Kyuubey, the white floppy haired cat thing that everyone loves to hate, is an incubator, an alien species that is trying to save the universe. So just what are they trying to save the universe from… that would be the Heat Death of the universe. The heat death of the universe is one of the several theories on the eventual end of the universe. Before I can begin to explain the Heat Death of the universe I first need to cover a couple of topics.
1- Closed systems- Closed systems in physics are systems where nothing can enter or leave. This means that the amount of matter and energy in the system cannot change. The entire universe can be considered a closed system.
2- Entropy is the measure of disorder in a system, and it will increase over time, without the input of an outside force.
3- Law of Conservation of Energy- Energy cannot be created or destroyed, but it can be transformed into different types. A caveat to this is that some energy in any transformation is lost to heat and leads to an increase in entropy.
4- The universe is constantly expanding.
Thus, the Heat Death of the universe will be due to the constant expansion spreading the existing energy out over a larger area reducing the amount of energy available in any one spot. Additionally, there will be a continual loss of energy to heat over time as energy is converted between different forms. Eventually, the universe will reach a state where all matter has fallen apart and the universe is in a very low energy state. Not to worry, though; if the theory is correct, this will not happen for 10 duotrigintillionth years. It seems that the incubators are very long term thinkers.
The grand plan of the incubators to prevent the eventual heat death of the universe was the creation of the magical girl/witch system. In this system, the incubators grant the wishes of young girls, something that must take energy, to fight witches (magical girls who have fallen into despair), which takes even more energy to do. Now somehow out of this whole process, the incubators harvest the emotional energy of the magical girl/witch, and that somehow is more energy than they put into the girls in the first place. This energy can then be used to exert a force to prevent the expansion of the universe, and used to reduce the increasing entropy of the universe.
Why the plan is doomed to fail
1- You can’t get something from nothing, and the laws of thermodynamics state that while you can convert one type of energy into another, it’s not a perfect conversion. Also, the emotional energy of the girls had to come from somewhere, and given that the universe is a closed system, that energy came from the universe. Essentially, emotional or mental energy is biochemical energy created by the body, and where did the body’s energy come from? The universe, so essentially the grand plan of the incubators is using up the usable energy in the universe even faster speeding up the heat death of the universe.
2- Given that Madoka is a magical girl show, and we give it some leeway if the emotional energy collected by the incubators is, in fact, energy coming from outside the universe or outside the system, then yes, the plan might work. However, the plan is still doomed to fail, in fact, since adding all of the extra energy to the universe would potentially create a situation that could lead to a big crunch, or in anime terms the spiral nemesis.
Sorry, Kyuubey, you are still one of the biggest jerks in anime and your plan is doomed to fail.