uppose hypothetically we put a spacecraft into orbit around the Sun to chase and recover an asteroid. Of course we place a clock on it to control the timing of the on-board computer that will autonomously run the spacecraft, and we synchronized the clock with precision Earth clocks before launch. After 10 years the spacecraft returns with its precious sample, ready to deliver it to anxious aging scientists at home. If on average during its journey it traveled at 30 km/s (that's the Earth's orbital speed around the Sun), what can we say about the clock on the spacecraft when it gets back home.