Alter vu is a term that describes the feeling of remembering something differently, or experiencing visions or dreams of events that never happened, allegedly as the result of changes to a worldline.
Breakthrough: An Amazing Experiment in Electronic Communication with the Dead is a book published in 1968 about Konstantīns Raudive's work with spirit communication.
Doubles of living people, which sometimes appear as apparitions. They may lack shadows or reflections, and may be seen as bad omens.
An extraordinary substance once believed to be exuded from physical mediums during seances in the late 19th and early 20th Centuries.
A manifestation of a group consciousness, like a mass thoughtform, which can become powerful enough to take on a life of its own.
Looking at the available evidence and various reported sightings throughout history, we have some possible explanations for the existence of ghosts.
A painting from the late 16th Century seemingly depicts the world's first satellite.