Before we look at what happens as B decelerates, it's worth switching back to A's frame of reference again.
The above diagram shows exactly the same spacetime points as in the previous diagram, except it 's seen from A's point of view.
The bottom dotted line shows A's clocks as seen from B, just after it had accelerated and had started it's journey.
The top dotted line shows A's clocks, as seen from B at the end of the journey.
Now think about what happens as B begins to slow down. As B begins to move back into A's frame of reference, A's clocks start to show less difference from each other. The closest "A" clock, the clock on the star, shows essentially what we expect it to show from A's point of view. The clock with twin A on Earth has to start moving forward in order to match the clock on the star.
Once again, B sees one of A's clocks, the one on Earth this time, moving forward at a furious rate.
By the time B has finished its one second deceleration, all of A's clocks must read the same time (the time that A's clock reads on the star). Twin A's clock gets the same boost as the star's clock did: 9/20 + 4/5 = 5/4.
Twin B sees A go from being a few months younger, to being several months older!
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The above diagram shows exactly the same spacetime points as in the previous diagram, except it 's seen from A's point of view.
The bottom dotted line shows A's clocks as seen from B, just after it had accelerated and had started it's journey.
The top dotted line shows A's clocks, as seen from B at the end of the journey.
Now think about what happens as B begins to slow down. As B begins to move back into A's frame of reference, A's clocks start to show less difference from each other. The closest "A" clock, the clock on the star, shows essentially what we expect it to show from A's point of view. The clock with twin A on Earth has to start moving forward in order to match the clock on the star.
Once again, B sees one of A's clocks, the one on Earth this time, moving forward at a furious rate.
By the time B has finished its one second deceleration, all of A's clocks must read the same time (the time that A's clock reads on the star). Twin A's clock gets the same boost as the star's clock did: 9/20 + 4/5 = 5/4.
Twin B sees A go from being a few months younger, to being several months older!
start
prev
next
