Billion years ago, there was an extra-ordinary event without which nothing would exist. It was the beginning of the universe. It was the time when a large amount of energy in an infinitely small space violently expanded and led to the creation of universe and everything else that we see around us today. It can perhaps be regarded as the greatest scientific achievement to understand the history and nature of how the universe came into being.
There are various viewpoints on what happened before the Big Bang, however it is a very big question. Astrophysicists have claimed that there is no answer to what happened before the Big Bang however there are several theories. It is supposed that one can hypothesize as there are no tools to reach the truth.
A profound issue that is easy to understand is the distinction between if the universe is finite or infinite and that’s either in terms of time and space. Other questions deal with whether the universe goes on forever or does it have a limit? These questions have been asked for centuries. Plato’s colleague Archytas said,” Imagine a warrior with a spear at the edge of the universe, and he hurls the spear. Does one imagine it goes on forever or does it hit something and bounce back?” In that case, what’s the limit? These leads us to two possibilities, either the universe is infinite or it ends, and if it ends, what’s the end? Cosmologists wrestle with the same question.
When Copernicus replaced the geo-centric model with the heliocentric model, it was a revolutionary move and not just astronomical. These ideas were incomprehensible and highly questionable in earlier times. The Statue of Giordano Bruno in Rome was burned at stake by the Catholic Church for not only believing in an infinite universe but also believing in the existence of innumerable stars and planets and the life around them and perhaps people.
The next venture towards the infinity of the universe was by Isaac Newton who postulated an infinite universe which was infinite in extent, time and space. He was followed by Wright who imagined infinite inhabited worlds in the universe. But this was difficult to believe conceptually. It was so because, in an infinite universe every sideline must end in a point of light whether it’s a star or a galaxy. Since the light from each star diminishes the square of the distance, the number of stars rises by the same factor. And so, logically, the night sky must be as bright as the daytime sky in an infinite universe. This was a paradox that Newton never resolved. So, it took longer to understand how the universe exactly works and to resolve the paradox.
Galaxies once were regarded as “Island Universes”. Isolated realms of gas, dust and billions of stars that were separated by distances unimaginably far apart. In fact, no galaxy is an island as said by researchers, Galaxies prefer company. The gravitational pull of a large mass of galaxy attracts like-sized and smaller neighbours. Galaxies may gather hundreds of these or congregate millions to form a huge cluster. Another dichotomy arose as an argument on whether the Milky Way, the system of stars we inhabit was the whole universe or whether there were other island universes. Herschel tried to map the universe which he knew was vast. But at the turn on the twentieth century, two very different ideas were in play. In one of them, the fuzzy nebulae were hypothesized to be distant systems of stars like the Milky Way perhaps hundreds of thousands of light years away. However, the countervailing model which was accepted said that these fuzzy patches of light were just star formations within our own large galaxy which was the universe. This was resolved by Edwin Hubble who made the breakthrough discovery by measuring the distance astronomically to few dozen galaxies. By the end of his career, he had extended the size of the known universe by a factor of thousand.
The universe is made up of dark and mysterious material than the light and visible stuff that we are familiar with called dark matter. Astronomers are confident that dark matter really exists because the law of gravity has passed many tests, and if we add dark matter into computer simulations, we evolve large scale structures that look just like our universe.
In 1964, by accident Cosmic Background Radiation was discovered in relic of the early universe which together with other observational evidence made the Big Bang the accepted theory in science. Recent observations even seem to suggest that the expansion of the universe is accelerating. Big Bang can be described as all space stretching everywhere all at once. The universe did not expand into anything, the space was just expanding into itself. The universe has no borders, by definition, there is no outside the universe. The universe is all there is. In this hot and dense environment, energy manifested itself into particles that only for the tiniest glimpses of time. From gluons, pairs of quarks were created which destroyed on another perhaps after giving off more gluons. These found other short-lived quarks to interact with forming new quark pairs and gluons again. Matter and energy were not just theoretically equivalent. It was so hot that they were practically the same stuff.
Somewhere around this time matter won over antimatter. Today we are left with all matter and maybe no antimatter at all. Instead of one massive force in the universe, there were now several versions of it acting under different rules. By now the universe has expanded into billion kilometers in diameter which leads to a decrease in temperature. The cycle of quarks been born and converted back to energy suddenly stopped. The quarks began forming new particles like protons and neutrons. There are many combinations of quarks that can form all sorts of hadrons but only very few are very stable for a reasonable amount of time.
The universe which has grown to one hundred billion kilometers was then cold enough to allow most of the neutrons to decay into protons and to form the first atom, hydrogen. The universe can be imagined as an extremely hot soup, ten billion degree celsius filled with countless particles and energy. Over the next few minutes, things cooled and settled down very fast. Atoms formed out of hadrons and electrons making for a stable and electrically neutral environment. Some call this period the dark age because there were no stars as hydrogen gas didn’t allow visible lights to move around. When hydrogen gas clumped together after millions of years and gravity put it under great pressure, stars and galaxies began to form. Their radiation dissolved the stable hydrogen gas into plasma that still permeates the universe today and allows visible light to pass. Finally, there was light.
However, while talking about what happened at the very beginning that is The Big Bang, we don’t know at all about what happened there. Our tools break down, natural laws stop making sense. To understand what happened there, we need a theory that unifies Einsten’s Relativity and Quantum Mechanics, something that countless scientists are working on currently. But this leaves us with lots of unanswered questions. Were there universes before our own? Is this the first and the only universe? What started the Big Bang? Or did it just occur naturally? These questions are based on laws that we don’t understand yet. We don’t know and maybe we never will. But what we do know is that the universe as we know it started here and gave birth to particles, galaxies, stars, the Earth and us. Since we ourselves are made of dead stars, we are not separate from the universe, we are a part of it. It can also be said that we are the universe’s way of expressing itself.