I am traveling at 90% of the speed of light in a given direction. I generate a new beam in the direction that I am traveling. If I was to measure the speed of the new beam in reference with the speed that I am currently traveling would that new beam of light be moving forward at 10% of the speed of light? ------>------>------>----->(me*)_____>____________>_____________> ^ new beam of light ^ measure ref. speed is the same speed I am moving at. (90% the speed of light) I ask this to clarify my understanding of the limit the speed of light imposes. Another question.... If I was traveling at 50 percent of the speed of light, and I shine a light perpendicular to myself as I am moving forward what effect would this have on the new beam of light? How would this effect be observed by me and a observer? ---->-------->------->------->---->(me*)---------->----> 50% speed of light l l l l \/ New beam 100% speed of light. I promise this isn't a homework question. I am just trying to fully understand what effects are produced by the speed of light in relation to a individuals position.