1. The problem statement, all variables and given/known data Frame S' has an x component of velocity u relative to the frame S and at t=t'=0 the two frames coincide. A light pulse with a spherical wave front at the origin of S' at t'=0. Its distance x' from the origin after a time t' is given by x'^2=(c^2)(t'^2). Transform this to an equation in x and t, showing that the result is x^2=(c^2)(t^2). 2. Relevant equations I think the relevant equations are: x'=(gamma)(x-ut) and t' = (gamma)(t-[ux/c^2]) 3. The attempt at a solution x'^2=(gamma)([x^2]-(2xut)+([ut]^2)) t'^2=(gamma)([t^2]-(2tux/c^2)+([ux/c^2]^2)) plugged into the equation x'^2=(c^2)(t'^2) and reduced somewhat.... (x^2)-(2xut)+((ut)^2) = ((c^2)(t^2))-2tux+((c^2)((ux/c^2)^2) I think my algebra is crud somewhere, but the farthest I can seem to get this down to is.... (x^2)(1-(u^2)) = (t^2)((c^2)-(u^2)) Thank you for looking at my problem!! I hope I put enough clear information down, this is my first time here, please let me know if I need to clear anything up, and thanks again!