Ghost hunting gems

I didn't blog about another Oxford Skeptics in the Pub event earlier in the year, but yesterday's post about Trystan Swale reminded me that I had taken some notes when Hayley Stevens came to speak about "I'm a ghost hunter - get me out of here!"  Hayley is co-fonder and host of the Righteous Indignation podcast with Trystan Swale.

She described some of the equipment used by paranormal investigators and had great fun pointing out that whether or not the equipment reveals anything at all, there is no evidence of any connection with ghostly happenings.

The 'ghost box'.  These are actually a hand held transistor radio with a scanning mode.  (AM and FM operation).  You are advised not to raise the aerial (perhaps just in case it picks up actual recognisable radio stations?).  These ghost boxes are sometimes used to detect 'electronic voice phenomena' (EVP), in which the voices are not heard at the time by observers, but appear on recordings that are later played back.

'EMF meters' - strangely seem to be calibrated in gauss - and hence they are not picking up EMF (as in electro-motive force - which is measured in volts)  but magnetic flux.  EMF in this case seems to stand for 'electro-magnetic field'.  However, as a physicist I'm not quite sure where the 'electro' bit comes in as gauss is a magnetic unit, not electric, and of flux, not field.  The typical range of operation is 1 to 10 milli-gauss which is much less than the earth's natural field.  They usually have an variable tone audible output too, and by sweeping them around a room they can be made to make sounds even in areas which had previously been surveyed and shown not to have a measurable signal.  It seems that these boxes are commonly implicated in deliberate fraudulent activities by 'paranormal investigators' who want to 'show' that there is something there.

Trigger objects - investigators often use coins or crucifixes or objects/areas sprinkled with talcum powder to observe whether they have been interfered with.

Green laser with a beam splitter  - which creates a network of beams around a room, making it possible to see any object moving through the room.

Orbs - a well known optical phenomenon that has been known to photographers since the earliest days.  Spots of light are produced by items that are in a field of view but not in focus, often highlighted by flash photography.  Apparently it is 'known' in the paranormal community that each orb represents a ghost.  It is not known exactly how they know this.

Scrying - a technique where the observer sits in front of a mirror in a room that is barely illuminated.  Water is poured down the mirror and it apparently produces surprising results, even to us skeptics.

Table tipping - a common way to make it appear that there is some paranormal activity in the room.  Everyone puts their hands on the table and movements in the table get amplified by the well studied ideo-motor effect.

Another good evening.  It was good to see the range of technological toys that are wielded by the ghost-hunters and to hear some stories from a skeptical ex-hunter.