Supernovae - Solution
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B and E simultaneously, then D, then A,
E, then D, then B, then
A and C simultaneously.
B, then A, then D, then E, then C.
B, then D, then E, then A and C
The chronological order of A and B
is the same in all frames of reference.
The spacetime points A and B can be connected by
an object or signal which travels slower than the speed of light.
(In technical terms, A is in the future light-cone of B.)
Therefore, B must happen before A in all frames.