Origin and Evolution of Earth: History and Timeline

Origin and Evolution of Earth: Earth was formed around 4.54 billion years ago. Early theories like the Nebular Hypothesis, Revised Nebular Hypothesis, Binary Theories, etc. explain the Earth’s origin and evolution. On the other side, modern theories like the Big Bang Theory, Star Formation Theory, and Planet Formation Theory explain the origin and evolution of the Earth.

Earth’s evolution involves mainly the creation of the Lithosphere, Atmosphere, and Hydrosphere. The evolution of the Earth also explains that around 3.5 billion years ago life emerged on this planet. While “evolution” typically refers to biological changes it can also apply to the processes shaping planets, stars, galaxies, and the universe, despite their distinct nature. In this article, we will discuss the origin and evolution of the Earth in detail.

Origin and Evolution of Earth

The Origin of Universe

The word ‘Universe’ means everything in space. Physical components like electrons and protons. Non-physical elements like light and space itself. The Big Bang Theory explains the origin of the universe around 13.8 billion years ago.

Early Theories of Origin of Earth

There are some major early theories based on the Earth’s origin are discussed below.

Early Theories of Origin of Earth
Nebular Hypothesis	The Nebular Hypothesis is an early theory that explains the origin of Earth. Immanuel Kant proposed the Nebular Hypothesis. He was a German philosopher. This theory is about the formation of the Solar System. According to the Nebular Hypothesis, the Sun and planets were created from a vast cloud of dust and gas. It was known as a nebula. This cloud collapsed because of a passing star or supernova waves. As the dust and gas gathered together, they eventually formed the Sun and the other planets.
Revised Nebular Hypothesis	In 1796, Pierre Laplace modified the Nebular Hypothesis. The Reverse Nebular Hypothesis is also known as the Solar Nebular Disk Model. According to this model, the matters came out from that nebula gathered at the center and created the Sun. The center hollow increased by the gravitational force. It pulled in more dust and gas into it and became hotter and denser. A Protoplanetary disc formed around the Sun as matter accumulated gradually. Terrestrial planets (like Mercury, Venus, Earth) formed near the disc’s center. These planet contains more metallic components like iron and nickel. Gas giants like Jupiter, Neptune, Saturn formed on the cooler edges of the disc.
Binary Theories	The theory is also known as Planetesimal Hypothesis. The Binary theory was proposed by Chamberlain and Moulton in 1900. According to this theory, a star collided with the Sun. After the star moved away, the separated material gradually came together to form the planets. These planets then started revolving around the Sun.

Modern Theories of Origin of Earth

Now, we will discuss the modern theory based on the Earth’s origin.

Modern Theories of Origin of Earth

Big Bang Theory

The Big Bang Theory is a modern explanation for the origin and evolution of the Earth. Edwin Hubble introduced this theory in 1920. It is also called the Expanding Universe Hypothesis. According to the theory, the universe is continually expanding. Initially all matters of the universe was concentrated at the center in a small space. At that time the temperature and density was really high. Approximately 13.7 billion years ago, a massive explosion happened. This leads to the creation of the universe. Following the explosion, atoms formed, and over time, energy transformed into matter.

Planet Formation According To Big Bang Theory

According to Big Bang Theory, there are three stages in the formation of the Planets:

• During the initial phase, gas lumps in the nebula came together. The force of gravity shaped a central core with surrounding gas discs.
• In the second stage, matter within these discs condensed gradually. It gave rise to small, round objects known as planetesimals.
• In the third stage, planetesimals underwent further aggregation. The step forms larger celestial bodies referred to as planets.

Formation of Stars	Nebula is a cloud of gas and dust in space, mainly composed of hydrogen and helium, serving as a star’s birthplace. Protostar is an early stage of star formation where nuclear fusion hasn’t started, resembling a star but lacking core heat for fusion. T Tauri Star represents an intermediate stage between protostar and low-mass main sequence star, undergoing gravitational contraction and less than 10 million years old. Main Sequence Star’s core temperature allows fusion reactions, converting hydrogen to helium. The Sun is an example of a main sequence star. Red Giant forms in later stages as the star runs out of hydrogen fuel, with fusion occurring around a hot, dense helium core, releasing energy and expanding against gravity. Fusion of Heavier Elements involves helium fusion preventing core collapse. Fusion progresses to carbon until iron appears, causing core collapse. Massive stars become supernovae, smaller stars become white dwarfs. Supernovae and Planetary Nebulae: Planetary nebula is an outer layer lost during Red Giant to White Dwarf transition. White dwarfs become black dwarfs when they stop emitting light. Supernova is the explosive death of a massive star, leading to neutron stars after the event.
Our Solar System	Understanding the origin of Earth requires knowledge of the planet’s formation. The process begins with stars, which are localized lumps of gas within a nebula. Within these lumps, gravitational forces lead to the formation of a core within the gas cloud. In the next stage, the gas cloud starts to condense, and the material surrounding the core transforms into tiny spherical shapes. Through a cohesion process, these small spherical objects become planetesimals. Gravitational attraction causes these planetesimals to stick together, leading to the formation of larger bodies through collisions. In the final stage, a large number of small planetesimals accrete to form fewer, larger bodies in the shape of planets.
Moon	The moon is the Earth’s only natural satellite. A satellite is a companion that orbits around a planet, and the moon is Earth’s companion. Satellites, including the moon, move around a planet from west to east. Satellites do not produce their own light; instead, they reflect the light of the sun. The moon takes 27 days, 7 hours, and 43 minutes to complete both its rotation and revolution around the Earth. The moon is the fifth largest natural satellite in the solar system. The formation of the moon is believed to be a result of a giant impact called the ‘big splat.’ A large body, about one to three times the size of Mars, collided with the Earth shortly after its formation. The impact caused a significant portion of the Earth to separate and form the moon. This material continued to revolve around the Earth and eventually became the moon approximately 4.44 billion years ago.

Evolution of the Earth

Initially, the Earth existed as a desolate, rocky, and high-temperature entity with a sparse atmosphere containing hydrogen and helium.

Lithosphere	Increasing density inside Earth led to rising temperatures. Materials separated based on density, with heavier elements like iron moving towards the center. Lighter elements migrated towards the Earth’s surface. Over time, Earth cooled, solidified, and condensed, forming the outer layer called the crust. Earth is structured into layers: crust, mantle, outer core, and inner core. Moving from the crust to the core, density increases. Summary of layers: crust (outermost), mantle, outer core, and inner core (centermost and densest).
Atmosphere	The solar wind, stronger closer to the sun, caused the expulsion of gas and dust from terrestrial planets like Mercury, Venus, Earth, and Mars. Earth’s cooling process led to the escape of gases and water vapor from its interior, initiating the evolution of the current atmosphere. The early atmosphere primarily consisted of water vapor, carbon dioxide, nitrogen, methane, ammonia, and limited free oxygen. The release of gases from the Earth’s interior is referred to as “degassing.”
Hydrosphere	Frequent volcanic eruptions released water vapor and gases into the atmosphere. As the Earth cooled, water vapor condensed, leading to the formation of rain. Carbon dioxide in the atmosphere dissolved in rainwater, causing a further drop in temperature and more condensation. The increased condensation resulted in more rain. Rainwater collected in depressions, giving rise to the formation of oceans. Life was initially confined to the oceans for an extended period. Oceans became saturated with oxygen through photosynthesis. Approximately 2,000 million years ago, oxygen began to accumulate in the atmosphere, marking a significant change.

Geological Time Scale

The evolution of life from unicellular bacteria to the modern man is given below:

Eons	Era	Period	Epoch	Age/Years before Present	Life/Major Events
	Cainozoic  (from 65 million years to the present times). Mesozoic  65 – 245 Million Paleozoic  240 – 570  Million	Quaternary  Tertiary  Cretaceous  Jurassic  Triassic  Permian  Carboniferous Devonian  Silurian  Ordovician  Cambrian	Holocene  Pleistocene Pliocene  Miocene  Oligocene  Eocene  Palaeocene	0 – 10,000 Million 10,000 – 2 Million 2 – 5 Million 5 – 24 Million 24 – 37 Million  37 – 58 Million 57 – 65 Million  65 – 144 Million. 144 – 208 Million. 208 – 245 Million. 245 – 286 Million 286 – 360 Million 360 – 408 Million. 408 – 438 Million. 438 – 505 Million 505 – 570 Million.	Modern Man Homo Sapiens  Early Human Ancestor. Ape: Flowering plants and Trees. Anthropoid Ape. Rabbits and Hare. Small Mammals: Rats and Mice. Extinction of Dinosaurs. Age of Dinosaurs. Frogs and Turtles. Reptiles dominate – replace amphibians. Fresh reptile: Vertebrates: coal beds. Amphibians. Fresh trace of life on land; Plants. First fish. No terrestrial life: Marine invertebrate.
Proterozoic  Archean  Hadean	Pre-Cambrian  570 – 4800  Million			570 – 2500 Million 2500 – 3800 Million 3800 – 4800 Million.	Soft bodied arthropods.  Blue green algae: unicellular bacteria. Oceans and continents form: Oceans and atmosphere are rich in carbon dioxide.
Origin of Stars  Supernova  Big Bang	5000 – 13,700Million.			5000 Million 12,000 Million 13,700 Million.	Origin of the Sun. Origin of the Universe.

Origin Of Solar System

The solar system formed about 4.6 billion years ago from a giant cloud of gas and dust known as the solar nebula. This nebula began to collapse under its own gravity, possibly due to a nearby supernova explosion or shockwave. As it collapsed, the material started to spin and flatten into a rotating disk. At the center, the pressure and temperature increased, leading to the formation of our Sun.

Meanwhile, particles in the disk collided and stuck together, forming planetesimals, which further accreted to form planets, moons, asteroids, and comets. This process, known as accretion, continued for millions of years until the solar system stabilized into its current form.

Origin Of The Life

Life began on Earth approximately 3,800 million years ago.

• The initial life form was blue algae.
• Chemical reactions played a crucial role in creating molecules capable of multiplication and transformation into living organisms.

Origin and Evolution of Earth – FAQs

When did life originate on Earth?

Life originated on Earth approximately 3,800 million years ago.

What was the first form of life?

The first form of life on Earth was blue algae.

What played a crucial role in the development of life?

Chemical reactions played a crucial role in creating molecules that could multiply and change into living forms.

How long ago did the chemical reactions occur to create life?

The chemical reactions leading to the creation of life occurred around 3,800 million years ago.