There is something that has always bothered me about Einstein's famous twin paradox. One of a set of twins gets in a rocket and leaves Earth at a relativistic speed, and then returns. While only a short time has elapsed for the rocket-bound twin, his brother is an old man because time dilation slowed the passage of time for the twin in the rocket. But in relativity there are supposed to be no preferred frames of reference. It should be possible to view the rocket ship as stationary and the Earth as having moved away from the rocket ship at relativistic speeds. How does time know that it is the rocket that is accelerated and not the Earth? Before someone tells me it is an effect of the rocket motor's acceleration, consider a third person, a triplet of the original twins. He sets out at the same time as the first twin. They both are in rockets that accelerate to near the speed of light in a brief fraction of their travel time, and then coast until they turn around and reaccelerate back to the Earth. This time however, the third triplet stays coasting near the speed of light for twice as long as the other travelling twin, and arrives back on Earth to find his first brother long dead, and his second brother (who had been in the other rocket ship) very old, while he--the third triplet--is still young. Yet both travelling triplets were accelerated and decelerated for exactly the same amount of time--only the time spent coasting differed! It seems to me that the twin paradox cannot be real unless there is a preferred frame of reference, that of the Earth which stays behind.