Aug 16, 20204 min read

The History of Cosmos

Updated: Aug 24, 2020

-brought to you by The Spacestellar

" Have you ever wondered, what makes all of us exist today..?? "

" Does this Universe we observe today, was the same all time..?? "

It all began 13.8 billion years ago. The entire universe which spreads billions of light years today, was once a size of electron which exploded to about it's current size within a fraction of second. This came to be famously known as The Big Bang. Even the time did not exist before the big bang. English astronomer Fred Hoyle first coined the term "Big Bang". A Belgian priest George Lemaitre first suggested the Big bang theory in the 1920s. After its initial expansion, the universe cooled sufficiently to allow the formation of subatomic particles, and later atoms. Giant clouds of the primordial elements were formed. These atoms combined to form larger atoms and elements. The earliest of them were hydrogen and helium. The strong forces of gravity led to the formation of gas clouds. Due to the gravity, hydrogen and helium atoms started combining which gave rise to the higher elements. According to the Big Bang theory, the universe at the beginning was very hot and very small, and since then it has been expanding and cooling down. From the day big bang took place, the universe is continuously expanding.

But the question is,

" How valid is this theory..?? "

" How come the scientists are so sure about this theory..?? "

There are many questions which ask the validity of Big bang theory, but many experiments and results obtained synchronizes exactly with what the Big bang theory predicts, thus making it true.

Results obtained from the astronomical observations, data from the computer simulations and experiments from the Large Hadron collider predicts that Big bang has actually happened. Where as it's proof is present in the form of Cosmic microwave background.

According to Big bang, during the initial days of Universe ( first 3 lakh years) , it was so hot that, it was not even possible for the proton and electron to combine and form atoms. Formation of stars and galaxies could not be even imagined. Matter existed in the form of highly ionized plasma. From this ionized plasma, light was emitted. But due to the presence of neutral atoms, light was redirected by the free electrons present. That was the reason why light couldn't travel to large distances. The Universe seemed to be like infinite bulbs hidden by some kind of smoke. But, as the Universe started expanding, it's density and temperature came down such that it was suitable for the protons and electrons to form atoms. This is the first time that the atoms came into existence and this came to be known as epoch of recombination. Since there were no free electrons left to redirect the emitted light, the Universe for the first time got transparent. Before the formation of atoms, the light emitted from the hot plasma, which was in the form of infrared radiation was now free to travel throughout the Universe. If the Big bang theory is true, this light must exists today as well. To our surprise, this light is present even today throughout the Universe. Due to the expansion of Universe for 13.8 billion years, the wavelength of this light has got stretched and it is not infrared radiation anymore. Whereas, it is in the region of microwave in the electromagnetic spectrum and it is detected throughout the Universe, which we call as the cosmic microwave background.

Big bang even predicts that, the size of Universe was of size of a sand grain when it's age was negligibly small and it expanded billion billion times of it's initial size within a fraction of second.

The Universe which is about 13.8 billion light years has got enormous number of stars and planets. Only a small part of these Universe is visible for us, which we call The Observable Universe. In this observable universe, we can find cosmic web, which has trillions of local group of galaxy cluster. In the galaxy cluster, we can find billions and billions of galaxies. Within these galaxies, we find billions of stars and planets revolving around these stars. One of these galaxies in which our solar system exists is the Milky way. The Milky way has got a large number of stars with at least one planet revolving around the stars. Sun is one of the star which is revolving around the center of Milky way. Our Sun has got eight planets which forms a Solar system. Our Solar system has got eight planets revolving around the Sun. The eight planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. These planets follow certain trajectories or path known as Orbits. All the planets follow an elliptical orbit around the Sun.

The Earth, one of the planet in our Solar system is the home planet for various living organisms. It was formed 4.6 billion years ago. The distance from the Sun, atmosphere and habitable conditions are the main reasons for the existence of life on earth. In the initial days, Earth was thought to be flat and the center of Universe(geocentric). But the scientific study of the space science discovered that, Earth was geoid in shape and it revolved around the Sun along with the other eight planets(heliocentric).

Thus from 4.54 billion years, earth has seen many changes. The earth was initially red hot. Due to this condition, volcanic eruptions took place at a lot of places which formed rocky hills and mountains. Later the earth gradually started cooling down. Then, it rained for several thousand years, which led to the formation of rivers and seas. The surface of earth contained a lot of gases which was released to form a thick atmosphere which forms a protective layer from the harmful UV rays released from the Sun.

In the later stages, living organisms were formed on earth. They started evolving to form multicellular large organisms. And finally, we have come all across this. Though we have made so many discoveries and inventions, we have not even figured out 5% of the mysteries of cosmos.