Origin of the Earth. Different hypotheses of the origin of the Earth

When you leave on an early frosty morning outside and feel the crunching of snowflakes under your feet or you meet the dawn on the river bank in hot July, it's very difficult to imagine that once upon a time there was nothing of this. In general, nothing: no snow, no river, no grass, not even the Sun. There was only an endless space in which particles of dust rushed, crashing into each other at enormous speeds. This period is difficult to call it. It is not prehistoric, it is some kind of an out-of-history: it was so incomprehensibly long ago, and so hopelessly lifeless was then space ...

However, the origin of the Earth is inextricably linked with this stage in the formation of the universe. The conditions that subsequently led to the appearance of our planet began to form from the very moment of the Big Bang. Various hypotheses of the origin of the Earth and the origin of the world have arisen in the minds of people since when a person first thought about his place in the universe and about what exists outside of his usual territory.

Mythology

All peoples have legends about the origin of the world. They are united by the divine principle underlying the mythological creation. Out of chaos, the first deities appear, which give rise to the doubt of supernatural beings, as well as everything that exists: to the ocean, to dry land, day and night, to people. Concepts of the origin of the Earth from different peoples are often associated with the desire of God to create a firmament in the middle of the world's waters. At different times myths about the creation of the world were supplemented, or new versions appeared. Thus, in Hinduism, the origin of the Earth and the entire universe is considered in five variants. The basis for the universe, according to different traditions, is the sacred sound Om, the first man Purusha, who sacrificed parts of his body to create the world, the breath of Maha-Visnu. Also, as the beginning of everything there is "primary heat" and "cosmic egg".

Cosmogony of the Slavs

The origin of the Earth according to ancient Slavs is in many respects similar to other mythological representations. Initially, the universe was not ordered. At that time there was only one god Rod, who structured the primordial Chaos. He created the earth from the conjunction of the sea and heavenly elements. Then his son Svarog began to organize the space. He breathed life into everything earthly, created man and explained to the first people the laws by which to live.

Under the influence of Christianity, the myth has somewhat changed. In the annals there is a tradition about God floating on the pristine waters on a boat and meeting the devil. God sends a demon to the bottom of the sea for a handful of sand and creates from it an earthly firmament.

Name

With the mythological legends about the world order, the origin of the name "Earth" is also connected. In the thinking of the distant ancestors of all modern nations there was no idea of the spherical shape of the planet, and indeed of the planet itself too. The origin of the name "Earth" is connected, on the one hand, with the legend of a flat, saucer-like surface with land and seas resting on the backs of giant animals. In different nations, these were elephants, a turtle or a whale. On the other hand, the origin of the word "earth" is associated with the division of the universe into three levels: the sky, the space inhabited by humans and animals, and the underworld, or the underworld. Both these moments influenced the appearance of the familiar designation of our planet in different languages. The origin of the name "Earth" among the ancient Slavs is associated with the concepts of "bottom" and "soil". The earth is what is under the sky, below: the ground underfoot, the foundation. Thus, the origin of the name "Earth" is based on an understanding of the world of people as a "flat saucer" and as a space located below the heavenly dwelling of the gods.

In addition, in the culture of our ancestors, the word "land" was correlated with all relatives, with a familiar territory. The alien and often hostile was designated as distant, and its name had a similar origin. "For the far end of the world" - phraseology, meaning "very far." The ancient Slavs often referred to the kingdom of the dead as well.

It is interesting that the roots, from which the name of the planet arose in other languages, are similar to the Slavonic meaning. So, the origin of the word "Earth" in English is also associated with the notion of the bottom and the ground underfoot.

How did anything come from nothing?

Naturally, modern scientific ideas about the appearance of the universe are very different from those that underlie any religion. Today, all models of the universe are built on the theory of the Big Bang. According to it, about 13.77 billion years ago, the universe arose as a result of a difficult-to-imagine explosion in its power. The state in which she was until this moment is called singular. By its characteristics it was so different from everything that is now known that even scientists can hardly understand what processes were taking place in it.

Soon after the Big Bang, the young universe began to expand. The huge temperature indices and the velocity of its constituent particles did not allow them to unite into larger objects. However, as the expansion increased, the temperature decreased. About a million years passed, while the Universe cooled to 4000 ºС, and elementary particles began to form atoms. Helium and hydrogen were the first to appear, and atoms of heavier elements formed behind them.

At the next stage of the development of the universe, the dust and gas particles that formed it began to collide and form ever larger objects. Slowly formed galaxies with stars and planets. The universe continued to expand, and this process is still going on.

The Milk Way's Native Slice

The presentation "The Origin of the Earth" in the lessons often begins with a story about the history of the solar system. It started about 4.6 billion years ago. The appearance of our piece of the Galaxy resulted in the same processes that resulted in the formation of many parts of the universe. The Milky Way itself appeared about 7-8 billion years earlier. To the formation of the solar system, the gravitational collapse of a relatively small region of the molecular interstellar cloud resulted. Understanding the processes that took place then in this place of the Universe is quite a challenge because of their distance in time. It is possible to judge the events that gave rise to the formation of the solar system in a form known to us only by building theories on the basis of the studied cosmic and physical laws and correlating their conclusions with what we actually observe.

The "hot" hypothesis

At the end of the XIX century, the origin of the Earth and the entire solar system was actively studied by astronomers T. Chamberlain and F. Multon. They put forth a so-called hot hypothesis. To create a theory, they were prompted by the discovery made at that time. It became known that deep beneath the surface of the Earth there is literally hell fire: the subsoil temperature reaches 1000 ºС.

The "hot" hypothesis assumes that the Earth, like other planets, was originally a hot ball, which then gradually began to cool down. The appearance of these hot clusters of matter was explained by the interaction of the young Sun with another, comparable in magnitude to the gravitational attraction, the object. The star passed in relative proximity to our luminary. As a result, they formed a kind of bridge, consisting of the substance of both cosmic bodies. Gradually the stars parted, and the bridge broke up into separate hot "islands" of matter, called planetesimals. They later became planets and satellites, known now.

In the beginning it was cold

However, this is by no means the only theory explaining the origin of the Earth. Hypotheses in the scientific world begin to dominate when they explain a large number of visible facts. In the second half of the last century astronomers and physicists turned their attention again to the concept of the initially cold planets.

For the first time the nebular theory was formulated in the XVIII century. Presumably, it was expressed by Emmanuel Swedenborg, then Immanuel Kant picked it up. The main development of the hypothesis was in the works of Pierre-Simon Laplace. The stages of the origin of the Earth and the solar system as a whole, according to this theory, were built somewhat differently than in the one described above, and the first of them was the formation of a nebula or nebula. It was a gas-dust clot concentrated as a result of the collapse of a section of the molecular interstellar cloud. Nebula, due to the impact on it of the force of attraction from neighboring similar formations, began to rotate. In the nebula due to rotation, gravity appeared, which led to a decrease in its radius. The consequence of this was an increase in the speed of movement. The young nebula looked like a centrifuge, and its shape, originally close to the ball, became more and more like an ellipse. After some time, the centrifugal force at the equator balanced the force of attraction, and from the middle zone of the nebula began to peel off one after another rings. They consisted of all the same particles of dust and gas, which gradually began to unite into larger objects. Over time, they "grew" to the planets, and the temperature of new space bodies did not allow them to call them hot.

Heat of the bowels

Today, the nebular theory is considered the most likely scenario for the formation of the solar system. The development of the hypothesis took place with the participation of many scientific disciplines, certain provisions of Laplace were changed or supplemented. The high temperature of the earth's interior also received an explanation that does not contradict the theory.

There are two main reasons for warming up: radioactive decay and gravitational subsoil differentiation. The first gives about 15% of the heating. The main importance is the separation of the initially mixed elements into several layers under the action of gravity. This process led not only to an increase in the temperature of the bowels, but also to the formation of that inner structure of the planet, which we all study at school: core, mantle, bark.

The Young Earth was a cosmic object close to the sphere in shape, consisting of several chaotically mixed elements. Modern observations, however, show that the structure of the planet has a fairly ordered structure. The basic elements making up the Earth are oxygen in the composition of oxides, silicon, iron and aluminum. Each of them affects the density of matter.

Differentiation

The mass and volume of the Earth, determined in the 18th century, allowed scientists to calculate its average density. It was found to be approximately 5.5 g / cm ³ . The value of the parameter for the surface is only 2.8 g / cm ³ . The observed values suggested that heavier elements are concentrated in the center of the globe, and the lungs make up the surface layers.

The ordering of the elements began from the very moment of the appearance of the planet. Under the influence of gravity, iron began to "settle" in the center, and the compounds of aluminum and silicon, on the contrary, "float" to the surface. Iron, changing the place of its position, displaces the center of gravity of the planet. Due to certain physical laws, a large amount of thermal energy is released, which leads to heating of the inner layers of the Earth. The magnitude of the energy generated is enormous. However, studies show that the planet has never been completely molten. This again confirms the nebular hypothesis.

Cooling and heating

Of course, the heat of the bowels is constantly consumed to heat the surface, and some of the energy is lost. However, it is successfully compensated by solar radiation. The energy of differentiation is used in all processes occurring on Earth: the movement of continents, the formation of mountains, volcanism.

According to scientists, to date, the process of separation of elements was completed by 85%. After the end of differentiation, the Earth will become a geologically inactive planet, similar in this plan to the Moon. It will happen in about 1.5 billion years.

Bombing

In addition to the differentiation of subsoil and the decay of radioactive elements at the first stages of the formation of the Earth, a certain role in the warming up of its inner layers was played by asteroids. Increased temperatures contributed to frequent collisions of small space bodies with the planet. According to one of the versions, the most impressive of these collisions led to the appearance of the Moon. From Earth, a body the size of Mars collided. As a result, a rather impressive piece of matter was knocked out of the planet, which later became a companion. The collision had other results: the speed of the Earth's rotation increased noticeably and its axis bent. Also, asteroids and comets are considered one of the probable sources of water.

The appearance of life-giving moisture

The origin of water on Earth is a rather extensive topic. The most likely to date is the version of its "delivery" of asteroids. Indirectly, the hypothesis is corroborated by data from space research, which resulted in the discovery of water on several small bodies of the solar system. Scientists inclined to this version, indicate that water is a fairly volatile substance, and therefore in the hot conditions of the young Earth, most likely, it would completely evaporate. Hence the low probability of terrestrial origin of water. Probably, much needed for all living matter got to the planet with asteroids and comets from the main belt located between Mars and Jupiter.

However, the exact origin of water on Earth is still a question without an unambiguous answer. There is an opinion that several factors played a role in this process. Among them is the degassing of magma, the melting of volatile elements from it. Water vapor and some other compounds were ejected to the surface of the Earth during volcanic eruptions. Then the evaporation condensed, so gradually the oceans accumulated, the hydrosphere was formed.

The appearance of water, as well as the problem of the origin of the Earth, is not solved until the end. Probably, both processes played their role here: both bombardment and degassing of magma. The latter also contributed to the formation of the atmosphere.

The origin of the living on Earth

Another widely discussed issue related to the history of the Earth's development is the emergence of living organisms. To date, there are several hypotheses that describe the origin of life on Earth. The biology taught ten years ago opened the veil of secrecy to the students: life appeared in the waters of the world ocean, in the so-called primary broth. Since then the picture has changed a little, has acquired new data.

The lesson "The Origin of Life on Earth" begins today with a story about the RNA world. Ribonucleic acid, according to the latest research, is the first molecule on the planet with the ability to reproduce itself. The next stage on the way from the inanimate world to organic was the acquisition of borders. RNA molecules probably in one way or another found themselves inside hollow spheres, which in the thickness of the ocean's water are formed by fatty acids. So there was a prototype of the simplest cell: an RNA molecule surrounded by a membrane.

The formation of a metabolism between the environment and RNA was made possible by the ability of the latter to attract certain nucleotides and repel others. The origin of life on Earth biology and related sciences have not yet been fully studied. There remain many unclear questions. Among them, for example, the emergence of fission and the formation of multicellular organisms.

Great symbiosis

Less foggy today is the history of the appearance of various organelles in the cell. It all began with the appearance in the first microorganisms of the ability to phagocytosis, the absorption of nutrients from the environment with the formation of food vacuoles. A new way of feeding led to an increase in the size of cells: the predator should be larger than the victim. Hereditary material was stored in the form of a genophore, precursors of chromosomes. They were attached directly to the membrane. Phagocytosis was accompanied by the appearance of a strong current in the cytoplasm, in the zone of which there were also genophores. There was a danger of losing part of the genetic material or disturbing its structure. As a result, a cavity formed in the cell, separated by a membrane from the cytoplasm. Gradually, it transformed into a nucleus. So the first eukaryotic cells appeared.

Such organelles, as mitochondria and flagella, most likely originated also in the process of phagocytosis. The predecessors of modern cells, absorbing food, acquired symbionts, friendly microorganisms. They, using nutrients that enter the cytoplasm, began to perform the functions of regulation of various intracellular processes. According to the concept of symbiogenesis, thus, the already named mitochondria and flagella appeared in the cell. Many modern studies confirm the validity of the hypothesis.

Alternatives

RNA-world as the predecessor of all living things has "competitors". Among them there are creationist theories, and scientific hypotheses. For many centuries there was an assumption about the spontaneous generation of life: flies and worms appear in rotting waste, mice in old rags. Refuted by thinkers of the XVII-XVIII centuries, she received a second birth in the last century in the theory of Oparin-Haldane. According to her, life arose as a result of the interaction of organic molecules in the primary broth. The assumptions of the scientists were indirectly confirmed in the famous experiment of Stanley Miller. It was this theory that was replaced at the beginning of this century by the hypothesis of the RNA world.

In parallel, there is an opinion that life has originally an extraterrestrial origin. They brought it to our planet, according to the theory of Panspermia, all the same asteroids and comets that "took care" of the formation of the oceans and seas. In fact, this hypothesis does not explain the appearance of life, but states it as a fact, an inalienable property of matter.

If we summarize all of the above, it becomes clear that the origin of the Earth and life on it today - these are still open questions. Modern scientists, of course, are much closer to unraveling all the secrets of our planet than thinkers of Antiquity or the Middle Ages. However, much still requires clarification. Various hypotheses of the origin of the Earth succeeded each other at those moments when new information was found that did not fit into the old picture. It is possible that this can happen in the not so distant future, and then new theories will replace the established theories.