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- My question is about on of the "famous" Einstein's mental experiment: the train and the lightnings, i don't understand why the result is what it is, I thought for day but I don't understand this particular case, If you can help me to understand I'll very grateful.

(excuse me for my english, but I'm studying physics and I am not a native English speaker)

One observer OE, is on the ground, we take him as the fixed frame of reference.

The other OT is on the train that is moving relatively to the OE at a costant velocity ( they are both inertial frame of reference).

So, two lighning strike the two points A and B when the train is with back and end in the same points ( A and B) and the two observer are aligned.

The observer OE is at equal distance from A and B, so the light, which travel at constant speed c, arrive at the same time at his eyes, the two events are simultaneous.

The observer OE anyway see OT traveling to B and move away from A, the speed of light is always c, so he conclude that OT observers first the light from B and then the light from A.

The result: OT see first ligh from B and then from A in his frame of reference.( like what think OE)

I agree with that, but now there is the problem( more than one):

1- If the speed of light is the same in EVERY inertial frame of reference, in the reference of OT that speed is c, so i think when the two lightning strike in A and B, they are equal distance from the center where there is OT 'cause the first assumption (when A and B are ALIGNED) so i think light will arrive at OT at the same time also in his frame of reference, if i don't observe that i think light speed is greater than c from B to OT and lower from A to OT, but this is a contradiction, and I don't understand how to escape from that my surely wrong interpretation.

2-If A and B are fixed with OE, and they arrive at OE in the same time, when I am OT, I see OE traveling in the opposite direction so I see light from A arrive first to OE and the B, ( because always c is the speed of light), but in this case OT see the "same" event but from different perspective and this for me is clear, also with Minkowskii diagrams, i see two events simultaneous for OE and for the OT perspective they're not.

3-If A and B are fixed with OT, they are simultaneous for OT but OE see what the original experiment say: OT see first A and then B, this time I am totally agree with that.

So what is the difference between 1 and 3, and why if the speed of light is the same, c, OT see first B and then A, if they are aligned and equal distance from OT.

Thank for answer.