Universe – Origin and Evolution, Big Bang Theory – Geography Notes for UPSC

The Universe

The Universe is a very important topic for UPSC. In this post, we will discuss the Theories of the Origin of the Universe and Stage In The Development Of The Universe. This notes is a part of our Geography Notes for UPSC.

The Universe is a vast space which includes galaxies, stars, planets and other forms of matter and energy in it. The universe is endless, only 4 percent of the universe, according to astronomers. The other 96 percent of the substances in the universe cannot be seen or easily understandable.

• It consists of both physical (subatomic particles like electrons, protons to galactic super-clusters) and non-physical (light, gravitation, space etc.) components.

Theories of Origin of the Universe

In 1927, Abbe Georges Lemaitre, a Belgian astronomer was the first to propose, a theory on the origin of the universe. In 1920 he provided evidence that the universe is expanding. These are three most popular theories for explaining the universe’s origin and evolution

1. The Steady-State Theory
2. The Pulsating Theory
3. The Big Bang Theory

The Steady-State Theory

• This theory is proposed by Bondi, Gold, and Fred Hoyle
• According to this theory, the number of galaxies in the observable universe remains constant, and new galaxies are constantly being formed out of empty space to fill up the gaps left by galaxies that have crossed the observable universe border.
• As a result, the size and overall mass of the observable universe remains constant. As a result, the universe’s steady state is preserved.

Pulsating Theory

• This theory states that the universe is pulsing, or expanding and contracting alternately. The cosmos is expanding at the present time.
• According to pulsing theory, the universe’s expansion could be halted by gravitational attraction at some point in the future, causing it to constrict.
• The universe will begin to expand after it has been reduced to a particular size. Pulsating universes result from the universe’s alternate expansion and contraction.

The Big Bang Theory

The Big Bang Theory is the prevailing cosmological model for the universe’s birth. It states that 13.8 billion years ago, all of space was contained in a single point of very high-density and high-temperature state from which the universe has been expanding in all directions ever since.

• After Edwin Hubble proposed the constant expansion of the Universe.
• 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.
• At some point in time, the Universe was condensed into a single particle and later started expanding infinitely after a huge explosion.
• The expansion later gave birth to nebulae that in turn, coalesced into stars and planets.

Big Bang Theory is also called expanding universe hypothesis.

You can do the experiment of a balloon and find what the expanding universe means.

Take a balloon and mark some points on it to represent the galaxies. Now, if you start inflating the balloon, the points marked on the balloon will appear to be moving away from each other as the balloon expands. Similarly, the distance between the galaxies is also found to be increasing and thereby, the universe is considered to be expanding.

The new measurement technique called gravitational lensing confirmed the universe’s age and the strength of dark energy. Dark energy is responsible for the accelerating expansion of the universe. Scientists used gravitational lensing to measure the distances light travelled from a bright, active galaxy to the Earth and some details of its expansion.

Stage In The Development Of The Universe

The Big Bang Theory considers the following stages in the development of the universe.

1. In the beginning, all matter forming the universe existed in one place as a “tiny ball” (singular atom) with an unimaginably small volume, infinite temperature and infinite density.
2. At the Big Bang the “tiny ball” explodes violently. This led to a huge expansion. It is now generally accepted that the event of the big bang took place 13.7 billion years before the present. The expansion continues even to the present day. As it grew, some energy was converted into matter. There was particularly rapid expansion within fractions of a second after the bang. Thereafter, the expansion slowed down. Within the first three minutes of the Big Bang event, the first atom began to form.
3. Within 300,000 years from the Big Bang, the temperature dropped to 4,500 K (Kelvin) and gave rise to atomic matter. The universe became transparent.

The Evolution of The Universe Since the Big Bang

Time	T in °C	Event
10-43 Sec	1032	The cosmos goes through a superfast “inflation,” expanding from the size of an atom to that of a grapefruit in a tiny fraction of a second.
10-32 Sec	1027	Post-inflation, the universe is a seething, hot soup of electrons, quarks, and other particles.
10-6 Sec	1013	A cooling cosmos permits quarks to clump into protons & neutrons.
3 min	108	Still too hot to form into atoms, charged electrons and protons prevent light from shining.
3,00,000 years	103	Electrons combine with protons & neutrons to form atoms, mostly hydrogen & helium. Lithium & beryllium were formed in trace amounts. Light can finally shine.
1 billion years	-200	Gravity makes hydrogen and helium (primordial elements) coalesce to form the giant clouds that will become galaxies; smaller clumps of gas collapse to form the first stars.
15 billion years	-270	As galaxies cluster together under the influence of gravity, the first stars die and spew heavy elements into space: those will eventually turn into new stars and planets.

Big Crunch – The Death of The Universe

At some point, the universe would reach a maximum size & begin collapsing. The universe would become denser & hotter again, ending in a state like that in which it started — a single point of very high density.

Accelerating Expansion of The Universe and Dark Energy

• It is the observation that the expansion of the universe is such that the velocity at which a galaxy is moving away from the observer is continuously increasing with time (Hubble’s law). It implies that the universe will get increasingly colder as matter spreads across space.
• The accelerated expansion of the universe is thought to have begun since the universe entered its dark-energy-dominated era — roughly 5 billion years ago.
• Dark energy is an unknown form of energy that is hypothesised to permeate (spread throughout) all of space, tending to accelerate the universe’s expansion

Different Views on the Universe

• Pythagoras was the first person who applied the term cosmos to the order of the universe.
• Geocentric View: – Claudius Ptolemy, a Greco-Egyptian astronomer in 140 AD and stated that the earth was at the center of the universe and all other celestial bodies are revolving around it.
• Heliocentric view: – Copernicus proposed a ground-breaking theory in 1543 AD, claiming that the Sun, not the earth, is the centre of the universe. It is called a heliocentric view.
• In the 5th century AD Aryabhatta and in 6th century AD Varahamihira also suggested a Heliocentric view.
• In 1805 AD a British astronomer William Herschel studied the universe with a telescope and observed that the solar system is only a small part of the galaxy.
• In 1925 AD American astronomer Edwin P Hubble calculated that the universe has a diameter of approx. 27 billion light years and comprises seven galaxies.

For Updates and Study material Join Our Telegram Channel

Some Important FAQ