Human beings have gazed at the stars with a massive dose of curiosity, awe, and interest from the beginning of time. Considering the vastness and complexity of the Universe that we have found ourselves in, this is understandable. Primitive humans could not unlock the secrets of the Universe, but that did not stop them from appreciating it.
By paying close attention, primitive humans noticed the predictability of the celestial bodies’ movement like the moon, sun, stars, and others. As science improved with time, humans started to develop a much deeper understanding of the cosmos. The more the scientists discovered, the greater the sense of awe, amazement, and wonder.
The Big Bang
From what was a mere fraction of an inch, the Universe has transformed into a structure of unfathomable dimensions today, and it all started almost 14 billion years ago with the Big Bang. Even though it is called a bang, the Big Bang was not an explosion that happened in space, but an appearance of space in every part of what we now call the Universe and that is the consensus of scientists. The Big Bang Theory holds that the birth of the Universe was an extraordinarily dense and indescribably hot, single point in space.
Astrophysicists have not explained what happened before the Big Bang precisely, but they have been able to give an excellent and increasingly more precise picture of how the Universe came about, and how it was formed.
They have been able to do this due to complex space missions, advanced physics calculations, and ground-based telescopes in different parts of the globe. It has been a costly venture with billions of dollars spent on the research, but it has been worth it.
The Very Early Universe
At the beginning of time, the conditions and the energies present were so complex and extreme that even modern physics could not fully explain what happened shortly after the Big Bang. However, that has not stopped the scientists from trying their best to explain, and one such is the eternal inflation theory.
This theory holds that inflation continues perpetually across the Universe, but no one is certain entirely. So, even in the 21st century, physicists are still attempting to have a complete and comprehensive understanding of what happened moments after the Big Bang.
The Early Universe
Following the end of the cosmic inflation, the Universe became filled with hot quark-gluon plasma left behind after reheating processes. From this stage on, scientists have given a better and more explicit explanation of what happened. Hence, they can access and study the energies that dominated the Quark epoch using sophisticated detectors and particle physics experiments.
The Dark Ages and Emergence of Large-Scale Structures
The Dark Ages in this context is a reference to 370,000 to around one billion years following the Big Bang. Following the recombination and decoupling processes, the Universe became transparent and sufficiently cool for light to travel vast distances.
However, there were no giant structures like the galaxies and stars that produced light in this period. The formation of galaxies and stars resulted from gravity, which influenced the dense zones of gas. The estimate is that stars did not appear for hundreds of millions of years following the recombination process.
During the Dark Ages, the temperature of the Universe plunged to around 60K from 4000K. In this period, there were just two sources of photons. These were photons produced from the recombination and decoupling processes, and these can still be detected as the well-known cosmic microwave background (CMB).
The second source of photos happened to be the neutral hydrogen atoms. In about a few hundred millions of years following the Big Bang, the first set of stars were formed – they were called the Population III stars. These stars were the early sources of visible light anywhere in the Universe following recombination.
Galaxies, Clusters, and Superclusters
Astrophysicists have calculated that structures might have started forming around 150 million years. The early galaxies were created in the period from 380 to 700 million years. The emergence of these first stars triggered the gradual decline of the Dark Ages.
As the process continued, the Dark Ages dragged on until about one billion years, and it was at that time that the Universe adopted the appearance that it has today.
The formation of the galaxies, clusters, and superclusters depended on the matter. Matter became aggregate under the influence of the force of gravity, and this led to the formation of galaxies. As hinted above, the stars of that period were collectively called Population II stars, and those of the Population I category came later.
With time, gravity continued pulling the galaxies together to form groups; these groups are referred to as clusters and superclusters, depending on the size. Observations of the Hubble Ultra Deep Field have led to identifying some small galaxies aggregating to create bigger ones that are still being observed.
To date, scientists are still observing these galaxies in a bid to unravel their deepest mysteries. Of the earliest galaxies formed, just about ten of them are known at present, but it is hoped that more will be revealed with time.
It will interest everyone in knowing that the appearance of the Universe as it is today has been like that for billions of years. The fact that it will maintain the same appearance billions of years into the future is even more fascinating.
Today, scientists understand that dark energy dominates the Universe so much so to the extent that dark energy is considered to be the single largest component in the Universe. It is so vast that it makes up almost 70% of the physical Universe. As astrophysicists keep working day and night to unravel the mysteries of our Universe, our sense of wonder and awe will never end –it has always been like that since the beginning of time itself.