answer:Inside the spaceship time seems to pass normally. You don’t observe any slowing and you age normally. It’s only observers in other frames of reference who see the time dilation (slowing). When you turn on a light, those photons still travel at speed c as usual & that’s what you measure with your ship-bound equipment. All observers everywhere agree that light travels at exactly c – which is the basis for all the other weird effects. There’s a “Straight Dope” column devoted to this topic: If you turn on your headlights while driving at the speed of light, what happens?