My question: If an observer at the middle of a spaceship shines laser in both directions and the ship changes on contact with laser, what will earth observer see? was closed as homework-like. It's a genuine confusion that came to me while watching Scienceclic's video on special relativity.

In what universe is that "homework-like"? Are genuine conceptual doubts also discouraged at Physics SE now?


2 Answers 2


But this is actually a great homework question (I might steal it!). The answer reveals itself as soon as you draw and correctly interpret the spacetime diagram; that's almost the definition of a good homework problem at this level.

  • $\begingroup$ The answer "reveals itself" to those who know the answer and remains obscure to those who don't. One should not belittle the efforts of those who strive to learn and understand. $\endgroup$
    – Themis
    Sep 17 at 17:32

Sorry but how can one understand “How can this apparent contradiction be resolved?” as conceptual but not as a “please-solve-this-for-me” aka assignment-like question?

Where have you highlighted the conceptual difficulty?

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    $\begingroup$ Dude that's YOUR interpretation. I watched a youtube video, pictured this scenario and was confused. My concept was not clear and WillO resolved it. As simple as that. If you want to assume something without any substance (that it was a homework problem I was just posting), go right ahead. $\endgroup$ Aug 25 at 7:53
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    $\begingroup$ First you can afford to be polite and avoid duding. Second, the previous answer by @WillO supports the interpretation of a homework-like question. I agree it’s a great homework question but thr community consensus is clear that, even if you were not assigned this question, it can still be closed as homework-like or “check-my-work”, as per link in the comment below this post. $\endgroup$ Aug 25 at 12:10
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    $\begingroup$ For the record, I was happy to post an answer once it became clear that you were focusing on concepts and had made a substantial effort. Unfortunately, that's almost never the case with questions like this. $\endgroup$
    – WillO
    Aug 26 at 3:49

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