The vast empty space around us that consists of stars, solar system, galaxies etc is called Universe. It also includes the entire creation and existence, visible and invisible; material and living; approachable and unapproachable for the beings. Whenever we see towards sky, many questions come in our mind. “How big is the universe?” “How was it created?” “Who created this?” “When was this created?” “How will it end?”. A simple answer to all these questions comes in our mind is that God created this universe at his will and he is the master of this universe. Whenever he wishes he can destroy the whole universe. If answer is God, then a new question arises why or how God created the universe. Who created God? How God looks like? What was God doing before he made the universe? And now what he is doing to this universe? Now God is the part of religious debate, we will not going to discuss here about this, but we will try to understand the creation of universe using laws of Physics.
Astronomy is one of the oldest and most profound of the sciences. Edwin Hubble, an American astronomer found that stars are not uniformly distributed throughout space, but are gathered together in vast collections called galaxies. By measuring the light from galaxies, Hubble could determine their velocities. Hubble was the first to realize that all galaxies are moving away from us. Moreover, according to Hubble the further galaxies were from us, the faster they were moving away. The more distant the galaxy, the faster it was receding, with a speed proportional to its distance away (Hubble’s law).The ratio of speed to distance is always the same number and is called the Hubble’s constant. The universe was not unchanging with time as everyone had thought previously. It was expanding. The distance between distant galaxies was increasing with time.
The expansion of the universe was one of the most important intellectual discoveries of the 20th century. It indicates toward an important point whether the universe had a beginning. If galaxies are moving apart now, they must have been closer together in the past. Hubble’s law sets a limit on the age of the universe. Because universe is continuously expanding, if we trace the expansion back to the beginning point, we can work out how long ago that was. It turns out to be approximate 15 billion years. Was this the beginning of the universe? The age of our Milky Way galaxy has also been calculated in two ways. First method is by studying the observed stages of evolution of different sized ancient stars in globular clusters.
A second method for estimating the age of our galaxy is based on the present abundances of several long-lived radioactive elements in the solar system. According to these calculations, the age of our galaxy is again comes out to be approximate 15 billion years.
Many scientists’ starts from early age like Ptolemy, Aristotle, Copernicus, Galileo to modern age Albert Einstein, Stephen Hawking announced different theories about universe. Everyone explains the creation process according to his ability. The branch of science, Cosmology deals with the problem of the creation of the universe. The most accepted theory for the creation of the universe is the Big Bang theory which states that the universe has expanded into its current state from a pioneer condition of tremendous density and temperature. Initial the Universe was in an extremely hot and dense state, with time began expanding rapidly. At that time Matter somehow transformed into universe. There are some scientific evidence supports the Big-Bang model of cosmology.
Prior to the big bang, all the matter which exists in the universe as we know it today was compressed into a mathematical point a very small portion like the tip of the pin, a singularity. The temperature during the Big-Bang was 10 to 12 billion degrees Centigrade, and most elements were formed during the first 30 minutes of the expansion. After the initial expansion, the Universe cooled with time and energy is converted into various subatomic particles, including protons, neutrons, and electrons. In the years after the big bang, the universe rapidly expanded. To understand the expansion, consider a balloon with dots on it. As air is pumped into a balloon, the dots on the surface get further and further apart. Similarly, as the universe grew older and expanded, the objects like stars in it got further and further apart.
Some objects randomly came together and combined to form larger objects. Larger structures came after fusion of smaller particles.
About thousands of the years after the Big Bang, the temperature of the Universe had dropped sufficiently for electrons and protons to combine into hydrogen atoms. Atomic hydrogen constitutes about 75% of the baryonic mass of the universe. First element formed after Big Bang would have been Hydrogen, which is now the building block of all other elements in the universe. With time Hydrogen combined to form Helium and other heavier gases. When oxygen combined with Hydrogen, water is formed. Water led to the evolution of life. The heavier elements were created in the interiors of stars. During explosions these elements spread far apart in the universe. Gravity plays important role before, during and after the Big Bang. According to Newton’s law of gravitation every particle attracts every other particle in this universe with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centres. Within galaxies changes in temperature and pressure caused gas and dust to form evident clouds. Under the effect of gravity, gigantic clouds of elements produced after Big Bang amalgamates to form stars and galaxies. When the mass of these clouds becomes sufficiently large then under the effect of gravity, the cloud compressed, nuclear reactions began and a new star was born.
The explosion from zero volume at zero time created the space and time by converting matter into energy and vice versa. In 1915, Einstein introduced his comprehensive General Theory of Relativity. In this, space and time were no longer absolute. Space and time are changing quantities that are affected by the matter and energy in the universe. Movement of massive objects only can change space and time. They were defined only when universe comes into existence, so it is meaningless to talk of a time before the Big Bang. Since Time itself began at the moment of the big bang and universe create itself form nothing i.e. from zero volume under the effect of gravity. We can explain this by using the concept of Black hole. Black hole is a two dimensional surface, mathematically termed as vent horizon which has a singularity at the centre. The black hole, which floats in space, is a star so massive that it has collapsed in on itself. Nothing, including light, can escape its gravity. Its gravitational field is so powerful it doesn’t only warp and distort light but also time. Time, thus, doesn’t exist in the black hole. More is the mass of planet, more is its escape velocity, e.g. for moon escape velocity is 2.4 km/s and for earth is 11.2 km/s. If planet was heavy enough, the escape velocity could reach or exceed the speed of light itself, so not even light could escape its gravitational pull. Such an object which is so massive and dense that not even light can escape it, is called a black hole. Black holes are extremely deep wells in the space time sheet. Ligo (The Laser Interferometer Gravitational-Wave Observatory) detected the gravitational waves coming from a distance of 1.39 *109 light years where two black holes combine to form a single black hole .During combination some mass is converted into energy which generated the gravitational waves and Ligo detected them.
The universe is like a dream. For billions of years, there was nothing but utter darkness. Then after the big Bang, there are an uncountable amount of planets, solar systems and galaxies in our universe. There is no limit, no end. The laws of Physics help to understand how life on Earth came into being. Time is ineluctable. It’s like a river which is continued to move along one direction. You can throw a stone into it, create waves in it. But after some time it again move in smooth manner. Time always corrects itself. No matter what you do, time just keeps flowing in the same direction.
You endeavour to alter things, control them as well as try to have your own way but you are not able to make it. Nature wants symmetry and everything is followed by certain laws of physics. There is no chance of probability. Everything happens on its time. Space and time always moves forward, similarly you can only move forward. As entropy of universe always increases or remains constant, we can slow down time by approaching speed of light but we cannot go back in time. Time once move forward, you cannot get back in time, so in future to make a time machine is impractical. The time, space and gravitation have no separate existence from matter. Gravitation is responsible for the creation of earth as well as life on earth.
It is the law of nature that if something is born, then it will die one day. Nothing is existed forever. Our current universe is perishable and there is a continuous cycle of creation and destruction of our universe. Everything in the world is moving under certain laws. Entire universe is ever-changing energy, converts matter into energy & energy into matter. The place where we are right now corresponds to some place in a very small volume in the very early Universe. The universe started with gases which finally led to the formation of water which in turn giving birth to life. Every action of creation was smooth and systematic. Will the universe die one day? Yes, there are two possibilities, the expansion that started with the birth of universe will continue, but becomes slower and slower. With time all stars going to die one by one and all the matter will disappear in the black hole. The universe will become nearly empty. Second case the universe stops expanding at some point of time. Due to Gravitation, the attractive forces between all the massive objects will then cause the universe to collapse on itself. The universe will again become infinitely hot and small. Matter again falls back into black hole. Then there will be another Big Bang which starts another universe. But as our universe takes billion years for creation, so it must take billion years for destroy.
