History of Big Bang theory
Now, before you take any step forward about knowing more on big bang theory it is important that you earn about what is the history of big bang theory as it will help in better understanding.
Starting over the history, what is the first thing that is needed to be discussed here, what gave birth to this big bang theory or you can say what is the thing that led to the indication of big bang theory at very first step? So, on answer to this, in 20th century there were some observations made related to universe or you can say spiral galaxies by an American astronomer named as Vesto Slipher which calculated their Doppler redshift in result the only thing that was found was that all of the spiral galaxies were moving away from our own.
Moving forward in the year 1922, Russian cosmologist Alexander Friedmann through his examines developed what you may be knowing by the name of Friedmann equations and that were that time derivedusing Einstein’s equations of general relativity. Before this, Friedmann discovery about universe being in the state of expansion was that pure conflict to Einstein’s Cosmological Constant which finally made him believe that this discovery was not at all wrong and universe is actually in the state of expansion.
Then, in 1924 Edwin Hubble’s calculation of great distance to the nearby coiled nebula showed that these structures were certainly another galaxies, along with which he carried out with his calculations offinding out a distance between these objects and thus in 1929 came up with the discovery according to which there is some relation between the universe and other celestial bodies, which is now also known by the name of Hubble’s law.
And on the other side, in 1927 Georges Lemaitre (a Belgian physicist and Roman Catholic Priest) was working upon the equations derived by Friedmann and that too independently, as a result of which he discovered that this distance between universe and celestial bodies is increasing because of the expansion of universe. In 1931 he took this theory forward and suggested that now if the universe is expanding, that clearly indicates if one moves back in time then what they are going to find is that universe actually started from nothing, well nobody really knows that but it is truly believed that universe at first was too much dense and hot. However, there were lots of discussions about this in 20s and 30s and lots of critics came forward to make this theory go false, also Lemaitre was accused of making this theory come into existence. There were some other theories which were derived at this same time discussion about how whole of the universe came into existence and what it is all about, such as Milne model and Oscillary universe model which was derived on the basis of Einstein’s theory of relativity according to which universe was moving on those definite or indefinite cycles.
As the World War II got into rest, followers of steady state model and big bang theory were on a debate and big bang theory was already into the air and was grabbing more and more popularity. And finally got confirmation with the discovery of cosmic microwave background radiation in 1965 and thus made it come out as the best theory about the beginning and development of universe. And moving forward, it got to have that solid base as astronomers and cosmologists made all of their efforts between the era of 60s to 90s.
Moving forward, there were number of modifications made in this theory in late 90s and 21st century so as to make it more understandable by people. In 1988, it was also found that expansion of universe is accelerating which was also supported by various observations made by ground based CMB and many other galaxy redshift surveys. Also from years of 2003 to 2010, NASA took lots of pictures that were really very detailed version of universe and it clearly explained that this universe is created about 13.8 billion years ago, as per defined in the calculations made in big bang theory. So these positive results all of the people believe that there is not any other theory derived yet which can explain the evolution of universe in so much detailed and proper manner as done by this one.
Now, the only work that is been done is upon finding about that how does these galaxies emerge when universe was forming up and also finding clues to the concepts of dark matter and dark energy.