Lecture 1 || Evolution of Earth || Ncert + GC Leong || UPSC prelims 2025 || TheIASLab

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TOPIC WISE LINK:
• Lecture 1 || Evolution...
• Lecture 2 || Interior ...
• Lecture 3 || Geomorphi...
• Lecture 3 Part II || G...
• Lecture 4|| Continenta...
• Lecture 5| Convectiona...
• Lecture 6| Sea Floor S...
• Lecture 7| Plate Tecto...
• Lecture 8| Convergent ...
• Lecture 9| Convergent ...
• Lecture 10| Convergent...
• Lecture 11| Divergent ...
• Lecture 12| Karst Land...
THE ORIGIN AND EVOLUTION OF THE EARTH
1. Theories of Earth Origin
a. Early Theories
b. Modern Theories
2. Star Formation
3. Formation of Planets
4. Our Solar System
5. Earth
a. Origin of Life
b. Latitude
c. Longitudes (Meridian)
d. Standard Time
e. Eclipse
Early Theories of Origin of Earth
The major early theories of the earth’s origin are discussed below.
Nebular Hypothesis - This theory was developed by Immanuel Kant and modified in 1796 by Pierre Laplace. According to this hypothesis, the planets were formed out of a cloud of material associated with a youthful sun, which was slowly rotating.
In 1900, Chamberlain and Moulton considered that a wandering star approached the sun which resulted in the formation of a cigar-shaped extension of material that got separated from the solar surface. This separated material continued to revolve around the sun and slowly got condensed into planets.
The binary theories considered a companion to be coexisting with the sun.
In 1950, the Nebular Hypothesis was revised by Otto Schmidt (in Russia) and Carl Weizascar (in Germany). According to them, the sun was surrounded by a solar nebula consisting mainly of hydrogen and helium along with dust. The friction and collision of particles led to the formation of a disk-shaped cloud and planets were formed through the process of accretion.
Origin of Earth Modern Theories
Big Bang Theory
The Big Bang Theory explains the origin of the universe. It is also called the expanding universe hypothesis.
In 1927, Abbe Georges Lemaitre, a Belgian astronomer was the first to provide a theory on the origin of the Universe. It was Edwin Hubble who provided evidence that the universe is expanding.
According to this theory, all matter that formed the universe existed in one point (tiny ball) called singularity having an unimaginable small volume, infinite temperature and infinite density.
The great event of the big bang happened some 13.7 billion years ago. The tiny ball exploded which led to a huge expansion and this expansion continues even today. There was rapid expansion within fractions of a second after the bang. Thereafter, the expansion slowed down. With the expansion some of the energy was converted into matter. Within the first three minutes from the big bang event, the first atom began to form.
Within 300,000 years from the big bang, temperature dropped down to 4500 K and gave rise to atomic matter. The majority of atoms formed were hydrogen, along with helium and traces of lithium. Huge clouds of these elements fused through gravity to form stars and galaxies.
Once there were two theories for explaining the origin of the universe - the Big Bang theory and the Hoyle’s concept of steady state.
The steady state theory considered the universe to be roughly the same at any point of time.
However, with greater evidence becoming available about the expanding universe, the Big Bang theory was confirmed which proposes that the universe originated from a single violent explosion of a very minute amount (tiny ball) of matter of high density and temperature.
Evolution of the Earth
The earth was a barren, rocky and hot object with a thin atmosphere of hydrogen and helium.
Lithosphere - With the increasing density, the temperature inside the earth increased and the materials started getting separated depending on their densities. The heavier elements like iron moved towards the centre and lighter ones moved towards the surface. With the passage of time the earth cooled, solidified and condensed into a smaller size and formed the crust (the outer layer of the earth).

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Sir very nice video pls upload more geography videos

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Sure I will !