Why Faster-Than-Light Travel Enables Time Travel

PBS Space Time · Explainer · 12 min · 2017 · YouTube title: Superluminal Time Travel + Time Warp Challenge Answer

Why it's here

HN points to it in warp drive discussions as a math-free explanation of why superluminal travel causes causality problems.

What it covers

A PBS Space Time episode explaining why faster-than-light travel is equivalent to travelling back in time, using relativity and Minkowski diagrams for different observers.