Pepper's ghost
A Victorian theatre illusion that makes a ghostly figure appear on stage, still used in theatres and theme parks.
Also: Dircksian phantasmagoria, stage ghost illusion, Haunted Mansion illusion
Pepper's ghost is named for John Henry Pepper, a lecturer at the Royal Polytechnic Institution in London, who demonstrated it in 1862 in a staging of a ghost scene from a Charles Dickens story. The idea was developed by the engineer Henry Dircks in 1858, and Pepper improved and promoted it, so the two men disputed credit. It made a ghost appear to walk among living actors and became a hit in theatres across Europe and America. The effect is an optical illusion, and the audience was told so. It lives on in theme-park haunted houses and in displays of recorded figures such as the 2012 concert appearance of the late rapper Tupac Shakur, which many described as a hologram.