1. The problem statement, all variables and given/known data The spacetime interval between the origin in frame S and an event, A, is found to be r = 8 lightseconds. In frame S' moving in Standard orientation with respect to S at speed v = 0.5c event A is measured at a distance r' = 6 lightseconds from the origin. (a) What is the time interval between the origin in S' and event A? (b) Could an event at the origin and event A be causally related? Explain your answer 2. Relevant equations 3. The attempt at a solution I am studying for upcoming exam so the solution isnt as important as understanding the question, but as far as i know the spacetime interval is invariant which is throwing me way off here, I'm certain if i can get part a i understand part b but am completely at sea with part a) any help will be greatly appreciated, cheers.