I believe with practice one can transform their OBE to manifest their spirit form to appear as an apparition in the physical world in real-time. This could explain some of the ghost encounters. The Tibetan monks can increase their body temperature just by thought. Therefore it is possible we can transform our OBE into a form of a visible apparition (ghost body) in the conscious world (real world) at any geographic location in real-time to communicate with people.


Meditation Changes Temperatures:
Mind controls body in extreme experiments
http://www.news.harvard.edu/gazette/2002/04.18/09-tummo.html