Science & Technology

An Eerie Augmented Reality Illusion from the 1850s Is Still Being Used Today

When you think of augmented reality, you probably think of smartphones and video game consoles — the kind of advanced technology that can place an imaginary figure in just the right way to make it appear as if it really exists in your surroundings. In fact, augmented reality is nothing new. As far back as the 16th century, people were documenting ways to fool audiences into seeing things that weren't there. Even more surprising? You've most likely encountered some of that centuries-old technology today.

A Bloke and Mirrors

Imagine you're a citizen of Naples in the mid-1500s. The Scientific Revolution is just gaining steam, and it seems like every day you're hearing about a new invention or discovery. Even in that context, it would likely still be astonishing when you enter a darkened room to see the ghostly apparition of a statue — an apparition that couldn't possibly be there, and yet one that you can see as plain as day. While we don't have evidence that anyone actually created this illusion in the real world of the 16th century, it's certainly possible as the scholar and polymath Giambattista della Porta wrote about it in 1558.

The key to della Porta's illusion was a piece of transparent glass that had a mirror finish on one side, so that with the right lighting you could both see through it and see what it reflected. You'd place that glass at an angle between the spectator and the room they're looking at so that the angled glass reflected a second room the spectator couldn't see. Once you illuminate a statue, person, or any other object in that second room, their reflection would appear on the glass and make it look like they were actually in the first room — but with a ghostly glowing appearance, since the illumination wouldn't spread to anything that really exists in the room you're looking at.

It wasn't until 200 years later, however, that this illusion really had its heyday. In the late 1850s, engineer Henry Dircks described something nearly identical to the British Association for the Advancement of Science, although this time in the context of a stage production. Dircks' version put an actor in a hidden chamber underneath the audience and illuminated him with limelight, a 19th-century form of stage lighting. A pane of reflective glass would sit on the stage at a downward angle to reflect the actor, who would appear as though he was moving around onstage. Dircks never used his design in a theater, but he did exhibit a working model.

If the fact that we now call this trick "Pepper's ghost" is any indication, the man who had the greatest success with it was the chemist John Henry Pepper. He made improvements to Dircks' design, most notably by lying the hidden actor down on a slope at the same angle as the mirror to correct for any distortions. Pepper's illusion became popular on theater stages where ghostly skeletons would haunt murderers who, try as they might, could never wound them with the thrust of a sword. But eventually, it fell out of favor in drama and shifted to the sideshow circuit. One popular format was the "girl to gorilla" illusion, where a woman in a cage would transform into a gorilla and break through the bars to the thrill of the spectators in the room.

Nothing New Under the Sun

These days, it's rare to visit a sideshow and even rarer to see Pepper's ghost in a play. No, if you've encountered this illusion, it was likely at Disney's Haunted Mansion. There, Disney's Imagineers put Pepper's ghost into overdrive: In addition to reflecting the images of animatronic characters beneath the riders so they appear as dancers on the ballroom floor, the attraction also places dancing ghosts in the air, reflected from figures directly above the riders' heads.

Tupac's "Hologram" at Coachella 2012

But that's not the only place that Pepper's ghost lives on today. Remember when the late Tupac Shakur's "hologram" appeared at at Coachella in 2012? That was no hologram — that was Pepper's ghost, albeit one that reflected a CGI image that cost six figures. The illusion also plays a starring role in teleprompters and in the head's up displays you'll find in fighter jets and luxury automobiles. Cutting-edge technology can do impressive things, but the modern world still has a place for smoke and mirrors.

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For more on how the Haunted Mansion works, check out "The Haunted Mansion: Imagineering a Disney Classic" by Jason Surrell. We handpick reading recommendations we think you may like. If you choose to make a purchase, Curiosity will get a share of the sale.

Written by Ashley Hamer September 28, 2018

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