by Mark Townsend
Although electrical equipment is easily the most likely source of sudden EMF meter readings, there are others.
Though they're designed to detect fields at 50 Hz, EMF detectors can be surprisingly sensitive to simple movements of magnetic objects. Walk past one with something magnetic in your pocket and you might get a reading.
You can even get a reaction by waving a tin can next to an EMF meter. Even though the can is not magnetic, it contains steel. Steel is highly magnetically permeable. That means it distorts the local geomagnetic field. Moving it disturbs the local geomagnetic field, causing a reading on the EMF meter which sees it as a low frequency field.
So anything made of steel or iron which is vibrated (like the drum of a washing machine) could cause disturbances big enough for an EMF meter to detect. Even a steel filing cabinet being vibrated by heavy traffic might be enough to get a reading.
Why use EMF meters?
Given that all you can tell from an EMF meter is that there was a disturbance to the local magnetic field, of unknown magnitude and frequency, are they any use in paranormal research?
You could use the same argument about most bits of equipment used in vigils. Since no one knows what causes paranormal phenomena, or what effects they may have on the environment, it is legitimate to try measuring any environmental parameter you can to find out. So you can certainly justify using EMF meters on that basis.
The problem is that EMF meters were designed to monitor electromagnetic pollution. The designers were not too concerned about field frequency or direction because that wasn't the point. They only wanted an overall figure for personal exposure to electromagnetic fields.
This means that EMF meters are not really suitable for looking for EIFs (experience-inducing fields) which cause certain people to hallucinate.
EMF meters could, in very broad terms, be useful in differentiating between hot-spots (where phenomena have been reported) and control areas (where they haven't).
So what happens if we find 'anomalous' readings but can find no obvious cause? Are they paranormal? On their own anomalous readings are just that. However, if such readings coincided with a report of a paranormal incident, they could be interesting. Even then, you would need to make sure there wasn't a mundane cause for the unusual reading.
How fields fall with distance
EMFs from any source usually get less as the distance from the source increases. Quite often, this can be approximated as one of three basic types of fall off with distance:
Inverse first power of distance
(also referred to as one over the distance or reciprocal of distance)
at double the distance the field is reduced to a half
at three times the distance the field is reduced to a third and so on
an example is the magnetic field from a net current in a distribution circuit
Inverse square of distance
(also referred to as one over the distance squared or inverse second power of distance)
at double the distance the field is reduced to a quarter
at three times the distance the field is reduced to a ninth and so on
an example is the magnetic field from some transmission lines (either with a single circuit or two circuits but untransposed phasing)
Inverse cube of distance
(also referred to as one over the distance cubed or inverse third power of distance)
at double the distance the field is reduced to an eighth
at three time the distance the field is reduced to a twenty-seventh and so on
an example is a transmission line with transposed phasing, or a domestic appliance
In practice, fields rarely follow these power laws exactly, departing from them particularly at very small distances or very large distances. Nonetheless, there is usually a good range of distances where these are good approximations.
The definite effects of EMFs
EMFs definitely have some effects on us as humans – but at high field levels, bigger than we usually meet in the environment.
These established effects include:
Induced currents in the body
They also have effects on equipment (including VDUs and pacemakers)
These effects are well understood and there are exposure guidelines in place to protect against these effects.
The possible effects of EMFs
There are other concerns about EMFs. Over the past 20 years, scientists have linked exposure to everyday levels of EMFs with various health problems, ranging from headaches to Alzheimer's disease. The most persistent of these suggestions relates to childhood leukaemia. But the evidence is not straightforward.
A number of epidemiological studies, particularly in the US and in Scandinavia, have suggested an association between the incidence of childhood leukaemia and EMFs or the proximity of homes to power lines.
Not every study has found the same association, but taken as a whole, the epidemiological studies certainly show a statistical association
Because of problems inherent in epidemiology, finding an association does not mean there is a risk.
No causal link has been established between cancer (or any other disease) and EMFs and there is no established mechanism by which these fields could cause or promote disease.
Nonetheless, the possibility remains that EMFs are a cause of disease, and in these pages we summarise:
The evidence on childhood cancer and other different specific diseases
Electric fields and airborne pollutants: Information on one particular suggested mechanism
The Expert View
The quantum energy of 50 Hz electromagnetic fields is too small to break chemical bonds. It is clear that power-frequency EMFs or radiation does not cause ionisation in the same way that x-rays or alpha particles do. Instead, the main known way 50 Hz fields interact with people is by inducing currents.
What currents do magnetic fields produce?
Any alternating magnetic field will induce an electric field, which in turn produces a current in a conducting medium. The human body is conducting and will therefore have a current induced in it – albeit, usually, a very small one. As shown on the right the current circulates round the body.
In power-frequency calculations, it is common to assume the human body has a radius of 0.2 m and a conductivity of 0.2 S m-1. Using this model, a magnetic field of 160 microteslas (µT) induces a peripheral current density of 1 mA m-2. More accurate numerical calculations can be done which take account of the actual shape of the body and the varying conductivities of different tissues.
What currents do electric fields produce?
Alternating electric fields also induce currents in the body. As shown on the right, for a vertical field, they run up and down the body. The calculation has to take account of the perturbation to the field caused by the body itself. For a typical person standing in a vertical field, a current of 1 mA through the body is induced by 70 kV m-1; more on numerical calculations.
Anomalous EMF readings
Paranormal researchers often get excited on ghost vigils when there is a sudden high reading on an EMF meter. This is thought by some to indicate paranormal activity, maybe even the unseen presence of a ghost.
Unfortunately, there are a great many possible mundane causes for a sudden jump in magnetic field readings. Sadly, EMF meters are not good at telling them apart. Since the meter cannot tell you where to look, you'll need to poke around the area and see if you can see a possible source of the field disturbance. If you have a spare EMF meter available, you could try putting it close to the suspect area to try to localise the source.
So what could have caused such a disturbance?
The most likely cause of a magnetic field disturbance in any dwelling is operation of electrical equipment. Such equipment can deliver changes to the local field by being turned on or off or changing state in some way (eg. a washing machine moving between cycles). Electrical equipment is a potent source of magnetic field disturbances.
Some EMF meters can detect electrical wiring behind walls. However, such wires are relatively poor producers of magnetic fields. The high density of wiring and electrical devices in an appliance makes them much better sources of fields.
Not all electrical equipment that could be the source of fields will necessarily be obvious in a room. It could be behind walls or, more likely, under floorboards. Any equipment that contains relays, transformers, capacitors or switches could produce some brief, powerful magnetic disturbances.
Some electrical equipment is on all the time, or most of it, and operates automatically, even in the middle of the night. You should also consider any equipment you've brought with you on the vigil as a possible source.
Do ghosts emit electromagnetic fields?
There is a widespread idea among paranormal researchers that ghosts emit an electromagnetic field and that their presence can, thus, be detected by EMF meters. However, there seem to be no formal studies to support this idea. Instead, there are a few anecdotal reports that EMF meters 'spike' during paranormal activity at haunted locations OR that haunted locations produce more variable EMF fields than non-haunted places. In both cases, it is difficult to trace any original, first-hand reports of these claimed connections and what reports are available are vague and lacking in crucial technical detail. So, why do some people claim that ghosts emit EM (electromagnetic) fields?
Asking the right questions
Do ghosts really emit electromagnetic fields? Before we can answer that question, there is a more important one to be answered. Are EMF meters even capable of demonstrating that ghosts emit EM fields? And before we can answer that question, we need to ask - do ghosts even cause hauntings?
So, firstly, do ghosts cause hauntings? The answer isn't as obvious as you might think! No one denies that hauntings exist. People undoubtedly experience odd goings-on at certain locations from time to time, but are ghosts really responsible for them? This may seem an odd question until you realise that apparitions are only witnessed in a minority of hauntings. What is more, there are few, if any, accounts of apparitions actually 'doing' any of the things we associate with haunting. They are not seen knocking on walls or tables, moving objects, whispering in corners, nor is their rare appearance usually accompanied by strange smells or a sudden feeling of cold. It is just assumed that ghosts are doing all these things associated with hauntings.
Thus, the whole idea that a ghost is responsible for, or even vital to, a haunting appears to be based not so much on evidence as popular culture. Looking purely at the evidence, apparitions may simply be one possible, nonessential, phenomenon that can appear during a haunting !
It therefore seems to be an assumption too far to expect EMF meters to address the question of whether ghosts emit EM fields (for other popular assumptions that go beyond the evidence in ghost research, see here). Looking purely at the evidence it is therefore more meaningful to ask if EMF meters are capable of answering these two questions based on anecdotal observations:
•are hauntings associated with elevated or more highly variable EM fields?
•is observable paranormal activity associated with EM field spikes?
Where did the idea come from?
The idea of ghosts emitting electromagnetic fields seems to have emerged relatively recently. It is tempting to speculate that the idea arose simply because investigators started using the meters, in the same way that the idea of paranormal orbs (which proved to be photographic artifacts) coincided with the early use of digital cameras. Whenever instruments are used at haunted locations, there is inevitably a tendency to attribute unusual readings to the haunting, even without any other corroborating evidence.
A more speculative notion is that the idea may have been prompted, in some way, by Persinger's laboratory work that suggested that some ghostly experiences might be magnetically-induced hallucinations (EIFs - experience inducing fields).
Why use EMF meters at all?
EMF meters are designed to measure mains-frequency magnetic and electric fields in buildings to see if they exceed certain levels*. It is, therefore, difficult to see why such an should detect ghosts, given that it is unlikely they are mains powered! It is likely that the popularity of EMF meters in ghost research arose simply from the fact that they are easily and cheaply available.
When used to detect electromagnetic pollution, EMF meters produce perfectly useful readings. It is easy to measure a continuous high field produced by nearby electrical equipment, for instance. However, ghost researchers look for unusually high variability and/or 'spikes' in areas of low readings, mostly away from electrical equipment. To do this, they need to understand how EMF meters behave away from the application for which they were designed. This behaviour tends to vary between models.
An EMF meter detects changing electromagnetic fields (hence E.M.F.). Most models only detect changing magnetic fields but some can measure varying electric fields too.
EMF meters were originally designed to look for electromagnetic pollution, though their main users seem to be ghost hunters these days (judging by adverts on the web). Most are therefore set to be highly sensitive to fields varying at 50 or 60 Hz, the mains frequency in the UK and the US respectively.
EMF meters can detect either magnetic, electric or both types of field together. Most, however, are designed to measure only varying magnetic fields. If it is not obvious what kind of field your meter is detecting, check the units it is using. Electric fields are measured in volts per metre (V/m) and magnetic fields usually in milliGauss (mG) or nanoTesla (nT).
As mentioned above, the units for electric fields are volts per metre (V/m). It is more complicated for magnetic fields because some EMF meter manufacturers insist on using obsolete units. Many use milliGauss (mG) even though scientific publications use nanoTesla (nT). To convert, 1mG is 100nT.
Some meters come with ports to attach computers for automated recording. Also, some electronically-minded researchers have converted meters without ports so that they too can connect to laptops. This is a great idea as it allows much greater accuracy and frequency of readings as well as relieving observers of a tedious chore. You feed the output from the instrument into a data logger or specialist software.
There are, however, things to consider when doing computer sampling from EMF meters. For a start, if you take readings faster than the sampling frequency of the meter, you will not gain any higher frequency resolution even if it it looks like it!
Even more serious, you can only do frequency analysis if you have an accurate frequency response curve for the meter to apply corrections. The manufacturer may supply this, though it's unusual. Alternatively, you could get a linear sensor (like a fluxgate magnetometer) though these are usually rather expensive .
In all cases, you also need to consider the Nyquist criterion (where you need to sample at twice the rate of the top frequency you want to measure) for sampling and problems associated with aliasing (where higher frequencies affect the measurement of lower ones).You need to understand these before doing digital sampling.
When choosing an EMF meter, there are several important specifications to consider.
Firstly, there are some meters out there that have no dials or displays for readings at all. They just buzz or show a light when a certain certain threshold is exceeded. Though it is true that the figures you get from EMF meters are not hugely helpful for paranormal research they are certainly better than no figures at all. With a threshold detector, you've no idea if a reading was just fairly high or huge.
Perhaps the most important specification to consider is frequency response . It is useful to get a meter sensitive to extremely low frequencies (under 10 Hz) as this region has been implicated in magnetically induced hallucinations. If you can get a model where the manufacturer supplies a frequency response curve ,that's far better than one without it.
Another important specification to consider is the number of measurement axes. Electromagnetic fields have direction as well as size (which is why compasses point north). If a meter doesn't mention axes it almost certainly has just one axis. The problem with a single axis meter is that if you rotate it, even slightly, during a vigil, subsequent readings will change. That's because it's at a different angle to the fields. This means you can't compare the earlier readings with the later ones. The solution is to fix the meter in place or use a tri-axial model. Single axis meters will underestimate every field they measure by differing amounts making comparisons between locations problematic.
Another important specification is sample rate . Faster is definitely better.
The other important specification is scale or range. This specifies the maximum and minimum field the meter can detect. This is important because you may come across fields that are either too weak or too strong to measure. Try to go for meters with the biggest scale you can.
The graph above shows a typical frequency response of an EMF meter to magnetic fields. Along the bottom is frequency. The vertical axis shows sensitivity. At 50 Hz the meter has a sensitivity of 1. This means that a 50 Hz field of 1000 nT will show up, correctly, as 1000 nT on the meter. However, at a frequency of 1000 Hz, the meter is 10 times more sensitive! So a 1000 Hz field of 1000 nT will show up as 10,000 nT!
This frequency response is deliberate. It is weighted to mirror how magnetic fields are absorbed by the human body. That's because EMF meters were designed to monitor electromagnetic pollution not look for ghosts!
So when you see a reading of 1000 nT on your EMF meter, you've no idea what the real figure is because you don't know the frequency of the field. Most magnetic fields in a domestic environment will be mains frequency (50 Hz UK, 60 Hz US). But there are other frequencies possible and these will be either under- or over-represented. Even worse, there may be several different frequency mixed together to produce an overall figure that doesn't truly reflect any of them. So figures taken from an EMF meter are not particularly useful in terms of scientific measurement.
Different EMF meters will have different frequency responses making comparing readings problematic. If you're doing a positional baseline, it is better to use two meters of the same model.
by Maurice Townsend
There is now so much laboratory evidence in favour of magnetically induced hallucinations that some paranormal researchers are taking it as read that they are the source of certain anomalous experiences, notably some kinds of ghost. However, the field evidence for such magnetic fields is slight at present. But that could soon change as equipment capable of detecting them is now being deployed at haunted locations. If these magnetic fields exist outside the laboratory, what exactly is causing them?
There have been several articles in Anomaly recently concerning theories on the true nature of ghosts. In particular, there has been a lot about the possibility that they may be hallucinations induced in susceptible people by suitable ambient magnetic fields. While the results of lab experiments are impressive and compelling, there is still little evidence from the field to back this theory up. Initiatives like MADS (described in Anomaly 34) are designed to fill that gap. It will, at last, be simple to measure relevant magnetic fields in allegedly haunted locations.
An important question concerns the detailed nature of any such fields found at haunted locations for MADS to research. They are unlikely to be just like those produced artificially in the laboratory, so we need to investigate what they really ‘look’ like in the field. Once we know that, we can try to ascertain what aspects are absolutely necessary for strange experiences to occur.
Once such fields, and their principal components, have been identified then the next intriguing question becomes, ‘where do they come from’. At first sight, there seem few obvious sources for such fields, perhaps explaining why ghosts are not common. I decided to research the possibilities so that the search could be narrowed down. I hope this will assist investigators when they are researching possible field sources in haunting cases.
Defining the Fields
Before we can identify possible sources of relevant magnetic fields, we need to define exactly what we are looking for. I am indebted to Dr Jason Braithwaite for reviewing the relevant papers (from Persinger et al) concerning the laboratory experiments which have induced ghost-like hallucinations.
The best results have come from what could be broadly described as weak, complex, time-varying magnetic fields. Because the nature and potential sources of such fields are difficult to characterise at this stage, Braithwaite introduced the general term Experience- Inducing Fields, or EIFs for short. This definition relates to all, or any, fields that could have experience-inducing properties. This distinction is helpful for a number of reasons. Firstly, while not all magnetic anomalies will have implications for experience, some will have the ability to influence equipment (which could be interpreted as paranormal) but will not alter the operation of the brain in any way. Those fields could be characterised as Event-Related Fields (ERFs) as they pertain to a tangible physical event. Secondly, it focuses the researcher theoretically on the potential relevance such fields might have.
There are three main aspects to EIFs that have been demonstrated experimentally to be of crucial importance. The following figures are by no means absolute limits: things might happen outside them. However, experiments within these bounds have produced reliable, strong results. So it makes sense to look for fields within these parameters first, at haunted locations.
At present, the evidence suggests that EIFs are varying magnetic fields with low frequency (approx 0.1 to 30 Hz, and certainly under 50Hz) and a moderate intensity (from 100 to 5000 nT) or amplitude (or, more correctly, flux density). For comparison, the average geomagnetic field, which is not generally considered strong and does not vary greatly over time, is around 50,000 nT. An important point to remember is that EIFs are most likely to overlay whatever ambient static magnetic field is present in the area. This would usually be the geomagnetic field itself. Confusion often arises here because the geomagnetic field is usually described as being ‘static’ (ie. does not change over time), whereas, in fact, it does change over time, but very slowly (over hours). There might also be other local permanent distortions to the local magnetic field, such as the presence of the mineral magnetite in the geological strata below the site. At present, such permanent static fields are NOT considered important to inducing hallucinations, however. Therefore, EIFs, if present, would most likely appear as fluctuations on top of the local static field (though see discussion below).
There is another important factor that greatly enhances the chance of hallucinations: field complexity. This is more difficult to characterise. As an example, a typical laboratory experiment may use a simple 30 Hz sine wave field but pulse it for, say, 1s every 3s for a period of 30mins (during this time the field may also vary in amplitude across the pulses as well). Thus, the field fluctuates overall, in addition to the fundamental sine wave. Such overall variance could involve any, or all, of the major field variables: amplitude, frequency and direction. Laboratory studies have used amplitude-modulated, frequency-modulated and complex pulse-patterned sequences with great success. Overall field variations might be repetitive, with the field eventually returning to its original state after a certain period, or they may be chaotic with no obvious repetition. The time period over which fields need to vary is probably (from experiments) in the millisecond to multiple minute region. Simple continuous waveforms, like sine waves, are not at all as effective. The reason for this is that such simple fields are considered not to ‘contain’ the complex information profile that a brain would accept as sensory information. Incidentally, the direction of a magnetic field (which is conventionally said to flow from the north pole of a bar magnet to the south pole) determines which way it will produce a force on another nearby magnetic object.
There are two other important issues concerned in producing magnetic hallucinations, not directly related to the field characteristics. The first is that not everyone is susceptible to hallucinating when subjected to the EIFs outlined above. Current estimates suggest that only around 20 - 30% of the population show a substantially increased susceptibility, due to increased neuronal instability in specific brain regions. Secondly, susceptible people need to be subjected continuously to the EIFs for a significant time, say 20 to 30 minutes, before hallucinations are reported. This applies if the person is static. I will mention people moving around in fields later on. There is, therefore, an important exposure component to EIFs – the effects are not instantaneous.
The hallucinatory phenomenon is thought to arise because the frequency of the external magnetic waves is similar to that used internally by the brain for cognition. This stimulates brain activity, through a process called neural entrainment, which can confuse the brain into producing hallucinations.
Naturally Occurring EIFs
Could fields with the relevant characteristics occur naturally? The first obvious place to look is the geomagnetic field. This is the magnetic field that is constantly present at the Earth’s surface and in which we are all immersed continuously. It is what makes a compass point north. It is caused by a dynamo effect in the molten core of our planet. Though this effect produces a highly stable field, like that of a bar magnet, the field is constantly changing, primarily due to the effects of the sun impinging on it. The sun is constantly bombarding the Earth with the solar wind, which consists of highly energetic, charged particles. These interact with the geomagnetic field and cause changes reflecting the sun’s own activity. Features such as solar flares can have a major effect on the geomagnetic field. The most significant changes to the geomagnetic field take place over periods of hours. Thus, from a human perspective, the geomagnetic field appears relatively stable.
The geomagnetic field might appear, given its slow variations, an unlikely candidate for EIF, at first sight. Having said that, there have been some studies that have reported correlations between geomagnetic activity and the occurrence of spontaneous hauntings. These correlational studies did not involve field investigations and are considered controversial. As any statistician will tell you, a correlation does not always imply a causal link.
There are certain geomagnetic variables that change at frequencies required for EIFs. Unfortunately, it turns out that these variables, though they have relevant frequencies, are far too weak to produce EIFs, as shown in the table (Campbell, 2003).
Factor Typical frequency Typical Amplitude Comments
Pc1 pulsations 0.2 - 5Hz 0.1 nT Pc = pulsation continuous, caused by magnetosphere processes
Schumann resonances 7.8, 14, 20, 26Hz 0.05 nT Caused by lightning energy resonating between the earth and ionosphere.
Atmospherics 5 - 100+ Hz 0.05 nT Caused by distant lightning
Geomagnetic storms can bring larger amplitude changes in the geomagnetic field. A storm is defined as a period (usually of several days) when there is a large reduction in the horizontal component (parallel to the ground) of the geomagnetic field. On average, one big geomagnetic storm per year might bring a field reduction of around 250 nT, but most will be much less (maybe 10 per year bringing about 50 nT reduction). Therefore, only the largest, most infrequent storms have the sort of amplitudes we are looking for in EIFs. However, these changes typically occur over hours, or minutes at the fastest. Even the Pc1 pulsation component of the geomagnetic field, which has the correct frequency, varies only by a maximum amplitude of a few tenths of one nT (Belyaev, 2003). In summary, there are no natural variations of the geomagnetic field that provide both the amplitude and frequency together to be classed as EIFs, even during geomagnetic storms. Indeed, as we will see later, most of us live in an environment where such natural magnetic variations are entirely swamped by more powerful local artificial sources. So the geomagnetic field can, effectively, be dismissed as a likely source of EIFs.
Another natural source of EIFs that has been suggested is tectonic strain. Essentially, the Tectonic Strain Theory (TST) states that stresses within the Earth’s crust, less than those required to produce an earthquake, may result in highly localised surface electromagnetic disturbances through piezoelectricity in sub-surface rocks. Piezoelectricity is the phenomenon whereby certain crystals, notably quartz, produce an electric charge across opposite crystal faces when under physical pressure or strain.
The TST is the reason why many ghost researchers these days get excited if a geological fault lies near an allegedly haunted location. A fault is a crack in the Earth’s crust. Like any crack in a solid object, it is an indicator of strain, or pressure for movement, in the local area. Strain generally builds up around a fault until it is released through a physical movement (usually) underground, resulting in an earthquake. Thankfully, the vast majority of earthquakes are, in fact, tremors and are so small they are only noticed by seismologists using sensitive equipment.
The TST looks attractive, in principle, but it does have its critics. I have always had problems understanding it, when considering the physical details of the processes involved. Quartz generally occurs underground within other rocks, like granite, where its crystals are separated by other minerals. If you crush granite, an electric charge will build up across individual quartz crystals. However, since the crystals are orientated randomly, the charges (on opposite sides of each crystal) do not align. Therefore, they tend to cancel each other out rather than combining to form a strong overall electric field. There is a tiny overall field where stressed granite (under strain from lateral stress near a fault) is exposed at the earth’s surface, due to the fact that there are no crystals above the surface to completely cancel the field. But it is very small indeed.
Another problem that arises is that any electric field that might conceivably be produced by straining quartz underground will, in any case, be static. There is no movement (except for extremely slow tectonic movement, usually measured in mm per year) in the rocks and so no change in any field produced. This means there could be no magnetic field. In order to get a magnetic field you need to move electric charge through an electric field (such as when current flows down a wire). With no physical movement, there is no magnetic field.
Things change dramatically if the rock fractures, as has been demonstrated in granite crushing experiments (Zhu, 2001). Then, measurable electric (and magnetic) fields can be generated, through both the piezoelectric effect and something called seismoelectric conversion (caused by acoustic waves). The effect is amplified by the presence of water. While this process produces magnetic fields, you have to bear in mind that it involves the rock fracturing, not simply getting strained. There is little or no evidence for underground rock fracturing, even near faults, except during and immediately prior to an earthquake (Robb, 2005).
We do have some measurements of the kind of magnetic fields that might be produced by rock fracturing immediately prior to an earthquake. As a method of predicting earthquakes it is controversial, but the evidence does exist. One of the best known examples was the Loma Prieta earthquake in California in 1989. This was preceded by a weak (up to 60 nT) magnetic field with low frequency (0.01 to 10 Hz) up to 55 km away from the epicentre and three hours prior to the quake. However, even this field is not quite up to the strength required for an EIF and it took a 7.1 magnitude earthquake to generate it.
A further problem with TSTs is the very specific locality of the phenomena they set out to explain. In particular, the phenomena are often restricted not just to a single house but to particular rooms or even parts of rooms (sometimes in upper storeys). Houses nearby are seemingly unaffected. It seems unlikely that widespread tectonic strains could give rise to phenomena localised to just a couple of metres. However, it is possible that environmental factors within a house may amplify (or even attenuate) more widespread field disturbances. Also, a house may appear haunted, though next door does not, merely because an EIF-susceptible person lives in one and not the other.
Artificially Occurring EIFs
In a paper on the electromagnetic environment around Moscow (Belyaev, 2003), it was found that the magnetic fields at frequencies around 1 Hz were around 10 times higher in the suburbs, and 100 times higher in the city centre, compared to the countryside. In the city centre fields up to 250 - 300 nT at a frequency of 0.5 Hz were measured. These are strong enough to constitute EIFs. The fields were attributed, unsurprisingly, to electrical equipment in the city. This indicates, quite eloquently, that we should probably look first for artificial sources of EIFs in investigations before looking for, generally weaker, natural alternatives.
Artificial sources contribute significantly to the magnetic fields in a domestic environment, as a quick survey with an EMF meter will show. However, the 0.1 to 30 Hz frequency range of varying fields is generally quiet. This is because most electrical and electronic devices operate using a mixture of DC (for motors, electronic power supplies, etc.), mains frequency (50/60 Hz) and higher. The DC (static) element is rarely pure, being derived from mains supply with rectifiers (often accompanied by transformers). The resultant DC current has a slight voltage ripple on it. However, due to the way rectifiers are designed, this ripple will typically be at mains frequency or above and so not contribute to EIFs. Similarly, the mains supply itself can be distorted by the electrical loads placed on it by various bits of electrical equipment. This gives rise to harmonics but these, too, have a higher frequency and lower amplitude than the mains fundamental frequency. So most domestic electrical appliances, as well as the mains supply itself, will not contribute to EIFs.
Probably the most important source of low frequency magnetic fields is the simple movement, or mechanical vibration, of magnetic materials. By magnetic materials I mean metals with a high magnetic permeability. This means that magnetic fields prefer to flow through them, rather than through the air. Common examples include objects made of iron and steel. The object itself does not have to be magnetised, so long as it has high permeability. You can test if an object is highly permeable by seeing if a magnet is attracted to it. It may, or may not, be able, in turn, to attract other bits of unmagnetised steel (eg. paper clips) to itself. All objects with high magnetic permeability (let’s call them HMPs, for short), whether magnetised or not, distort the earth’s magnetic field around them. In the accompanying figure you will see two objects, one weakly magnetic, the other merely highly permeable. Both distort the surrounding geomagnetic field dramatically. When such objects are vibrated, they drag the magnetic field distortion around with them.
An unmagnetised HMP distorts the geomagnetic field nearly as well as a weak magnet
To produce an EIF frequency disturbance in the ambient magnetic field, all we need to do is vibrate an HMP at a rate of between once every ten seconds (0.1 Hz) and thirty times a second (30 Hz). It doesn’t need to be a constant frequency motion since, as we have seen, varying fields actually work better! The distortion to the ambient magnetic field will move in sympathy with the movement of the HMP, so inducing an EIF frequency change.
The possible examples of such moving HMPs in the domestic environment are almost endless. A sheet of corrugated iron vibrating in the wind, an iron bedstead shaken by nearby heavy traffic, a steel filing cabinet in a seaside office swayed gently by the crashing surf. Anything made of a suitable metal, whether magnetic or not, vibrated at a suitable frequency, will give us the EIF frequency disturbance. Whether it attains a suitable amplitude for an EIF depends on the degree of vibration of the object and the amount of distortion the HMP brings to the ambient field.
As well as bits of metal, there are also machines that can act as moving HMPs. An electric motor can be imagined as a permanent magnet being rotated, pole over pole, between the opposing poles of two other permanent magnets. In the real world, all the magnets are electromagnets but the effect is the same. A rotating magnetic field will be produced with a frequency reflecting the rotation rate of the motor’s armature. Most motors in domestic use are likely to produce rotating fields at EIF frequencies. That’s because few will go round faster than 1800 rpm, which equates to 30 Hz. In addition, DC motors may spark where brushes meet the commutator. This would introduce a sharply pulsed field, at twice the frequency of rotation, which might still be low enough to contribute to an EIF.
There are many motors used in the domestic environment. They commonly occur in such things as pumps (central heating, fridges, air-conditioning), fans (computers, air-conditioning, some ovens), washing machines, vacuum cleaners, even hi-fi equipment and hair dryers. Such appliances can produce quite powerful rotating magnetic fields.
Vibrating HMPs may produce the right frequencies, but will they give us the right amplitudes for people nearby? It comes down to your physical distance from the source of the field disturbance. Assuming the amplitudes exceed minimum EIF level at their source, there is bound to be some critical distance, or zone, away from the source where the field amplitude will be correct. All you have to do is stay in that critical area for long enough and, if you are susceptible and the field varies enough over time, you may well get hallucinations. It is difficult to predict how far such a zone would extend without doing experiments. Magnetic fields decline quickly away from their source, falling with the inverse square law. As a guess, I would say EIFs would probably extend no further than a metre or two from a source likely to be encountered in a domestic situation, assuming the average geomagnetic field as a background. If there was a higher than usual ambient magnetic field, the range would decrease. Conversely, in an area of lower than usual ambient field, the range would increase. One might reasonably ask, how can you live in an area of lower than normal geomagnetic field? HMPs can distort the local magnetic field, as we have seen, and create areas where the local magnetic field is actually lower than average. Such HMPs would, obviously, not need to be moving to produce such an effect. This is the principle behind magnetic shielding. The magnetic field is ‘dragged’ into the HMP, so attenuating the ambient field around it. A place where the ambient field is low could be particularly promising, as it would require less of a field distortion to produce an EIF.
Interestingly, the degree of distortion caused by HMPs to ambient fields depends on such things as the shape of the source and its angle to the field, as well as the permeability and magnetisation of the metal. Long thin HMPs (like sheet metal) and curved ones (think of a horshoe magnet) disrupt the local magnetic field more than short, fat ones. Also, HMPs aligned with the ambient field will produce a larger effect than those at right-angles to it. Note, also, that the presence of vibrating HMPs would mean that hallucinations would only be experienced in quite small areas inside a house. This would fit in with the often observed fact that only certain rooms, or even particular spots, regularly produce ghosts.
Transformers and a relay (middle curve) combine transitions to produce seemingly chaotic fluctuations (top curve)
Another possible source of EIFs is combined magnetic transitions in mains frequency equipment. There are many pieces of electrical equipment that can produce such magnetic transitions. Though transitions are not EIFs in themselves, if you get enough of them in a small area, over a short period of time, they could have the same effect. By a transition, I mean a significant, slow (by electronic standards) change in the mains frequency magnetic field produced by electrical equipment. This would appear to a DC magnetometer (insensitive to mains-frequency) as a pulse. A transformer, for instance, though it operates at mains-frequency, takes time to become fully energised or drained (because the magnetic field induced is resisting the current change) when it is switched on or off. This produces a change in the magnetic field slow enough to be ‘seen’ by a DC magnetometer. Another example is a relay, which contains an electromagnet. When a relay is switched on or off, a static magnetic field will either rise or fall, producing a magnetic transition. Transformers and relays are common in the supply and switching sections of domestic electrical, and particularly electronic, equipment. Electrical house wiring may also show transitions (though not as powerfully) when equipment downstream is switched on or off or has a changing load.
In a house with lots of electrical equipment in use there may sometimes be enough pulses, close enough together, both in space and time, to constitute EIFs. If there are a few vibrating HMPs about as well, so much the better. It might seem unlikely that you would get enough pulses to constitute an EIF this way. But consider this, you only need one 100 nT pulse every ten seconds to qualify! As more and more electrical devices are operated in a house at once, the combined fluctuations will show a rise in amplitude and frequency as well as appearing increasingly chaotic.
Another important, though rarer, possible artificial source of EIFs is malfunctioning electrical equipment. This could include the mains supply itself. There are only a few ways most bits of electrical equipment can operate correctly, but any number in which they can malfunction. Therefore it is difficult to list particular examples of malfunctioning equipment producing EIFs. In general, though, accidental capacitances and inductances could possibly, in certain circumstances, give rise to low frequency currents (and hence magnetic fields). Fields can leak, unintentionally, from electrical equipment to nearby conductors (such as water pipes) through induction. Though these would be at the mains frequency, there might be resonances set up by the plumbing configuration that could be at a different frequency, possibly lower. Earthing problems are another possible source of unintentional fields. As I said before, it is difficult to come up with a concrete example, but it might happen and should be considered.
Of course, you may just happen to live in a magnetically dense area. As we saw with the unfortunate inhabitants of central Moscow, some places may be bathed perpetually in a sea of fields that qualify as EIFs. There may be nearby industrial users, such as factories, that could produce EIFs through HMPs and densely packed electrical equipment. So artificially produced EIFs may be outside the premises that are allegedly haunted. You should not assume EIFs are produced naturally just because they have no obvious source inside a house.
Another interesting source of EIFs is human movement! Although you may not have any moving fields within your home, you might move through reasonably strong, complex static fields sufficiently often to produce an EIF in your brain. If you think about it, walking between two areas of high magnetic field, with a low area in between, is no different from having a varying field pass through your head as you sit still. Given that you need to be exposed to such varying fields for some time, however, it might involve a lot of walking! It should be considered, however, particularly in a workplace that might well combine a lot of walking and a complex static magnetic environment. A probable example of this is an instance of a'haunted bed' (where some people lying in it experience strange ghostly sounds of a child crying). What is extremely interesting is that the bed has been found to magnetic, so that anyone tossing and turning in it would be exposing themselves to EIFs. This research is decribed here, on the MADS website. ( MADS = Magnetic Anomaly Detection System )
( http://atransc.org/ ) formerly AA-EVP
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