Submitted: Jun 23, 2008 - According to believers, a ghost is the spirit of a dead person that either has not moved on to the afterlife or has returned from it. The definition of "spirit" can vary. Some describe it as a person's soul, while others believe it is an energetic imprint that a person leaves on the world.

Humans have believed in -- or been skeptical about -- ghosts for thousands of years. They're even…