The Big Bang: All You Need To Know About The Origin Of The Universe

The Big Bang Theory is the most accepted theory about how our universe came into being.

Proposed out of a series of tedious mathematical models and complex calculations, the theory suggests that big inflation of matter from a tiny point of hot, dark, and dense singularity was responsible for the creation of our universe. After the big bang, the universe and everything inside it started taking shape with the cooling of matter.

The term Big Bang was coined by Fred Hoyle in 1949, while casually talking about the origin of the universe at the radio broadcast of BBC.

The common yet the most accepted hypothesis suggests that the entire universe and everything inside it, be the stars, sun, or planets, all emerged from one single point.

This point, known as the point of singularity, was extremely hot, dark, and dense, where the pressure and mass accumulating in it was becoming so high that it could not contain itself in such a small and tiny space.

This constant heat and pressure build-up in the small space led to cosmic inflation, leading to the formation of our universe.

Intrigued to find out more about the origin of our universe? Read on to know more exciting facts about the big bang theory.

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Before The Big Bang

About 13.8 billion years ago there existed nothing called the space or universe that we know of today.

The time before the big bang is known as the Planck Epoch, where all kinds of matter that is known to man today were all tightly condensed. The point where all finite matter is squished into one single tightly-packed mass, having extremely high temperature and density, along with high gravitational pressure is known as the point of singularity.

Such cosmic singularities lie at the heart of black holes.

Hence, black holes represent areas of extremely high gravitational pressure that squeezes matter into them. Before the big bang, all matter was stuck inside the black hole at the point of primordial singularity.

However, a recent scientific theory based on modern observations, called the Big Bounce Theory, suggests that before the big bang and creation of our present universe, there existed another universe or multiverse, whose product is our present observable universe.

It builds its hypothesis based on traditional Indian religious philosophies that point out that our universe goes under a cycle of creation and destruction, evolving out of a singular mass, growing its complexities before destruction.

According to this theory, our universe follows the cycle of creation out of a tiny singularity, ballooning into an expanding universe and contracting like a deflated balloon at the end of the cycle.

This cycle is said to once every trillion years.

Who proposed the big bang theory?

While the physical laws on which the big bang theory stands are based on the calculations and formulae of Hubble and Einstein, its hypothesis was first published by George Lemaître, a physicist from Belgium.

Inspired by Albert Einstein's theory of relativity, Alexander Friedmann, in 1922, deduced several equations known as the Friedmann equation, showing a Cosmological Constant. Applying these equations he concluded that the universe is in a constant state of expansion.

Later in 1924, Hubble first pointed out the existence of distant galaxies that were seemingly moving away from our own galaxy, the Milky Way. He identified this by visualizing the stretching of light emitted from other galaxies, which gave a sign of their gradual movement away from the earth.

Basing the above presumptions, Lemaître, in 1927, proposed the Big Bang Theory, where he explained the origin of the universe out of a dense singularity due to the expansion of matter from the primeval atom. He linked the recession of other galaxies with the expansion of the universe.

Hence, the farther other galaxies move away from ours, the more our universe expands. So the farther we go back in time, the smaller the universe would look like, after its emergence out of the primeval atom.

Big Bang Theory Evidence

While there is no solid evidence that favors the big bang, over the years scientists from all around the world have hypothesized on this theory using various cosmic clues from the universe.

The Big Bang theory, based on inflation theory, suggests that our universe began out of an initial expansion of particle energies having high mass density and temperature.

This has been proven by Hubble's law, pointing out that galaxies are separating from each other at speeds that are proportional to the distance from each other. Right at the beginning, when the universe expanded, these elementary particles spread out across the entire sky in random motions.

Most of those particles were hot masses of giant clouds, which after significant progress, cooled down forming planets.

As the universe expanded following the big bang model, it continuously created various light elements, mostly hydrogen and helium, through nuclear fission and fusion.

Finally, the most significant evidence of the Big Bang, suggests that as our visible universe came into being from a hot and tiny mass of infinite density when the universe cooled, it radiated out heat energy in the process.

This radiation (often called the 'afterglow' of the Big Bang) is known as the Cosmic Microwave Background radiation (CBM), which acts as the most comprehensive evidence in favor of the big bang.

The CBM was first discovered in 1965 by two radio astronomers Arno Penzias and Robert Wilson as the remnant of the radiant heat released from the cooling down of the universe.

What happened after the big bang?

Everything that we know about our eternal universe is a result of a fairly precise series of events that occurred only within a few seconds after the big bang.

From the starting point of the big bang, the series of events thereafter have been described in relation to their time of formation with reference to the cosmological scale.

The first fraction of seconds after the big bang is called the Planck Epoch where the hot and unstable universe began to expand rapidly, more than the speed of light.

This epoch also saw the creation and strengthening of the gravitational force along with the expansion of matter. Next, in the Inflation Epoch, expansion of the universe continued along with random motions of the matter at varying velocities.

At the same time, as these moving primordial elements kept on colliding against each other, new elements were continuously formed by coalescence of the collided particles or got destroyed due to collision, forming quark-gluon plasma.

Thereafter, in the Cooling Epoch, the density and temperature dropped, even more, leading to the coalescence of quarks and gluons into baryons like protons and neutrons.

These protons and neutrons combined together in a process known as nucleosynthesis, leading to the creation of hydrogen and helium in the early universe.

Soon after, atomic clouds were formed having gases like hydrogen and helium, gravity, and atoms. When these atoms accumulated together inside the clouds in an organized form, they became the starting point of galaxies inside the universe, which later led to the creation of numerous stars, planets, satellites.

Did you know?

Although George Lemaître proposed the Big Bang Theory based on the calculations of general relativity of Albert Einstein, Einstein himself did not approve it. He regarded the Big Bang theory to be correct in terms of calculations but pointless in relation to the laws of physics.

From the observation of a supernova in 1966, the concept of dark energy was proposed. Dark energy has been described as the accelerating expansion of the universe, causing the separation of one galaxy from another.

From the interactions of the positively charged protons and negatively charged electrons in the universe, the first ray of light that shined through the dark matter of the universe occurred after 379,000 years after the Big Bang, during the cooling epoch.

The oldest rays of light found in the universe date back to 379,000 years after the Big Bang and are what is known as the Cosmic Microwave Background radiation.

While the Big Bang Theory was proposed by George Lemaître in 1927, the name Big Bang was casually uttered by Fred Hoyle on BBC Radio in 1949.

When the question arises about whether the universe will forever continue to expand or not, two alternative theories are suggested, namely the Big Crunch and the Big Freeze.

Contrary to the inflation models, the Big Crunch Theory suggests that if the mass density of our universe exceeds its critical density due to continued expansion over millions of years, a time will come when the size of the universe will reach its maximum.

Thereafter, the universe will again become unstable and begin to collapse and contract on its own.

The Big Freeze theory suggests that if our universe never reaches its maximum and always remains below or equal to its critical density, then it will never contract. But its speed of expansion will certainly decrease.

This would go on till star formation stopped lead and all the stars of the galaxies burned out into black holes, eventually consuming all forms of matter into the black holes.

Another interesting hypothesis is the Big Rip hypothesis. It tells how every matter in the universe, be it stars, galaxies, planets, atoms, or nuclei, will be torn apart due to the incessant expansion of the universe.

The extensive dragging of all these forms of matter in the universe owing to its expansion will eventually lead to the destruction of the universe itself.

The accidental discoverers of the Cosmic Microwave Background Radiation (CBM), Arno Penzias and Robert Wilson were jointly awarded the Nobel Prize for Physics in 1978 for their discovery, which now stands as one of the most valuable observational evidence in favor of the Big Bang Theory.

Although we have deduced and reconstructed the origin of the universe from the Big Bang, we still do not know about the exact shape or size of our ever-expanding universe.

The solar system in our galaxy, the Milky Way, was formed after a whopping nine billion years since the occurrence of the big bang.

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