Entropy, a Small Word Containing Big Mysteries
What is entropy and why is it important?
Hiya!
I didn’t tell you, but a few months ago, a reader and radiation oncologist named Chris commissioned me through my Ko-Fi page to write an article about an academic paper he had recently published. In it, he argues that entropy could explain, and be responsible for, gravity and much more. If I’m honest, I’d never heard the word entropy before he contacted me. But I accepted the challenge, and by golly, I'm glad I did.
Attempting to understand entropy hurts my brain in the best way, and while writing the article for Dr. Watson, I quickly realized that explaining entropy requires more than a couple of paragraphs. So I thought I’d dedicate today’s newsletter to it!
Side note: If you already know all about entropy, then consider me impressed! Entropy is a difficult topic to grasp, and I apologize because you might find this newsletter a bit redundant. But I’ll tell you all about Dr. Watson’s and a couple of other theories involving entropy on Monday in Curious Life.
What is Entropy
The most common definition of entropy is that it measures the disorder or chaos within a system— on both macro and microscopic levels. The fact that hot things always cool down unless you interfere to prevent it is basically what the second law of thermodynamics is all about. It represents a foundational and simple truth about our world — that disorder always increases unless something actively prevents it. This disorder is called entropy.
Disorder within a system increases over time when left unchecked, like in a teenager’s bedroom. When I say “system,” I mean everything from black holes and the way Time flows to the cells in your body and populations as a whole. As energy disperses into the system’s surroundings, the system dissolves into chaos. The more disordered a system is, the more entropic it is.
Entropy measures everything within a system and all its potential arrangements, including the possible statistical locations of every atom within it. Knowing which direction atoms travel and their speeds helps us predict what the system will do next and how it might behave.
A system has increased entropy when in the presence of heat and decreased entropy in the absence of heat. So if a system has high entropy levels, it becomes difficult to predict where the atoms might be at any given time because heat speeds the movements of the particles. Whereas a system with low entropy makes it easier to predict where particles might be because they’re moving slower. It’s challenging, sometimes near impossible, to calculate entropy due to all the variables.
If it sounds complicated, it’s because it is.
Here, let’s use an example. An article by ThoughtCo about entropy has one using water that I found helpful, so I thought I’d share it:
A block of ice will increase in entropy as it melts. Ice consists of water molecules bonded to each other in a crystal lattice. As ice melts, molecules gain more energy, spread further apart, and lose structure to form a liquid. Similarly, the phase change from a liquid to a gas, as from water to steam, increases the energy of the system. […]
In other words, entropy levels rise when the water molecules in ice gain energy and lose structure as it becomes liquid because there’s more space for the molecules to spread out. As the ice melts, it’s increasingly harder to predict where the molecules might go at any given moment. The same is true when liquid water turns to steam. Trying to predict where they’ll go makes my brain glitch.
[…] On the flip side, energy can decrease. This occurs as steam changes phase into water or as water changes to ice.
I’ve always said we live in a world of opposites, and entropy is no different. Low entropy levels produce the opposite effects of high entropy systems. As entropy decreases, the molecules become more ordered and easier to predict. When water freezes, its molecules become structured into repetitive crystal lattices — and when steam loses energy (or entropy), the molecules settle back down to the surface.
Still confused? Check out this video I found that lays it all out. It’s almost fifteen minutes long, but it explains more information than I’m including in this article.
Why is Entropy Important
At first, it might seem that entropy is unimportant. After all, when would you ever need to know the precise location of an atom in an ice cube? Probably never. Yet, entropy is happening all around us every day. I think it’s significant because entropy really is everywhere at all levels of existence.
Entropy occurs within the cells of your body as they degrade. It’s happening in the form of heat from your coffee as the steam spreads in the air. But entropy also occurs on a larger scale — crimes are happening, revolutions are materializing, relationships are ending, businesses are failing, and fascism is rising. The examples never end because, as I said, entropy is everywhere.
“Disorder, or entropy, always increases with time. In other words, it is a form of Murphy’s law: things always tend to go wrong!”
— Stephen Hawking, A Brief History of Time
Entropy loves disorder, and thus perhaps so does the Universe. It requires effort to maintain order. Even within ourselves—we want to be lazy and impulsive. In some ways, it’s easier and requires effort not to. Plus, trying to predict the future is a deep-wired trait of Humanity. Our brain constantly attempts to forecast the future — and entropy is a way to do that.
Perspective Shift
Even this article barely scratches the surface of what entropy is. I didn’t even get into the mathematics and statistical measurements of it. A big part of entropy’s mystery is, in part, how complicated it is to understand. It tests the current limits of our minds. But also, entropy is everywhere, which means it has a crucial role that we’re just beginning to explore.
For instance, is entropy responsible for gravity? Or is it possible that life itself is a result of entropy? We’ll dive deeper into both possibilities on Monday.
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