Back in 1927, astronomer Georges Lemaître proposed a revolutionary idea. He suggested the universe began incredibly tiny, packed into a single point. For a long time, this point ballooned outwards, causing the universe to grow larger and larger, and this expansion might continue forever.

In 1929, another astronomer, Edwin Hubble, made a stunning discovery. He observed that galaxies weren’t just moving away from us, but the farther they were, the faster they seemed to be receding. Hubble’s observations lined up perfectly with Lemaître’s theory. The galaxies’ movement away from us indicated a universe still stretching, just as Lemaître proposed. This expansion hinted at a past where everything was crammed much closer together.

In the infant universe, everything was a super hot, dense soup of particles, light, and energy, far from the organized cosmos we see today. As space stretched and the universe grew, it also chilled. These tiny particles huddled together, forming the building blocks of matter – atoms. Over eons, atoms clumped into stars and galaxies. Early stars forged heavier elements, enriching the universe’s recipe for new star birth. Meanwhile, galaxies collided and merged, all while a cosmic dance of stellar birth, death, and debris creation unfolded, giving rise to asteroids, comets, planets, and even black holes. That’s the gist of how the universe exploded into existence! This grand expansion, sparking the creation of everything from stars to galaxies, earned it the nickname “Big Bang.”

The Big Bang theory wasn’t a slam dunk in 1927. The real turning point came in 1965 with the discovery and confirmation of the cosmic microwave background radiation. This evidence strongly supported the Big Bang. Over the next few decades (from the late 60s to the 1990s), astronomers and cosmologists tirelessly addressed theoretical issues within the Big Bang theory, further solidifying its position as the leading explanation for the universe’s origin and evolution. Stephen Hawking and other physicists contributed to strengthening the Big Bang theory. Their research, including published papers, demonstrated that singularities (points of infinite density) were unavoidable starting points within both general relativity (the theory of gravity) and the Big Bang model of the universe’s origin.

The Big Bang theory holds a lot of fame, but it also gets misinterpreted quite often. A common mistake is thinking it explains the universe’s very beginning. Instead, it focuses on how the universe went from an incredibly small and dense state to its current vastness. It doesn’t delve into what caused that initial state or what existed before it, or even what lies beyond the observable universe.

Another misconception is that the Big Bang is like a giant explosion. Not quite! It describes the universe’s ongoing expansion. While some versions propose a superfast initial expansion (possibly exceeding the speed of light), it’s not a traditional explosion in the way we typically think of them.

The truth isn’t something we can definitively prove for scientific theories, but we can certainly disprove them. When experiments and observations continually back up a theory, it gains strength and wider acceptance within the scientific community. However, if new evidence contradicts a theory, scientists have two options: either abandon the theory entirely or refine it to account for the new information.

The Big Bang theory isn’t just a story of the past; it’s a springboard to the future! This isn’t the end of the cosmic tale, but the beginning. We’re still unraveling the mysteries of dark matter and dark energy, the unseen forces shaping the universe’s fate. Could there be other universe beyond our own? Did inflation happen in a burst or a stutter? Every discovery is a new chapter, a thrilling twist in the ongoing saga of the Big Bang! Buckle up, while we explore the cosmos, the greatest adventure is yet to come.

-Dr. Abhishek Sarkar

Associate Professor, DAITM