An idea struck me as I was walking to class today. According to Wikipedia, entropy is defined as the number of specific ways in which a thermodynamic system may be arranged, commonly understood as a measure of disorder. I believe this is because the more ways you have of arranging an object, the more chance there is of it being completely disordered and random than being ordered and symmetrical and nice looking, though I could be wrong.
So, if this follows, to me the body seems pretty orderly when you are first born and growing up. The perfection of your heart, your brain, blood vessels, muscles, everything seems to fit together, to work together, in perfect harmony. As you grow older though, things start falling apart, diseases riddle your body, muscles atrophy, your brain was no longer the powerhouse it was when you were younger. And I drew up an analogy, perhaps due to the second law of thermodynamics that entropy would always be increasing, perhaps it is simply the entropy of your body that is steadily increasing through time, and that it is not "old age" that kills you but rather entropy.
This all seems pretty logical, but lets take it a step further. According to Boltzmann's entropy formula $S = k_b ln w$ where $k_b$ is the boltzmann constant and $w$ is the number of ways of being arranged, it seems as if to me if we could somehow know the number of ways our bodies could be arranged, that the entropy at a certain time would come out to a number, say 671. It states in wikipedia that this equation is for ideal gases, so I'm not sure if it is very applicable to human beings, there might be another equation generalizing?
If so, and the entropy really does come out to just a number, does that mean that there could be some entropy limit, say if we hit 3771 entropy, we would die? Of all the things I have said today, this seems pretty far-fetched, as we all die at different ages. But the thing is that different circumstances occur to us. Perhaps I broke my leg, and my entropy jumps up by 50 (though I'm not too sure how that works, it didn't really increase the number of states in my body did it).
So, does anything I've written today work? If so I might write a dystopic story about it for fun, where people have entropy clocks in the future.
Answer
The aging of the body has nothing to do with entropy. As has been pointed out, the body is not a closed system. It takes in energy all during its life and the overall thermodynamic state of 2 bodies of different ages but identical everything else (such as fat content, state of hydration, and so on) are equivalent. Aging is caused by many factors such as accumulation of lipofuscin in cells making molecular transport less efficient, shortening of telomeres making genetic errors and unrestrained growth more likely, and so on. It is a sort of built-in time-bomb to encourage renewal of the species and evolution. It also prevents overpopulation and the resulting scarcity of resources. Aging occurs, in short, so that the species can adapt to its surroundings in increasingly better ways. The exchange of energy with the environment does not change in kind throughout life.
The universe is another story. Disorder (entropy) increases until eventually time will end when events cease to occur due to the homogeneity of space.
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