This Spinning Arrow Might Make You Question Your Sense of Direction

'Round and 'round the arrow goes, but where it points—nobody knows. As spotted by Sploid, this befuddling optical illusion of a spinning arrow appears to be pointing right no matter how many 180-degree turns you give it. See for yourself:

Right Pointing Arrow: spin this arrow 180 degrees and it still points to the right- only in a mirror will it point left (and only to the left). Another incredible ambiguous object illusion by mathematician Kokichi Sugihara of Meiji University in Japan, the inventor of this illusion and art form. A clever combination of reflection, perspective, and viewing angle produce this striking illusion. ➡️ Follow the link in my profile for info about where to get this illusion arrow and other amazing items featured here on @physicsfun #illusion #ambiguouscylinderillusion #ambiguouscylinder #geometry #mirrorreflection #physics #ambiguousobject #kokichisugihara #physicstoy #math #mathtoy #mathstoy #optics #opticalillusion #3dprinting #perspective #science #scienceisawesome

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The illusion was designed by Kokichi Sugihara, a mathematics professor at Meiji University in Japan. Sugihara is adept at creating 3D objects that seem to defy the laws of physics, using a “combination of reflection, perspective, and viewing angle” to trick viewers, according to the physicsfun Instagram page, which posted the video.

The effect still works when the object is held up to a mirror, although instead of pointing right, the reflection shows the arrow pointing left each time. The object appears symmetrical when viewed from above, but when you look at it head-on, it appears to come to a point on one side. It all comes down to the way the edge is carved—a testament not only to Sugihara's mathematical ability, but also his craftiness.

Want to see more of Sugihara’s work? In another video, a rack of cylinders appears to be transformed into a rack of rectangles right before your eyes.

[h/t Sploid]

Can You Find the Lost Items in This Santa's Workshop Puzzle?

If the holiday season has you feeling stressed, here's an opportunity to take a break from making travel plans and brainstorming gift lists. This picture puzzle from Attic Self Storage features six hidden items, and it takes most people a few minutes to find them all.

The scene below depicts the chaos of Santa's workshop leading up to Christmas Eve. Hidden among the elves and toys are some lost items: a stocking, a nutcracker, Santa's hat, a mince pie, a Christmas cracker, and a robin. If you aren't sure what you're looking for, a visual key of the items is included at the bottom of the image.

Santa's workshop brain teaser puzzle.
Attic Self Storage

It took Attic Self Storage staff members 3 minutes and 26 seconds on average to solve the brain teaser, so that's the time to beat. After completing the challenge, see if you can spot the sheep hidden among the Santas in this holiday-themed puzzle.

You Can Gift Your Favorite Nerd a Subscription to Famous Letters From History


Letter writing may be a lost art at this point, but you can still give someone the gift of getting a great letter in the mail, without ever picking up a pen yourself. Letterjoy, a subscription service for historical letters, sends out a different archival letter each week, giving subscribers the opportunity to dig through their mail and find a work of great writing rather than a pile of junk advertisements.

As part of the service, Letterjoy sends out one authenticated historical letter or telegraph each week, according to monthly themes. The letters are largely drawn from the last 400-plus years of American history, sourced by Letterjoy founder Michael Sitver from historical archives and private collections. Previous monthly themes have included "presidents and the press," "the right to vote," "Civil War spies," and "the birth of aviation." The letters often come from famous figures like Abraham Lincoln, Albert Einstein, Winston Churchill, Clara Barton, and the Wright brothers.

Recipients don't just get a photocopy of an archival letter. Each letter is custom-designed by Letterjoy, either typed up on a Smith-Corona typewriter (for more modern missives) or handwritten by designers and enhanced with software. The goal is to make each letter look and feel as authentic as possible while maintaining readability—since the whole point is to read the letters, not just look at them.

Every letter comes with a context section that explains what the letter is and why it matters, including who the letter-writer and recipient were and the historical events surrounding its writing.

You can buy someone (or yourself) a yearly plan for $160 ($13.33 a month), a six-month plan for $100 ($16.66 a month), or a three-month plan for $50 (also $16.66 a month). Discounts are available for educators who want to use the letters in their classrooms.