|MadSci Network: General Biology|
The question of what happens to your energy after you die is a difficult and thorny one, because “energy” can be used to mean various things. In strict scientific terms, energy is defined as “the capacity to do work;” i.e., the potential to move a mass over a distance. In common usage, especially in this context, speaking of a person’s “energy” is often a reference to the person’s spirit, or soul. I am no expert in physics and certainly no theologian, but I will try my best to answer your question from a scientific point of view.
Much of the important thought in the Western tradition can be traced back to Aristotle, a Greek philosopher of the 4th century BCE. When Aristotle wrote his grand treatise on the workings of the universe, he devoted a large section of the book to physics—the way that objects move and the causes and consequences of this motion. The section before it in the book, dealing with the idea of primal causes and the existence of god, became known as the “metaphysics:” literally, “before the physics” or “beyond the physics.” (It is not clear whether this name stems from the position of the book within the treatise, or whether it is used metaphorically.)
In modern Western thought, we still make the division between physics and metaphysics. Physics is a science, in which the basic principles have been tested by experiments and empirical observation. Physics deals with observable, reoccurring phenomena, and seeks to use these phenomena in order to investigate the underlying laws of the universe—for instance, Newton’s laws of motion or Einstein’s Theory of Universal Gravitation. Metaphysics is a branch of philosophy, which allows much further-reaching speculation on the structure of the universe, but cannot be subjected to the same kind of rigorous scientific testing. For instance, the idea of the soul falls under the realm of metaphysics, because there is no way to reliably, repeatedly observe anything like a soul.
So, from a purely physical perspective, what happens to your energy after you die? Let’s first take a look at what happens to your energy while you’re alive. It is true that energy can neither be created nor destroyed; it merely changes form as it passes through the universe—and as it passes through your system. When we are alive, we are constantly taking in energy from the food we consume. This energy comes from nuclear fission in the sun. It is captured as chemical potential energy in plants, and when we eat those plants—or when we eat animals that have fed on the plants—we take the energy of these chemicals into our own bodies. Some of this energy goes into building our cells, but much of it radiates out as heat. So what we think of as “our” energy is actually a constant stream of energy, originally coming from the sun, that passes through our bodies. When a person dies, there’s no more input of energy from food, and the metabolic engine of your mitochondria shuts down. The body’s energy gradually dissipates. (This is why the body cools after death—there is nothing to keep the metabolism going, and nothing to produce the heat that we make in life.) Eventually, as the body decays, the rest of the chemical energy is spent in reactions or taken up by the organisms involved in the decay.
For many people, the idea that your energy disappears after death is a very disturbing thought. Humankind has devised an astonishing variety of religions, and almost all of them promise some kind of life after death, whether by reincarnation, resurrection in paradise, or some sort of union with divine “energy.” For me (and I speak personally here; certainly not all scientists feel this way), the thought that our energy dissipates after death is actually a comforting thought. The last of the energy that passed through me will go back to the universe as heat, and the chemical constituents of my body will be recycled into the earth and the bodies of other living things. All recognizable traces of me will vanish, but the magnificent ecosystem of the earth will go on functioning. The fact that I am alive now, experiencing my singular existence on this planet, is cause enough for wonder. Personally, I believe that if one lives responsibly, joyfully, and generously upon the earth, what happens after death is really irrelevant.
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