The Law Against Clean Houses

Have you ever spent hours cleaning your house and the next day it looks like a dozen toddlers and their puppies went on a rampage?

I’m here to tell you it isn’t your fault (unless you had such a party, in which case, you might consider professional help).


In fact, there is a law against clean houses. It’s called the Second Law of Thermodynamics.

The Second Law of Thermodynamics states that any spontaneous process increases the randomness of the universe.

Oooookay, what does that have to do with the state of your living room? It means that when you put your dirty coffee mug in the sink it isn’t going to clean itself. This sounds like a no-brainer, but it is actually a basic law of nature that has huge implications for the world in which we live (make that the universe).

Let’s start by defining entropy. Entropy is a measure of how many states a closed system can take on. In physics, this usually refers to the molecular level, but I’m talking about vacuuming the floor so let’s look at a larger scale.

Say you have a living room with 4 walls and 1 chair. You like to have your chair against the wall, so you have 4 places this chair could be. This is a system with 4 states:
state 1 – chair on West wall,
state 2 – chair on East wall,
state 3 – chair on South wall,
state 4 – chair on North wall.

One system, 4 states.

Now add a second chair to the mix. This increases the entropy of your system, it adds to the number of states you can have. You can have
chair 1 on the West wall and chair 2 on the East wall,
or chair 1 on the East wall and chair 2 on the North wall

One system 16 states. You have more ways to arrange your room. Your system hasn’t changed. It’s still the same living room, but you have more entropy. Adding the chair gives you more ways to arrange your room. (See chart at the end of this post if you don’t believe me).

What this means is that the more “stuff” you have (people and pets included) the more places your “stuff” can be can be.

Zack and Tau
Cat and teenager organized, coat randomly tossed.

If you keep your keys either in a tray by the door or on your dresser there are two places the keys should be. You would like them to be in one of two states. State one, in the tray, or state two on your dresser. Unfortunately, within your house are a number of other states where they could be. You could have left them in your pocket, lent them to your teenager, accidentally dropped them and kicked them under the couch, the kitten could have eaten them, and on and on.

If you randomly left your keys lying around the chances of them being dropped into your tray or onto your dresser is much smaller than the chance they are somewhere / anywhere else.

Now this analogy is fine as far as it goes. However, it gets worse.

On the molecular level everything has some level of motion (unless it is at absolute zero, but I won’t go into that now). The colder it is the slower the motion, the hotter it is the faster.

You might think that ice, for instance is motionless.

DSC_0027 2.jpg

However, the water molecules are actually moving, but they are moving slowly enough that the majority of the molecules can stick together, ie they can form bonds. If enough molecules stick together they will form ice. If you add energy (heat) the molecules speed up. If you add enough heat the molecules will move too quickly to easily form bonds and the ice will become water.


Add still more heat and the molecules will be ricocheting so rapidly your ice becomes steam. Add still more heat and the water molecules will break down into hydrogen and water and on it goes.

So, back to the chair analogy. Instead of static furniture, imagine the room has 2 toddlers and 2 puppies. They careen around the room the way kids and puppies do, occasionally ricocheting off each other. Because this motion is random, eventually the kids and pups will be randomly scattered around the room. It’s possible that all four will end up in a pile, but not likely, well, it actually is likely, so let’s use a different example.


Instead of your roomful of youngsters, imagine a cup of coffee with trillions upon trillions of molecules bouncing away. DSC_0006

When you add milk to your coffee you can watch the two liquids mix.

DSC_0007 2

At first the milk sinks to the bottom of the cup, then it swirls back into the milk until your coffee is a uniform color.


You are watching the Second Law of Thermodynamics at work. The milk and coffee molecules mix together and without some serious work, will never un-mix. In theory, it is possible that all the milk molecules will some day gather at the top of the cup and all the coffee molecules at the bottom, but that is sort of like the chance of winning the lottery at the same times as being struck by a meteorite while a girl-child is born in a specific town in Africa and given your exact same name and…. That is to say, if you sit around for the length of time the universe has been in existence you might have a better chance of seeing it happen. Or not.

Now that you have a clear understanding of the Second Law of Thermodynamics you can see how it applies to housework. The more “stuff” you have (children, pets, keys, dirty coffee mugs, etc) the greater potential for disorder (entropy), and without work that chaos will naturally increase. So, you might as well drink your coffee, your housework isn’t going anywhere on it’s own.

Besides, drinking that coffee gives you energy to do work. So have a sip then go tackle the mess.



Chart of potential chair arrangements for two chairs in a room with 4 walls:

Chair 1 Chair 2 Chair 1 Chair 2 Chair 1 Chair 2 Chair 1 Chair 2
East x x x x x
West x
South x
North x
East x
West x x x x x
South x
North x
East x
West x
South x x x x x
North x
East x
West x
South x
North x x x x x




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