How To Turn the World Upside Down [Video]

Build eyewear that flips your perspective around
Upside-down viewer
Upside-down viewer Photograph by Sam Kaplan

Feel like dancing on the ceiling? All you need are some Legos and two prisms. The largest facet of a prism acts like a mirror: Light rays enter through the smaller sides and reflect off the big facet’s inner surface, flipping an image vertically. Harness that optical trick with one prism for each eye, and you’ll be walking around in your own upside-down world.

Thanks to reader Christopher Marley for the idea. Got your own 5-Minute Project? Send it to


Time: 5 minutes

Cost: $20

Difficulty: 1/5


  • Two right-angle triangular prisms
  • Legos
  • Hat with a sturdy brim
  • String or rubber bands


  1. For each prism, place a four-stud baseplate upside down, centering the biggest side of the prism on top.
  2. Build a brace on each side that matches the prism’s height—a tight vertical fit will pin the prism in place.
  3. Place a two-stud baseplate upside down on top, aligned so the right angle of the prism nestles between the two rows.
One Prism With Lego Frame
One Prism With Lego Frame Katie Peek
  1. Place the two prism frames side by side and add another small baseplate to join them together.
  2. Loop the string or rubber bands over the hat brim or crown, positioning each prism in front of an eye.

This article originally appeared in the June 2015 issue of Popular Science, under the title “Turn The World Upside Down.”