Orbiting Time Dilation: Who is Younger?

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Discussion Overview

The discussion revolves around the concept of time dilation experienced by two ships orbiting a planet in opposite directions. Participants explore the implications of special relativity in this scenario, particularly focusing on who would be considered younger upon meeting, and the effects of relative velocity on time perception.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant questions whether the planet is rotating and how that affects the orbits of the ships.
  • Another participant asserts that the planet is not rotating.
  • It is proposed that if the planet is in an inertial frame, equal times elapse on the ships between meetings.
  • Several participants discuss the implications of special relativity, with some arguing that it predicts time dilation due to the relative velocity between the ships.
  • There is a claim that the aging or elapsed time will be the same for both ships when they meet, despite their differing perceptions of each other's clocks.
  • One participant expresses confusion about when relativity applies and seeks clarification on what the ships would observe regarding time dilation.
  • A participant mentions working out time-dilation for radially separated observers and expresses intent to calculate for orbiting observers in the future.

Areas of Agreement / Disagreement

Participants express differing views on the application of special relativity in this scenario, particularly regarding time dilation and the aging of the ships. The discussion remains unresolved with multiple competing interpretations present.

Contextual Notes

There are limitations in the assumptions made regarding the inertial frame of the planet and the effects of relative velocity. The discussion does not resolve the complexities of time dilation in this specific context.

g_sanguinetti
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Two ships orbit a planet in opposite directions. Each time they pass each other who is younger?
 
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Is the planet rotating ? If so, how are the orbits aligned wrt to the poles ?
 
The planet is not rotating.
 
Assuming the planet is in inertial frame, equal times elapse on the ships between meetings.
 
Doesn't special relativity predict time dilation between the two ships since there is a relative velocity between them?
 
g_sanguinetti said:
Doesn't special relativity predict time dilation between the two ships since there is a relative velocity between them?

No,; this a common misconception.
 
g_sanguinetti said:
Doesn't special relativity predict time dilation between the two ships since there is a relative velocity between them?
They may see each others clocks running differently, but the ageing, or elapsed time will be the same for both when they meet.
 
George Jones said:
No,; this a common misconception.

So then, when does and when does not relativity apply?
 
Mentz114 said:
They may see each others clocks running differently, but the ageing, or elapsed time will be the same for both when they meet.

What do they see?
 
  • #10
g_sanguinetti said:
What do they see?

That is a difficult question to answer. I've worked out the time-dilation between radially separated observers here -

https://www.physicsforums.com/showthread.php?t=244511

I'll try and do the sums for orbiting observers at some time. Watch this space.

M
 

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