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I am learning that the order of causally disconnected events is the same for every observer regardless of your point of view, but it's beyond my comprehension what exactly it is? Are there real time examples? here is the diagram from the you tube video.enter image description here

for observer A event order is 1,2,3 for observer B event order 2,1,3 but 2 is always happening before 3 for both observers because 2 is causally disconnected. In order to change the order of 2 we have to travel faster than speed of light.

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  • $\begingroup$ Possibly related: Why is causality preserved in special relativity? $\endgroup$
    – jng224
    Commented Feb 5, 2021 at 15:21
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    $\begingroup$ I think you are mistaken. The order of causally disconnected events may not be the same for two different observers. As they are causally disconnected, this is no paradox. The ones which are causally connected are the ones who preserve the order. Use the diagram in your picture and try to find a reference system in which 2 causally connected events A $\rightarrow$ B appear as B $\rightarrow$ A. You'll find that that observer must travel at $v>c$. $\endgroup$
    – Pablo
    Commented Feb 7, 2021 at 21:50

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You can find the same thing in classical physics. Imagine a waves parallel to the shore. Every point along the wave breaks at the same time.

Because this all happens at the same time, you know that point A breaking at this time is not the cause of point B breaking. The cause of both points A and B breaking was set up in the past perhaps by a storm that generated the waves.

It is similar in special relativity, except that the speed of light is the speed of cause and effect. Things that are not totally simultaneous can be far enough apart that neither can cause the other.

For points separated like this, depending on the frame of reference, either can be in the future of the other, or they can be simultaneous. This is one of the most counter-intuitive parts of relativity. See my answer to Understanding the difference between timelike and spacelike separations for more.

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