This Demonstration describes the situation where an observer (Tina) leaves the Earth with uniform acceleration . After some time , she decelerates again at until she reaches her destination. In order to return to Earth, she repeats this procedure in the opposite direction. All in all, Tina's journey separates into four phases that last each.
The first diagram shows the worldline of Tina in a spacetime diagram. The second diagram shows her velocity during the journey. The third diagram shows Tina's proper time that is received by Eric at his proper time . The fourth diagram shows the reciprocal situation to diagram three.
A detailed description of all four diagrams is given in T. Mueller, A. Kind, and D. Adis, "A Trip to the End of the Universe and the Twin 'Paradox'," American Journal of Physics, 76(4), 2008 pp. 360–373.