The document discusses theories of the formation of the solar system and Earth. It describes how the solar system is thought to have formed from a large nebula of gas and dust about 4 billion years ago. Gravity caused the nebula to contract and spin, forming a disk with most matter located in the central core, which became the Sun. In the outer disk, collisions and clumping of objects led to the formation of planets like Earth. The document also outlines the early development of Earth's atmosphere, hydrosphere, and lithosphere over time.

1. By: Ms. Nargis Shamim

2. So what we are going to study in this chapter?
Early
Theories(Origin of
Earth)
Modern
Theories(Origin of
Universe)
Formation of
Planets
Our Solar System The Moon
Evolution of the
Earth
Evolution of
Lithosphere,
atmosphere and
Hydrosphere
Conclusion

3. Introduction..
The solar system formed about 4billion years ago.
• There are many theories about the formation of the solar system.
In this explainer, we will look at our best theory of how the solar
system formed.
• The solar system is thought to have formed from a
nebula. A nebula is a large cloud of gas and dust in
space. The plural of nebula is nebulae.
• We sometimes refer to nebulae as “clouds” because they are
loose collections of floating particles. However, nebulae are
very different than the clouds we see on Earth. Most nebulae are
bigger than our entire solar system.
• The nebula in the photo is called the “Pillars of
Creation” because scientists see a star system
beginning to form inside it.

4. Theories of the Origin of
the Earth
Various theories for
the origin of Earth
have developed over
the period of time.
Theories for the earth
origin has been
classified into two
categories
i.e., Early theories and
Modern theory

5. Early
V/S
Modern
Theories
• In 1755,German philosophers Immanuel Kant gave
Nebular Hypothesis.
• Mathematician Laplace revised it in 1796 (Laplace
Nebular Hypothesis)
• In 1905 Chamberlain and Moulton gave
Planetesimal hypothesis.
• Sir James Jeans and Sir Harold Jaffrey supported
this arguments Tidal Hypothesis.
• Planetesimal hypothesis and Tidal Hypothesis.

6. Early Theories
The Gaseous Hypothesis of
Kant
Nebular Hypothesis
• Immanuel Kant, a
German
philosopher, proposed
his own
theory regarding the
Origin of the Earth in
1755, which was
based on Newton's law
of gravity.

10. 2. Planetesimal Hypothesis.
In 1905 Chamberlain and Moulton gave Planetesimal hypothesis.
a small and tiny particles which is behaving like planet in the space;
Sir James Jeans and Sir Harold Jaffrey supported this
arguments
Why these theories are known as
Binary Theories?

11. Modern Theory
Big Bang theory
(Origin of Universe)
• After Edwin Hubble proposed the constant expansion of the
Universe, another Belgian cosmologist came up with the Big
Bang Theory in 1931.
• According to the big bang theory, all of the matter that made up
the universe resided in a single location with a volume smaller
than an atom, an unlimited temperature, and an infinite density.
• The theory suggests that the Universe, at some point in
time, the whole universe orginated from a single primordial
atom through explosion.
• The expansion later gave birth to nebulae that in turn, coalesced
into stars and planets.
• Big bang Theory is also known as Expanding Universe
Hypothesis
1. The distance between the galaxies is also found to be
increasing and thereby, the universe is considered to be
expanding.

12. 'Father' of the Big Bang Theory
Fr. Georges Lemaitre

13. Our Solar System
• Our solar system consists of the sun (the star), eight planets, 63 moons,
asteroids, comets and huge amounts of dust-grains and gases. The solar
system is believed to have been formed about 5 – 5.6 billion years ago
and the planets were formed about 4.6 billion years ago. The eight
planets namely Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus
and Neptune revolve around the sun in fixed elliptical orbits.
• Mercury, Venus, Earth and Mars are called the inner planets and also
terrestrial planets, which means earth-like as they are made up of rocks
and metals. The other four planets – Jupiter, Saturn, Uranus and
Neptune are called outer planets as well as jovian (Jupiter-like) or Gas
Giant planets. They are mostly larger than terrestrial planets and have a
thick atmosphere mainly of helium and hydrogen.
• Pluto was earlier considered a planet, however it is now believed to be a
“dwarf planet”.

14. Moon
• The moon is the only natural satellite of the earth. The word
satellite means “companion”. The satellites move around a
planet from west to east. They do not have their own light but
reflect the light of the sun. The moon takes 27 days and 7
hours and 43 minutes for both its rotation and revolution
around the earth. It is the fifth largest natural satellite of the
solar system.
• It is believed that the formation of the moon is a result of a
giant impact called ‘big splat’. A large body (somewhat one
to three times the size of Mars) collided with the earth just
after it was formed. Due to this heavy impact, a large part of
earth got separated. This portion of blasted material continued
to revolve around the earth and eventually formed the present
moon (4.44 billion years ago).

15. 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 center 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).
• The different layers of the earth starting from
the surface are crust, mantle, outer core and
inner core. From crust to the core, density
increases.

16. Continue..
• Atmosphere – The solar wind was most intense nearer the sun; so it
blew off lots of gas and dust from the terrestrial planets – Mercury,
Venus, Earth and Mars. During the process of cooling of earth, gases
and water vapour escaped from the interior of the earth thereby starting
the evolution of the present atmosphere. The early atmosphere mainly
had water vapour, carbon dioxide, nitrogen, methane, ammonia and
small amounts of free oxygen. The process of release of gases from the
interior of the earth is called “degassing”.
• Hydrosphere – The frequent volcanic eruptions provided the
atmosphere with water vapour and gases. With the cooling of the earth,
water vapours condensed and brought rain. The carbon dioxide in the
atmosphere got dissolved in rainwater which further lowered the
temperature leading to more condensation and more rain. The rain
water got collected into depressions to give rise to oceans. Life was
limited to oceans only for a long time. Oceans got saturated with
oxygen through the process of photosynthesis and then some 2,000
million years ago oxygen began to flood the atmosphere.

17. Conclusion
There were many theories by the various personalities but we are following
the modern theory of the origin of the earth. Thus, it can be concluded that
• Our solar system formed about 4billion years ago.
• The solar system began as a large cloud of gas and dust particles. Gravity
caused the cloud to contract and heat up. The cloud began spinning as it
contracted, and it formed a disk shape.
• Most of the matter in the disk was located in the central “core,” which is
where the Sun formed.
• Objects in the outer region of the disk collided and clumped together to
eventually form the planets.