In quantum physics lectures, half-integer spins are generally introduced as “objects that do not come back to their original state after one full turn but that do after two.” As a consequence, students often consider this behavior to be purely quantum mechanical. However, spin-1/2 is above all a geometrical property of the rotations group and can, therefore, also have practical consequences at the macroscopic scale.
In the American Journal of Physics, a recent article demonstrates a macroscopic object of spin-1/2: The spinorial ball.
To illustrate this, we introduce and describe in this work a new pedagogical tool named the spinorial ball. It allows students to concretely manipulate a macroscopic 1/2-spin, which helps them to build intuition as to how the latter behaves under rotations.
The ball used for illustration is a LED football containing an electronic 3D gyroscope, powered by an internal battery, whose faces change colors when it is rotated.
It is made of :
- a 3D printed frame divided in two halves of a truncated icosahedron
- 32 addressable multicolor LEDs (WS2812E)
- Arduino compatible Adafruit Feather 32u4 basic proto controller (And an additional FeatherWing Proto board receiving the LED strip connector)
- Adafruit Bosch BNO055 9 DOF inertial measurement unit
- a 3.7 V 1,1 Wh liPo Battery
See more in the paper here. The information on the LED ball is on GitHub. Via X.