In episode eight of the Shedding Light on Motion series, we look at that most poetic of all Laws. For every action there is an equal and opposite reaction. How does a rocket engine work? Why do guns recoil when fired? How do our muscles work? What propels us when we’re swimming? And how exactly is gravity a two-way interaction? All these questions, and many more, are answered in this excellent video.

Streaming video file encoded with permission for digital streaming by Infobase on September 19, 2017.

Part A: Introduction (1:20); --Part B: Action-Reaction Pairs in Collisions (7:43); -- Part C: Moving the Earth (5:38); -- Part D: Pushing Off Each Other (17:58); -- Credits: Shedding Light on Motion: Episode 8— Newton's Third Law (0:26); .