In the night, with clear sky, we see beautiful sky with stars shining. For centuries, human being are watching and thinking of how universe is developed into today’s wonderful universe. You can see a small portion of stars from the whole universe. In imagination too, we don’t have the the idea to measure how much big is the ‘Universe‘. Scientists and cosmologists are still working on the idea how much big is Universe and how was it created. Astronomer Fred Hoyle is the person who first used this word- ‘Big Bang‘. Now, Big Bang theory is a new direction to solve the ‘mystery’ of our universe.
To understand how universe was born, we have to start from the beginning- let’s go to 20 billion years ago. There was no stars, galaxies, planets- nothing. The external galaxies (Those which are other from our galaxy) are receding at a speed which is proportional to their distance from our galaxy. Astronomer Hubble first noticed that. he concluded that universe is expanding. Any expansion starts from a tiny particle. According to the cosmologists, big bang theory states that universe began by expanding a infinitesimal volume with very high density and temperature. Many people thought that the universe today is the result of a tremendous explsion. Before that universe was smaller than a single sand particle. Days after days, years after years, it is continuously expanding and today it seems that the size of the universe is not changing, as the expand rate is so less.
But the actual concept is big bang is not that. It refers to the ‘expansion’ of universe itself. The greatest scientists Albert Einstein, Edwin Hubble and Stephen Hawking were tried their best to solve the mystery of universe’s creation.
In 1915, Albert Einstein formulated his famous theory of relativity which follows the rule of expansion in free space, after that great astronomer Sitter applied his research over it and with relativity theorem and concluded that universe may be expanding. This was the first time to state universe’s expansion theorem.
Though there is so many idea about the expansion of the universe, there are only three possible matters to discuss about the probability of the expansion. The fate of the universe can be determined by how faster universe expanding relative to how much matters it contains.
The three possibilities of expanding universe is:
- Open Universe
- Flat Universe
- Close Universe
If the universe was open universe, then it would expand forever with a good rate of expansion. If it was flat universe, universe would expand, but the rate of expansion would too slow, eventually it becomes zero with respect to time. If the third possibility occurs, universe will stop expanding and it will start to collapse.
Thou in 21st century, many new theorem says that universe is not expanding. The fate of universe may be “Big Freeze“, which states that at the maximum expansion, the universe will reach at absolute zero temperature, in this situation, (1-100 trillion years later) the gas needed for star formation will be exhausted and the total universe will collapse to its initial position.This “Heat death” scenario can be occurred to all these universe expansion model at the minimum temperature only.