The “Antenna” Theory and Heat Effects

The antenna theory, the first attempt to explain no thermal effects, was mentioned briefly earlier in this book. Actually, this theory still explained no thermal effects as heating effects, by postulating the maximal transfer of energy from the radiation to the human body by frequencies whose wavelengths equaled the dimensions of the body. In that way, a field strength below the thermal level was supposed to cause body heating.

There are, of course, problems with this idea (for one thing we don’t spend all our time lying down!). Nevertheless, the EP9A became very interested in this concept because the 100-Mhz frequency is centered within the 88-108 MHz band assigned to commercial FM stations, which are common in the environment. However, it was soon pointed out that unless a person was very close to the FM transmitter and received adequate power from the signal, tissue heating could not occur even if a resonance situation was produced.

Heat is molecular motion; the faster the motion, the more heat there is. The molecules of every material object are in constant motion, with the rapidity dependent upon the ambient (environmental temperature). This motion stops only at absolute zero, far below zero Fahrenheit . The molecules of the body are, therefore, continuously in motion proportional to the body temperature. This is called “kT” or kinetic temperature. In order for heat to have any biological effect, enough energy has to be transferred to make the molecules move even faster. The energy in the environmental FM radiation was simply not enough to produce perceptibly more molecular motion than that of kT, and it therefore could not increase body temperature at all, even if the person was lying down.

According to this concept, microwaves produce their heating effect by causing oscillations o body molecules that are of a size to e resonant with the wavelength of the applied microwave radiation. Unfortunately, this is not the case. Microwave heating is actually produced by an increase in the motion of water molecules. This poses a real problem for the theorists. The size of the water molecule is far to small to be resonant with microwaves. In fact, water is optimally heated by infrared radiation, which has much shorter wavelengths than microwaves. At this time, we really do no know exactly how microwaves produce their heating effect, even in the ubiquitous microwave ovens. A number of theories have been proposed, and the interested reader is referred to a review of this problem by Dr. Jearl Walker in an issue of Scientific American.