5

I'm having trouble getting my head around the time dilation paradox.

Observer A and B are at the same "depth" in a gravity well. Observer B then descends into the well. A will observe B's time as going slower than their own. B will observe A's time as going faster than their own.

What happens if B were to ascend the well back to A's depth, would B's local time speed back up to the same rate as A's, but B would be younger (relative to A)?

What about the paradox caused by relative motion (ignoring gravity)? If A is moving relative to B, A and B will both observe the other's time as going slower. If A and B were together initially, then B moves away and returns, do their clocks agree? they can't both be younger than each other :s (i get thats the paradox, but what explanation resolves it?)

Thanks

Andrew Bullock
  • 153

3 Answers3

7

Calculations show that younger will be the observer who suffered accelerations/decelerations.

Vladimir Kalitvianski
  • 14,125
3

Answer to the first question: yes, B will be younger than A.

Ted Bunn
  • 20,263
2

As I've been brought to understand this - the person who has descended down the gravity and then returned has not been accelerating at a constant rate throughout the journey (the change in direction requires a change in acceleration), and this causes the differential aging.

This is the same thing for the original twin paradox where one of them travels at near light speed and then returns. This may be oversimplifying things - but you seem to be after a lay explanation.

HorusKol
  • 186