Strange question, I know, but I feel this is a good place to ask the question: What would be classed as a "Ghost" detection?
I do not believe in anything; ghosts, deities, witches, skeletons with bows and arrows, zombies or anything else. But I'm obsessed with Ghost hunting YouTube channels. I know it's a load of nonsense, however, like Mulder, somewhere deep down "I want to believe". I understand it's all side effects of being human with good filmography that make this entertaining.
These hunters use some strange equipment, "Rem Pods", EMF testers, "Spiritboxes", etc. These are all easily debunked.
But it got me thinking; What would actually prove the existence of a ghost? What phenomena and what evidence would actually be required?
I don't think anything will ever be found as concrete evidence, but without knowing what the acceptance criteria is, we're ultimately always going to be looking in the wrong place.
PS. It's Halloween soon so thought this may be a fun thought experiment.
More generally - reliable, useful, macroscopic physical actions, requiring non-trivial judgement.
https://existentialcomics.com/comic/495
On a more practical level, there's a distinction to be made between (A) whether there is something unusual and detectable, versus (B) whether it supports a huge extra set of supernatural baggage.
This distinction is especially important in the related field of UFOs.
My mother loved to go out with my aunts on weekends. One night while I was sleeping my father heard sounds of high heels in the corridor that had wooden floor. He got out of the room to check whether my mom had returned. There was no one. Being a skeptic he will never tell you that was a ghost.
At another time I was feeling depressed and laying on my bed on a side. Windows closed. I felt this kind of "slow wind" touching my arm. I actually felt better right after that.
And I also witnessed a nasty accident while watching thru the window that's probably too much for HN audiences.
As for a detector, get depressive people inside the house and examine what happens to them.
Shortly after my mom passed, I was making dinner in the kitchen when I heard, clear as day, what sounded like my mother's voice yell out my name (it sounded like the type of yell she used to get my attention). When I looked over toward the direction I thought I heard the voice, our dog (that my mother found in a shelter for us), was sitting in front of me, intensely staring at me and acting super excited, which was unusual.
Skeptical me just thinks it was some random event. My wife (believer) was hugely annoyed at me for ignoring such an obvious sign. If so, my mom's up in the sky cursing my intelligence, or lack thereof.
That event still trips me out and I think about it a lot, but my brain won't allow me to believe it was anything supernatural.