The Big Bang Simplified

From exploding misconceptions to the mystery of spacetime itself, this mind-bending Big Bang breakdown takes you deep into the universe’s earliest moments Discover how space expanded faster than imagination, why time began here, and what scientists still cannot explain today.

Introduction

You may have wondered some questions in your mind like was the universe always like this as it is today? (vast, filled with the galaxies, the stars etc.). Or did this stuff come from something? What was that? These questions are the ones that make us curious about our universe. So there is the widely accepted theory which you guys I believe have heard of the Big Bang theory. In this blog, I am going to start from the very basics about it and help you guys try to create a better intuition about it, because there are some misconceptions related to it.

Understanding the Big Bang

The Big Bang states that our universe began about 13.8 billion years ago from a very hot dense state, it later cooled down and then matter started to form. What do I mean by hot dense state? Let me break down clearly, so right now (not only now but for the first time it was observed by Edwin Hubble through his Hubble telescope) the scientists are observing that the universe is expanding and the distances between the galaxies is increasing but the galaxies aren’t moving away. That means the space you see all around is stretching and they call it Dark energy for its cause**(which is something different, a sort of mysterious force)**.Now if we try to imagine our universe in the past, the universe becomes smaller and smaller, the distances start shrinking and the universe becomes more and more dense, parallel to it the temperature also rises up and thus there is a magnificent increase in the density.

So it’s like you take a balloon and then you mark some dots using a marker on its surface then fill it up and during filling it you will notice the dots are separating from each other and what really is happening is the surface between the dots is increasing. So what if you took out all the air from the balloon, the dots you marked will come closer. Same applies here, the universe becomes so dense and hot (not suitable for the particles to exist) that it reaches a mathematical limit called the singularity. We’ll come to the singularity later.

Big Bang: Was it an explosion or something else?

Most people think that the big bang could have been an explosion somewhere in space, where all matter was concentrated. But we know now this intuition is wrong: matter couldn’t exist at that much of the temperature and at that infinite density. So the Big Bang isn’t an explosion rather it was the expansion of spacetime itself from the singularity and spacetime(the 3 spatial directions and time which are one as per the General Relativity)is still stretching all over.

The Cosmic Inflation

Now you may question how fast the spacetime expanded during the Bang Bang 💥?For this I need you to imagine that balloon again. For this you take an empty balloon but fill it up so fast (more than the limit of balloon) that in just 2 or 3 seconds the balloon stretches fast and explodes. From this, we can imagine the singularity or that mathematical limit as The balloon before filling it up and then we can imagine the rapid expansion of the balloon as the space expands extremely fast. This is a simple analogy explaining how fast space had expanded when the big bang happened.

So this states that the space expanded from the subatomic size to very large cosmic size in just a tiny fraction of a second ***(around 10^-36 or10^-32 seconds).*The universe is still expanding out there…**I know this sounds crazyyy!! But I need you to give yourself a minute and imagine how fast the space expanded there. You may think I was mentioning spacetime, so what about time? You see, time itself started with the Big Bang.

MISCONCEPTION: So most people ask this question, “What was before the Big Bang?” .The question doesn’t make any sense because as I told you the time itself started with this rapid expansion, so there is no ‘before’ but is indeed the ‘after’ .Right now I know there would be a lot of questions coming to your mindlike what caused the Big Bang, did the universe actually come from nothing etc. As you know we covered some good stuff till now and If I started to talk about it, this will take us forever. Instead we will focus on some other things now and I’ll try to cover some of these in the upcoming blogs. Also I don’t want to keep it too heavy in the very first blog.

The Big Bang Singularity

As I said, if we imagine the time to reverse, the universe starts to come closer and closer, the distances shrink down, the density increases and the temperature also increases. There comes a point where our equations stop making sense like they show infinite density. How does it show infinite density? So we know density = mass/volume so if we go on and on squeezing the universe, the volume decreases or even maybe the concept of volume vanishes at the singularity. It also shows infinite temperature and it’s impossible for the particles to exist there. Atoms, nuclei, protons, neutrons, etc. can’t exist at that enormous temperature. So in short the universe reaches its limit where equations stop making sense and that mathematical limit is what we call the singularity. Now you understand how the universe began from a dense hot point…

The SpaceTime

Spacetime can be defined as it is the 4 dimensional continuum which is affected by matter and energy. Space is like an arena, where things, objects are present like planets are present in space. The space comprises x-axis, y-axis and z-axis and the most important thing is that it is a physical thing, like a fabric which can stretch and squeeze (as per the general relativity). The time (t-axis) on the other hand is considered a Dimension in higher physics which is relative.

You can understand it like time is what measures, and space is where things happen and these are two bounded things. Now… There is the Quantum fluctuations that proposes that spacetime emerged from these tiny fluctuations and this led to the rapid expansion of space and the sort of creation of time and hence the Big bang took place.

Conclusion

In this blog, we understood the Big Bang in a different and better way and I tried my best to get those misconceptions out. I explained it through examples and I took you guys to the very mathematical Limit where our equations stop making sense. I hope you understood this well and now you can tell someone what exactly is The Big Bang all about. In the upcoming blogs, I will cover the questions like what caused the big bang? Is that the quantum fluctuations? Topics like CMB and how the particles formed after the Big Bang and many more in this cosmic journey… Till then take care.