Earth is part of our solar system, which is in turn part of the intermediate rotating arm of the Milky Way galaxy. There are innumerable stars and solar families in the three rotating arms of our galaxy, and many galaxies like the Milky Way together form a galaxy cluster. All the clusters of the galaxy are collectively called the universe.
In other words, the combination of the smallest molecules to the giant galaxies is called the universe.
There are mainly four theories about the origin of the universe, of which the first principle is the most popular and recognized:
- Big Bang Theory – Abbe Georges Lemaitre.
- Inflation Theory – Alan Guth.
- Steady State Theory – Thomas Gold and Hermann Bondi.
- Pulsating Universe Theory – Allan Sandage.
Let’s discuss each theory one by one.
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1 ) Big Bang Theory
In 1927, Georges Lemaitre (1894-96) proposed this theory for the origin of the universe, galaxy, and solar system. Later, in 1967, Robert Wegner presented an explanation of this theory.
Based on scientific observations, the origin of the universe and its development can be discussed as follows:
The state when the entire universe was concentrated at one hot and dense point, 15 billion years ago. The excessive concentration led to the sudden Big Explosion of Bindu, which has been given the analogy of the Cosmic Explosion or Big Bang. With this, time, place, and object were derived. Shortly after the explosion, the point expanded to the size of a volleyball, which later became a ball of fire with a radius of about 10 billion miles. After the stage of Agniball, when the age of the universe was one second and its temperature decreased a little, then the original particles and antiparticles were produced, which later formed the atom. A minute after the explosion, the universe expanded to become a large thermal nuclear reactor. As a result, the nuclei of the helium atom were formed in this state from the hydrogen nucleus.
After a few hundred thousand years, a bright mixture of matter and radiation spread out. After a few billion years, the clouds of hydrogen and helium collapsed to form galaxies and stars. About 98% of the composition of the Sun and other stars is made up of hydrogen and helium. The central part of the stars became hotter due to the nuclear fusion of matter. The stars started shining, and heavy substances started forming in the center of the stars.
About 10.5 billion years after the Big Bang, that is, 4.5 billion years ago, the solar system evolved in which planets and satellites were formed.
Today, galaxies are capitalized as superclusters. These capitalized galaxies are 100 to 400 million light-years away from each other. The space between them is black. Due to the impulse received from the time of their creation, the distance between them is increasing.
World-famous physicist Stephen Hawking has quoted in his book ‘A Brief History of Time’ that about 15 billion years from today (according to the latest discoveries – 13.7 billion years ago), the universe was in the form of a pea. Supporting the ‘Big Bang theory, he writes that “After the great explosion, the form of the universe expanded. Today the same pea-sized universe is infinite and infinite.”
American astronomer Edwin Hubble reported that the distance between galaxies is increasing. As the distance between the galaxies is increasing, the speed of their moving away is accelerating. We can compare it to an inflated balloon. If we make some small dots on this balloon, then as the balloon expands, these points will also move away from each other.
Now if these points are considered galaxies, then along with the expansion of the balloon, i.e., the universe
3 ) Steady State Theory – Thomas Gold and Hermann Bondi
The Steady State Theory of the origin of the Earth was proposed by Thomas Gold and Hermann Bondi in 1948. This theory was based on the idea that the Earth was formed from a vast cloud of dust and gas that condensed and eventually cooled to form a planet. The authors argue that this process would have taken tens of thousands of years, but it could not have lasted forever because of internal pressure forces within the planet that caused it to expand and cool over time. They also argue that there must have been some external source of heat in order to keep it going.
The main problem with this theory is that it does not account for how all the various elements on Earth came together in one place at one time—something that seems impossible according to many scientists today.
4 ) Pulsating Universe Theory – Allan Sandage
The Pulsating Universe Theory is a type of model that attempts to explain why the universe is expanding. The theory was first proposed by Allan Sandage in 1979, who believed that the expansion rate of the universe has been changing throughout time. He argued that this change could be explained by a process called “pulsation.”
The Pulsating Universe Theory assumes that there is a constant pressure acting upon the matter in the universe. This pressure causes the expansion of space to slow down and speed up at different times depending on how fast or slow it is moving.
This model does not explain why things exist in the first place, but it does help us understand why our universe is expanding so rapidly today.