Light Cones and Simultaneity

[thenewmans]

Please tell me if I have this correct. A particle has both a future light cone and a past light cone. In the past is everything that can affect the particle without exceeding Special Relativity. Now let’s say you have 2 entangled particles and you measure them so that each measurement is taken outside of the other particle’s light cones. Determining which measurement was taken first requires a specific inertial frame of reference. If that’s correct then you can’t determine which measurement was taken first absolutely since you can always pick a specific inertial frame of reference which disagrees. (The events don’t require entanglement. I’m just thinking about QM.)

 

[azntoon]

Yes, your understanding is correct. In order to determine which measurement was taken first, you need to have a specific inertial frame of reference. However, due to the fact that different frames of reference can disagree on the order in which measurements were taken, it is impossible to determine which measurement took place first absolutely.