Consider two objects, a and b, traveling toward each other at, say, 100 m/s. There are three observers, OA, OB, and OC. With respect to OA, a is stationary. With respect to OB, b is stationary. From OC's point of view, both objects are approaching each other at 50 m/s. From OA's perspective, b collides with a at 100 m/s. From OB's perspective, the opposite occurs. From OC's perspective, both objects collide at 50 m/s each. It seems to me that the result of each of these scenarios would be different. OA would see a go backwards, OB would see b do so, and OC would see both cease motion. Only one of these events would actually occur. Does that not imply that one of the observers had a "correct" viewpoint? Additionally, it seems to me that a collision between two cars traveling at 50 m/s toward each other will have different results than one car traveling toward a stationary one at 100 m/s. Is that correct?