun and having the form of disk (toroid) should be located in the center of its cross-section. It might seem that the most massive planet should be formed in the middle of the row of planets, while the less massive ones should be located on each side of it.
If we draw the line across the section of Schmidt’s gas-dust cloud, that divide this section into two equal symmetrical parts(ref. Fig. 1a), then one half of planets with one half of aggregate mass should be situated on one side of this symmetry line, while the other half – on the other side, as shown in (Fig. 1b). But (Fig. 1c) represents quite another picture. Meanwhile, this is a scheme of distribution of actual masses of planets and diameters of their orbits.
Schmidt explained this situation by the fact, that distant planets, apparently, being situated far from the Sun, have scattered the substance of proto-planet disk to interplanetary space, predominantly to the periphery of the Solar System. Not counting Uranus being situated just in the center of disk cross-section, on one side of the symmetry line there appeared six planets with overall mass of 415 Earth masses, while on the other side – only two planets weighing only 17 Earth masses. One can hardly agree with the fact that Neptune had scattered such a huge amount of matter – about 400 Earth masses. Besides, the facts that Neptune is more massive than Uranus, and Mars is less massive than Earth and Venus contradict the hypothesis of Schmidt. According to the latter, everything should be vice versa.
The fact that one third of all the satellites of planets of the Solar System circulates in direction opposite to that of the rest Solar System is utterly beyond the framework of Schmidt’s hypothesis. Such satellites are: Neptune’s Triton – one of the largest satellites in the Solar System, Saturn’s Phoebe, four small outer satellites of Jupiter and five satellites of Uranus (the latter rotate in the same direction as Uranus does).
According to the hypothesis of Schmidt, all the celestial bodies of the Solar System, except the Sun itself, had been created from single cloud that, being captured by the Sun, circled the latter in one (forward) direction in full compliance with the law of conservation of momentum. Then, all the bodies of the Solar System, having originated from this gas-dust cloud, should circulate the Sun in the same direction.
Just imagine that you are sailing down the river. Entering the river delta, where the river-bed is divided into a dozen of branches, you sail down one of them to the sea, regarding this fact as quite natural. But what would you say, if someone asserts that in one (or several) branches of the delta the water flows in opposite direction so that one cannot reach the sea down such a branch? A similar situation is for the hypothesis of Schmidt, as well as other nebular hypotheses asserting that all the celestial bodies of the Solar System (both those circulating the central body – the Sun or a planet – in forward direction, and those circulating against the “current”, i.e. in reverse direction) have originated from the single proto-planetary cloud that, both before and after its capture by the Sun, moved in one (forward) direction. This is a violent contradiction with the law of conservation of momentum that, in this particular context, can be called the law of conservation of momentum and direction of motion.
From the standpoint of the law of conservation of momentum, Schmidt’s hypothesis, as well as all the other nebular hypotheses, contradicts the fact that half of the planets of Solar System has large slope of equator plane to orbit plane, that exceeds 23˚ for Earth, Mars, Saturn and Neptune; Uranus has the slope of 98˚. If all the planets had been formed from the single cloud, they should have the same inclinations of their orbits to the plane of Sun’s equator and should not have slopes of planes of their equators to the common plane of their orbits. And if we suppose that these characteristics changed in the course of time, then these changes should be more or less equal, equivalent.
2. Hypotheses of capture
We can see that the nebular hypothesis of Schmidt, as well as all the other nebular hypotheses, faces a number of insoluble contradictions. In order to avoid them, many researchers put forward the idea of individual origin of the Sun, as well as all the other bodies of the Solar System. These are so-called hypotheses of capture.
According to these hypotheses, the Solar System is subject from time to time to penetration of celestial bodies from the outside, i.e. from other parts of the Galaxy, from other galaxies and from intergalactic space. Being influenced by various factors (attraction by the Sun and planets; collisions with other wandering celestial bodies or asteroids and comets of the Solar System; passing through the gas-dust cloud when the Solar System is located in this cloud in process of its circulation around the center of Galaxy), these foreign bodies are being decelerated and, having slowed down their motion, become “prisoners” of the Sun or a planet of the Solar System, having changed their hyperbolic orbits for elliptical ones.
However, the hypotheses of capture, though having avoided a number of contradictions characteristic of the nebular hypotheses, are not free from their own contradictions that are not specific to the latter. First of all, there is a big doubt that such a large celestial body as a planet, especially a giant one, can slow down enough to change its orbit from hyperbolic to elliptical one. It’s obvious, that neither dust nebula, nor attraction of the Sun or a planet can create such a strong braking effect.
So, only the version of collision remains. But can two planetesimals remain intact as a result of head-on collision; wouldn’t they drop into small pieces in such a case? After all, under the influence of the Sun’s gravitation, they would develop speeds of some dozen kilometers a second. One may suppose that the both planetesimals would fall to pieces; the latter would partly drop to the Sun’s surface and partly dash away into open space in the form of large cluster of meteors. And maybe only some fragments would be captured by the Sun or one of its planets and become their satellites – asteroids.
One more objection to the authors of hypotheses of capture concerns the probability of such a collision. According to the estimations made by many celestial mechanicians, the probability of collision of two large celestial bodies not far from the third, still larger celestial body is negligibly small, so that such a collision can take place once for some hundred million years. Besides, this collision should occur very “successfully”, i.e. the collided celestial bodies should have definite masses, directions and speeds of movement; they should collide in the definite place of the Solar System. At that, they should transfer to nearly circle orbit and, besides, remain safe and sound. Not a simple task for Mother Nature to solve, isn’t it.
Furthermore, one can put the following general question to the authors of hypotheses of capture: are there wandering, “homeless” celestial bodies (the more so, large ones as giant planets are) in cosmic space at all? If there are, why haven’t they collided yet with one of the numerous stars of the Galaxy, past which they moved during billions years? And how have the giant planets in the open space arisen? One may suppose that all the celestial bodies in cosmic space move along elliptical orbits around one or another central body: planet, star, Galaxy center, etc. This fact considerably reduces the probability of collision of two big celestial bodies in the vicinity of the third, still larger body.
Let us suppose, nevertheless, that such a capture has occurred. Then a number of questions arise. Why do all the captured planets and the majority of other celestial bodies of the Solar System circle the Sun in one and the same direction and nearly in one and the same plane? Why do they have nearly circular orbits? Why are the small terrestrial planets situated near the Sun, while the giant planets are far from it? Why is there certain regularity in the interplanetary distances? Why do some planets rotate around their axes in forward direction, while the other (Venus, Uranus) – in reverse direction? The hypotheses of capture do not answer these questions; at least they answer not all of them.
As to the capture of wandering planetesimals without collision, merely due to the force of gravitational attraction (of the third body), such a capture is either impossible at all, or negligibly improbable, so that this capture can be regarded not as a regularity, but as almost unlikely chance. Meanwhile, there are a lot of large bodies in the Solar System: planets, their satellites, asteroids and big comets; this fact refutes the hypotheses of capture.
3. Other hypotheses
Along with hypotheses of capture and nebular hypotheses, there are also hypotheses, according to which, planets and other celestial bodies of the Solar System occurred as a result of ejection or separation of some part of Sun’s matter: either at nova or supernova outburst, or due to quick axial rotation of the Sun long ago.
However, the celestial mechanicians have proved that if an ejection takes place in some place of Sun’s surface, then the separated substance would either leave the Sun to interstellar space along a hyperbolic orbit and then dissipate, or, if the speed of separated part is not enough, it would circle the Sun along an elliptical orbit and fall to the surface in the same place. Such a blob of gas cannot generate planets. But if, in spite of the calculations of celestial mechanicians, a planet could occur in that way, then it would consist of gases (hydrogen and helium) that form the outer layer of the Sun and other stars. And where from is the silicate component of the planets – rocks and metals?
Besides, the hypotheses of planet formation from the Sun substance cannot explain, why one third of the satellites of the planets of Solar System circulate around their centers in reverse (with respect to rotation of the Solar System) direction; why one half of the planets of the Solar System has big slopes of planes of their equators to the planes of their orbits; why the orbits of planets are almost circular; why some planets rotate around their axes in forward direction, while the other – in reverse one; etc.
[Table of contents] [Foreword]
[COSMOGONICAL HYPOTHESES] [EXPANSION OF CELESTIAL BODIES]
[DEEP DIFFERENTIATION OF SUBSTANCE. ORIGIN OF CONTINENTS AND OCEANS] [DECELERATION OF CELESTIAL BODIES IN GAS-DUST ENVIRONMENT]
[EVOLUTION OF THE SOLAR SYSTEM] [ORIGIN OF THE SOLAR SYSTEM]