Origin Of Universe

Everything that exists from Mega clusters to the tiniest subatomic particles, comprises the Universe. Scientists agree that the age of the Universe is about 13.79 billion years old as 2015. The universe comprises of a number of galaxies. Optical and radio telescope studies indicate the existence of about 100 billion galaxies in the visible universe. The Big Bang Theory is most acceptable for the origin of the Universe.

Theory and Hypothesis:

The Gaseous Mass Theory by Kant (1755)

• It is also known as the Nebular Hypothesis. He suggested that gaseous clouds of molecular hydrogen or “Nebulae” collapsed due to gravitational instability and formed stars and galaxies.

• Stars are formed with a proto-planetary disk surrounding it. Initially quite hot, the disk contains grains of rocks and ice that coagulate later to form planets like the Earth.

The Nebular Hypothesis by Laplace (1796)

• He suggested that hot nebulae emitted radiation causing higher velocity and rotation around it, leading to a bulge in the centre. This rotating ring of hot matter cooled later to form planets around a nebula or a sun-like star.

The Planetesimal Theory by Chamberlin and Moulton (early 20th century)

• They theorized that planetesimals are formed by the ejected mass of the proto-Sun (cold sun) when it gets intruded by a foreign body like another star. These planetesimals accrete into landmass we know as planets.

The Tidal Theory by Jeans and Jeffreys (1925)

• According to this theory, a hot star like the Sun and other intruding stars get attracted to each other while remaining in their orbits, resulting in ejected elliptical planetary formations like the Earth.

Otto Schmidt’s Interstellar Dust Cloud Hypothesis

• As per this theory, the primordial dust moving at high velocity started coalescing into a disk-shaped formation. These disk-shaped nebulae were further divided into rings containing asteroids that later fused into planets.

The Nova Hypothesis by Hoyle and Lyttleton

• The theory suggested that the formation of the Earth-like planets is caused by supernova explosions. The ejected mass separated from big stars cooled off to form planets.

The Binary Star Hypothesis by Russell

• The theory propounded the existence of binary (two) stars, the bigger one of which ejected mass under the influence of a third one coming close at higher speed, leading to the formation of planets.

THE BIG BANG THEORY (1931)

The theory suggests that the Universe about 1370 crore (13.7 billion) years ago, was condensed into a single particle and later started expanding infinitely after a huge explosion and matter, energy, space, and time came into being. The expansion later gave birth to nebulae that in turn, coalesced into stars and planets.

• In the beginning, all matter forming the universe existed in one place in the form of a “tiny ball” with extremely small volume, infinite temperature and infinite density.

• Around 13.7 billion years before the present, the tiny ball exploded violently. This led to huge expansion.

• Within 3,00,000 years from the Big Bang, temperature dropped to 4,500 K (Kelvin) and gave rise to atomic matter.

FORMATION OF PLANETS:

Stage-1:

• The stars are localized lumps of gas within a nebula. The gravitational force within the lumps leads to the formation of a core to the gas cloud and a huge rotating disc of gas and dust develops around the gas core.

Stage-2:

• The gas cloud starts getting condensed and the matter around the core develops into small rounded objects. These small rounded objects by the process of cohesion develop into what is called planetesimals. Larger bodies start forming by collision, and gravitational attraction causes the material to stick together. Planetesimals are a large number of smaller bodies.

Stage-3:

• These large numbers of small planetesimals accrete to form a fewer large bodies in the form of planets.

EVOLUTION OF EARTH:

• The formation of the planet Earth is estimated to have happened around 4.54 billion years ago. Oxygen, iron, silicon, and magnesium are the primary elements the bulk of Earth is made of.

• The initial Earth was in a molten state owing to the constant collisions with foreign bodies from outer space. As the Earth’s surface cooled over time, the solid crust was formed and was inundated with water.

• Geologically, there has been constant formation and disintegration of landmass (supercontinent) on the Earth.

Major Supercontinents:

• The first supercontinent named “Rodinia” was assembled 3-1.4 billion years ago.

• The supercontinent “Gondwana” existed 550 million years ago that later disintegrated to separate South America from Antarctica.

• “Pangaea” was another prominent one that broke up around 175 million years ago.

Four Aeons of Earth’s History:

1.  Hadean (4500-4000 Million Years):

    - Earth is formed with extremely hot temperatures and constant volcanic activities.

2.  Archean (4000-2500):

    - The eruption of first life forms.

3.  Proterozoic (2500-541):

    - The emergence of multicellular life forms. A major part of Earth is covered in ice.

4.  Phanerozoic(541-present):

    - The supercontinent “Pangaea” formed later disintegrating into Laurasia and Gondwana, leading to the current geography. Life forms come out of the sea and thrive on land.

Spheres of Earth:

• Lithosphere: The crust or the outermost solid layer of the Earth. It is further divided into tectonic plates.

• Atmosphere: The mix of gases surrounding the Earth is called the Atmosphere.

• Hydrosphere: With 71% of the surface covered in water, the hydrosphere is the water-filled area on the Earth.

• Biosphere: It’s believed to be the zone existing between land, water, and air. It’s where life thrives.

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Subject: Geography

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