This may act as a useful damper on flights of fantasy to the stars at near-light speed from which astronauts return just a few years older, while their stay-at-home friends and relations have died hundreds of years previously in true Einsteinian fashion. Alas, it will be a while yet before large, massive objects like space ships and human beings in them achieve velocities of nearly 300,000 kilometres a second, part of the problem being that their masses will greatly increase at this speed, necessitating a complementary increase in the energy used to propel them until, at light speed, the energy required becomes infinite. This will be a problem.
There is world enough and time for humans to reach the stars, but only after many generations of the astronauts on board have lived, bred, and died of old age. No Rip Van Winkle among them will return home to claim his compound interest.
Dowlish Wake, Somerset