1. The problem statement, all variables and given/known data Two space ships, each a hundred metres long when measured at rest, travel toward each other with a speed of 0.85c relative to the Earth. 2. Relevant equations λ = 1 / √1 - (v2/c2) x' = λ(x - vt) L' = L / λ 3. The attempt at a solution Well to be honest i may be missing an equation or something but that's what i was given. I find that the relative velocity of one spaceship to another (according to newton) would be 1.5c. This doesn't work using the equations above. I know i have to find the relative velocity according to Einstein's theory but i don't know how.