Introduction to Big Bang Theory
Big Bang Theory is the most heard, most talked about and one of the most researched theory on origins of our Universe up until the very present day. The name ‘Big Bang’ as it sounds, must have been the largest explosion sound of our universe, however, it was unheard of; until Lemaitre, a catholic priest and a physicist , started the talks about how the universe might have started in a large explosion.
Until the late 1920s, the concept on the origin of our Universe was: the universe had always been there and is static. However, with the observations made by Edwin Hubble on the red shift of galaxies showcased the idea that galaxies were moving far from us and from each other as well. The further the galaxy is, the faster it is moving away from us. This meant only one thing, the universe is expanding or accelerating and this may be due to the space itself being expanding.
This came as a great surprise to many scientists who believed in a static universe. Even, Albert Einstein was baffled by this idea, whose views were contradicted by Hubble’s observations. His general relativity theory also predicted that universe cannot be in a static state, which he had always ignored to and had used an astronomical constant to balance his equations to prove a static universe. After the observations made by Hubble, Einstein termed this as ‘biggest blunder of his life’.
After the experimental observations, a great debate in the scientific community arise, if universe is expanding, then there must have been a point in time when it could have started. However, contemplating such ideas is not that easy, and it took the greatness of Stephen Hawking to clarify some theoretical concepts for the big bang.
Stephen Hawking is best known for his work with black holes. Working on the black holes, he had an idea that if we can wind back the time for the universe using general relativity concepts, there must be a singular point in time when everything must have started called the point of singularity. His work from black holes suggested that at this point of singularity, all the matter and energy that exist today must be very densely packed and the gravity of such point should be infinitely high . How big or how small the point can be is still a debated topic, however scientists agree that at this point of singularity the universe should be infinitesimally small, as of the Planck order.
That single point of energy, a very small ball of infinite density and gravity exploded to give rise to the universe. Theoretical physicists believe that 4 known forces of nature( gravity, electro magnetic, nuclear and weak forces) must have been in perfect balanced state in the singularity moment. However, there must have been a imbalance in the force distribution or force field, and this may have triggered the bang and subsequent start of time and space.
However, there were many complications to this theory in initial phases. One of the earlier challenges that the theory faced, is that, if the universe started with a bang and expanded, it should not have been accelerating at this point, it should have started slowing down due to the gravity. Gravity should have started pulling everything together and the expansion should have halted. However, solution to this problem was found by discovery of the presence of the dark matter and dark energy. Dark energy was proposed as the factor that was fuelling the expansion of the universe and was proposed to push things apart in our universe.
Another problem the theory faced was the uniform distribution of matter in the universe. If the big bang had occurred in a bang kind of fashion, the distribution of the matter should have been non uniform. However, the universe has uniform distribution of matter in every direction of look. This was proved by Arno and Penzias working on their radio telescope from Bell labs. During their work, they detected uniform influx of micro waves from all directions and coming from an unknown source. Similar experiments done in MIT during that time, analyzed the data obtained by Arno and Penzias and concluded that these cosmic micro waves are remnants of Big Bang. WMAP satellite later imaged these micro wave radiations.
The theory of Inflation proposed by Alan Guth also sought the answers for this problem. The theory explained that a point in time after the big bang, the universe must have gone an exponential expansion. This theory of cosmic inflation also helps to account for other problems like distribution of matter and antimatter in early stages, temperature fluctuations in the early stages that led to the formation of atomic particles.
There still has to be a lot of work done to finalize this theory, especially for the point of singularity, where the known laws of physics do not apply. Scientists have come up with different explanations/propositions to account for this,and provide an alternative to big bang theory. Concepts of multiverse, parallel universe are the most prominent of all.
The fundamental concept or hypothesis of physics is that: the physical or mathematical laws should be applicable universally to all the objects, their dynamics within the universe. This statement has proven to be difficult to validate because of problems of general relativity to describe singularity for big bang theory. Or conceptualization that the statement may not hold true for parallel universe or multiverse. However, concepts of multi verse or parallel universe are theoretical and experimental proof is hard to gather. quantum mechanics may hold a clue to this; string theory may have a bigger role to play. But, based on current observations and physical description of universe, Big Bang theory seems to be more convincing.
