Let's say there is a football field with a mirror set up in one of the end zones. If I am standing at the 50 yard line with a laser, and I point it at the mirror (facing me) in the end zone and shoot of a single blast of the laser and then record it's velocity as it bounces back and hits a sensor that I am holding, it will measure c (speed of light). If I do the same thing but move away from the mirror at a certain velocity after shooting off the blast of the laser, I'd still get a measurement of c because my both myself and my sensor have time dilated, so the sensor measures more slowly, thus compensating for my movement and keeping c consistent. If I do the same thing, but move towards the mirror at the same velocity that I moved away from it, c still remains consistent, but I don't understand why. i would think that me and my slowing down would actually anti-compensate for my movement, and that I would measure time as faster because I'm moving towards it AND my instrument is slowing down. What am I missing here? Thanks!