(adsbygoogle = window.adsbygoogle || []).push({}); The use of the word "see" in relativity

1. The problem statement, all variables and given/known data

From Spacetime and Geometry by Carroll:

problem 1.3) Three events A, B, and C are seen by observer O to occur in the order ABC. Another observer O' sees events to occur in the order CBA. Is it possible that a third observer sees the events in the order ACB? Support your conclusion by drawing a spacetime diagram.

2. Relevant equations

I've done this, constructed the diagrams and the answer is yes. Disturbingly my instructor has decided to interpret the problem differently than I. He thinks the problem is ambiguous and that 'seeing' could mean the physiological act as opposed to thinking of entire frames as observers. The consequence of this is as follows:

So he's accepted the following, which I believe is rubbish:

Take 1 inertial frame, put three spatially seperated observers in it. so you have three vertical world lines. Now put three events on the x-axis, spatially separated. Draw the light cones of these events. The boundaries of these light cones (the light rays themselves) intersect the vertical worldlines in different orders. So these observers "see" the events occur in different orders.

But this is not a lack of simultaneity, all of these observers can do physics and determine and agree on the actual spacetime coordinates of each of the events. I wanted others to weigh in on this.

Thanks (apologies if this is the wrong place for it, but it was a homework problem)

Kevin

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# The use of the word see in relativity

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