We explain what the Big Bang theory is and its characteristics. Also, the theories of the expanding universe and the end of the universe.
What is the Big Bang?
The Big Bang theory holds that the universe began after a big explosion 13.81 billion years ago. Before this, all the matter that exists in the universe today was concentrated in an extremely small point called singularity. The massive explosion that this point experienced marked the beginning of the expansion of the universe.
As it expanded, the universe cooled, allowing the formation of elementary particles, atoms, stars, galaxies, and other cosmic objects over time.
The term big Bang It was first used by British astrophysicist Fred Hoyle during a radio broadcast in 1949. Although Hoyle was critical of the theory and preferred an alternative model to explain the origin of the universe, he used the expression big Bang to refer to the idea of a sudden expansion from an extremely dense and hot initial state. The name caught on and was eventually adopted as the conventional name to describe the beginning of the universe.
Characteristics of the Big Bang theory
The Big Bang theory has the following characteristics:
- It is the most accepted theory to explain the origin of the universe.
- It proposes that the universe formed from a big explosion 13.81 billion years ago.
- It was first named this way by the American Fred Hoyle in 1949.
- According to this theory, protons, electrons and neutrons were the first particles to form after the explosion.
- Stars and galaxies began to form a few million years after the Big Bang.
Origin of the Big Bang
The data available to scientists suggests that The explosion that gave rise to the universe occurred approximately 13.81 billion years ago. This stage is called primeval universe. It is assumed that at that time the particles had a very high energy.
In this explosion the first protons, neutrons and electrons were formed. Protons and neutrons were organized in nuclei, while electrons, due to their electrical charge, were organized in orbits around them. This is how matter originated.
The formation of stars and galaxies
The stars we know today began to form after the Big Bang. For a long time, stars were believed to be 13.25 billion years old, that is, they appeared approximately 560 million years after the Big Bang. However, today we know that there were previous galaxies, so it is believed that the first stars formed more than 13.5 billion years ago.
Theoretical models and observations of planets around young stars suggest that planets begin to form a few million years after the formation of their parent star. That’s why, It is estimated that the planet formation process began shortly after the appearance of the first stars.
The expanding universe
Some of the evidence that supports the theory of the Big Bang and the expansion of the universe are:
- Olbers paradox. This paradox raises the question of why the night sky is not completely illuminated by all the stars that exist. The answer to this paradox lies in the expansion of the universe: if the universe expands, the distances between galaxies increase over time, making their light less intense and therefore the night sky not completely illuminated.
- Hubble’s Law. From observation, it has been verified that galaxies are moving away from each other. The speed-distance relationship discovered by Edwin Hubble shows that more distant galaxies move away more quickly, which is consistent with an expanding universe.
- Homogeneity of matter distribution. When you look at the universe on a large scale, you can see that matter (such as galaxies and galaxy clusters) is evenly distributed. This means that the universe appears to be the same in all directions. This uniformity is consistent with the idea that the universe is expanding.
The end of the universe
The most accepted theory about the possible end of the universe is known as the Big Freeze.. This theory is based on the fact that our universe is expanding and that it is expanding faster and faster. The reason behind this accelerated expansion is dark energy, a force of unknown nature that pushes celestial bodies apart.
What the Big Freeze theory suggests is that, as galaxies move further away, the formation of new stars will decrease, and existing ones will stop shining. With fewer stars and less activity, the universe will cool, and without the light and warmth of stars it will become an excessively cold and dark place.
Other theories that analyze the end of the universe as we know it are the Big Crunch and the Big Rip. The Big Crunch theory posits that the expansion of the universe will slow down over time, leading to a collapse in which the universe will reach an extremely dense and hot state.
In contrast, the Big Rip theory suggests that the expansion of the universe will not only persist, but accelerate over time. Thus, there will come a time when the forces that hold cosmic structures together will be overcome by the force of expansion. This process will lead to the absolute dispersion of everything that makes up the universe, resulting in a state in which matter and energy will be infinitely separated.
History of the Big Bang Theory
The Big Bang theory was formulated by several scientists throughout the first part of the 20th century.
- Alexander Friedmann (1888-1925). In 1922, he first formulated the theory of the expanding universe based on Albert Einstein’s equations of general relativity, published in 1915. Friedmann developed mathematical models that indicated the possibility of an expanding universe.
- Georges Lemaître (1894-1966). In 1927, independently and based on the work of Einstein and de Sitter, Lemaître reached conclusions similar to those of Friedmann about the expanding universe. His contribution also included the notion of a “primeval atom” that exploded, an idea that resembles the concept of the Big Bang.
- Edwin Hubble (1889-1953). In 1929, he provided convincing evidence of the expanding universe by observing galaxies moving away from each other. The relationship between the speed of galaxies and their distance, known as Hubble’s law, was a crucial step in supporting the idea of an expanding universe.
References
- European Space Agency. (2014). the universe. ESA Kids. https://www.esa.int/
- Marcos, L. (2023). All theories about the origin of the universe. Esquire. https://www.esquire.com/
- NASA Science. (2021). What is the Big Bang? https://spaceplace.nasa.gov/
