But as a said, my sister is convinced that she's haunted. Certainly if you were to choose a haunted house location you probably could choose no better than my sister's place - a big rambling, isolated 17th century farmhouse - there is a ruined castle and monastery at the end of their garden. The spooky associations there date back a thousand years to ghostly sighting of monks, allegedly the phantoms of those murdered in Viking raids.
She says she's seen ghostly people in period clothes walk past and through walls, in locations where they later found out that doors used to be.
The house is a bit creepy though. I did have one spooky experience there, not in the main house itself, but in the small cottage that they own nearby. In the middle of the night I suddenly woke up freezing cold, panicking and unable to move my legs, it felt as if there was a heavy weight on them. I put this down to perhaps a bout of “sleep paralysis”. I later told my sister that I didn't get a good night's sleep, to which she answered - "so did old Tom sit on your bed?". Apparently several people have reported being "sat on" as they slept and it was put down to "Tom" who was a long time resident of the cottage. Although spooky, I'm still not convinced, I still think there's a rational explanation.
Probably the single incident that spooked me most though was related to my mother's death. She used to say that she was "a little bit psychic". But a year before she died she did do some strange things - she had a conversation with my father about being OK if he remarried if she died and specifically mentioned a mutual friend (he subsequently did marry that person). But the spookiest thing was that we found after her death that she had gone from no life insurance to signing up for 5 policies in the year before her death (which as I said before was an accident and entirely unexpected) - as a result my father was financially secure after her death, could buy a house and invest the rest and live comfortably off the income.
Perhaps as a scientist I should not have a closed mind, but an open one - after all as Shakespeare says, there are far more things in heaven and earth… Just because we cannot explain something at the moment doesn't mean we never will.