Does light have inertia? Suppose a light pulse is emitted in a moving train in the direction of train’s movement. Should it move at its constant speed even in the moving train? And if there is a front window in the path of the light pulse, should it shoot out through the window to go ahead of the train and leave the train to lag behind? When we walk in the train in the direction of train’s movement, to an observer on the ground, our velocity will be added to train’s velocity. But should this be the case with the light pulse which will never show zero velocity in the train even to an observer aboard the train, and hence, should its velocity be added to train’s velocity to an observer on the ground. Now suppose that the train is moving at a speed much faster than light. The passengers sitting inside will also be moving at faster than light speed to observers on the ground. But should not the light pulse again travel at its own constant speed inside the train. Now if there is a rear window in the train, should the light pulse be, after some time, thrown back from the train through this window to lag behind the train, because it has little or no inertia? So, I want to know, whether the light pulse should face velocity addition problem or not? If it does not show velocity addition problem, can we use the speed of light as a reference for time? If we can, will it not lead us back to the absoluteness of time?