OK, I have an assessment task to create a 3D model of SOME of Einstein's thought experiments involving trains and mirrors, and present it to the class. Therefore a minimum of 2 thought experiments. The task is unique (ie each student is required to model a different part of the course), and I'm fairly confident with my understanding of SR, so I won't have many problems explaining it. My current plan is to model the following two thought experiments: Imagine a train consisting of two mirrors with a light pulse reflecting between them. The path of the light viewed by an observer on the train would be vertical. However, if the same clock is viewed by an observer on the platforms the train travels by at half the speed of light then the path of the light pulse would by diagonal according to Pythagoras' rule. The two observers then see the pulse of light travelling different distances in one second. Fairly easy to model, HOWEVER I need to model it in the best possible method. Two current ideas..: Simple box on wheels, 1 side open, hole in the top with a string attached to a ball. Box is projected, string is released, ball falls in a parabolic curve to the observer out of the box. Then go on to explain that the ball to an observer in the box sees it fall vertically. Then explain that as light isn't affected by gravity it would travel in a diagonal line, therefore travelling a further distance to an observer resulting in different 'clocks'. Volunteer sits on a swivel chair, which is spun and a ball is tossed vertically, which they see fall vertically. Repeated but with the volunteer projected at a constant velocity, to which they would see the ball fall in a parabolic curve. As with the other alternative, explain how light would travel diagonally and what the effect of this is. HOWEVER, this isn't really a practical model, as my entire presentation is limited to 6 mins and for it to be a viable model I would have to use every person (although it is a very small class) as a volunteer. Imagine that you are sitting in a train facing forwards. The train is moving at the speed of light. You hold up a mirror in front of you, at arm’s length. Will you be able to see your reflection in the mirror? Yes, the reflection will be seen because, according to the principle of relativity, it would not be possible for the person in the train to do anything to detect the constant motion with which he or she is travelling. However, a person watching this from the side of the track should see the light from your face travelling at twice its normal speed. But, since the speed of light is constant, distance and time become relative. this means that time passes differently for you on the train and for the person at the side of the track. This is the harder one to model, but I think it would be best done using two projectiles travelling horizontally, one travelling at 2x the speed of the other, and explain that as the speed of light is constant to all observers, the observer looking in the mirror would see the light travel their relative time to reach the mirror, while the observer on the platform would observe the same speed but over a different time. If anyone would be able to offer feedback, suggestions, criticism and whatnot, or even another of Einstein's thought experiments involving trains and mirrors which would be easier to model, it would be greatly appreciated.