From Order To Chaos
Time, we hardly notice it’s existence. Unless you’re in a hurry and time seems to be racing away, or when you’re bored and time doesn’t seem to be moving forward at all. But do we ever give a second thought about the existence of time, what really is time, and why it behaves the way it does?
Imagine a glass, falling from a table and shattering into pieces. It seems ordinary enough, doesn’t it? (well, shattering glasses is not a thing that happens on a daily basis, but still…). Why does it happen that way? Why does the glass result in broken pieces and not the other way around? Broken pieces of glass forming a glass to sit on a table sounds pretty strange (unless you’re into fantasy).
If you film the above scenario and play it forwards and backward, you’d be able to tell what really happened and what’s the reverse. It’s pretty much common sense because we all know that’s how it is. Broken pieces do not turn themselves into an unbroken perfect glass. It just does not happen! But why? Why does it happen that way and why do we KNOW that it happens that way?
It’s all got to do with the “Arrow of Time”. It describes the irreversible changing of everything in the universe. Arrow of time is the concept that describes the asymmetric property of time. Simply put, it describes how time has only one direction. It explains why the future is different from the past, why we remember the past and not the future.
The difference between the past and the future is specifically termed as the “Psychological arrow of time”. It is the direction in which we FEEL time passes (that is, from past to future), but this particular arrow of time is not what we’re interested in right now (nop…this article is not about psychology). The arrow that’s really important is the thermodynamic arrow of time, and the direction of the psychological arrow of time is the same as the direction of the thermodynamic arrow of time. Remember the scenario of the broken glass, and we were wondering why it happens to be that way? That’s where the thermodynamic arrow of time comes in.
The thermodynamic arrow of time is given by the 2nd law of thermodynamics (which, in my opinion, is the most fascinating law of physics) and it’s all about entropy. In simple terms, low entropy is a more ordered state, and high entropy is a more chaotic state. What the 2nd law of thermodynamics states is that in an isolated system, entropy can increase but never decrease. This is the law that applies to the universe when determining the direction of time.
So let’s apply this fascinating law of thermodynamics to the universe. It’s actually very simple. The universe is an isolated system as in the 2nd law. So we can come to the conclusion that the entropy of the universe can increase but not decrease. That means the universe can only go from order to chaos! And that is the direction of the thermodynamic arrow of time. Things go from an ordered state to a disordered state. Now that explains the broken glass scenario, doesn’t it? The unbroken glass is in an ordered state and the broken glass is in a chaotic state. From order to chaos; from unbroken glass to broken glass.
Why do things go from order to chaos? Well, it’s because there are very few ways for something to be ordered but many different ways for it to be disordered. Let’s take the broken glass example again (please don’t try this at home and break all the glasses). If you take the broken pieces of the glass, there is only one way you can arrange the pieces to get the original glass but if you take the glass and break it, there are many many ways it can break (it can break into a million pieces or just a few pieces and it can break into the same number of pieces in many different ways). So there are more disordered states than ordered states, and the universe only becomes more and more disordered (chaotic), and chaos is where the arrow of time is pointed at. And that is why time behaves the way it does.
As Professor Stephen Hawking explains in his famous book, “A Brief History of Time”, If you remember every word in his book, the order in your brain will have increased by about two million units, however, while you read the book, you will convert at least thousand calories of ordered energy into disordered energy in the form of heat by convection and sweating. And that will increase the disorder of the universe by about ten million million million times than the increase in the order of your brain (and that is if you remember every single word, otherwise the disorder will be much higher!).
Going from order to chaos is what’s been happening in the universe since the big bang of the primordial era to forming stars and solar systems to creating life on earth. What we’re headed to is more and more chaos; all the stars in the universe will become white dwarfs ending the stelliferous era (the beautiful age of starlight), and finally, all that remains will evaporate as radiation leaving nothing but a sea of photons behind. Then, entropy will stop increasing and the arrow of time will finally cease to exist.
All that about the end of the universe may sound a bit depressing, but it’s not coming anytime soon. As Professor Brian Cox states, it will take around 10,000 trillion, trillion, trillion, trillion, trillion, trillion, trillion, trillion (which is a googol) years! According to him, if you start counting one atom at a time to represent one year, you wouldn’t find enough atoms in the entire universe to count up to that number.
All these details may seem trivial if you’re a physics or cosmology geek, but for those of you whose forte isn’t physics but are fascinated by the wonders of the universe (like me), I hope you got a bit of an insight to something interesting.
Image courtesy — google images
