1. The problem statement, all variables and given/known data An observer in frame S standing at the origin observes two flashes of colored light separated spatially by Δx = 2300 m. A blue flash occurs first, followed by a red flash 5 µs later. An observer in S ' moving along the x axis at speed v relative to S also observes the flashes 5 µs apart and with a separation of 2300 m, but the red flash is observed first. Find the magnitude and direction of v. 2. Relevant equations I believe the necessary equation is v = Δx/Δt 3. The attempt at a solution So I initially thought I would simply have to plug in to the above equation Δx = 2300 m and Δt = 5 μs. But now I am realizing that would not give me the velocity of the observer. To find the velocity of the observer would I have to know the distance he traveled? And then use Δt = 5x10^-6?