ABSTRACT
In the Global Positioning System (GPS), all atomic clocks in all reference
frames (in orbit and on the ground) are set once and stay synchronized. We can use this same trick to place a GPS-type clock aboard the spacecraft of a
traveling twin. That clock will stay synchronized with Earth clocks, allowing
a clear resolution of the twins’ paradox in special relativity – why the traveler
expects to come back younger, and why the stay-at-home twin is not entitled
to the same expectation.
