The Greek creation myth, preached by Hesiod, states that “In the beginning, Chaos reigned. And Chaos gave birth to Gaia, Tartarus, Eros, Erebus, and Nyx. They then created the heavens, the days, and the seas.” But today, as scientific enquirers, when we look up into space and wonder- What are those shiny objects? Are there anything else other than stars? How are these stars formed? And the most important question that arises in our mind- Why is the space so beautiful? It’s hard to answer the last question because its beauty has evolved over the past 13.7 billion years. Well, why 13.7 billion, you ask? That’s when our universe began, and that’s when ‘Time’ started ticking. We will now be looking into how this universe began and what happened 13.7 billion years ago.

BANG! BANG! BANG!

Our universe, as we know it now, was just a point of infinite, dense mass. When the clock started ticking, a trillionth of a second later, this point mass had expansively exploded faster than the speed of light. The sudden death of this expansion, now recognised as cosmic inflation, led to reheating, i.e., at about 10 billion degrees Fahrenheit, our soup of a universe consisted of the raw materials required to build all our stars and galaxies—everything that exists today.

E=mc² , the equation that made Einstein famous, equates energy with matter. But until 380,000 years after the Big Bang, there was no concept of energy or mass. The universe was so hot and dense that matter and energy (photons) were tightly coupled. The universe was essentially a dense, hot soup of particles and radiation, and photons would scatter off charged particles such as electrons and protons frequently, making the universe opaque to light.

As the universe started to cool, the electrons started to combine with the protons to form hydrogen atoms, finally setting the photons to be free. This process is called recombination. Once matter and radiation decoupled, photons were free to travel through space without significant scattering.

Red spot Blue spot

Wilkinson Microwave Anisotropy Probe (W.M.A.P) was a spacecraft that measured the radiant heat remaining from the Big Bang. The data collected by WMAP, played a pivotal role in establishing the Lambda CDM model, which is the current model of cosmology. The age of the universe according to this model is roughly around 13.772 billion years, with an expansion rate of 69.32 (km.s^-1)Mpc^-1.

The collected data shows that the universe currently consists of 46.28 % of ordinary baryonic matter, 24.02% of cold dark matter (that neither emits or absorbs light) and 71.35 % of dark energy.

Cosmic Microwave Background

Before the discovery of Cosmic Microwave Background, there was no proper evidence for the Big Bang theory. The discovery of CMB radiation was an accident. Two radio astronomers, Penzias and Wilson, were given the task of designing a super-sensitive 6-metre horn antenna in order to detect the radio waves bounced off of Echo balloon satellites. They tried to remove all the radio and radar noises, along with the heat signatures, to make it super sensitive. When they finally observed the result, to their surprise, they found a particular noise that was 100 times stronger than they expected. This noise was steady and was found during winter, summer, spring, and all 365 days of the year. At the same time, there were three other scientists who were on a search for microwave radiation in the same spectrum.

Since the universe began, which is when the big bang happened, there have been neutrons and charged particles along with photons. These electrons interacted closely with the photons, and hence, these photons could not escape the electron’s capture. The light particles were trapped and could not travel for a long distance without interacting. This was the reason the universe was kind of opaque. It took our universe around 300,000 years to cool down (around 3000 °C), so that these charged particles formed atoms and then molecules. Due to this, the light particles finally became free and were able to travel throughout the universe. This first ray of light is what we call the cosmic microwave background.

The universe has been expanding, stretching, and cooling itself. Since light can act as a wave, it was also stretched along with this expansion. As a result, it has lost a huge amount of energy falling under the microwave part of the spectrum. A question might arise: was there a time when these cosmic microwave background waves were small enough to be seen by our eyes? Just imagine, the huge amount of energy released during the birth of the universe could be seen through our own eyes. Sadly, it is not possible! CMBs are literally the first rays of our universe. It depicts the beginning of our universe; before these cosmic rays, the universe was opaque and hence could not be seen. The nature of the early days of our universe remains a subject of much debate.

The Cosmic Microwave Background is like the biggest telescope through which you can see the border of the universe, if one exists. Due to this amazing discovery, Penzias and Wilson were awarded the Nobel Prize in the year 1978 in Physics. These scientists sealed the approval of the big bang theory with their discovery.

Cosmic Microwave Background provided essential backing for the hypothesized Big Bang theory, making it the most widely accepted theory regarding the birth of the universe. This theory can explain all four fundamental forces in nature. But there is one reason why the big bang theory is still not approved by everyone: In the standard model, with the help of 17 fundamental particles, we can explain every physics behind it, except gravity! There is a lot of research going on in that field to combine gravity into the standard model of particles.

There is another theory on which scientists have been fantasising, called “String Theory.” According to this theory, every single particle in the standard model is made up of strings, which can then be combined to form atoms and molecules. But this theory is still a big IF, considering a lot of things have yet to be proven for it to be accepted.

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This article is a contribution from the Astrophysics Club (Dhruva) of Rashtreeya Vidyalaya College of Engineering (R.V.C.E.), Bangalore. And the authors are:

References:

• NASA
• ESA
• The Collector

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