The question of the origin of the Earth, planets and the solar system as a whole worried people since ancient times. Myths about the origin of the Earth are traced among many ancient peoples. The Chinese, Egyptians, Sumerians, Greeks had their own idea of the formation of the world. At the beginning of our era, their naive ideas were replaced by religious dogmas that could not be denied. In medieval Europe, attempts to search for truth sometimes ended in the bonfire of the Inquisition. The first scientific explanations of the problem relate only to the XVIII century. Even now there is no single hypothesis of the origin of the Earth, which gives scope for new discoveries and food for an inquiring mind.
Mythology of the ancients
Man is an inquisitive creature. From ancient times, people differed from animals not only in their desire to survive in the harsh wild world, but also in an attempt to understand it. Recognizing the total superiority of the forces of nature over themselves, people began to deify ongoing processes. Most often, the merits of creation of the world are attributed to celestials.
Myths about the origin of the Earth in different corners of the planet were significantly different from each other. According to the ideas of the ancient Egyptians, it hatched from a sacred egg, molded by the god Khnum from ordinary clay. According to the beliefs of the island peoples, the gods fished the earth out of the ocean.
Chaos theory
The closest to the scientific theory came the ancient Greeks. According to their concepts, the birth of the Earth came from the original Chaos, filled with a mixture of water, earth, fire and air. This fits with the scientific postulates of the theory of the origin of the Earth. The explosive mixture of elements rotated chaotically, filling everything that exists. But at some point from the bowels of the original Chaos, the Earth was born - the goddess Gaia, and its eternal companion, Heaven, the god Uranus. Together, they filled lifeless open spaces with the diversity of life.
A similar myth has developed in China. Chaos Hun-tun, filled with five elements - wood, metal, earth, fire and water - circled in the shape of an egg through the boundless Universe, until the god Pan-Gu was born in it. Awakening, he found only lifeless darkness around him. And this fact saddened him greatly. Gathering strength, the deity Pan-Gu broke the shell of the chaos egg, releasing two principles: Yin and Yang. Heavy Yin descended, forming the earth, light and light Yang soared upward, forming the sky.
Earth theory class theory
The origin of the planets, and in particular the Earth, by modern scientists has been sufficiently studied. But there are a number of fundamental issues (for example, where did the water come from) that cause heated debate. Therefore, the science of the Universe is developing, each new discovery becomes a brick in the foundation of the hypothesis of the origin of the Earth.
The famous Soviet scientist Otto Yulievich Schmidt, better known for his polar studies, grouped all the proposed hypotheses and combined them into three classes. The first includes theories based on the postulate about the formation of the Sun, planets, moons and comets from a single material (nebula). These are the well-known hypotheses of Voitkevich, Laplace, Kant, Fesenkov, recently revised by Rudnik, Sobotovich and other scientists.
The second class combines the ideas according to which the planets were formed directly from the substance of the Sun. These are the hypotheses of the origin of the Earth by scientists Jeans, Jeffries, Multon and Chamberlin, Buffon and others.
And, finally, theories that do not unite the Sun and planets with a common origin belong to the third class. The most famous Schmidt hypothesis. Let us dwell on the characteristics of each class.
Kant's hypothesis
In 1755, the German philosopher Kant briefly described the origin of the Earth as follows: the original Universe consisted of motionless dusty particles of various densities. The forces of gravity led their movement. They stuck to each other (accretion effect), which ultimately led to the formation of a central hot clot - the Sun. Further collisions of particles led to the rotation of the Sun, and with it the dust cloud.
In the latter, separate clumps of matter gradually formed - the embryos of future planets around which satellites were formed in a similar pattern. The Earth formed in this way at the beginning of its existence seemed cold.
Laplace concept
The French astronomer and mathematician P. Laplace proposed a slightly different version explaining the origin of planet Earth and other planets. The solar system, in his opinion, was formed from a hot gas nebula with a bunch of particles in the center. It rotated and contracted under the influence of universal gravitation. With further cooling, the rotation speed of the nebula grew, rings exfoliated from it around the periphery, which decayed into the prototypes of future planets. The latter at the initial stage were hot gas balls, which gradually cooled and solidified.
Lack of Kant and Laplace hypotheses
The hypotheses of Kant and Laplace explaining the origin of planet Earth were dominant in cosmogony until the beginning of the twentieth century. And they played a progressive role, serving as the basis for the natural sciences, especially geology. The main drawback of the hypothesis is the inability to explain the distribution of the angular momentum (MKR) inside the solar system.
MKR is defined as the product of body mass and the distance from the center of the system and its rotation speed. Indeed, based on the fact that the Sun possesses more than 90% of the total mass of the system, it must also have a high MKR. In fact, the Sun has only 2% of the total MKP, while planets, especially giants, are endowed with the remaining 98%.
Theory of Fesenkov
The specified contradiction in 1960 was tried to explain by the Soviet scientist Fesenkov. According to his version of the origin of the Earth, the Sun and the planets were formed as a result of the compaction of a giant nebula - “globules”. The nebula had very rarefied matter, composed mainly of hydrogen, helium and a small amount of heavy elements. Under the influence of gravity in the central part of the globule, a star-shaped condensation arose - the Sun. It was spinning fast. As a result of the evolution of solar matter into the surrounding gas-dust environment, matter was occasionally released. This led to the Sun losing its mass and transferring to the created planets a significant part of the MCR. The formation of the planets took place by accretion of the substance of the nebula.
Theories of Multon and Chamberlin
American researchers astronomer Multon and geologist Chamberlin proposed similar hypotheses for the origin of the Earth and the Solar system, according to which the planets were formed from the matter of gas branches of spirals, "elongated" from the Sun by an unknown star, which passed at a fairly close distance from it.
Scientists have introduced the concept of “planetesimal” into cosmogony - these are clots condensed from the gases of the original substance, which became the embryos of planets and asteroids.
Jeans judgment
The English astronomer and physicist D. Jeans (1919) suggested that when another star approached the Sun, the cigar-shaped ledge came off the latter, which later broke up into separate clumps. Moreover, large planets formed from the middle thickened part of the “cigar”, and small planets formed along its edges.
Schmidt hypothesis
In questions of the theory of the origin of the Earth, Schmidt expressed his original point of view in 1944. This is the so-called meteorite hypothesis, subsequently physically and mathematically justified by the students of a famous scientist. By the way, in the hypothesis the problem of the formation of the sun is not considered.
According to the theory, the Sun at one of the stages of its development captured (pulled to itself) a cold gas-dust meteorite cloud. Prior to this, it had a very small FCD, while the cloud rotated at a considerable speed. In the strong gravitational field of the Sun, the differentiation of the meteorite cloud by mass, density and size began. Part of the meteorite material fell on the star, another, as a result of accretion processes, formed clumps of embryos of the planets and their satellites.
In this hypothesis, the origin and development of the Earth is dependent on the influence of the “solar wind” - the pressure of solar radiation, which pushed light gas components to the periphery of the solar system. The Earth thus formed was a cold body. Further heating is associated with radiogenic heat, gravitational differentiation, and other sources of internal energy of the planet. Researchers consider a very low probability of the hypothesis to be that the sun captures such a meteorite cloud.
Assumptions of Rudnik and Sobotovich
The history of the origin of the Earth still excites scientists. Relatively recently (in 1984) V. Rudnik and E. Sobotovich presented their own version of the origin of planets and the Sun. According to their ideas, the initiator of the processes in the gas-dust nebula could be a nearby supernova explosion. Further events, according to researchers, looked like this:
- Under the influence of the explosion, the compression of the nebula began and the formation of a central clot - the Sun.
- From the forming Sun, RTOs were transmitted to planets by electromagnetic or turbulent-convective means.
- Giant rings resembling the rings of Saturn began to form.
- As a result of the accretion of the material of the rings, planetesimals first appeared, which subsequently formed into modern planets.
All evolution took place very quickly - for about 600 million years.
Earth composition
There is a different understanding of the sequence of formation of the internal parts of our planet. According to one of them, protozem was an unsorted conglomerate of iron-silicate substance. Subsequently, as a result of gravity, there was a separation into the iron core and silicate mantle - the phenomenon of homogeneous accretion. Proponents of heterogeneous accretion believe that at first the refractory iron core was accumulated, then lighter fusible silicate particles adhered to it.
Depending on the solution to this issue, we can talk about the degree of initial warming up of the Earth. Indeed, immediately after its formation, the planet began to warm up due to the combined actions of several factors:
- The bombardment of its surface by planetesimals, which was accompanied by the release of heat.
- The decay of radioactive isotopes, including short-lived isotopes of aluminum, iodine, plutonium, etc.
- Gravitational differentiation of the bowels (assuming homogeneous accretion).
According to some researchers, at this early stage of planet formation, the outer parts could be in a state close to the melt. In the photo, planet Earth would look like a hot ball.
Contractional theory of the formation of continents
One of the first hypotheses of the origin of the continents was contraction, according to which mountain building was associated with the cooling of the Earth and a reduction in its radius. It was she who served as the foundation of early geological research. On its basis, the Austrian geologist E. Suess synthesized all the knowledge that existed at that time about the structure of the earth’s crust in the monograph “The Face of the Earth”. But at the end of the XIX century. evidence has emerged that in one part of the earth's crust, compression occurs, in the other - extension. The contraction theory finally collapsed after the discovery of radioactivity and the presence in the Earth's crust of large reserves of radioactive elements.
Mainland drift
At the beginning of the twentieth century. the hypothesis of continental drift is emerging. Scientists have long noticed the similarity of the coastlines of South America and Africa, Africa and the Arabian Peninsula, Africa and the Hindustan, etc. The first to compare the data Pilligrini (1858), later Bikhanov. The very idea of continental drift was formulated by American geologists Taylor and Baker (1910) and the German meteorologist and geophysicist Wegener (1912). The latter substantiated this hypothesis in his monograph, The Origin of the Continents and Oceans, which was published in 1915. Arguments that were given in defense of this hypothesis:
- The similarity of the outlines of the continents on both sides of the Atlantic, as well as the continents bordering the Indian Ocean.
- The similarity of the structure on adjacent continents of geological sections of the Late Paleozoic and Early Mesozoic rocks.
- The fossilized remains of animals and plants, which indicate that the ancient flora and fauna of the southern continents formed a single group: this is especially evidenced by the fossilized remains of dinosaurs of the genus Listrosaurs found in Africa, India and Antarctica.
- Paleoclimatic data: for example, the presence of traces of late Paleozoic ice cover glaciation.
Earth crust formation
The origin and development of the Earth is inextricably linked with mountain building. A. Wegener argued that continents, consisting of fairly light mineral masses, seemed to float on the underlying heavy plastic material of the basalt bed. It is assumed that at first a thin layer of granite material supposedly covered the entire Earth. Gradually, its integrity was violated by the tidal forces of attraction of the Moon and the Sun, acting on the surface of the planet from east to west, as well as by centrifugal forces from the rotation of the Earth, acting from the poles to the equator.
Granite (presumably) consisted of a single supercontinent Pangea. It lasted until the middle of the Mesozoic era and disintegrated in the Jurassic period. A supporter of this hypothesis of the origin of the Earth was the scientist Staub. Then came the unification of the continents of the northern hemisphere - Laurasia, and the unification of the continents of the southern hemisphere - Gondwana. Between them, the rocks of the bottom of the Pacific Ocean were sandwiched. Under the continents lay a sea of magma, along which they moved. Laurasia and Gondwana rhythmically moved either to the equator or to the poles. When shifted to the equator, supermaterials were frontally compressed, while pressing on the Pacific masses with their flanks. Many consider these geological processes to be the main factors in the formation of large mountain ranges. Movement to the equator occurred three times: during the Caledonian, Hercynian and Alpine mountain building.
Conclusion
A lot of popular science literature, children's books, and specialized publications have been published on the formation of the solar system. The origin of the Earth for children in an accessible form is set out in school textbooks. But if we take the literature of 50 years ago, it is clear that modern scientists look at some problems differently. Cosmology, geology and related sciences do not stand still. Thanks to the conquest of near-Earth space, people already know what planet Earth is seen in the photo from space. New knowledge forms a new understanding of the laws of the universe.
Obviously, to create from the primordial chaos of the Earth, planets and the Sun, powerful forces of nature were involved. It is not surprising that the ancient ancestors compared them with the accomplishments of the Gods. Even figuratively it is impossible to imagine the origin of the Earth, pictures of reality would certainly surpass the wildest fantasies. But according to the bits of knowledge collected by scientists, an integral picture of the world is gradually being built.