Twin A is the "home twin" while twin B is the "travelling twin".
A and B are initially co-located, could be on the Earth for all I know.
B is accelerating away from A, and is returning when he is ten light years away from A.
Scrollbar "Acceleration distance":
Choose how long B accelerates. 0.1 - 5.0 light years in A's rest frame.
Choose B's proper acceleration. 0.01 - 2.00 c per year.
(1 c per year is about the same as one g.)
Choose from whose frame of reference to see the journey. "A-view" or "B-view".
Run the scenario as viewed in the chosen twin's frame of reference.
Pause the run.
Resume a paused run.
Reset the run.
Run as Applet
You can run the simulation either as an Applet or as an Application, se how here