0
$\begingroup$

For the Twin Paradox what happens if after the space twins flies to his destination he remains there and sends a light signal to the earth twin. When the earth twin receives the signal he flies to meet up with the space twin. When they meet up for which twin would more time have passed? The space twin or the earth twin?

$\endgroup$
3
  • $\begingroup$ Where did you get stuck? $\endgroup$
    – WillO
    Feb 2, 2021 at 7:20
  • $\begingroup$ Which twin would have more time pass when they meet up? $\endgroup$ Feb 2, 2021 at 8:26
  • 3
    $\begingroup$ Draw a diagram! $\endgroup$
    – m4r35n357
    Feb 2, 2021 at 9:50

1 Answer 1

4
$\begingroup$

If the travelling twin "stops" at a destination at rest with respect to Earth, and the Earth twin travels on an identical space ship (same speed) to meet him, then they will both be the same age when they meet up.

If the travelling twin keeps going at a constant speed and direction forever (does not "stop" in the Earth sense) and the Earth twin hops on a faster space ship and catches up to him, then the Earth twin will be younger when they meet. This is the case that's the real mirror of the usual twin paradox: the "travelling" twin never changes velocity, so in his frame of reference he is at rest the whole time, and the Earth twin went away from him and then came back.

$\endgroup$
1
  • $\begingroup$ Excellent answer. I was going to post the second scenario as a question and am glad I already found the answer here. And brilliant to mention that this is the real mirror of the usual twin paradox. I'm amazed I haven't found anyone mention this in all the myriad other discussions of this paradox ... $\endgroup$
    – Chris
    Aug 27, 2022 at 20:22

Not the answer you're looking for? Browse other questions tagged or ask your own question.