So, imagine I am stood on earth holding a clock. My friend Jack passes me in his super fast space ship travelling at say 0.7c He also has a clock and as he passes me his clock is synchronised with mine. He then continues his journey.

A second friend Jill is on a return journey to earth in her super fast space ship coming from the opposite direction to Jack.

Jill also has a clock and as Jack and Jill pass each other, Jill’s clock is synchronised to Jack’s.

Jill then continues her journey and as she passes me on earth, I take a reading of her clock.

As there has been no acceleration between the synchronisation of the clocks, does Jill’s clock read the same as mine as she passes me?