Maxwell’s Demon

El Cazador de la Bruja and Maxwell’s Demon

First released in 2007, El Cazador de la Bruja, can be seen as the successor to Madlax, and with Noir, completes studio Bee Train’s girls with guns’ trilogy. In essence the story is one of discovery as the mysterious girl Ellis (the blond) travels with the bounty hunter Nadie (the red head), in order to discover more about her unknown past. Nadie and the viewer quickly discover the Ellis is gifted with supernatural powers related to Maxwell’s Demon, as if the word Bruja, Spanish for witch, in the title(El Cazador de la Bruja) wasn’t enough of a hint.

El Cazador de la Bruja
Nadie and Ellis

The term Maxwell’s demon is often thrown around in El Cazador de la Bruja in reference to Ellis’s power of causing objects to heat up. The demon in this case is not of the mythological variety, but comes instead from a Scottish physicist by the name of James Clerk Maxwell. To understand Maxwell’s demon, we first have to explain the second law of thermodynamics.

Technical Definition

Second law of thermodynamics– the total entropy of an isolated system always increases over time, or remains constant in ideal cases where the system is in a steady state or undergoing a reversible process. The increase in entropy accounts for the irreversibility of natural processes, and the asymmetry between future and past.

Now for non-physics majors

Before we can begin to break down what the second law of thermodynamics is saying, we need to define a few of the terms present in the definition. A system in physics is referring to the area that is being examined and can range in size from extremely small to extremely large. Also systems can be open, which means mass and energy can enter and leave, or closed in which nothing can enter or leave. In regards to the second law of thermodynamics we are talking about a closed system.
Entropy is the amount of disorder or chaos in the system. The higher the chaos the less work that can be done by the system.
Steady state means that the system is unchanging.
A reversible process is one that can run in two directions and is demonstrated below

A <—> B

A can turn into B and B can turn back into A

Now that that’s over with, we can begin to grasp the second law of thermodynamics. At a basic level it means that the amount of chaos or disorder in a system increases over time. The only time it would not increase is if nothing is happening or a reversible reaction is occurring. The increase in disorder can only be reversed if an outside source of energy is applied to the system.


Any parent reading will understand the phrase the messy room is not going to clean itself. The finality of the second law comes into play when you remember that the universe itself is a closed system. A really big closed system, but a closed system nonetheless. This helps to explain the heat death of the universe, one of the theories on the end of the universe. It basically states that the universe will eventually run out of energy, becoming a cold lifeless void as everything eventually cools off.

Maxwell’s Demon

Maxwell’s demon is a thought experiment by James Clerk Maxwell, postulating on a hypothetical situation that could break the second law of thermodynamics. There are three parts to the experiment.
1- A closed system not in equilibrium, meaning that there will be some hot particles and some cold particles.
2- The system is divided in half and connected by a door that can be opened and closed.
3- The demon that controls which particles can move through the door.

Maxwell's Demon
Maxwell’s Demon

According to the second law of thermodynamics the temperature of the room would slowly equalize as the hot and cold particles become equally distributed across the entire system. As we can see in the diagram above this does not happen when Maxwell’s demon is present. The demon is only allowing hot molecules through the door creating a hot side and a cold side to the system.

It would seem at first glance that the second law of thermodynamics has been broken by the demon, however things are not always how they appear. Leó Szilárd, a Hungarian physicist, later stated that Maxwell’s demon does not violate the second law because the demon has to expend some effort in determining which molecules to let through the door. While the demon is not actively moving anything, it is spending energy to determine which molecules to let through. Thus energy is being used in some fashion and the second law is not broken.

The Demon Discovered

In 2010 researchers at the University of Tokyo created a molecular staircase that molecules could walk up and down on as a result of random motion. The scientists then acted as Maxwell’s demon in a way by placing an electric field across the step each time a molecule moved upward such that it could not move backward down the steps.

Maxwell's Demon
Maxwell’s Demon

This creates a system with an area of high energy and an area of lower energy as seen in the picture above. Now before you all start having dreams of a new clean energy system, be aware researchers rank this along the lines of the current state of nuclear fusion: lots of energy goes in and only a small amount of energy goes out.

So what about Ellis

Ellis the second female lead of El Cazador de la Bruja is a witch whose main power seems to be the ability to heat up or cool down materials using a power that is described as Maxwell’s demon. I know the clip is a bit long, but you will see several instances of Ellis using her powers.

The two main examples in the video are melting a person’s shoe, and heating a gun to the point where the metal turns red hot. If her powers were really based on Maxwell’s demon, this would be impossible. As you recall, Maxwell’s demon only changes the division of particles or energy in the system, it cannot spontaneously create areas of high energy. So Ellis might be able to make the gun a bit warmer, but not to the point where it would glow red.


Given the results of recent experiments we can call Maxwell’s demon in El Cazador de la Bruja in confirmed.


As for Ellis’s powers being based on Maxwell’s demon, well that’s busted since Maxwell’s demon would not allow for the large rapid increases in temperatures she demonstrates in the show.


Please leave any comments or questions in the comments section below and if you want some more anime physics looking at thermodynamics then head over here for why Kyubey fails physics.

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