confused about this thought. Object A and B are d distance apart, as measured by an object exactly in the middle of them, object C. A and B are moving towards each other at c/2, again measured by C. According to C's frame of reference, all three objects will collide at the exact same moment, causing whatever effects their collision causes. But from A's frame of reference, C is moving towards A at c/2, and B is moving towards A at 0.8c. So from A's reference, A hits C first, then it hits B. How is this reconcilable? If they were, for example, pool balls, how can we figure out the velocity of C after the collision?