Dissecting the Bang
This article is a part of a series of articles on Cosmology. This is article 3/4.
In the last article, we talked about the universe, the Higgs Field and the shape of the universe. But an important part in Cosmology is one we haven’t discussed yet. The Big Bang.
What Banged?
If you study the entire Big Bang framework, you will undoubtably have an answer to why is there an arrow of time, why the Universe has evolved the way it has and why there are clusters of dust, some that glow(like stars) and some that consume(like black holes). But one fundamental question the Big Bang’s Framework leaves is What Banged? How did it bang? Why did it bang? The answers to these questions were found long after Georges Lemaître, the one who, from Einstein and Maxwell’s equations, proposed the Big Bang, had ascended to the heavens. The Answer, as we will see, comes from a revolutinary new theory known as Inflationary Cosmology. And the credit for this framework was bestowed upon the force that deserves it:- gravity.
Repulsive Gravity
When originally developing the theory of General Relativity, Einstein was faced with an obstacle. His equations, the ones he was willing to sacrifice his life for, showed that the universe is exapnding. What is wrong with that, you might ask. Well, the consensus among the scientific community at the time was that the universe was static, it was neither shrinking or expanding. To counter this, Einstein took a page out of Maxwell’s notebook. When conditions are prevalent, gravity can be repulsive. Just like when conditions are met( like poles coming togehter), magnets rush away from each other, Einstein argued that gravity, instead of the regularly attracting, pushes things apart. This, he carefully calculated, and found the value to be a constant, and termed it the Cosmological Constant. Years later, when Hubble discovered that the space was expanding, he erased the constant from general relativity, before it made a spectacular comeback in the 1980s. Alan Guth, along with Henry Tye, together, at the Stanford Linear Acceleration Centre, had discovered something amazing. They combined Higgs Field with repulsive Gravity, and the results are stupendous.
Combining the Higgs Field and Repulsive Gravity
Remember our Magnetised Bowl and Ball experiment(if you dont, read about it here)? We are going to use it here. So after combining the equations of relativity and Higgs Field, Guth and Tye arrived at the following conclusion.
When we placed the pagnetised bar on the top, the ball would very much want to go there. But due to the strong repulsive force of the llikely magnetised bowl, the bowl, even when it manages to land on the bar, is immediately pushed away and then into the valley. The same thing happens to the Higgs Field. When it finally perches on the zero value, the repulsive gravity environment omnipresent during the big bang pushes it aside to a nonzero value, and this happens isntantly, in about 10-³⁵ seconds. When they calculated the factor by which repulsive gravity pushes the potential energy of the Higgs Field away, Guth and Tye found a value that was a googol (or 10¹⁰⁰, that is 1 followed by 100 zeroes, and 10¹⁹ times or about a quintillion times the number of particles in the obserable universe!) times larger than the constant Einstein originally proposed. This, short lived, enormous burst of energy, meant that Guth and Tye gave something the big bang was missing- a bang!
Towards Darkness
This model, which was proposed by Guth and Tye is called the model of Inflationary Cosmology. Another aspect of Inflationary Cosmology is to explain why the universe, is expanding. Now, this was proposed originally by Hubble in 1927, but what was of cosensus was that the rate by which it was accelerating away from us, was slowing down, retarding. Well, this was refuted by many astrophysicists at the time, including Fritz Zwicky,(who, was such a pro- symmetry man, he called a coworker a spherical bastard, because he was a bastard from any angle you look at him) who observed that in a number of galaxies, the matter content was not enough to hold the star systems inside the galaxy’s gravitational field to hold them in the galaxy.He hypothesized that there is more matter than we thought in each galaxy, that, does not give off light. This was confirmed by the shocking observation in 1990s, by groups led by Saul Perlmutter and Brian Schmidt, observed the rate is increasing. They proposed that the universe’s expansion was slowing down for 7 billion years ATB, but after that, it has been constantly speeding up. Their calculations predicted something amazing- about 25% of th matter in our universe is not giving off light, and hence, not visible, and the matter we can actually detect, is only about 5% of the total contents of the universe. This has been named Dark Matter and so far the only concreate proof that it exists is how it behaves with gravity. Its like a person stopped to abide by the speed limit at a speed camera trap at a highway, but after passing it, he just went ham and drove like Lewis Hamilton. In the figure below, if the dot is the galaxy we observe, it is immersed in dark matter that is represented by the gray area.
What about the remaining 70%? That is something we consider Dark Energy. This was also given by the groups led by Perlmutter and Schmidt. But, this 70% is a remarkable number. Why? Because of two reasons. Firstly, it means that what we see, is only a meagre 5% of the universe. This observation, expands the Copernican Revolution, not only are we not the centre of the cosmos, we are like a float, in a ocean with invisible floats, and consider ourselves the olnly ones there. The second, more important reason is that the 70%, along with 30% constituted by Dark Matter and ordinary Matter, would meet the 100% prediction made by the original Inflationary model! But, although the progress is very encouraging, the Inflationary Model has not been confirmed, since the predictions about the compostions of dark matter and energy are numerous, we need to synthesize not only instruments that can read these things, but also get dark matter to be visible in the first place, and according to mathematicians, it may take about 80% of the world’s economy.
This is it for this article. Although I have left out many problems that Inflation has solved, (mainly the Horizon and Flatness problems) for the sake of brevity, I highly reccomend checking these links out to understand how Inflation solved these problems, and how they were Problems in the first place!
Horizon Problem:- 1)https://en.wikipedia.org/wiki/Horizon_problem
2) https://www.cambridge.org/core/books/structures-in-the-universe-by-exact-methods/horizon-problem/4F247515052F48C53F0816EB0E9CAE20
Flatness Problem:- 1)https://en.wikipedia.org/wiki/Flatness_problem
2) https://astronomy.swin.edu.au/cosmos/f/Flatness+Problem
Thank you for reading! I hope you learned something new and Enjoyed it!