"We are still doing Special Relativity here. Flat spacetime, no gravity." This is a superb bit of pedagogy, despite the medium, thus the submission here. It d

"We are still doing Special Relativity here. Flat spacetime, no gravity." This is a superb bit of pedagogy, despite the medium, thus the submission here. It does essentially require you understand https://en.wikipedia.org/wiki/Einstein_notation https://en.wikipedia.org/wiki/Einstein_notation and/or basis-independent abstract index notation, however. The "Physics for Mathematicians" work discussed on HN recently at <https://news.ycombinator.com/item?id=39305931 https://news.ycombinator.com/item?id=39305931> has an excellent crash course at <https://nicf.net/articles/general-relativity/#abstract-index-notation https://nicf.net/articles/general-relativity/#abstract-index...>. It's important to note the poll/quiz question's requirement that "the distance between the rockets in the initial rest frame remains constant", which is reflected in the Minkowski spacetime diagrams in the thread. The author's treatment does not fix other distances. This is discussed at greater length and in a variety of different ways (all with the same outcome) at https://en.wikipedia.org/wiki/Bell%27s_spaceship_paradox https://en.wikipedia.org/wiki/Bell%27s_spaceship_paradox