Who are we? - A question from a physicist
Who are we? Where do we come from? Archaeologist, priests, biologists, philosophers, and even physicists ask this question. I am a physicist, and we consider the night sky our answer book. We have billions of stars, planets, galaxies and dust clouds all in varying sizes and matters. From our solar system to the Milky Way, to the Black holes, each is originated from the one epic event that happened 13.8 billion years ago, the birth of our universe – an event we called the Big Bang.
This ground-breaking theory was not suggested by the genius Albert Einstein, instead, this idea was raised by a Belgian priest and cosmologist Georges Lemaître later in 1927, who took reference to Einstein’s theory of general relativity - how gravity causes space and time to bend in the universe - and proved his prediction of the expansion of the universe through his own observation of the night sky. He later boldly proposed that the universe must have originated from a fraction of an inch, where all particles and energy are in an extremely dense and compact circular point.
The First atom formed
Since everything is so squashed, the surrounding temperature of this tiny universe was about 10^32 Kelvin. It was so hot that matter and energy were not just theoretically equivalent, they were practically the same thing. Energy was in forms of small particles named gluons, which will decay and react with itself during the process. This enormous amount of energy then spit into the four forces we always deal with nowadays, strong nuclear force, electromagnetic force, weak nuclear force and gravity acting on matter. As time passes, the universe expands, temperature drops, and allowed particles neutrons to decay into a proton and electron. This produced the first-ever atom – Deuterium, an isotope of Hydrogen.
Too hot to Shine
However, at about 380,000 years after the Big Bang, the universe entered a dark age. This is because there were no stars formed at that time and since the temperature was still very high, the atoms possess a vast amount of energy which lead to self-destructive collisions. Atoms were very unstable. Even if there was light, it will not be able to past through the plasma of protons, neutrons and electrons and will be scattered into fog. It took a few more hundred years until matter is cooled enough for the recombination of atoms, allowing the universe to become transparent and light to pass through.
Finally, roughly 400 million years after the Big Bang, the universe stepped out of pitch-black after the first star is born. It is a process which has lasted for more than half a billion years, when clumps of gas collapse and draw towards each other by gravity, forming stars and galaxies. In modern times, according to the observable universe, astronomers have suggested an estimate of two trillion or more stars present, more stars than all the grains of sand on planet Earth. The Sun, the closest star to us, was formed 4.5 billion years ago, while our home galaxy, the Milky Way, was formed 13.6 billion years ago, and has an estimate of a billion stars.
Will the universe expand forever?
Before the 1990s, physicists believed that gravity would slow down the universe’s expansion and the universe will reverse and go back to a tiny ball sooner or later. They also suggested that the universe would keep on expanding forever.
Since then, technology has improved, and astronomers are now able to tell that the universe is expanding and is speeding up. They call the mysterious force Dark energy which they believe makes up 68% of the universe and is causing the inflation of the universe balloon at an ever-faster rate.
Furthermore, physicists predicted two outcomes with the acceleration: either light from other are no longer able to reach us causing a big freeze, or the violent acceleration rips apart all matter and trace of anything that ever existed.
Evidence of the Big Bang
The discovery of the cosmic microwave background in 1964 was by two Americans, Robert Wilson and Arno Penzias. They were originally planning to detect a circular range of hydrogen around the Milky Way. However, they have always detected a faint hum no matter when and where they point the antenna (a super radio sensor).
During the year of trial and improvement, the researchers once thought pigeon droppings caused the anomaly, and later sent the pigeons away. However, they came back and started to nest inside the instrument again and eventually, the birds were shot to keep them from nesting in the antenna.
Obviously, the hum is now known as the cosmic microwave background, which can also be interpreted as the humming of the Big Bang. It was unleashed at the time of “recombination” of atoms after the universe becomes cooler and transparent.
How do we know the Big Bang happened 13.8 billion years ago?
Today, scientists use Albert Einstein’s relativity and the actual expansion rate of the universe – known as the Hubble constant – to work backwards to determine the universe’s age.
The expansion rate is calculated using the cosmic microwave background using the Planck space telescope in 2013.
Is the Big Bang really the start? If not, what happened before the expansion?
The Big Bang theory might have answered a lot of questions, but also have created more such as this question. Our universe is actually a 4-dimensional space and time is one of the vectors. When the explosion happened, time began. Some may say the explosion started the clock while others believe that the Big Bang was not the start – the universe shrunk into the tiny particle and is now expanding again.
Conclusion
The construction of the world we know interspersed across billions of years and gradually formulated into a planet perfectly designed to host and provide for us. While scientists have developed countless theories and investigations as to how the universe was formed, what we know is comparable to a grain of sand in the Sahara Desert. Yet this ambiguity and limitlessness are precisely what constitutes the beauty of our universe.
