Hypotheses of the origin of the Earth. Origin of the planets

The question of the origin of the Earth, planets and the solar system as a whole excited people since ancient times. Myths about the origin of the Earth are traced in many ancient peoples. The Chinese, the Egyptians, the Sumerians, the 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, not tolerating objections. In medieval Europe, attempts to find the truth sometimes ended in the fire of the Inquisition. The first scientific explanations of the problem refer 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 inquisitive mind.

Mythology of the Ancients

Man is a inquisitive being. From ancient times people differed from animals not only by the desire to survive in a harsh wild world, but also an attempt to understand it. Recognizing the total superiority of the forces of nature over oneself, people began to idolize the ongoing processes. Most often, it is to the celestials that the merit of the creation of the world is attributed.

Myths about the origin of the Earth differed from one another in different parts of the world. According to the ideas of the ancient Egyptians, she hatched from the sacred egg, which was molded by the god Khnum from ordinary clay. According to the beliefs of the island peoples, the earth was fished by the gods from the ocean.

Chaos theory

Nearest 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 into the scientific postulates of the theory of the origin of the Earth. The explosive mixture of elements chaotically rotated, filling all that exists. But at some point from the bowels of the original Chaos Earth was born - the goddess Gaia, and her eternal companion, Heaven, - the god Uranus. Together they have filled lifeless spaces with a variety of life.

A similar myth was formed in China. Chaos Hun-tun, filled with five elements - wood, metal, earth, fire and water - circled in the shape of an egg across an unlimited universe, until the god Pan-Gu was born in it. Awakened, he found only lifeless darkness around him. And this fact greatly saddened him. Gathering strength, the deity Pan-Gu broke the shell of the egg-chaos, releasing the two beginnings: Yin and Yang. The heavy Yin descended, forming the earth, the light and light Yang soared upward, forming the sky.

Class theory of Earth formation

The origin of the planets, and in particular of the Earth, by modern scientists has been sufficiently studied. But there are a number of fundamental questions (for example, where did the water come from), causing heated debate. Therefore, the science of the universe is developing, every new discovery becomes a brick in the foundation of the hypothesis of the origin of the Earth.

The famous Soviet scientist Otto Schmidt, better known for polar research, grouped all the proposed hypotheses and combined them into three classes. The first includes theories derived from the postulate of 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 representations according to which planets were formed directly from the substance of the Sun. This hypothesis of the origin of the Earth scientists Jeans, Jeffries, Multon and Chamberlin, Buffon and others.

And, finally, the third class includes theories that do not unite the Sun and planets with a common origin. Schmidt's hypothesis is best known. Let us dwell on the characteristics of each class.

Hypothesis of Kant

In 1755, the German philosopher Kant, the origin of the Earth, was briefly described as follows: the original universe consisted of immobile dust-like particles of varying density. Gravity forces led them to move. There was sticking them on each other (the accretion effect), eventually leading to the formation of a central red-hot clot - the Sun. Further collisions of particles led to the rotation of the Sun, and with it a dust cloud.

In the latter, separate clusters of matter gradually formed-the embryos of future planets around which satellites formed according to a similar pattern. Formed in this way, the Earth at the beginning of its existence seemed cold.

The concept of Laplace

The French astronomer and mathematician P. Laplace proposed a somewhat excellent variant, explaining the origin of the planet Earth and other planets. The solar system, in his opinion, was formed from a glowing gas nebula with a cluster of particles in the center. It rotated and contracted under the influence of universal gravitation. With further cooling, the speed of rotation of the nebula grew, on the periphery of it flaked rings, which disintegrated into prototypes of future planets. The latter at the initial stage were hot gasses, which were gradually cooled and solidified.

The lack of hypotheses of Kant and Laplace

Hypotheses of Kant and Laplace, explaining the origin of the planet Earth, were dominant in cosmogony until the beginning of the twentieth century. And they played a progressive role, serving as a basis for natural sciences, especially geology. The main drawback of the hypothesis is the inability to explain the distribution within the solar system of the angular momentum (MKR).

MKR is defined as the product of the body mass at a distance from the center of the system and the speed of its rotation. Indeed, based on the fact that the Sun has more than 90% of the total mass of the system, it must have a high MKR. In fact, the Sun has only 2% of the total MKR, while the planets, especially the giants, are endowed with the remaining 98%.

Theory of Fesenkov

This contradiction was tried in 1960 by the Soviet scientist Fesenkov. According to his version of the origin of the Earth, the Sun with the planets formed as a result of the condensation of a giant nebula - the "globule". The nebula had a very rarefied matter, composed mainly of hydrogen, helium and a small number of heavy elements. Under the influence of gravity in the central part of the globule arose a starlike condensation - the Sun. It rotated rapidly. As a result of the evolution of the solar matter into the surrounding gas-dust environment, matter was emitted from time to time. This led to the loss of the Sun's mass and the transfer to the created planets of a significant part of the MKR. Formation of the planets took place by accretion of the substance of the nebula.

Theories of Multon and Chamberlin

American explorers astronomer Multon and geologist Chamberlin suggested similar hypotheses of the origin of the Earth and the solar system, according to which planets were formed from the substance of gas branches of spirals, "elongated" from the Sun by an unknown star that passed at a sufficiently close distance from it.

Scientists have introduced into cosmogony the concept of "planetesimal" - these are clots condensed from the gases of the original substance, which have become embryos of planets and asteroids.

Judgment of Jeans

The English astrophysicist J. Jeans (1919) suggested that when approaching the Sun with another star from the latter, a cigar-like protrusion broke off, which later broke up into separate clots. And from the middle thickened part of the "cigar" large planets were formed, and on its edges - small ones.

Schmidt's conjecture

In the questions of the theory of the origin of the Earth, the original point of view in 1944 was expressed by Schmidt. This is the so-called meteorite hypothesis, later physico-mathematically grounded by the students of the famous scientist. By the way, in the hypothesis the problem of the formation of the Sun is not considered.

According to theory, the Sun at one of the stages of its development captured (attracted to) a cold gas-dust meteor cloud. Before that, it owned a very small MKR, the cloud was rotating 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 meteoritic material hit the star, the other, as a result of accretion processes, formed clots-embryos of planets and their satellites.

In this hypothesis, the origin and development of the Earth is dependent on the effect of the "solar wind" - the pressure of solar radiation, which repelled light gas components on 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. A major drawback of the hypothesis is the researchers consider a very low probability of capture by the Sun of a similar meteorite cloud.

Assumptions 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 the planets and the Sun. According to their ideas, a close explosion of a supernova could serve as the initiator of processes in the gas-dust nebula. Further events, according to researchers, looked like this:

1. Under the action of the explosion, the nebula contracted and the formation of a central clot-the Sun.
2. From the emerging Sun, the MRC was transmitted to the planets by an electromagnetic or turbulent convective path.
3. Began to form giant rings, reminiscent of the rings of Saturn.
4. As a result of the accretion of the material of the rings, first appeared planetesimals, subsequently formed into modern planets.

The whole evolution took place very quickly - for about 600 million years.

Formation of the Earth's composition

There is a different understanding of the sequence of formation of the inner parts of our planet. According to one of them, the proto-earth was an unsorted conglomerate of iron-silicate matter. Subsequently, as a result of gravity, a separation into an iron core and a silicate mantle occurred - a phenomenon of homogeneous accretion. Proponents of heterogeneous accretion believe that a refractory iron core was accumulated first, then more fusible silicate particles were accumulated on it.

Depending on the solution of this question, it can also be about the degree of initial warming up of the Earth. Indeed, immediately after its formation, the planet began to warm up due to the joint actions of several factors:

• The bombardment of its surface with 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 subsoil (assuming homogeneous accretion).

According to a number of researchers, at this early stage of the formation of the planet, the outer parts could be in a state close to the melt. In the photo the planet the Earth would look like a hot ball.

Contract theory of continental education

One of the first hypotheses of the origin of the continents was the contractional one, according to which the formation of the mountains was associated with the cooling of the Earth and the reduction in its radius. It was this that served as the foundation for early geological research. On its basis, the Austrian geologist E. Suess synthesized all existing at the time knowledge about the structure of the earth's crust in the monograph "Face of the Earth." But at the end of the XIX century. There appeared data indicating that compression occurs in one part of the earth's crust, and tension in another. Finally, the contraction theory collapsed after the discovery of radioactivity and the presence of large stocks of radioactive elements in the Earth's crust.

Drift of continents

In the early 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 Hindustan, etc. The first to compare the data of Pilgrinny (1858), later Bihanov. The very idea of continental drift was formulated by American geologists Taylor and Baker (1910) and German meteorologist and geophysicist Wegener (1912). The latter substantiated this hypothesis in his monograph The Origin of Continents and Oceans, which was published in 1915. Arguments that were advocated in support 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 the adjacent continents of geological sections of Late Paleozoic and Early Mesozoic rocks.
• Petrified remains of animals and plants, which show that the ancient flora and fauna of the southern continents formed a single grouping: especially the fossilized remains of dinosaurs of the genus lystrosaurs, found in Africa, India and Antarctica.
• Paleoclimatic data: for example, the presence of traces of the Late Paleozoic cover glaciation.

Earth crust formation

The origin and development of the Earth is inextricably linked with mountain building. A. Wegener argued that the continents, consisting of fairly light mineral masses, seem to float on the underlying underlying plastic material of the basalt bed. It is assumed that at first a thin layer of granite material supposedly covered the whole Earth. Gradually, its integrity was disturbed by the tidal forces of the Moon and the Sun's attraction, which act 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.

Of granite (presumably) was a single supermateric Pangea. It existed until the middle of the Mesozoic era and disintegrated in the Jurassic period. The proponent 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 were found the rocks of the bottom of the Pacific Ocean. Under the continents there was a sea of magma, along which they moved. Laurasia and Gondwana moved rhythmically to the equator, then to the poles. With the shift to the equator, the supermaterials were frontalally compressed, with the flanks pressing the Pacific mass. These geological processes are considered by many 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, 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 forth in school textbooks. But if you take the literature of 50 years ago, it can be seen that modern scientists are looking 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 the planet Earth looks like from space. New knowledge forms a new understanding of the laws of the universe.

It is obvious that the mighty forces of nature were used to create from the original chaos of the Earth, the planets and the Sun. Not surprisingly, 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 surely exceed the wildest fantasies. But a whole picture of the surrounding world is gradually forming along the lines of knowledge collected by scientists.