the gif small motion picture, which is deeply loved by netizens, has a history of 30 years, but in fact, the infinite loop motion picture has an even longer history: as early as 1832, there was a magic little animation that loops infinitely on paper-Finage Mirror.

the classic form of the Finacci mirror is to divide a circular disk equally into several parts, with a frame in each frame and a slit at the edge of each frame. When watching, the viewer looks at the picture through the slit in front of the mirror. When the disc rotates, the image in the slit moves:

the whole picture of this disc is as follows:

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the way of observation is as follows:

the Finacci mirror can only show a very short cycle of animation, and it can only be observed by one person, and it is quickly replaced by new technology. However, the technology of the Finacci mirror is relatively simple, and it can be easily made at home, so it is still a very good little scientific toy.

Let's take a look at the method of making a simple version of the Finacci mirror.

the materials you need: paper jam (preferably not too soft), compasses, rulers, pencils, a bamboo stick or chopsticks that can be used as a rotating shaft.

first draw the frame of the grid. Draw a big circle and divide it into eight equal parts (whether you draw the ruler or directly use the horn, you can measure it as you like. Draw a slit on each line of the octave sector and end up with the following:

(if you are too lazy to draw, you can download the blank drawing: http://www.rigb.org/docs/phenekistascope_blank_experimental_0.pdf)

next, draw the frame of the small animation you want in each fan grid. The simplest way to draw is to draw the same object and let it move outward some position in each frame. You can also try various other painting methods.

(if you are too lazy to draw, you can download a patterned drawing: http://www.rigb.org/docs/phenekistascope_frg_experimental_0.pdf)

next, cut out the round paper, cut off each slit, and then insert a bamboo stick at the center of the circle to act as a rotating shaft. A simple Finacci mirror is done:

then you can look at it and face a mirror. Look at the patterned side of the Finacci mirror towards the mirror and look through the slits in the paper. Turn the piece of paper and you can see that the pattern on it becomes animated.

(although the shot is not very clear, you can still see _ (: pictures "∠) _)

Why do you have to go through the slit and observe it directly? Of course not. If you look at the rotating pattern directly, you can't see the pattern clearly:

the purpose of the slit is to ensure that the viewer can see the pattern only when the next frame reaches the same position as the previous one. For example, in the one we made above, there is a difference of 8 laps between the two slits, and the same is true between the two patterns, so every time you can see the pattern in the slit, there is a difference of 8 laps between the previous frame and the previous frame. At this time, the next pattern is transferred to the position of the previous frame. In this way, under the effect of visual retention, people will feel that the pattern is moving in place.

there is another kind of Finacci mirror designed with slits and patterns on two circles respectively, so that it can be observed without a mirror:

I have to say that the magic degree of the Finacci mirror patterns in the past is not inferior to that of today's gif. Let's enjoy a few more:

. )

the drawings mentioned in this article are from the Royal Institution website. The introduction page of the experiment is here: http://www.rigb.org/families/experimental/spinema