Big Bang Theory – Evidence, Stages, Big Bang Theory UPSC

By BYJU'S Exam Prep

Updated on: November 14th, 2023

The Big Bang theory is the comprehensively acknowledged cosmological model illustrating the origins of the perceptible universe. It also describes the stemming evolution at a large scale. The Big Bang theory’s cosmological model elaborates on how the cosmos expanded from the high density, the high-temperature starting point. The Big Bang theory presents a complete illustration of the broad-spectrum phenomena.

According to modern estimations, the Big Bang theory events occurred roughly 13.8 billion years ago. The cosmos cooled sufficiently after its initial expansion (inflation) to allow the development of subatomic particles and, eventually, basic atoms. The article furnishes complete information about the Big Bang theory and other relevant details.

What is Big Bang Theory?

The Big Bang Theory presents a model that can be perceived by humans. The theory elaborates on the origin of the universe. The forces such as gravitation and electromagnetic forces emerged after the Big Bang theory.

Big Bang Theory Notes PDF

The cosmological, astrophysical theory was brought forth by Georges Lemaitre. It includes numerous stages, such as the heavy particle era, light particle era, radiation era, and matter era.

Features of Big Bang Theory

The Big Bang Theory is the most widely acknowledged cosmological scenario used to study the universe’s beginning. The majority of cosmologists think the universe began 13.8 billion years ago. The features of the big bang theory are as mentioned herein-

  • The Big Bang theory claims that at some time in the past, all of space was enclosed in a single point of extremely high density and heat, from which the cosmos has continued to inflate in all directions ever since.
  • The cosmos cooled sufficiently after its initial expansion (inflation) to allow the development of subatomic particles and, eventually, basic atoms.
  • The Big Bang produced a large number of hydrogen and helium atoms, including trace quantities of lithium and beryllium.
  • Giant clouds of these primordial elements (hydrogen and helium) eventually merged to create stars and galaxies due to gravity.
  • According to the Big Bang Theory hypothesis, the cosmos has been extending in all directions from its genesis.

Who Proposed Big Bang Theory?

The Big Bang Theory was first proposed by a Belgian Catholic priest and physicist named Georges Lemaître in 1927. Lemaître was the first person to propose that the universe was expanding and that it had originated from a single, incredibly dense point, which he called the “primeval atom.”

His ideas were initially met with skepticism, but over time, scientific evidence accumulated supporting his theory. Today, the Big Bang Theory is widely accepted among scientists as the most plausible explanation for the origins and evolution of the universe.

Stages of the Big Bang Theory

The Big Bang theory states that everything was simply energy at the beginning. This energy was transformed into tiny particles (like photons). These early photos were dispersed by early electrons because there were earlier free electrons. Subsequently, atoms were generated when electrons were mixed with protons and neutrons (atomic nuclei). The Big Bang Theory is divided into four stages:

  • Heavy Particle Era
  • Light Particle Era
  • Radiation Era
  • Matter Era

Evidence Supporting the Big Bang Theory

Three pieces of evidence support the Big Bang theory. The list of the pieces of evidence has been presented here that led to the confirmation of the Big Bang theory.

  • The measured abundances of elements
  • The observable expansion of space
  • The introduction of the Cosmic Microwave Background (CMB)

Assumptions of the Big Bang Theory

This principle only applies to the universe’s large-scale features, but it does indicate that there is no edge to the cosmos, implying that the big bang occurred not at a single spot in space but rather all over space at the same moment. The Big Bang theory is in accordance with the following assumptions:

  • The first is that Albert Einstein’s general theory of relativity accurately captures how all matter interacts with gravity.
  • The second assumption, known as the cosmological principle, holds that an observer’s vision of the cosmos is unaffected by his location or the direction in which he looks.

The Emergence of Primary Forces After the Big Bang

The formation of protons and neutrons also began just after the Big Bang. The four fundamental forces of nature evolved after the Big Bang Theory:

  • Gravitation
  • The strong force
  • The weak force
  • The electromagnetic force

Postulates of Big Bang Theory

The Big Bang Theory is actually based on a set of postulates, or fundamental assumptions, that describe the nature and evolution of the universe. But what exactly are these assumptions?

  • The theory postulates that the universe is expanding and has been since the moment of the Big Bang.
  • The theory suggests that the universe was much hotter and denser in the past. As the universe expanded, it cooled down, and matter and energy began to form into galaxies and other structures.
  • The Big Bang Theory predicts that during the first few minutes after the Big Bang, light elements like hydrogen and helium were formed.
  • According to the theory, the universe started as an infinitely hot and dense point called a singularity.

Misconceptions of Big Bang Theory

There are several common misconceptions and misunderstandings about the Big Bang Theory. Here are a few of them:

  • The Big Bang was an explosion: This is false as the ‘Big Bang’ refers to the expansion of the universe from an extremely hot, dense state.
  • The Big Bang explains the origin of the universe: This is false. While the Big Bang Theory is the most widely accepted explanation for the universe’s origins, it doesn’t explain everything.
  • The Big Bang Theory conflicts with religious beliefs: The theory is a scientific explanation of the universe’s origins and doesn’t necessarily conflict with religious beliefs.

Big Bang Theory UPSC

The topic is extremely essential for the IAS exam. Questions can often be asked pertaining to this topic from the Prelims and Mains exam. The conceptual understanding of the concept can assist the candidates in preparing well for the upcoming exam. Establishing and instituting an effective and efficient strategy for covering the important segments of this topic will lead the candidates toward a comprehensive understanding of the syllabus and the details.

Practising the questions related to this topic will assist the aspirants in revising the core concepts and also gaining an in-depth comprehension of the fundamentals. Check here the questions and assess the level of your preparation for the upcoming exam.

Question: What does the Big Bang theory explain? [A] Origin of Stars [B] Origin of Galaxy [C] Origin of Solar System [D] Origin of Universe

Answer: Option [D] Origin of Universe

Questions in the Mains exam can also be expected from the Big Bang Theory. For the Mains exam, the candidates need to substantiate the answers with well-illustrated examples. In this exam, the candidates will be required to present descriptive answers and elucidate them with complete details.

Question: How did the Big Bang theory result in the establishment of the galaxies and stars? What can be understood by the expanding Universe Theory?

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