After a devastating oil tanker collision in San Francisco Bay in 1971, John Francis made an extraordinary decision that would reshape environmental activism. He chose to stop using motorized transportation and took a vow of silence that would last 17 years. His remarkable journey, captured in the new short documentary “Planetwalker,” evolved into a profound meditation on human connection and environmental consciousness. In this conversation, we talk with Francis and the film’s directors, Nadia and Dominic Gill, about a story that offers insights into how environmental activism has changed over 50 years, revealing the powerful connection between how we treat each other and how we treat our planet.