What is the Big Bang, and how did the Universe Begin?

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One of the noblest questions humanity has ever put forth is, “how was the Universe created?” Perhaps unsurprisingly, the most generous answer to such a question is “we do not know.”

Throughout humanity’s history, many creation myths and scientific explanations strived to offer an answer, but in our current era, one theory seems to stand above all, the Big Bang Theory.

Through this article, we hope to answer some of your questions, such as:

  • What is the Big Bang theory?
  • What happened after the Big Bang?
  • Who came up with the Big Bang theory?
  • Who named the Big Bang theory?
  • What are some of the paradoxes/mysteries of the Big Bang theory?

Before we dwell into these questions, let us give you some background regarding how little and how much we know about our small world and consider this, we only know that we live in a vast Universe for less than 100 years.

The Big Bang Theory
Credit: NASA

How did we find out that we live in a Universe?

Our Earth is one out of billions of billions of planets in the Universe, and the same goes for our star, the Sun. The ancient Greeks and Indian philosophers developed the earliest cosmological models of our world [1].

These models were geocentric, meaning that they placed the Earth in the center of the world. However, this changed when astronomer Nicolaus Copernicus developed the heliocentric model in 1543, which put the Sun in the center [2].

Based upon his contributions, the famous physician, Isaac Newton, developed the law of universal gravitation/attraction. His observations stated that every particle attracts other particles with force based on their mass/weight[3].

The German and Danish astronomers Johannes Kepler and Tycho Brahe built upon these works. They established the laws of planetary motion while the Italian astronomer, Galileo Galilei, pioneered the use of telescopes [4].

Galileo discovered the conglomeration of stars in our Milky Way galaxy, the moons of Jupiter, and thus undermined the idea that everything revolves around Earth. Studies and observations caught up, and humanity realized that there are more stars and planets than one could count.

Photo for the space
Credit: NASA

The second galaxy


For many years we believed that our galaxy was the equivalent of the whole Universe, with clouds of nebulas around it. However, one of these nebulas was particularly interesting due to its brightness.

It was called the Andromeda nebula, and it has always been visible to us even while looking at it with the unaided eye. When modern telescopes appeared, an astronomer by the name of Edwin Hubble intensely studied the Andromeda Nebula, and in 1923, he concluded that this nebula was, in fact, another galaxy[5].

Hubble continued his observations and discovered many other galaxies and devised the Hubble sequence – a system of classification for these celestial objects based upon their morphologies. Thus, this was the beginning of our understanding of the true vastness of our Universe. 

Hubble’s findings proved that our galaxy is just one out of many others in the Universe. His discovery is practically the beginning of the Big Bang theory. Still, it was not Hubble who devised the thesis, but rather, his findings influenced others to theorize upon the Universe’s creation.

Andromeda Galaxy
Credit: NASA

What is the Big Bang theory?

Hubble concluded that objects were moving away from Earth. This remark is now known as the Hubble constant. Celestial objects are not only moving away from us, but they are doing so faster than the speed of light, which should be theoretically impossible[6].

Because of this observation, we realized that space is expanding, and it continues to do so to this day, which is one of the bases of the Big Bang theory.

Though objects cannot move faster than the speed of light, space itself is not susceptible to these laws; thus, space itself is expanding. Apart from this, the Big Bang theory states that the early Universe was a scorching place[7].

In the first stages of the Big Bang, everything was compressed into one incredibly dense point, which was smaller than an atom. Something caused this unfathomable small object to expand at incredible speeds suddenly. The expansion itself is often confused with an explosion, but it wasn’t an explosion[8].

The expansion of the universe
Credit: NASA

Since this expansion started, the temperatures began to cool down. This cooling down meant that the Universe should be uniformly filled with radiation if the theory was plausible. The speculated radiation was indeed discovered and was later named as cosmic background radiation[9].

This residual glow can be seen on old analog TV’s. If you turn the TV between channels, the screen will be filled with black and white specks, and around 1% of them are caused by photons that have remained since the inception of the Universe.

Two significant stages followed after the Big Bang: 

  • The Radiation Era
  • The Matter Era

What happened after the Big Bang?

After the Big Bang occurred, the two stages named the Radiation Era, and the Matter Era helped in the shaping of our Universe [10]. These stages are themselves devised into different epochs. The Radiation Era is designed in 8 epochs:

  • Planck Epoch
  • The Grand Unification Epoch
  • The Inflationary Epoch
  • The Electroweak Epoch
  • The Quark Epoch
  • The Hadron Epoch
  • The Lepton and Nuclear Epochs

• The Radiation Era

The epochs in the Radiation Era, summarize the process in which gravity was created and broke off from other forces of nature. Besides gravity, the other forces, such as strong nuclear, weak nuclear, and electromagnetism, also broke off. Before this, it was believed that all these forces were part of one another.

Particles such as quarks formed but couldn’t undergo the formation of subatomic particles due to high temperatures. After the temperatures dropped, quarks were able to bind together and form protons and neutrons.

Protons and neutrons fused and created nuclei during the last epochs. This fusion led to the creation of the first chemical element in the Universe, helium. The ability to form elements, thus ended the radiation era and gave way to the Matter Era.

• The Matter Era

The matter era features three epochs, with the last one, the stellar epoch, being the one we are currently living in.

  • Atomic Epoch
  • Galactic Epoch
  • Stellar Epoch

After the Universe further cooled down, electrons were able to attach themselves to nuclei through the process of recombination. This attachment led to the creation of the Universe’s second element, hydrogen.

Now that hydrogen and helium were present, the Universe was slowly painted with atomic clouds. These clouds contained small pockets of gas, and gravity may have been powerful enough for atoms to collect.

These clusters of atoms became the seedlings of galaxies. The first stars began to form, but they were very massive and ended their lives very quickly. Through events such as supernova explosions, elements created in the primary star’s cores were blown into the Universe, leading to the creation of more stable stars, moons, and planets.

The Matter Era
Credit: NASA

Who came up with the Big Bang theory?

Based upon Hubble’s works, an astronomer and Catholic priest by the name of Georges Lemaître, proposed in 1927 an expanding model for the Universe. He also based his works upon those of Einstein and De Sitter[11].

Hubble and Milton Humason formulated in 1929 what is today known as the Hubble Law. It was the first direct proof that the fabric of existence was itself expanding and, thus, the concept of the expanding Universe.

The law itself stated that the higher the distance between two galaxies, the greater their relative speeds of separation. The discovery later resulted in the formulation of the Big Bang model. After this was proven, Lemaître proposed in 1931 the “primeval atom” hypothesis.

He believed that the Universe began with the expansion of this primeval atom and thought that cosmic rays were the remnants of this event. These remnants were later dismissed; however, the presence of cosmic background radiation took up the role of the real relic of the early Universe.

The expansion of the space
Credit: NASA

Who named the Big Bang theory?

Though Lemaître and Hubble can be the most credited for the theory, they didn’t have the chance to name it. The naming happened randomly during a radio broadcast in 1949 when astronomer Fred Hoyle, the creator of the Steady State theory, referred to Lemaître theory as “the big bang idea.” As such, the name stuck out of convenience rather than anything else.

What are some of the paradoxes/mysteries of the Big Bang theory?

The fact that our Universe is expanding is in itself a bit frightening. However, something is accelerating this expansion. This force is known today as dark energy, and it permeates all of space.

We can only see 4.9% of the visible matter in the actual Universe. The other components, such as dark matter, represent around 26.8% of the world, while dark energy constitutes approximately 68.3%.

Both dark matter and dark energy are an invisible theoretical matter which we currently have little information about. These invisible types of mass have their existence proven only by certain phenomena, which only tells us that vast chunks of matter are missing [12].

The Dark Matter
Credit: NASA

Though the Big Bang theory seems to have many substantial areas covered with undeniable facts that have and can be proven, many things remain uncertain or clouded in mystery. Throughout most opinions, the Big Bang stands above all in its completeness. It will continue to be our best explanation for the creation of the Universe for a long time as we continually fill in the missing information.

Did you know?

– The Universe doesn’t have a center, and its shape is still widely disputed to this day.

– The theory known as the Big Freeze, states that the Universe will continue to cool down as it expands. Thus, all life will cease to exist.

– The Big Crunch theory states that the world will expand up to a point after which everything will re-collapse and possibly create another Big Bang.

– Many theorists believe that our Universe is but one out of several disconnected worlds, collectively denoted as the multiverse.

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