Modern artistic rendition of the nebular hypothesis: (a) interstellar matter attracts into a volume or cloud, (b) the center ignites, (c) the surrounding fluid-like cloud begins to contract inward and rotate, (d) proto comet-like planets begin go form, rotating at high speeds; earth known have been rotating once per every ten hours, (e) the modern star system forms.

“We have to say that it is only the will of god that can move a body; and so, the moving force of bodies is not in the bodies that move since this force is nothing but the will of god.”

— Nicolas Malebranche (c.1670), The Search after Truth

“If it only with respect to circular movement that we can say that matter by itself always tends to move in a straight line, being the simplest and most natural movement, but it cannot always do this because everything that has extension is full of matter, so matter cannot always move in a straight line without encountering other matter that prevents it from continuing its movement and so it is forced to move in a curved or circular line, which necessarily makes certain portions or volumes of matter always move in a circle and produce many vortices of matter. And there is no doubt that it is only from this that the roundness of the earth, sun, moon, and all the stars and planets come, as our Cartesians rightly mentioned.”

— Jean Meslier (1729), The Testament (pg. 400-01)

“Swedenborg’s ‘nebular hypothesis’ for the origin of the solar system, described in his Principia Rerum Naturalium, was derived from his philosophy of ‘like-partedness’, the idea that every entity is recursively composed of smaller, homologous versions of itself, and that it likewise forms a component part of a larger entity. For the solar system, Swedenborg proposed that the sun had developed a dense surface layer that was forced outward by the centrifugal force of its rotation, into the equatorial plane of the solar rotation. Continuing its outward motion, this ring eventually thinned and broke apart into smaller bodies that formed the planets and smaller bodies.”

— Glen Cooper (2007), Biographical Encyclopedia of Astronomers (Ѻ)

“The first attempt to explain the constitution and the mechanical origin of the world in a simple manner by ‘Newtonian laws’ — that is, by mathematical and physical laws—was made by Immanuel Kant in the famous work of his youth (1755), General History of the Earth and Theory of the Heavens. Unfortunately, this distinguished and daring work remained almost unknown for ninety years; it was only disinterred in 1845 by Alexander Humboldt in the first volume of his Cosmos.”

“In seeking to trace the cause of the original motions of the planetary systems, the following five phenomena, enumerated in the last chapter, are available: the motions of the planets in the same direction and nearly in the same plane; the motions of the satellites in the same direction as the planets; the motions of rotation of these different bodies and of the Sun in the same direction as their orbital motions, and in but slightly different plain's; the small eccentricity of the orbits of planets and satellites; finally, the great eccentricity of comets' orbits, as though their inclination had been left to chance.

So far as I am aware, Buffon is the only one who has endeavored, since the discovery of the true system of the world, to trace the origin of the planets and their satellites. He supposes that a comet, falling upon the Sun, drove from it a torrent of matter, which reunited at a distance in several globes, varying in size and in distance from the Sun; these globes, having become opaque and solid by cooling, are the planets and their satellites.”

Left: Swedish polymath Emanuel Swedenborg’s 1734 depiction of the formation of the solar system (“De Chao Universali Solis”); figure 1: the crust formed by the original nebula as it solidified is about to burst; figure 2: the state of confusion and collapse as pieces of the sun are scattered through space; figure 3: the crust has reformed as a disc surrounding the proto-sun; figure 4: the pieces have separated into individual spheres: the planets. [1] Right: a near infrared light image (Ѻ) of Beta Pictoris, a 8-20 million year old newly forming solar system caught in the act of “being born”, as Neil Shubin describes it, the first so-called confirmation of Swedenborg’s 1734 nebula hypothesis prediction.

“Whatever be its nature, since it has produced or directed the motions of the planets, it must have embraced all of these bodies, and. in view of the prodigious distances that separate them, it could only have been a fluid of immense extent. In order to give them a nearly circular motion about the Sun, in the same direction, the fluid must have surrounded this body like an atmosphere. The consideration of planetary motions tbus leads us to think that, as the result of excessive heat, the solar system originally extended beyond the orbits of all the planets, and that it contracted by successive steps to its present limits.

In the assumed primitive condition of the Sun, it resembled those nebulae which are shown by the telescope to be composed of a more or less brilliant nucleus, surrounded by nebulosity which, in condensing toward the surface of the nucleus, transforms it into a star. If, by analogy, we conceive of all the stars being formed in this manner, we may imagine their earlier nebular state, itself preceded by other states, in which the nebular matter was more and more diffuse, the nucleus being less and less luminous. By going back as far as possible, we thus arrive at a nebulosity so diffuse that its existence could hardly be suspected.

Philosophical observers have long been impressed with the peculiar distribution of certain stars visible to the naked eye. Mitchel has remarked on the improbability that the stars of the Pleiades, for example, could have been compressed within the narrow limits which inclose them by mere chance, and he has hence concluded that this group of stars, and similar groups in the heavens, are the effects of an original cause or of a general law of nature. These groups are the necessary result of the condensation of nebulae having several nuclei; for it is evident that, if the nebular matter were continually attracted by these various nuclei, they would ultimately form a group of stars like that of the Pleiades. The condensation of nebulae having two nuclei will similarly form stars lying very close together, and revolving about one another, like the double stars whose motions have already been observed.

But how has the solar atmosphere determined the motions of rotation and of revolution of the planets and satellites? If these bodies had penetrated deeply into this atmosphere, its resistance would have caused them to fall upon the Sun. We may thus conjecture that the planets were formed at its successive limits, by the condensation of zones of vapors which the Sun, in cooling, must have alxiudoned in the plane of its equator.

Let us recall the results given in a preceding chapter. The atmosphere of the Sun could not have extended out indefinitely. Its limit was the point where the centrifugal force, due to its motion of rotation, balanced the attraction of gravitation. Now, as cooling contracted the atmosphere and condensed at the surface of the Sun the molecules lying near it, the motion of rotation accelerated. For, from the law of areas, the sum of the areas described by the radius vector of each molecule of the Sun and of its atmosphere, when projected on the plane of its equator, being always the same, the rotation must be more rapid when these molecules approach the center of the Sun. The centrifugal force due to this motion thus becoming greater, the point where it equals the weight is nearer the Sun. If we then adopt the natural supposition that the atmosphere extended, at some period, to an extreme limit, it must have left behind, in cooling, the molecules situated at this limit and at the successive limits produced by the acceleration of the Sun's rotation. These abandoned molecules must have continued to revolve around the Sun, sinco their centrifugal force was balanced by their weight. But since this equilibrium did not obtain in the case of the atmospheric molecules in higher latitudes, their weight caused them to approach the atmosphere as it condensed, and they did not cease to belong to it until this motion brought them to the equator.

Let us now consider the zones of vapor successively left behind. To all appearances these zones should form, by their condensation and the mutual attraction of their molecules, various concentric rings of vapor revolving around the Sun. The mutual friction of the molecules of each ring should have accelerated some and retarded others, until they had all acquired the same angular velocity. Thus the linear velocities of the molecules farthest from the center of the Sun must have been the greatest. The following cause would also contribute toward the production of this difference of velocity. The molecules farthest from the Sun, which, through the effects of cooling and condensation, came together to form the outer part of the ring, always described areas proportional to the time, since the central force which controlled them was constantly directed toward the Sun. This constancy of areas requires that the velocity increase as the molecules move inward. It is evident that the same cause must have diminished the velocity of those molecules which moved outward to form the inner edge of the ring.

If all the molecules of a ring of vapor continued to condense without separating, they would finally form a liquid or solid ring. But the uniformity which this formation demands in all parts of the ring, and in their rate of cooling, must have rendered this phenomenon extremely rare. Thus the solar system offers only a single example of it, that of the rings of Saturn. In almost all cases each ring of vapor must have broken into several masses which, having only slightly different velocities, continued to revolve at the same distance around the Sun. These masses must have assumed a spheroidal form, with a motion of rotation corresponding in direction with that of their revolution, since their inner molecules had smaller linear velocities than their outer molecules; they thus formed as many planets in a vaporous state. But if one of them had possessed sufficient power of attraction to bring all the others successively together about its own center, the vaporous ring would thus have been transformed into a single spheroidal mass of vapor, revolving about the Sun and rotating in a direction corresponding to that of its revolution. This latter case has been the most common one. Nevertheless, the solar system offers an example of the first case in the four minor planets which lie between, Jupiter and Mars; unless we suppose, in agreement with M. Olbers, that they originally formed a single planet broken up by a violent explosion into several parts having different velocities.

Now, if we follow the changes which ultimate cooling must have produced in the vaporous planets whose formation we have just pictured, we shall witness the production, at the center of each, of a nucleus which continues to develop through the condensation of the atmosphere surrounding it. In this state the planet exactly resembles the Sun in its primitive nebular condition. Cooling must thus have produced, at the various limits of its atmosphere, phenomena similar to those we have described; that is to say, rings and satellites revolving around its center in the direction of its motion of rotation, and turning in the same direction upon themselves. The symmetrical distribution of Saturn's rings about its center and in the plane of its equator naturally results from this hypothesis, and would be inexplicable without it. These rings seem to me ever-present proofs of the original extension of Saturn'8 atmosphere and of its successive retreats. Thus the singular phenomena of the slight eccentricity of the orbits of the planets and satellites, the small inclination of these orbits to the solar equator, the identity in direction of the motions of rotation and revolution of all these txxlies with that of the solar rotation: How from our hypothesis and give it great probability.

If the solar system had been formed with perfect regularity, the orbits of the bodies which compose it would have been circles whose planes, like those of the various equators and rings, would have coincided with the plane of the solar equator. But it may be conceived that the endless varieties which must have existed in the temperature and density of the various parts of these great masses produced the eccentricity of their orbits and the deviation of their motions from the plane of this equator.

In our hypothesis, comets are strangers to the planetary system. In considering them, as we have done, to be small nebulae wandering from system to system, and formed by the condensation of nebular matter distributed with such profusion throughout the universe, we perceive that, when they arrive in the region of space where the solar attraction is predominant, it forces them to describe elliptical and hyperlx>lic orbits. But their motions being equally possible in all directions, they must move indifferently in all directions and at all inclinations to the ecliptic; which is in agreement with observation. Thus the condensation of nebular matter, by which we have just explained the motions of rotation and revolution of the planets and satellite's in the same direction, and in planes differing but slightly, also explains why the motions of comets do not agree with this general law.”

“If certain comets entered the atmospheres of the Sun and planets during the formative period they must have fallen upon these bodies, after pursuing spiral paths. The result of their fall would be to cause the planes of the orbits and the equators of the planets to deviate from the solar equator.
If in the zones left behind by the solar atmosphere there were molecules too volatile to combine among themselves or with the planets, they must have continued to revolve about the Sun. They would thus give rise to such an appearance as that of the zodiacal light, without offering appreciable resistance to the various Ixxlies of the planetary system, either because of their extreme rarity, or because their motion is very nearly the same as that of the planets which they encounter.

A close examination of all the details of the solar system adds still further to the probability of our hypothesis. The original fluidity of the planets is clearly indicated by the flattening of their figure, in conformity with the laws of mutual attraction of their molecules; furthermore, it is proved in the case of the Earth by the regular diminution of weight from the equator to the poles. This condition of original fluidity, to which we are led by astronomical phenomena, should show itself in the phenomena of natural history. But, to perceive it there, it is necessary to take into account the immense variety of combinations formed by all terrestrial substances mingled together in a state of vapor, when the reduction of temperature permitted their elements to unite among themselves. It is also necessary to consider the enormous changes that this fall of temperature must have brought about successively within the Earth and upon its surface, in all formations, in the constitution and the pressure of the atmosphere, in the ocean, and in the bodies which it held in solution. Finally, consideration should be given to violent disturbances, such as great volcanic eruptions, which must have modified, at various epochs, the regularity of these changes. Geology studied from this point of view, which unites it to astronomy, will acquire precision and certainty in many particulars.”