“The short answer is: it can’t. 3D holography as seen in movies like Star Wars, where you see a hologaphic image projected in the air is only science fiction. To this day there is no way to project a hologram in the air, although there are some tricks to make it look like a similar effect. One that is very recent is exciting a plasma with a laser, and since the air gets ionized you can even interact with the hologram (here you can read further:). Another technique is using translucid screens in a certain angle and projecting the “holograms” into the glass. This technique has been used in concerts and other shows involving special effects, like the time Tupac was “brought back to life”.
But, the deceased hiphop artist Tupac appeared with Snoop Dogg and Dr. Dre and Snoop Dogg at Coachella Music Festival in 2012.And in interview published through the Wall Street Journal The News Hub discusses how. Apparently the technology was simply a projection onto an angled piece of glass, so the image can both been seen and seen through. In the 1870’s moral dramas were the heroin would ascend to heaven at the end of a show; Pepper’s Ghost.
“Pepper’s ghost is an illusion technique used in the theatre, amusement parks, museums, television, and concerts. It is named after the English scientist John Henry Pepper (1821–1900) who popularized the effect in a demonstration in 1862. Examples of the illusion are the Girl-to-Gorilla trick found in old carnival sideshows and the appearance of “Ghosts” at the Haunted Mansion’.”
https://en.wikipedia.org/wiki/Pepper%27s_ghost December 1, 2018