What Will the Clock Read at the Turnaround Point in the Twins Paradox?

[Al68]

If we add a third observer to the twins paradox at the turnaround point (at rest with earth), and with a clock that was synched with the other two when the ship left earth, what will that clock read when this third observer sees the ship turn around?

Assuming v= 0.8c, distance = 8 ly.

Also, since this third observer and the ship's twin could look at each other's clocks (locally), what would each observe the other's clock to read?

Thanks,
Al

 

[Hurkyl]

If we add a third observer to the twins paradox at the turnaround point (at rest with earth), and with a clock that was synched with the other two when the ship left earth,

Do you mean... the third observer and the Earthbound twin have synchronized their clocks according to Einstein's convention? Or equivalently, measuring simultaneity relative to an inertial coordinate chart where both the third observer and Earthbound twin are stationary, their clocks read the same value at the same (coordinate) time?

what will that clock read when this third observer sees the ship turn around?

Just choose a coordinate chart and compute! (An inertial coordinate chart centered on Earth is probably the simplest)

Assuming v= 0.8c, distance = 8 ly.

As measured by what coordinate chart?

Also, since this third observer and the ship's twin could look at each other's clocks (locally), what would each observe the other's clock to read?

Again, just select coordinates and compute!


In what way are you having trouble making the calculations?

 

[Al68]

Do you mean... the third observer and the Earthbound twin have synchronized their clocks according to Einstein's convention? Or equivalently, measuring simultaneity relative to an inertial coordinate chart where both the third observer and Earthbound twin are stationary, their clocks read the same value at the same (coordinate) time?


Just choose a coordinate chart and compute! (An inertial coordinate chart centered on Earth is probably the simplest)


As measured by what coordinate chart?


Again, just select coordinates and compute!


In what way are you having trouble making the calculations?

Thanks for your thoughtful and complete answers to my questions.

Al

 

[Hurkyl]

Thanks for your thoughtful and complete answers to my questions.

You're welcome. But I did not intend to give a complete answer, but instead help you take this opportunity to gain experience through doing the problem (or to help correct whatever was preventing you from being able to do so, if appropriate). I apologize for denying you that opportunity, and will try harder to avoid spoiling the next problem.

 

[Al68]

You're welcome. But I did not intend to give a complete answer, but instead help you take this opportunity to gain experience through doing the problem (or to help correct whatever was preventing you from being able to do so, if appropriate). I apologize for denying you that opportunity, and will try harder to avoid spoiling the next problem.

Oh, don't worry, you didn't deny me that opportunity. After all, I had that opportunity before I ever posted. So don't worry, your detailed answers didn't spoil it for me.

Al