|MadSci Network: Biochemistry|
Dear Ryan, Not only is it possible for the body to emit a portion of its energy, the second law of thermodynamic requires that the human body as a machine must always be emitting some of its energy. As you may know, there are basically 5 types of energy: mechanical, chemical, electromagnetic, heat, and nuclear, and these are all utilized in the human body. I will try to address which are emitted from the human body and/or what keeps them contained within the body, starting with the easiest. The nuclei of every atom in the body are held together by the nuclear force (one of the fundamental forces of the universe), and this is contained within the body because it is almost always a more stable state for the nuclei to stay together than to come apart. The most common exception to this is probably potassium, which has a reasonable high incidence of unstable, and hence radioactive, isotopes as it is found in the body (foods like bananas have high amounts of it), and thus breaks down to emit radiation. However, although I am not a physicist I think that emitted radiation would be considered electromagnetic energy and not nuclear. Hence the body has and uses nuclear energy but doesn't really emit it because it is "contained" by atomic nuclei. Next is chemical energy. The body is constantly using chemical energy to run every reaction that ever occurs in it, and any molecules that leave the human body that were synthesized in it could be considered to be emitting that energy. For example you breathe out carbon dioxide constantly, and if the chemical energy in those molecules are used by a green plant during its respiration, then you have emitted that energy. So I would say that the physical barrier of skin that keeps your body and hence all its molecules intact is the barrier to that energy not being emitted. Next is electromagnetic energy. One thing that you often hear is how the human body has a weak electric and weak magnetic field associated with it. To the extent that we are made up of ions and thus are probably a charged object we would have a very weak electric field, and to the extent that we are a charged object subjected to the earth's magnetic field we would probably have a weak magnetic field in reponse to the earth's magnetic field, but although I don't know I would think these would have to be very weak since none of us attracts iron shavings or generates a current when we touch metal. However, we do emit electromagnetic radiation. From your physics you may remember that the spectrum of electromagnetic radiation from high energy to low energy consists of gamma rays, X-rays, ultraviolet, visible light, infrared, microwaves, and radio waves. Any physical object at any temperature emits thermal radiation, or what has been called black body radiation, and this is true for the human body. The wavelength of this radiation is determined by the temperature of the object. Given the temperature of the human body, we emit infrared radiation, and in fact infrared detectors can "see" a human body even in total darkness (in contrast, night vision instruments basically collect the tiny amounts of visible radiation that is reflected off a human body over intervals of hundreds of milliseconds and convert that into a picture, like a camera, and hence cannot work in total darkness). So we do emit electromagnetic radiation, and it is completely not contained. Next is heat energy. Heat is essentially energy transfer between objects at different temperatures, and this happens via conduction (direct contact), convection (warm air currents), and radiation. The human body emits heat energy via all three pathways, and there is really no containing it. Finally there is mechanical (kinetic and potential) energy. Kinetic energy is the displacement of an object over a distance, and as you can see every time we move our bodies we emit kinetic energy. I hope that answers your question. Feel free to email to me directly if it does not. Chris
Try the links in the MadSci Library for more information on Biochemistry.