China's in-orbit Shenzhou-16 crew, including Jing Haipeng, Zhu Yangzhu and Gui Haichao, on September 21 demonstrated the collision of steel balls with different weights to explain the law of conservation of momentum.

The experiment, made during the Tiangong Class livestreamed by China Media Group worldwide, is the fourth lecture of its kind. The Tiangong Class is China's space science education brand, introducing a series of classes in which the astronauts act as teachers in space and interact with students, especially teenagers.