Why does entropy happen? Entropy happens because there are vastly more ways a system can be in disorder than it can be in order.
Entropy is explained in the second law of thermodynamics. It says that the state of entropy of an isolated system will always increase over time. It has been rewritten since it was first discovered, and there are many different versions of it, but they all generally say the same thing. Although, over the years, the definition of entropy has changed and there are different types of entropy. Your idea of what entropy is can depend on the type of science or the type of scientists you are following. The idea of entropy was first considered in the 1820s, but the ideas were sorted out by Rudolf Clausius in the 1850s. He was a German physicist and he is known as one of the founding fathers of thermodynamics. He also came up with the term “entropy”, created from Greek words. He took the prefix “en”, which means “in” and the word “trope”, which meant “transformation”. He was working with steam engines and he was trying to work out why heat wouldn’t transfer from a cold thing to a hot thing, only the other way, and to work out where the heat energy went. His solution was that the heat energy was dissipated to the system in all directions and that this was entropy.
But, what is entropy? Let’s try to get a simple explanation. Entropy is a way of quantifying the amount of disorder in a closed system. By a closed system, we mean one that energy cannot be added or removed from. Our universe is a closed system because the amount of energy that is present has existed since the Big Bang and will always exist until the end of the universe. You cannot create energy and you cannot remove energy, you can only change what the energy is doing. And that is where entropy comes in. Everything that is ordered in our universe moves towards a system that is disordered.
To put energy somewhere or to take energy out of somewhere means that you are trying to put order into some part of the universe. If you boil water to make a cup of coffee, then the energy you have imparted from your gas burner to the water is contained in that cup of coffee. However, to keep the energy in that cup of coffee is difficult because the energy would rather be in a state of disorder than a state of order because it is easier. The only ways to keep the energy in the coffee cup are to keep adding more energy, or to make the coffee cup a completely closed system where energy cannot get in or out. The heat energy is going to leave the coffee cup and enter the air in the room until the coffee is the same temperature as the rest of the room. This is entropy. The opposite is also true. If you have a cup of ice coffee on the table, you have to use energy to remove the heat energy from the water to make the ice. Because of entropy, the heat energy in the room will slowly enter the ice coffee until it has warmed up to the same temperature as the rest of the room. Entropy continues until everything is disordered and there are no clumps of ordered energy anywhere in the universe. This is probably the end of the universe. Life is an example of ordered energy because we require energy to stay alive. However, the energy in our bodies and cells is always trying to return to a disordered state and we can only fight that for so long before we die.
So, why does energy happen? It is down to the randomness of things. There are far more ways that atoms can be arranged in ways that are disordered than there are that they can be ordered. Think about your bedroom, for example. If you clean your bedroom, put everything where it is supposed to be, clean up all the dust, and make it perfect, it is in a state of order. How many different ways are there that the room can be in perfect order? You can move the furniture around and you can put things in different places, but there are only so many ways that the room can be ordered. Now, what if you forget to put the hairbrush back where it is supposed to be? Or you put one of your books in the wrong place on your shelf? The room has started to become disordered. How many ways are there that the room can be disordered? There are vastly more ways that the room can be disordered than that they can be ordered. If you go down to the atomic level, there are even more. The only way to keep the room ordered is to apply energy by cleaning it up. If you don’t apply energy, it will slowly become disordered. This is the natural state of things and will happen to everything. Unless you apply energy to keep something ordered, it will become disordered, and because of energy, housework is hard to do. And this is what I learned today.
Photo by Lisa Fotios: https://www.pexels.com/photo/white-coffee-mug-on-brown-surface-1207918/
Sources
https://en.wikipedia.org/wiki/Rudolf_Clausius
https://science.howstuffworks.com/entropy.htm
https://en.wikipedia.org/wiki/Entropy