I'm actually an Aero major, and we have to take some relativity (it's useless, but they want us to know it), so here's the deal, and yes, it's hard to get your head around. light tracels at c. whatever reference frame you view it at, it's going at c, so if you're outside, standing still, and a car goes by at mach 1 with headlights on, the light from the headlights, as measured by you will be going EXACTLY C. However, if someone was out infront of the car going mach one, he, too would measure the light as going C. I know it's weird, and it defies a lot of the logic you've been presented, but it really is the way light and time and space work.