Plays with YouTube's privacy-enhanced embed The Speed of Light is NOT About Light
8 HN users recommended this explainer in 8 different months between 2017 and 2023.
2007–2026
2 strong recommendations 8 recommendations 5 citations HackerTube score 9
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.
Pull quote: “The video about “the speed of causality” is the one that caused me to level up” (HN, 2020)
Also tagged: special relativity, speed of light, causality, relativity, physics, spacetime
What Hacker News said
15 labeled comments from the HN archive; up to 20 are kept per video, favoring different commenters. Each one links back to the original thread.
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Citations, criticism and jokes
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