How did the universe form? What caused the formation of stars, planets, and galaxies? These are some of the questions that millions of people have asked throughout history. Specifically, scientists want to find explanations for all existing phenomena. This is the origin of the Big Bang theory. For those who don't already know, it's the theory that explains the origin of our universe. It also explains the existence of planets and galaxies.
If you're curious and want to know how our universe was formed, this post will tell you everything. Would you like to learn all about the Big Bang theory?
Characteristics of the Big Bang theory
It is also known as the Big Bang theory . It states that our universe as we know it began billions of years ago in a massive explosion. All the matter that currently exists in the universe was concentrated in a single point.
From the moment of the explosion, matter began to expand and is still doing so today. Scientists keep repeating that the universe is continually expanding. For this reason, the Big Bang theory includes the theory of the expanding universe. Matter stored at a single point not only began to expand, but also began to form more complex structures. We refer to the atoms and molecules that, little by little, were forming living organisms.
Scientists have estimated the date of the Big Bang's beginning to be approximately 13.810 billion years ago. This stage, in which the universe was newly created, is called the early universe. It is believed that particles in this early universe possessed enormous amounts of energy.
This explosion formed the first protons, neutrons, and electrons. The protons and neutrons organized themselves into atomic nuclei. However, the electrons, due to their electric charge, arranged themselves around these nuclei. In this way, matter originated. You can also read more about the origin of the universe in another related article.
Formation of stars and galaxies
Our solar system is located within the galaxy known as the Milky Way. All the celestial bodies we know today began to form long after the Big Bang.
The first stars are believed to have begun forming 13.250 billion years ago. They began appearing approximately 550 million years after the Big Bang. The oldest galaxies originated 13.200 billion years ago, making them the oldest as well. Our solar system, the Sun and the planets, formed 4.600 billion years ago. This star formation is fundamental to understanding the evolution of the universe and is related to the study of star births in various regions of the cosmos.
Evidences of an expanding universe and the explosion
To prove that the Big Bang theory makes sense, evidence must be reported that the universe is expanding. These are the evidences in this regard:
- Olbers paradox: The darkness of the night sky.
- Hubble's Law: It can be verified by observing that the galaxies are moving away from each other.
- Homogeneity of the distribution of matter.
- Tolman Effector (variation in surface gloss).
- Distant supernovae: A temporal dilation is observed in its light curves.
After the moment of the explosion, each particle was expanding and moving away from each other. What happened here was something similar to what happens when we blow up a balloon. As more air we introduce, the air particles expand more and more until they reach the walls.
Theoretical physicists have managed to reconstruct this chronology of events starting from 1/100th of a second after the Big Bang. All the matter that was launched was composed of the known elementary particles. These include electrons, positrons, mesons, baryons, neutrinos, and photons.
More recent calculations indicate that hydrogen and helium were the primary products of the explosion. Heavier elements formed later within stars. As the universe expands, the residual radiation from the Big Bang continues to cool, reaching a temperature of 3 K (-270°C). The effects of this radiation reflect the profound legacy of the Big Bang and have been the subject of ongoing study, along with technological advancements such as the James Webb Space Telescope , which have allowed for greater observations of the universe.
One of the great questions for scientists is whether the universe will expand indefinitely or if it will eventually contract. Dark matter plays a crucial role in this and is related to the structure of the universe. It is also a key aspect in the study of what lies beyond the observable universe , a fundamental topic when analyzing the Big Bang theory.
Discoverers and other theories
The theory that the universe is expanding was formulated in 1922 by Alexander Friedmann . He based his theory on Albert Einstein's theory of general relativity (1915). Later, in 1927, the Belgian priest Georges Lemaître built upon the work of Einstein and De Sitter and arrived at the same conclusions as Friedmann.
Therefore, scientists do not come to another conclusion, only that the universe is expanding.
There are other theories about the creation of the universe that are not as important as this one. However, there are people in the world who believe and consider them to be true. We list them below.
- Big Crunch theory: This theory bases its foundation on the fact that the expansion of the universe is going to slow down slowly until it begins to retract. It is about the contraction of the universe. This contraction would end in a large implosion known as the Big Crunch. There is not much evidence to support this theory.
- Oscillating universe: It's about our universe oscillating in a constant Big Bang and Big Crunch.
- Steady state and continuous creation: It maintains that the universe is expanding and that its density remains constant because there is matter in continuous creation.
- Inflation theory: It is based on the same characteristics as the Big Bang but it says that there was an initial process. The process is called inflation and the expansion of the universe is faster.
Lastly, there are some people who think that the universe was created by God or some divine entity.
