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Approximately 13.8 billion years ago, a miracle took place. From nothingness emerged a ‘bang,’ leading to the rapid expansion of the newly formed area. This isn’t an explosion that took place in ‘pre-existing space. It was a ‘bang’ that is the expansion of space itself. What was it, you ask? It was merely an infinitely dense and hot point. The point contained all the secrets of the universe, many of which we haven’t gained knowledge of yet. The point expanded greatly, and the first-ever explosion took place, forming the Universe as we know it. This ‘Big Bang’ is the origin of space, time and energy - the fundamental concepts that govern life and modern physics. The study of cosmology went through many breakthroughs in the 20th century, revolutionising the understanding of how the universe began.
A brief occurrence that lasted only a fraction of a second was the catalyst for the universe's expansion beyond the speed of light. The limit of speed observed in the universe is the speed of light, which is used as the benchmark for measuring speed and other variables. Therefore, the assertion that it could have been the expansion occurring at a rate greater than the speed of light sheds light on the magnitude of the impact. This is known as the "Cosmic Inflation." After the cosmic inflation ceased, the energy was utilised to create an explosion of matter and light. The universe had an unimaginably high temperature of almost 10 billion degrees Celsius. In this hot world, first emerged the subatomic particles - neutrons, protons and electrons. These particles lay the groundwork for different planets and star formation, as they led to the formation of the first atoms (Helium and Hydrogen) that exist at the core of a star. The formation of these atoms is known as ‘Nucleosynthesis.’ Most of today’s helium was formed in the short period of five minutes after the Big Bang. The universe had cooled down enough, and the formation of these nuclei ceased. However, it was still quite hot for the nuclei to attract electrons to form complete atoms. The universe, as a result, became opaque. The electrons formed a ‘fog’ and scattered light.
The universe eventually cooled enough for electrons to enter atoms during the Recombination Epoch. The wide cosmos was illuminated as "The Great Cosmic Fog" cleared, and light was able to traverse huge distances. The light that the first atoms emitted was so magnificent and brilliant that its effects can still be seen today. The "Cosmic Microwave Background," the oldest observable light in the universe, is the name given to this glow.
After a period of light comes darkness, and the universe was engulfed in the Dark Era. For 200 million years, no light could spread due to the absorbing effects of hydrogen atoms. The cosmos contained no stars, only a few varieties of atoms that randomly roamed around, unaffected by the darkness.
Soon, the lumpier-cooler areas formed thick, dense clouds of dust and gas. The centre of these clumps became hot enough for nuclear fusion to occur, forming the preliminary stars. As time passed, the stars became a colony, forming a galaxy. The stars emitted UV light, eliminating the fog that had plagued the universe since the dark ages, and making the universe transparent enough for astronomers to observe with their telescopes. The ‘Reionisation’ is what makes the universe observable today.
The Dark Ages, however, didn’t disappear without a trace. The newly formed galaxies, and the ones that formed in the future, have an undetectable component helping them maintain stability - Dark Matter. Invisible to the naked eye, or the electromagnetic spectrum, it was discovered only due to the gravitational effects it had on the galaxies. 85% of matter present in the universe is Dark Matter. One instance of its detection is in spiral galaxies, wherein the rotation curves flatten out over large distances. This would only be possible if some other unknown mass exists to exert this influence on the shape and behaviour of the galaxy. The gravity of dark matter has been thought to be helpful to the formation of galaxies. Its gravity might have helped pull the dormant dust and gas together, forming a compact core that can lead to the formation of multiple stars. A way to map out the presence of dark matter throughout the galaxy was found by the great physicist Albert Einstein, a process named Gravitational Lensing. Matter is something that occupies space and has mass. Since it occupies space, it causes the bending of light that comes from distant ends of the universe. The effect of bending of light can help physicists map out the presence of dark matter in certain areas of the universe. Despite it being present in such a high quantity, most of it is shrouded in a fog of mystery. ‘
After the formation of galaxies with the aid of dark matter comes another ‘dark’ term - Dark Energy. The initial big bang expanded nothingness into a vast, immeasurable universe, but it didn’t stop there. Studies and experiments have shown that the universe is still expanding. As light travels in the universe, the colour of the light tells us about the movement and direction of the light. It was observed that the wavelengths of many lights that travel away from the Earth appear stretched, scientifically known as ‘redshift.’ Edwin Hubble discovered that the velocity at which galaxies recede from us is proportional to their distance. The redshift phenomenon and Hubble’s law, derived from observational understanding, prove that the universe is expanding and that the rate of expansion is increasing every second. The acceleration of expansion is still an enigma, which led to the widely accepted theory of ‘Dark Energy.’ Scientists expected that the rate of expansion would slow down due to the effect of gravity, but when observations proved otherwise, it led the great minds into a dilemma. Thus, the concept of dark energy was introduced. Hypothetically, it is estimated to make up about 68% of the total energy density of the universe. Once again, such a large number, yet no evidence proving its existence.
Finally, we arrive at the apex of human life in the cosmos. Now, 13.8 billion years later, we are researching the cosmological history to learn more about our enigmatic origins in the formation of the universe. No one knows the events that occurred before the bang or where the universe's "roots" came from. Such types of questions are what motivate physicists and scientists to build machines, conduct studies of the cosmos, and formulate theories. Ultimately, these theories and bold hypotheses aid in the development of concrete answers to the question of where we came from. Humankind’s journey through time and space might never come to an end, and the influence of cosmic history will continue to drive young scientists and astronauts to dream and ponder upon the multitude of secrets that the universe has hidden from prying eyes.
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