By ghosts, I'm referring to creatures possesing characteristics normally associated with traditional ghosts/spirits. Things like:
- Invisible (bonus point if they could choose to be visible)
- Could phase through objects or teleport
- Could interact with objects
- Could shape-shift
They could be the spirits of the deceased, but other supernatural entities with similar characteristics also qualify, such as the jinn.
The idea of them being higher-dimensional beings is really neat, but I'm thinking of another possibility: what if they are based on virtual particles instead? After all, virtual particles are basically "there-but-not-really-there", yet still have physical effects eg. the Casimir effect. Are these creatures possible? My understanding is that virtual particles are basically background statistical fluctuations, but what if some behave non-randomly?