My other life: Rachel Murphy, 27
Other life: Ghost hunter
People might not expect it, but ghost-hunting is a very scientific process.
To help us detect the presence of spirits, we use camcorders, electromagnetic field readers, and devices that detect ultrasound; ghosts can communicate at frequencies that we can't hear. Having taken up position in the dark, we'll say, "If there is spirit energy in the room, know that we come in respect. Please show us your presence, by light or sound".
My husband Lee and I became interested in the paranormal after attending a spiritualist church. During our second hunt, at Canterbury, I saw a mysterious mist form rush towards me. I gasped, and so did other members of the group; they'd seen it, too. I was hooked.
Now we run regular ghost hunts ourselves, through a company called Paranormal Tours. On Friday nights we'll drive up to some of England's most haunted houses, such as Walton Hall in Warrington, and Woodchester Mansion in Gloucestershire. First there are psychic workshops and we'll scout for potentially haunted areas with a medium. The all-night vigil begins at dusk; we split into teams and go to different rooms. You become expert at staying awake all night - with the help of a lot of tea and coffee.
At Walton Hall last year a medium managed to connect to a spirit energy who, we learned, was particularly interested in the women in the room.
Later we listened back to our dictaphone recordings and heard an unknown male voice repeatedly saying, "hanky panky". Two of the women reported feeling their bottoms being pinched. On another occasion, in a cellar in Bodelwyddan Castle in Wales, we heard banging noises on the wall in response to our questions. There's a huge adrenalin rush when you suspect that you're in touch with a spirit. If nothing happens, we might do some glass divination with the medium. But we don't use ouija boards; they have a bad reputation.
All this might seem at odds with my background in mathematics, but the two aren't so different. On hunts we take a logical approach, and exclude all practical explanations first. But when pupils find out about my hobby - we featured on a local television programme recently - they usually think it's a bit weird. My Year 11 class follow me down the hallway singing the theme from Ghostbusters.
I know some people think it's nonsense, but I've seen too much to dismiss the paranormal. However, I don't think I'll ever afford my own haunted castle on a teacher's wages.
Paranormal tours: www.paranormaltours.com. Rachel Murphy was talking to David Mattin