Playing Catch: Solving the Spacelike Communication Challenge

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The discussion revolves around a spacetime diagram representing a game of catch between two individuals who are 10 ft apart. The original poster questions how communication is possible given that their separation is spacelike, particularly when considering the time it takes for the ball to travel between them.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants explore the implications of spacelike intervals and question the realism of the scenario presented. There is a discussion about the nature of the events involved in throwing and catching the ball, with some participants suggesting that the interval should be considered timelike instead.

Discussion Status

The discussion is ongoing, with participants expressing varying levels of understanding and confusion regarding the problem. Some have begun to clarify the concepts involved, while others express skepticism about the question's validity. There is no explicit consensus on the interpretation of the spacetime diagram or the nature of the communication challenge.

Contextual Notes

Participants note the importance of using the correct terminology, such as "separation" instead of "interval," and there is mention of confusion stemming from the format of the original question. The context of the problem is framed within the constraints of special relativity.

ehrenfest
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I am supposed to draw a space-time diagram representing "a game of catch (or a conversation) between two people at rest, 10 ft apart. How is it possible for them to communicate, given that their interval is spacelike?"

Firstly, how is this realistic when let's say that the ball takes 2 seconds to go between them. Then how in the world would -c*3+10*0.3084 be nonnegative>
 
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Where does the original question end?

Henceforth, please use the template. It eliminates such confusion.

If the events are something like throwing & catching (no matter how far apart), the interval between the events is clearly timelike.
 
Gokul43201 said:
Where does the original question end?

Henceforth, please use the template. It eliminates such confusion.

I was using PF Nexus which does not provide the template, but I will switch to PF Prime.

The original question is verbatim:


"Draw a spacetime diagram representing a game of catch (or a conversation) between two people at rest, 10 ft apart. How is it possible for them to communicate, given that their separation is spacelike?"


Notice that I erroneously used "interval" instead of "separation" in the thread-opening post.
 
Let's say A , the "thrower," is at (0,0) when he throws the ball. B, the receiver, is at (0,10) in A's frame.(Using (t,x) for events.) Only these events are spacelike and thus unrelated to the interval between throwing and catching.
 
OK. I kind of see the point of the question now. When A throws, B at that moment is outside the future of A. However, the resolution is that B at a later time is inside the future of A. This is a really weird question.
 
ehrenfest said:
OK. I kind of see the point of the question now.
I don't. It appears idiotic to me. I hope there's something non-trivial about it that I'm not seeing.
 
Gokul43201 said:
I don't. It appears idiotic to me. I hope there's something non-trivial about it that I'm not seeing.

LOL. You're probably right.
 

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