WHAT IS COSMOGONY OR COSMOGONIC THEORY? - SCIENCE - 2025

A cosmogony or cosmogon theory is any theoretical model that tries to explain the origin and development of the Universe. In astronomy, cosmogony studies the origin of certain astrophysical objects or systems, the Solar System or the Earth-Moon system.

In the past, cosmogonic theories were part of different religions and mythologies. However, thanks to the evolution of science, it is currently based on the study of various astronomical phenomena.

NGC 4414, a typical spiral galaxy in the constellation Coma Berenices, is approximately 55,000 light-years across and approximately 60 million light-years from Earth.

Today, cosmogony is part of scientific cosmology; that is to say, the study of all aspects of the Universe, such as the elements that compose it, its creation, development and history.

The first cosmogonic theories based on nature rather than the supernatural were postulated by Descartes in 1644, and developed by Emanuel Swedenborg and Immanuel Kant in the mid-18th century. Although his theories are no longer accepted, his effort prompted the scientific study of the origin of the Universe.

Most important cosmogonic theories

Despite the difficulty of studying the origins of the Universe through scientific methods, over the centuries several hypotheses have emerged in the field of cosmogony.

The most important, in chronological order, have been the following: the nebular hypothesis, the planetesimal hypothesis, the turbulent condensation hypothesis, and the Big Bang Theory, which is currently the most widely accepted.

Nebular hypothesis

The nebular hypothesis is a theory first proposed by Descartes and later developed by Kant and Laplace. It is based on the belief that, at the origin of time, the Universe was made up of a nebula, which was contracting and cooling due to gravity.

According to this hypothesis, the effect of gravitational forces turned the primitive nebula into a flat, rotating disk, with an increasingly large central nucleus.

The nucleus would slow down due to the friction of the particles that compose it, later becoming the Sun, and the planets would form due to the centrifugal forces caused by the spin.

It is important to realize that this theory would only explain the formation of the Solar System, because the philosophers of this time still did not know the true size of the Universe.

Planetesimal hypothesis

The planetesimal hypothesis was raised in 1905 by Thomas Chamberlin and Forest Moulton to describe the formation of the Solar System. It was the first to unseat the nebular hypothesis, which had been prevalent since it was developed by Laplace in the 19th century.

This theory consists of the idea that the stars, when passing close to each other, caused the expulsion of heavy materials from their nucleus to the outside. In this way, each star would have two spiral-shaped arms, formed from these discarded materials.

Although most of these materials would fall back into the stars, some of them would continue in orbit and would condense into small celestial bodies. These celestial elements would be called planetesimals, in the case of the smallest ones, and protoplanets, if we talk about the largest ones.

Over time, these protoplanets and planetesimals would collide with each other to form the planets, satellites and asteroids that we can see today. The process would be repeated in each star, giving rise to the Universe as we know it today.

Despite the fact that the hypothesis as such has been discarded by modern science, the existence of planetesimals continues to be part of modern cosmogonic theories.

Turbulent condensation hypothesis

This hypothesis, the most accepted until the appearance of the Big Bang Theory, was proposed for the first time in 1945 by Carl Friedrich von Weizsäcker. In principle it was used only to explain the appearance of the Solar System.

The main hypothesis was that, at the beginning of time, the Solar System was made up of a nebula composed of materials such as gases and dust. Because this nebula was in rotation, it gradually became a flattened disk that continued to rotate.

Due to the collisions of the particles that formed the gas cloud, several eddies were formed. When several of these eddies came together, the particles accumulated, increasing their size more and more.

According to this hypothesis, this process lasted several hundred million years. At the end of it, the central whirlpool would have become the Sun, and the rest, the planets.

Big Bang Theory

The Big Bang theory is the most widely accepted cosmogon theory today about the origin and development of the Universe. Essentially, it postulates that the Universe formed from a small singularity, which expanded in a huge explosion (hence the name of the theory). This event took place 13.8 billion years ago, and since then the Universe has continued to expand.

Although the veracity of this theory cannot be confirmed 100%, astronomers have found several pieces of evidence that suggest that it is really what happened. The most important evidence is the discovery of "background radiation", signals supposedly emitted in the initial explosion and that can still be observed today.

On the other hand, there is also evidence that the Universe continues to expand, which would give the theory even more firmness. For example, using images from various super-telescopes such as Hubble, the motion of celestial bodies can be measured. These measurements allow us to verify that, indeed, the Universe is expanding.

In addition, by observing distant points in space, and due to the speed at which light travels, scientists can essentially "look back" through telescopes. In this way, galaxies in formation have been observed, as well as other phenomena that confirm the theory.

Due to the continuous expansion of the stars, the Big Bang Theory predicts several possible options for the end of the Universe.

References

1. "Cosmogony" in: How Stuff Works. Retrieved on: January 24, 2018 from How Stuff Works: science.howstuffworks.com.
2. "Nebular Theory" in: Wikipedia. Retrieved on: January 24, 2018 from Wikipedia: es.wikipedia.com.
3. "Chamberlin - Moulton planetesimal hypothesis" in: Wikipedia. Retrieved on: January 24, 2018 from Wikipedia: en.wikipedia.com.
4. "Weizsacker Turbulence Hypothesis" in: Tayabeixo. Retrieved on: January 24, 2018 from Tayabeixo: tayabeixo.org.
5. "What is the Big Bang Theory" in: Space. Retrieved on: January 24, 2018 from Space: space.com.