Updated: Aug 23, 2021
Journey till the Big Bang Theory :
The widely accepted theory for the origin and evolution of the universe is the Big Bang model, which states that the universe began as an incredibly hot, dense point roughly 13.8 billion years ago. But… how do we know that?? George Loewenstein (1994) described curiosity as “a cognitive induced deprivation that arises from the perception of a gap in knowledge and understanding.” Lowenstein’s information gap theory holds that curiosity functions like other drive states, such as hunger, which motivates eating. Building on this theory, Loewenstein suggests that a small amount of information serves as a priming dose, which greatly increases curiosity. This is the same curiosity that lead to discoveries that changed our mindset about our universe…. 340 B.C. Aristotle, In his book On the Heavens suggested that the earth was not a flat disk but a round ball and gave the idea that all the stars and planets we observe revolve around the earth.. This was one of the very first ideas of Geocentric Models of our universe and is very important to understand the key to its existence. The model proposed by Aristotle and various other yearly astronomers suggested the idea of a finite universe but this changed in around 16th century.
Nicolaus Copernicus was an polish priest who proposed a heliocentric system, that the planets orbit around the Sun; that Earth is a planet which, besides orbiting the Sun annually, also turns once daily on its own axis; and that very slow changes in the direction of this axis account for the precession of the equinoxes. This led to a very long war of intellects between the two models. A very good explanation came in the 17th century along with one of the most exceptional and note worthy papers ever written in Physical Sciences, Principia Mathematica Naturalis Causae , written by Sir Isaac Newton.
Newton gave the idea of Gravity; he explained the movement of various celestial bodies. This resulted in the conclusion that the stars we see in sky are no different than the sun. This suggested that there are two possibilities which are yet to be confirmed, one that the universe is a finite space and the other that the universe is unending, but both yet drastically incomplete. 1823 A.D. Heinrich Olbers when gazing upon the night sky thought about the dark void observe and argued upon this peculiar phenomenon, this came to be known as Olber’s Paradox. He argued that In the hypothetical case that the universe is static, homogeneous at a large scale, and populated by an infinite number of stars, then any line of sight from Earth must end at the (very bright) surface of a star and hence the night sky should be completely illuminated and very bright. This contradicts the observed darkness and non-uniformity of the night. This brought us to an inevitable conclusion, that universe is in no way static, then…. What??In 1929, we finally received the answer this question. Edwin Hubble and Milton Humason gave the idea of Red Shift and Blue shift through the doppler effect. They observed that the objects that are many light years away from us are gradually drifting apart from us every second at an increasing acceleration. Which meant that the universe was expanding at a increasing rate each second but that brings us two questions, HOW and WHY?? The answer was Big Bang Theory.
The Big Bang th
eory: - You might know big bang as the explosion from an infinitely dense point that started the universe, but that model is out of date.
So here’s what we really mean when we say Big Bang: -
• 13.8 billion years ago, space was much smaller. In this tiny universe space is tightly curved • That means that if you Travel in a straight line you won't have to go far to get back to where you started.
• Universe doesn't contain any stuff yet, no matter or radiation it just pure space and this space has energy.
Inflation : The universe does not explode during the big bang, it rather expands. The universe expands exponentially in a process called inflation, this means that it keeps doubling in size which means that the curvature of space is getting lower and lower until space got so big it was essentially flat.(so hypothetically it started as a sphere)
The Hot Big Bang: -
• The energy inherent to space was turned into stuff like quarks, bosons and leptons (matter, antimatter and radiation). This is know as the hot big bang and this where all the matter and radiation in the universe came from. Although inflation stopped space was still expanding so over time matter became less dense and less hot.
• First there were only fundamental particles then after a micro second quarks condescended to form protons and neutrons. Then a second later neutrinos stop interacting strongly with other particles and flew free. Then antimatter and matter annihilated each other and mysteriously matter was left behind.
• Then protons and neutrons came together to form the first atomic nuclei of helium.
PRO HOT BIG BANG: -
• Then about 379,000 years later the hot big bang ended, and hydrogen and helium nuclei captured electrons to form the first stable atoms. And photons stopped interacting strongly with other particles and flew free as well. These primordial photons today are seen as cosmic microwave background.
• Then nebulas begin to form due to the force of gravity and matter coming together. A 100 million years after the big bang, the nebulas become dense and hot enough to form the first stars of the newly formed universe.
• 600 million years after the big bang event, the gravitational force between many stars resulted to form cluster of stars which grew bigger and bigger thus forming galaxies. At this time the photons or light which was released during the big bang started to dim out. The new galaxies formed started to go farther and farther away due to expansion of the space time fabric.
Evidences for The Big Bang: -
• The first evidence in support of big bang is the discovery of the expansion of universe around us. Edwin Hubble discovered through Doppler Effect of galaxies that the galaxies are moving away from us with a constant accelerating rate. If universe is expanding, then they must be together before.
• The cosmic microwave background radiation which can be detected through our satellite TVs is a crystal-clear evidence in support of big bang. This radiations shows the photons or light particles which were released during big bang.