A and B are twins,A notice B moving away from him with velocity v

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Discussion Overview

The discussion revolves around the twin paradox in the context of special relativity, specifically addressing the scenario where twin A observes twin B moving away at a velocity v. The implications of time dilation are explored, with both twins perceiving the other as younger due to their relative motion.

Discussion Character

  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants assert that both A and B perceive each other as younger due to time dilation effects, leading to confusion about the implications of this observation.
  • One participant references existing discussions on the twin paradox, suggesting that this is a well-explored topic within the forum.
  • Another participant emphasizes that the situation is not a paradox until the twins reunite in the same frame of reference, which necessitates acceleration for one twin.

Areas of Agreement / Disagreement

Participants generally agree that both twins see each other as younger, but the implications of this observation remain contested, particularly regarding the resolution of the paradox when they reunite.

Contextual Notes

The discussion does not resolve the underlying assumptions about simultaneity and the effects of acceleration on the perception of time between the twins.

IPhO' 2008
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A and B are twins,A notice B moving away from him with velocity v, so A notice that B is youngerv than him (time dilation) , In the same way, B notice that A is younger than him.
What happen?
 
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Search this forum for "twin paradox." There have been many discussions of this. In fact, there's one going on right now, with the title "Need help understanding the twins."
 


IPhO' 2008 said:
A and B are twins,A notice B moving away from him with velocity v, so A notice that B is youngerv than him (time dilation) , In the same way, B notice that A is younger than him.
What happen?

Image 4.26 in section 4.15 (Reversal of Time dilation) explains this all:

http://physics-quest.org/Book_Chapter_Non_Simultaneity.pdf


Regards, Hans
 


IPhO' 2008 said:
A and B are twins,A notice B moving away from him with velocity v, so A notice that B is youngerv than him (time dilation) , In the same way, B notice that A is younger than him.
What happen?
Actually, in this case, nothing is happening! Both are completely correct. Each sees the other as being younger than himself. This only becomes a "paradox" when the two twins are back in the same "frame of reference" (i.e. at rest relative to one another) together again. And that requires acceleration of one of the twins.
 

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