Have you ever wondered, how this world began? What is there in space? How everything in universe is following a pattern?
In this post, I have tried to explain these things as simple as possible.
What is Universe?
The name "Universe" is derived from Latin word “universum” means “The all” or “All things”.
In scientific terms, Universe is a collection of all known and unknown planets, galaxies, and other forms of matter and energy.
In simple terms, it is the collection of all, which includes all living and non-living things of unknown depths.
There are two popular theories about the birth of Universe. Even-though, Big Bang Theory is widely accepted, there was a time when scientists had a difference of opinion about the Universe formation. One sect believed in “Big Bang Theory” and another sect believed in “Steady State Theory” of universe.
The Steady-State Theory states that the Universe is eternal and there is no beginning or ending to it. This theory supports universe expansion but believes that the Universe doesn’t change over time. It requires the matters to be constantly created to compensate the Universe density and to keep it in constant.
Big Bang Theory states that the universe was in an initial singularity state in which all the matters & energies were in combined state. At some point the universe started to expand and cool. From that time, it started to act as per the known laws of physics to human kind. (If you want a nice and simple explanation about Big Bang Theory check this link)
Now we may have a question, what was there prior to Initial Singularity state?
The answer will be "It is difficult to explain because the universe was acting beyond our understanding". So all our calculations & theories starting from the point at which the Universe started to expand from singularity.
Is Steady State Theory still acceptable?
The observational tests after the 1950’s suggest that the Universe is changing. And the discovery of “Cosmic Microwave Background Radiation (CMB/CMBR)” in 1964 changed the perception of Birth of Universe.
CMB/CMBR is an oldest electromagnetic wave emitted at the early time of the Universe. It fills all the space. Big Bang Theory suggests a time, at which the matter and energy in the Universe were so dense and hot. When the Universe expanded, it cooled and photons and electrons started to combine. This time is called the Epoch of Recombination. The CMB/CMBR is the EM waves believed to be released at the time of the Recombination Epoch. So there was a time with no solid structures in the Universe, instead only scattered electrons and protons. This proves that “Steady State Theory” is wrong and backs up “Big Bang Theory”.
Big Bang Theory explains how this Universe as we see today formed from the Initial Singularity
At the beginning, Universe was dense and hot, so no formation was possible. Once the expansion started, it cooled eventually and the universe formation started in a way that particles formed. They combined and formed structures from atom to stars, galaxies and other mega structures.
Our Universe is vast and infinite. With our current knowledge, we are unable to predict the size of the Universe. The Universe is divided into observable Universe and the Universe beyond that.
So what is an observable universe?
With our current technological advancements, we are able to analyze or see a particular portion of universe which is nearer to our galaxy. This universe is called Observable Universe. The Universe beyond that is inaccessible to human kind. The Universe is still expanding and so the Observable Universe is decreasing in size.
Even we explained it simply, the formation was a long one, which consists of various epochs. To see in detail, please check my other post "Big Bang Theory".
For understanding purpose, Let us see the small structure and how they form the big one.
- A planet is an object with mass, always orbit a star.
- A star is a big giant energy source.Multiple Stars form sub Galaxies and Galaxies.
- Multiple galaxies combined and form clusters and super clusters.
Let us see this with an example,
- Earth is a planet which orbits Sun along with other 7 planets and other small objects. This is called Solar System.
- Our Solar System is part of Milky-way Galaxy and resides in the Milky-way Galaxy’s outer Spiral arm.
- Our Milky-way Galaxy is part of Virgo Super Cluster. But later it was discovered that our Virgo super cluster is part of an even bigger super cluster Laniakea Super Cluster.
Usually galaxy centers will have a giant black-hole. So the gravity near the center will be very high. Due to the higher gravity near the center, there is a possibility that the objects near to the galaxy center may collide and destroyed when exposed to another near by stars.
Since our Solar System is in the outer arm of the Galaxy, we are away from those high gravitation accidents and that is a believed reason that Earth is able to sustain life forms for a long time.
Apart from our Super Clusters, there are so many other Clusters and Super Clusters found in the observable universe. In-fact what humans analyzed and studied so far is a tiny part of a big ocean. Entire human kind may not be able to derive the size and objects of the entire Universe.
The universe we see now, is in the same structure for millions of years with very minor changes. But after thousands of millions of years, the universe will further cool up and it will cause serious changes.
The observable universe will limited to the local galactic clusters.
New stars won't form and existing stars will die.
The mega structures will decompose and turn into the basic objects of matters.
After some time, the matters may decompose.
Is that the end of Universe?
Some theories suggests that expansion may halt and reverse. Some theories suggests that quantum fields collapse and the forces, particles and structures take different form. But all these possibilities are likely to happen after several billion years.
Whenever there is a definite theory about universe, there is a discovery of new thing which breaks the already proven theories. This taught us only one thing, “Nothing is definite and Don't stop learning”.
So Keep Learning and keep sharing the knowledge !!!