The editorial offices of Testandmeasurementtips.com recently received a letter from an individual who headed up a group of investigators of paranormal phenomenon. It was a serious letter. To summarize, the group had concluded there was no legitimate method to record the activity of an alleged haunting. But the writer did have a question for us, prompted by a piece on gauss meters and ghost-hunting TV shows we did a few years ago. Their question: Can something consume energy without emitting a field itself?

With this question in mind, perhaps we can clarify things by reviewing what exactly causes electric and magnetic fields.

The simple answer is that electric fields are caused by electric charges, and magnetic fields are caused by electric currents.

There can be a bit of confusion on the above points. It’s possible to find posts on the internet that seem to imply that changing electric fields cause magnetic fields and vice versa. Perhaps the easiest way of illustrating that this idea is erroneous is to examine the typical way electric and magnetic fields are depicted in physics books. The typical rendition shows sinusoidal electric and magnetic fields moving in sync with each other. But if one of these fields caused the other, one might expect to see some sort of time delay between them–say, the electric field changing first followed by some proportional change in the magnetic field. But that’s not what happens. The two kinds of fields change perfectly in step with each other.

Fundamentally, any electric charge that is moving has both an electric and a magnetic field around it. And magnetic and electric fields don’t interact. This means that the electromagnetic field from a large object made up of billions of particles is really just the sum of the individual fields of each particle. So with that in mind, the electromagnetic field detected at a given point in space is just the time-delayed effect of the position, velocity, and acceleration of a charge at an earlier time.

Moreover, the only real detectable effect of electromagnetism is that charges can exert forces on other charges. Thus instrumentation designed to detect electric or magnetic fields do so by measuring how the charges inside the instrument are affected by the EM field. In a nutshell, EM fields are created by charges and their motion. Their effects are only observable when they produce forces on other charges at some later time.

One additional point to examine is how charges in nature can be accelerated in the first place. There are numerous ways but one primary means is via thermal energy. Recall that objects retain heat via the vibrations of their atoms. Adding heat to an object makes the atoms of the object vibrate more violently. The more heat added, the more violent and the higher the frequency the vibration. Thus an object’s temperature is proportional to the vibrational frequency of the atoms in it.

Further recall that each atom has an electric field surrounding it. That electric field goes out to infinity though its intensity diminishes with distance at the rate of one over the distance squared. When an atom is vibrating, an observer some distance away will see a field intensity (i.e. a wave motion) that is moving at the same rate as the atom’s vibration. Consequently, atoms that vibrate sufficiently fast due to heat energy will eventually emit visible light frequencies. The classic example is a steel mill where metals in process glow orange and white hot.

Materials that aren’t hot enough to emit light still radiate lower frequencies. Planck’s law describes the intensity (actually the spectral density) of electromagnetic radiation that a given body emits at a given temperature when it isn’t being heated or cooled. In general, Planck’s law shows that the higher the temperature of a body the more radiation it emits at every wavelength. Conversely, relatively cool objects–those not hot enough to give off visible light–don’t emit much radiation at any frequency.

All in all, we’d have to say a clinical discussion of EM radiation tends to take the subject out of the realm of the paranormal.