Tag Archives: STEM

Pepper’s Ghost, Part II

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this hummingbird 1_edited 1This is not the first Pepper’s Ghost illusion to appear on Pop Goes the Page. Back in 2020, we posted a kid-friendly version featuring a spirited fox. The illusion is basically a reflection trick, but it’s very effective when done right!

seeing spirits   You’ll need:

  • A clear plastic drink container lid
  • Paper (heavier paper or thin cardboard works best)
  • A small section of clear plastic (like the lid of a food container)
  • Scissors and pencil for construction
  • Cell phone

The project was originally designed and posted by artist Joshua Ellingson on his Instagram. First, wash a clear plastic drink lid. Then cut a half circle template out of paper. When you have a half circle that correctly fits at a 45 degree angle inside your cup lid, trace the paper template onto a piece of clear plastic. We used an acrylic gift box, but plastic food containers work great too. Tape the plastic half circle inside the cup lid. The hardest part is getting that 45 degree angle just right. I made about 4 templates before I finally nailed it. Here’s my finished cup with the plastic half circle:

Head to YouTube for a Pepper’s Ghost illusion on a black background. We tried a couple different ones, but had the most success with this hummingbird. Cue up the video on your phone, maximize it to full screen, and lay the phone on a tabletop. Place the cup lid on top. Finally, roll the video and turn off the lights! Your object will appear to float inside the cup lid! It’s really quite remarkable.

The original designer, Joshua Ellingson, also made a GIANT version of this craft with a thrift store bubble chair and his flat screen television. It’s a must see! And Disney’s Haunted Mansion famously employs this illusion, including an entire ballroom of ghosts!

Cotsen Ghosties

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book cover 3Last Halloween season we took a stroll through our special collections pumpkin patch. Today, we’re looking for ghosts! And we found them in this amazing optical illusion book titled Spectropia; or, Surprising Spectral Illusions. Showing ghosts everywhere, and of any color. Published by J.H. Brown in London in 1864, the book teaches the concept of “the persistency of impressions, and the production of complementary colours on, the retina.”

The illusion is very simple. In the image above, stare at the small black dot by the ghost’s neck for 20-30 seconds. Then look away at a white wall or ceiling. Her ghostly image will appear in your vision, except in different colors (in this case green wreath, blue ghost)!

Scientifically speaking, this is called an afterimage. The color receptors in your eyes work in pairs (red/green, blue/yellow, etc.). When you stare at the drawing and one color fatigues your receptors, the other receptor will step in and dominate for a bit.

The book has a very lengthy description of this concept, as well as viewing instructions that include having the “gaslight turned low.”

Spectropia also has a disclaimer at the beginning: “As an apology for the apparent disregard of taste and fine art in the plates, such figures are selected as best serve the purpose for which they are intended.”

I wish they might have reprinted the disclaimer before THIS image, which honestly is going to haunt me clear through December:

The book concludes with a grand finale image that is not a ghost, but a rainbow! Definitely try this one, because it is so cool to see the colors flip in the afterimage!

Looking more more optical spooky fun? Try making our tabletop Pepper’s Ghost illusion!

Images from Spectropia; or, Surprising Spectral Illusions. Showing ghosts everywhere, and of any color. J.H. Brown, London. Griffith and Farran.1864. Cotsen Children’s Library, Department of Special Collections, Princeton University Library.

A Library for the Birds

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A heads up for our readers…in addition to eggs and nests, this post contains multiple images of bird taxidermy, which some may find unsettling. If you do, no problem! Skip this particular post, and we’ll see you on the blog next Tuesday!

Deep within Princeton University’s Department of Ecology and Evolutionary Biology, there is a plain door with a fairly innocuous sign mounted nearby:

Behind that plain door, however, is an amazing treasure trove of natural history. It’s the Princeton Bird Collection, which contains a taxidermy catalog of over 6,000 bird specimens, some of which are over 150 years old! Many were collected by William Earl Dodge Scott, who was appointed Curator of the Department of Ornithology in 1879.

Princeton’s bird room contains a multitude of hulking gray metal cabinets. While I’m used to our library’s special collections cataloged and ordered on regular bookshelves, the bird room’s cabinets open to reveal horizontal wooden drawers containing various specimens. These collections are available for teaching and research, including the Stoddard Lab’s research on avian coloration and morphology.

The drawers also contain nests and eggs, which are similarly laid out for researchers:

There are larger nests as well, including this amazing one that I’m pretty much ready to curl up and take a nap inside:

Beyond the drawers are a fantastic assortment of standing taxidermy, both large and small. Below are just a few the staff unwrapped for me to photograph…from top left to bottom…an emu, ground hornbill, kiwi, barn owl, macaw, snowy owl, and golden eagle.

And check out this! It’s a quetzal, which hails from Central America. It was was considered sacred by the Ancient Mayas and Aztecs. The photo really doesn’t do it justice. The coloring on the bird is simply exquisite.

The bird collection also contains the documents and journals of Charles Roger, a professor of ornithology at Princeton from 1920-1977. The journals, which he began as an eager boy of eleven and continued until he was eighty-four are a fascinating and informative body of work. You can read more about the digitization of his works, and find some awesome coloring pages from our special collections here (as well as a couple fun bird projects!).

A very special thank you to Cassie Stoddard, Assistant Professor in Ecology and Evolutionary Biology, for arranging for me to photograph the bird room, and answering my questions about ducks!