Starting from the very beginning – inflation and inflatons

What is the beginning of the beginning of the beginning?

A few months ago, I had an engaging, yet extremely infuriating conversation with my friend Joey. He asked me, what came at the beginning, at the very beginning? Well, apart from the initial bewilderment at the ineptitude of the question, I cast my mind back to the beginning of my day. Perhaps he was asking about the fruit bowl I had for breakfast, or my train journey to work. I explained my morning to my friend, who scoffed at my response.

He even let out a “Pfft.”

“What, my answer not good enough for you?” I replied angrily.

“No, it’s just that I asked you about the beginning and you told me your morning routine.”

“Mate, can you be a bit more specific?? What the hell even is ‘the beginning’?”

“The beginning of life!”

“Oh, so now you want a biology lesson?”

“I said the beginning of life, not the beginning of your life!”

Appalled, I left the room.

The heated exchange, however frustrating, gnawed at me persistently. As I walked back home, I thought back. Like, way back. Countless history lessons from high school date back to 10,000 B.C. where developments in Africa and Eurasia were the headlines. But then I started thinking, what came before recorded history? Before all the dinosaurs, before any life? And what came before that? And what came before that before? And what about the before before the before before the before?

My head started spinning. I took a seat on the sidewalk nearby, trying to make sense of the epiphany I’d just had. I decided to take a dive headfirst into the depths of the universe, vowing to uncover the mysteries of the origin and pledging to have an answer to the seemingly dumb yet infinitely profound question Joey had asked. The following is my journey through time, and my attempt to figure out what came before the chicken and the egg.

Let’s start from the very beginning. The beginning of all beginnings. What was there when there was nothing? How was something born out of nothing? How did the ‘something’ grow when surrounded by nothingness? These aren’t just philosophical ramblings, but prudent inquiries that cosmologists spend their entire careers investigating. Cosmology is a branch of science which probes into the mysteries of the origin of the universe, what came after the bang and, more intriguingly, what came before it. Cosmologists are agents of this branch, championing their cause for finding science behind the unobservable proceedings.

How exactly can anyone answer the question Joey posed when the answer lies 14 billion years in the past? Well, the answer, according to inflationary cosmology, lies in the 10^(-35) seconds that preceded the big bang.

Yes, for 10^(-35) seconds before the big bang, out of a dense black hole spewed our universe. And in this time frame, the universe fanned out, spawning multiple galaxies making up countless solar systems and consisting of billions of stars. Then, after these first 10^(-35) seconds, the expansion stopped. Our universe stopped fanning out and ever since, has been expanding but at a minuscule rate. What followed this period, which we call inflation, was the standard big bang that we know of. Most of the galaxies have stayed in the exact same spots for the 14 billion years that followed.

Why did it slow down so drastically? Well, very simply, it’s because of gravity. Gravity is (primarily) attractive, which means it sucks objects nearby towards each other. Thinking about how your feet are attracted to the ground supports this claim. This discovery, made in the 18th Century, can be credited to Newton. Now, it’s not very clear whether the whole story of ‘the apple that fell on his head’ is true or not. But if there’s one thing we can say with certainty it’s that something (yes, maybe an apple) did lead Newton to describe the effects of gravity and how it’s an attractive force.

In fact, the discovery of gravity catalysed the discovery of the gravitational field which is one of the four main classical fields of physics. We’ll get to the other three in due time.

But if gravity slowed our expansion down, why wasn’t it there during inflation? To answer this, we first have to visualise the fact that inflation, this phenomenon that supposedly lead to this vast universe we have, originated from a dot, near the size of a speck of dust. Now imagine our entire universe (with billions of galaxies) compressed into this minuscule dot. Imagine the billions of stars in the billions of galaxies, now squashed into a shrunken tennis ball. All this leads to an extremely hot and dense state. For reference, temperatures are estimated to have reached up to 1000 trillion degrees Celsius at this point in time.

In this state, gravity too was clumped together, which lead to the birth of particles known as inflatons. These inflatons have one distinct property: they have what a non-scientist would call ‘negative pressure’. Think of it this way:

If I exert some pressure onto a tennis ball, forcing it to the ground, I am applying ‘positive pressure’ onto this ball. Gravity is the usual universal attractant which acts as this ‘pressure exerter’, pinning the ball, and everything else, to the ground. Instead of this positive pressure, now imagine the result of me extending ‘negative pressure’ onto a ball. Well, as logic would dictate, this negative pressure un-restricts the ball, in that it frees the ball of any limiting pressure that may be exerted on it.

Extrapolating this analogy by replacing the ball with our universe, you can see that gravity would cause positive pressure onto the universe, causing all its constituents to clump together. During inflation however, these inflaton particles exerted negative pressure. This caused all matter in the universe to spread out, thereby causing an expansion which resulted in the universe we know of today.

As it expanded, the universe also started to cool down (since everything wasn’t in such a hot, clumped-up mess). As temperature dropped, gravity started to exert its ‘positive pressure’, slowing down the expansion of the universe drastically.

And voila! We have the universe as we know it! Pretty simple, right? Well, no actually. While the non-scientific explanation I just provided does explain how inflation occurred and why it stopped, what we must be careful of is that all of this, in truth, is hypothetical.

Since we can’t peek back 14 billion years ago, all we have are theories. A theory might need countless agreements through experimental results to be proven, but only needs 1 dissimilar result to be disproven. Even the big bang theory is, in the end, a theory.

The inflaton particles I mentioned exist in the realm of quantum field theory (which I will delve into in a later post). They are hypothetical and therefore, require large assumptions.

As anti-climatic as that may sound, we still can’t discount the possibility of what I described as having actually happened. Cosmology is a field with constant ongoing research only boosted by innovations in quantum computing which allow for large-scale simulations of a time non-observable.

We’ll never be able to answer Joey’s question with absolute certainty, but we can get really bloody close to.