> I have always been told that acceleration is change in velocity over time. Is that wrong? Not per se, but it's more complicated when relativity gets involved

> I have always been told that acceleration is change in velocity over time. Is that wrong? Not per se, but it's more complicated when relativity gets involved. Wikipedia has some decent starting points: https://en.wikipedia.org/wiki/Proper_velocity https://en.wikipedia.org/wiki/Proper_velocity https://en.wikipedia.org/wiki/Proper_acceleration https://en.wikipedia.org/wiki/Proper_acceleration https://en.wikipedia.org/wiki/Four-acceleration https://en.wikipedia.org/wiki/Four-acceleration