How did the universe come into existence? The singular answer that pops in the heads of pretty much everyone on the face of the earth is “The Big Bang Theory.” It does not take a scientist to be aware of this term, with a lot of the present generation having a very (note the term “very”) brief understanding of the big bang theory thanks to the opening theme of the popular television series of the same name.
For those of you who have forgotten (we understand it isn’t the easiest thing to remember), the theory states that the universe started as an infinitely small, dense point called a singularity. All of a sudden, within a trillionth of a second, it expanded rapidly at a rate faster than the speed of light forming what we know as the universe today. The universe is unbelievably vast and carries an enigma of the same magnitude making any theory related to it, only ever partially correct. While the big bang theory is the most widely accepted one of them all, scientists have always known that it certainly isn’t entirely accurate. So what caused the birth of the known universe?
A possibility is being considered where a singularity probably never existed in which case the universe grew at a far more comprehensible speed than originally assumed, relatively speaking. Relative to what you ask? It is now believed that expansion had happened before the big bang, thus proving it to not be the starting point. Before we move on, let us understand the justification leading to the inception of the big bang theory.
This theory was proposed by a priest and astronomer named Georges LeMaître in the 1920s when scientists realized that the galaxies at the farthest points were moving away from us faster than the closest ones. This suggested the possibility that it’s not the galaxies that are moving, but the universe that’s expanding. From an expansion point of view, it is quite easy to visualize an expanding object to have been at its smallest at some point in time. The same was applied to the universe, rising the phenomenon of a singularity to have been the most probable starting point.
Building on the theory of expansion, we understand that light stretches as well. The galaxies at the farthest end are red-shifted, meaning their light wavelengths have stretched out and headed for the red, lower-energy end of the electromagnetic spectrum. A very important conclusion that can be drawn from this is the fact that everything started out with higher energy in the past making the universe awfully hot at that point of time.
Many examples exist in this very universe today that substantiate the same. To name a few, let us talk about the plasma soup that created the young universe. We also have a fairly good understanding of what those particles have merged into, which coincides with the exact ratio of particles we see in the universe today. We also see traces of proof in the form of the weak, super-stretched leftover radiation that makes up the cosmic microwave background.
Everything seems to be falling into place, right? Well, not really, as is with anything to do with this mystery of a universe. Let us now dive into the deviations that question the accuracy of this theory. The cosmic microwave background proposes the idea that the universe is flat, which contradicts with the whole big bang expansion theory calling for the universe to be curved. Secondly, everything in the universe seems to about the same temperature. Finally, it is believed that the proposed big bang should have produced mega high-energy particles called magnetic monopoles but none of them has been found or traced yet.
These deviations from the popular theory lead to the proposal of the inflation theory that discusses the birth of the universe to be a result of the fluctuations in the void of space. The basis behind this new theory is a quantity called vacuum energy. We understand that no matter of radiation existed before the big bang as per the inflation theory. That being said, a vacuum is still full of energy as a result of the pairs of quantum particles that constantly blink in and out of existence.
This resultant energy led to the exponential expansion of the universe enlarging it by a factor close to 1026 in a fraction of a second. This expansion caused fluctuations in the vacuum energy leaving the fabric of space uneven. This essentially means that random spots existed where the energy density was slightly higher or slightly lower than average. Eventually, all that energy decayed into matter and radiation.
The inflation theory fixes a lot of the holes in the big bang theory. It works with a flat universe and the rate at which it happened allows for uniformity in temperature (one of the variations in the big bang theory) as it suggests the possibility that every point in the universe might have once been in contact. Inflation also says that magnetic monopoles may have existed prior to expansion, but their density would have plummeted to insignificant levels afterwards.
What’s more, the fluctuations in energy provide an excellent theory as to how galaxies and stars are formed. Humanity, as we know it today, came into spectacular existence due to those seemingly random clusters of energy, so before we look into the big bang as the mother of all existence, we might want to look closely into the hidden dawn of the universe.