I came up with a sort of thought experiment to help me ask this question. It goes as such: Jack, Jill, and Joe sit near two buttons (Button A, and Button B). Joe sits directly in the middle of the two buttons, and is to push the buttons at the appropriate time. Jack and Jill sit on the left (closest to Button A) and right (closest to Button B), respectively. When Joe pushes the button, three events are possible of happening: Event A, Event B and Event C. If Joe pushes Button A first, Event A happens. If Joe pushes both buttons simultaneously, Event B happens. If Joe pushes Button B first, then Event C happens. Because of the positioning of everyone (so the light reaches them appropriately): Jack perceives Joe pushing Button A, and as such, would expect Event A. Joe knows he pushes both buttons simultaneously and expects Event B. Jill perceives Joe pushing Button C, and expects Event C. Which one actually happens? I have read that because of the principle of relativity, absolute simultaneity is thought to not exist - but I figured that the result of some event occurring would reflect that there is absolute simultaneity. Could someone help me reflect on this? Thanks. P.S. the idea regarding causality here is that the ordering of the button presses causes the corresponding event.