Why the Speed of Light Is the Speed of Causality

HN commenters send people to it whenever a thread confuses the speed of light with a light-specific limit, and several say it deepened their understanding of relativity.

PBS Space Time argues that the speed of light is better understood as the speed of causality, the universal limit on how fast cause and effect propagate. Light travels at that speed because it is massless, but the limit itself is a property of spacetime.