We all have order and disorder in our lives – and in the universe.
Back in March, I gave my room a good spring clean. Since then, disorder has gradually set in, and so now my room is as messy as ever. But from a theoretical physics point of view, there is a natural explanation for why my room gradually goes from being tidy to being messy: the tendency of entropy to increase over time.
Entropy is often described as a measure of disorder, but it is more accurately described as a measure of how many microstates there are for every macrostate. In the context of messy rooms, we might think of a macrostate as specifying a general degree of messiness – so when a mother disapprovingly tells her son “Look at the state of your room,” she’s talking about a macrostate. A microstate, on the other hand, would constitute a detailed description of someone’s room which might include among other things the locations of all the books and bits of paper in the room and how far open the drawers are. The reason rooms tend to get messy over time is that there are a lot more ways (ie microstates) that a room can be in a messy (macro)state than in a tidy (macro)state. So there are lots of different ways I can leave a load of books and papers on my desk, but there are relatively fewer ways I can leave them neatly lined up on my shelf or tid- ied away in a closed drawer. If I pick up a book or a paper to read and put it down without thinking where I’m putting it, then the chan-ces are that I’m going to leave it in a place that will make my room look messier.
