5 minute read
The story of our UNIVERSE
Since ancient times, cosmology – the study of the universe as a whole – has piqued human curiosity. Its origins can be traced to early civilisations’ attempts to understand the grandeur of the cosmos. Ancient Greek thinkers such as Aristotle and Ptolemy proposed geocentric models where Earth lay at the centre of the universe, surrounded by celestial spheres carrying the stars and planets. Though these early hypotheses prepared the way for later astronomical theories, it was not until the advent of modern scientific research that cosmology started to take on its current form. Parallel to this, religious writings such as the Bible presented their own interpretations of creation, igniting discussions and debates that still affect contemporary philosophy and science. The Big Bang model is currently at the forefront of contemporary cosmological theory. It not only offers a rational account of the universe’s origins, but it also serves as the foundation for comprehending the evolution of the universe.
The Big Bang idea was first proposed in the early 20th century based on the research of scientists such as Georges Lemaître. It was then supported by data and observations that were accumulated over the course of the following decades. Though initially viewed with scepticism, the concept of a single event commemorating the universe’s creation gained momentum as observational astronomy progressed. According to the Big Bang theory, the universe started as an incredibly hot and dense singularity 13.8 billion years ago, from which all matter, energy, space and time swiftly expanded. The cosmos began to expand, and it eventually evolved into its current shape.
The discovery of the cosmic microwave background (CMB) radiation in the middle of the 20th century was one of the major advancements that supported the Big Bang theory. This radiation was thought to be remnant thermal radiation from the early universe, and it offered strong evidence for the Big Bang theory’s prediction of the universe’s initial hot and dense state. Additionally, the discovery of the redshift of galaxies provided more evidence in favour of the notion. The more space a galaxy had, the faster it was receding from us, according to astronomers’ observations. A hot, dense condition of the cosmos expanding is consistent with this observation, which is captured in Hubble’s Law.
Inflation theory extends the Big Bang model by proposing a period of extremely rapid expansion in the universe’s first fractions of a second. This rapid expansion resolves fundamental puzzles of the standard Big Bang model, such as the horizon and flatness problems. By stretching the universe exponentially, inflation ensures that regions now widely separated were once in proximity to reach thermal equilibrium, which explains the uniformity observed in the CMB radiation. Additionally, inflation predicts a flat geometry for the universe, matching observations, and provides a mechanism for the origin of cosmic structure by amplifying quantum fluctuations into the seeds of galaxies and large-scale structures.
Cosmology also addresses the enigmatic dark matter and dark energy components of the universe. Dark matter does not directly emit light or energy that can be detected, but it interacts gravitationally with normal matter and is thought to make up around 27% of the universe’s mass-energy content. The gravitational pull it has on galaxies and galaxy clusters suggests its existence. Even more mysterious is dark energy. Its elusiveness makes it difficult for physicists to pinpoint its basic components, which are thought to be non-baryonic particles. By contrast, dark energy, which makes up approximately 68% of the universe, violates accepted theory by acting as a repulsive force that accelerates the expansion of the cosmos. As a result, galaxies are drifting away faster and faster over cosmic time. The exact nature of dark energy is still up for debate; hypotheses range from dynamic fields circulating throughout space to a cosmic constant. When combined, these enigmatic elements control the cosmic energy budget, influencing the universe’s large-scale structure and evolution.
The density of the cosmos and the behaviour of dark energy are two crucial aspects that determine its fate. If dark energy continues to dominate and speed up the expansion of the universe, it could lead to a “Big Freeze”, in which cosmic expansion proceeds unchecked. In this scenario, the universe would eventually cool down to almost absolute zero, becoming sparse and barren as galaxies drift further apart and stars burn out over enormous timeframes. As an alternative, dark energy might cause a “Big Crunch” or cyclic universe, in which the universe’s expansion stops and reverses, possibly resulting in the universe’s collapse and rebound. These disparate results highlight how dark energy has a significant influence on determining the fate of the universe.
With the help of cutting-edge physics experiments, theoretical modelling and observational astronomy, modern cosmology is still developing. The aim of projects like the James Webb Space Telescope, the Large Hadron Collider and the Sloan Digital Sky Survey is to uncover deeper facts about the origins, evolution and composition of the universe. In the end, cosmology holds a special place at the intersection of physics, astronomy and philosophy, offering a profound comprehension of the fundamental nature of life. As our comprehension of the cosmos expands, so does our admiration for its rich beauty and complexity.
