Universe, the home where we survive is one of the biggest unknown things that we have always tried to explore and know about. Scientists have discovered a lot of known and strange objects including black holes, supernova, unnova, quasar, etc. but when they try to get in-depth information about the reason and process of their existence, research pauses at the question - How this Universe was born. Every scientist is eager to find an answer of this question so that they can tack the journey of other massive bodies present in the universe today.
The most popular explanation about how the universe began is the Big Bang Theory. In simple words, the theory says that the universe was started with a small singularity. The age of the universe is estimated to be approximately 13.799 billion years. Around 13.7 billion years ago, after its initial appearance, the singularity inflated outwards with a big boom to the cosmos that we see today.
Scientists believe that before the big bang our limitless universe with all its radiations and particles was a hot and dense mass that was just few millimeters wide. This indecipherable state is theorized to be existed just for the fraction of first second of time. According to NASA, in the first second when the universe began, surrounding temperature was about 10 billion degree Fahrenheit. From that time to till date the universe is expanding and cooling. The basic particles of Cosmos are proton, electrons and neutrons.
Chronology of the Universe
- Singularity: This term referred as a generic phase when the universe was extremely hot and dense.
- Inflation: In the fraction of second, cosmic inflation lead to the phase transition due to which the universe grew exponentially. After inflation stopped, reheating started to attain the temperatures needed for the production of the elementary particles of universe.
- Cooling: With the expansion of universe the temperature started decreasing and universe gets its life.
- Structure Formation: The regions that were dense attracted nearby small matter became even denser forming star, galaxies and other structures. This happened due to the gravitational forces.
- Expansion: The observations say that the universe is still expanding which means that with time the galaxies are further moving away.
Evidence that proves the big bang theory is real
* First strong argument is the belief that the universe has a beginning.
* Next that initially the universe was compact in a singularity this is concluded because all the galaxies are still moving away in all directions on their own and at a great speed.
* Thirdly, the high temperature of the universe at the initial state. In 1965, Radio astronomers Arno Penzias and Robert Wilson discovered 2.725 degree kelvin cosmic Microwave Background radiation (CMB) as the remains of this heat.
* Lastly, the presence of the hydrogen and helium atoms in the universe. These elements, due to gravity, collapsed to form stars and galaxies.
But the big bang theory leaves many questions still unresolved like why big bang itself happened?, that why many alternates to the bag bang came into light.
Alternate theories for the big bang
* In 1999, Paul Steinhardt and Neil Turok, the two physicists working in Cambridge, England gave a competing theory that our universe is generating and regenerating itself in an endless cycle of creation.
* Some researchers go further and state that our universe is just one of the many parallel universes. Each with its own laws of physics.
* Some others think that the beginning of universe happened due to the collision of a 4D black hole, and the emitted dust particles formed, in what we live in.
* Another theory says that the universe is a giant hologram or just an image of a 2D shell.
Many more theories have been proposed but the Big Bang Theory is still widely accepted as the most reliable answer. However, the researches are going on and will keep on going until and unless we find a perfect answer that would help us extend our imagination beyond our capabilities and knowledge.
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