Temporal Tops
| Physics, Biology: | Color Blending, Temporal Aliasing |
| Grade Range: | Elementary School, Middle School |
| Format: | Hands-on |
This is a fun demo for students to play with. Most will find the illusions to be mesmerizing!
Materials
- Set of Tops
Safety Precautions
Please read the General Safety section of the Demonstration Safety page before performing this demonstration.
Demonstration
- Set out the tops on the table. If the event has over 400 guests, have a plastic bin on the table for the students to spin the tops in.
- Allow students to come up to the table and spin the tops. Have them try to identify the source of the illusions they see on the tops when they are spinning.
Why This Works
This demonstration is focusing on the effect known as Temporal Aliasing. Temporal Aliasing is when an object is moving quickly, or an image is changing rapidly, and the motion is too fast for our eyes to follow. Our brains then receive the blurred image, and try to process it as a non-blurry image. The result is that we "see" a pattern, color, or motion that isn't actually there. The tops are known as Benham's Tops, and were originally made by a toymaker in the early 20th century. The effect that is seen on them is based on how quickly the tops are spinning. If the tops are spinning fast, then they will have distinct circles on them and a greater color change. If the tops are spinning slowly, then the lines are blurry, and there might be some mild color change seen on them. The tops with a solid black side, however, have a unique feature due to our eyes. Everyone's eyes are slightly different, even when it comes to the number of images, or "frames", we see per second. On average, we can see 60 frames per second, but individually we see either slightly more or slightly less than that. The tops with a solid black side, when spinning, create a color illusion based on how long the black lines appear to be. Since our eyes all see slightly different numbers of frames, we will all see different shades of colors in the lines!
Additional Information
- If students are extra curious in this demonstration, you can ask them to try watching the tops while blinking quickly. How does the effect change? Why?
- This demonstration pairs well with the Stroboscope, Color Mixing, and the Mirror Mirage