That’s a Moire (Pattern) Science

Hi –

This week in Science we learned about moiré patterns and kinegrams.

First we looked at the shadows of two combs projected on the wall.

Then we looked at the shadow that two identical combs form when one comb is moved over the top of the other.

We noticed that there were new wavy shadows that weren’t there when we looked at the combs separately. These shadows are a ‘moiré pattern.’

(Note to grown-ups: A moiré pattern appears when two identical patterns overlap. If the two patterns are on semi-transparent materials and are slightly offset, light and dark areas are created, forming a new pattern.) We thought the moving patterns were pretty interesting.

Next, we did a similar experiment with flexible window screen. When we moved one piece of the screen over another, we could see moiré patterns:

Everyone got a piece of screen. We folded the screen over on itself and moved it around to make our own moiré patterns:

Then we looked at the shadow of two transparencies covered with identical thin stripes – separately and overlapping –

and other overlapping (identical) patterns as well.

We also looked at a photo of a bridge over a highway (note the section where the fences appear to overlap) and pictures of my dining room curtains (note the patterns where the curtains overlap).

More moirés!

What happens if you move a striped transparency over a picture made out of striped areas?

We tried it. When we moved the transparency over the donut shape, it appeared to spin like a window fan. The wheels of the car looked like they were turning too. These ‘moving’ pictures are called ‘kinegrams.’

Once we had figured out all of that, we looked at the book, Gallop! A Scanimation Picture Book by Rufus Butler SEDER. Which is the reason that we are doing this lesson this week.. 🙂

Each page has a picture that appears to move and change as you open it up. The author calls these pictures ‘scanimations.’ How do they work?

To understand the ‘scanimation’ process, we reviewed ‘lenticular images.’ We learned about them in class a few weeks ago.

The pictures in Gallop! are made from a combination of kinegrams and lenticular images. A series of pictures have been cut into vertical slices and the slices alternate across a page:

Two edges of a vertically-striped transparency are attached to the left-hand page, while the remainder of it rests on top of the lenticular images on the right side.

The transparency masks all but one of the image sets at any given time. When the left-hand page is opened up, it pulls the striped transparency to the left, revealing the different lenticular images in sequence. If the transparency is moved quickly, the brain retains each picture and blurs it together with the next image. This creates the illusion of motion. Put them all together, and you’ve got a galloping horse.

We took a jumping-jack break – because sometimes you need one