It was asked on the IRC today, "How can zombies live without the heart pumping blood?" And at first, it seems like it is a big hole in the zombie mythos. After all, everything needs a heart to live, right?

Well no. What is more accurate is that everything needs energy to live. How that energy is obtained doesn't matter. And once you understand this, you can begin to see how a zombie can come into being.

First, you start off with the usual limits of human physiology. For anything to change this, it is going to take time. For anything small, such as a bacteria or virus, it is going to take a long time. A pathogen, be it bacteria, parasite, virus or prion, is going to need to invade the host. Then it is going to need to multiply, and spread or travel to the infection control point. Usually the brain and spine.

Now, during that infection period, the pathogen is not only mutliplying and migrating. It is changing things in the host, in order for the host to become the zombie. What those changes are, and how they come about, that varies depending on the archetype. But what if one thing that is changed, is how the cells in the body get the energy they require.

Here we are going to dip into Avogadro and Einstein. You will see why.

Take hydrogen. It is the smallest atom. The atomic weight is 1.0079g. Divide that by Avogadros number and we have the weight of a single atom. So 1.0079g / 6.0221415 x 10^23. That would be known as m.

Next, we deal with something big. The speed of light. Squared. 8.98755191 x 10^20 cm^2/s^2. That is c^2.

So E = mc^2. In the case of the single hydrogen atom, that would be 0.0000000001504208 Joules.

Seems a really small number, right? Well for the whole human body for one day, you need about 9400 Joules to move, think, breathe, etc. Zombies won't be using all these functions, but I will calculate as if they are, just to make it harder.

To get that 9400 joules, we need 62,491,357,578,208 atoms. And how many atoms are there in a single cell? Well the rough estimate is 7,000,000,000,000,000 atoms. So, in order to power a zombie for one day, we need less than 1% of a single cell, if that cell contains the smallest (and therefore least energy-containing) atoms. In fact, we can use a single cell to power the body for 112 days.

Now, there is still an issue delivering this energy all around the body. That is what blood is usually used for, and by making the heart redundant, we can't do that. But with so many cells to strip down, we don't actually need to do that at all. Take apart the cells slowly, all over the body, and the zombie literally feeds on itself. Bonus, any flesh it eats can be "digested" in the same fashion. Rather than slowly broken down by enzymes and acids, it is stripped apart at the molecular level. Anything unused would look untouched, much as in many archetypes.