A nice illustration of a century-long rationality-killing "debate":

http://www.einsteins-theory-of-relat...n-paradox.html
"The Twin Paradox was born in 1911, after Paul Langevin restated Einstein's time dilation of traveling clocks as an interesting variant: one of two twin brothers undertakes a long, very fast space flight and on his return to Earth, finds his brother quite a bit older than himself. The twin paradox came in when skeptics argued that the 'away twin' could just as well have viewed himself as stationary, with the Earth and his twin brother speeding away from him and return to him later. In such a case, the Earth and the 'home twin' must be the younger ones, because they were in the 'moving frame of reference'. When compared to the original postulate, this is obviously paradoxical. Relativists then say, "remember, the away twin had to suffer 'g-forces' to get up to speed, then again to turn around and head back and finally, again to land on Earth. So, the situation is not symmetrical". Skeptics reply, "so what, we can make the journey arbitrarily long, so that the "g-forces" parts become negligible". Further, they say, "we are told that acceleration does not affect the rate of good clocks. So, the twin paradox stays"."

In fact, Einstein was the author of both turning-around-g-forces-are-immaterial and turning-around-g-forces-are-essential explanations:

http://www.academia.edu/3771200/Eins...d_twin_paradox
Albert Einstein 1911: "The clock runs slower if it is in uniform motion, but if it undergoes a change of direction as a result of a jolt, then the theory of relativity does not tell us what happens. The sudden change of direction might produce a sudden change in the position of the hands of the clock. However, the longer the clock is moving rectilinearly and uniformly with a given speed in a forward motion, i.e., the larger the dimensions of the polygon, the smaller must be the effect of such a hypothetical sudden change."

http://en.wikisource.org/wiki/Dialog...f_rela tivity
Albert Einstein 1918: "During the partial processes 2 and 4 the clock U1, going at a velocity v, runs indeed at a slower pace than the resting clock U2. However, this is more than compensated by a faster pace of U1 during partial process 3. According to the general theory of relativity, a clock will go faster the higher the GRAVITATIONAL POTENTIAL of the location where it is located, and during partial process 3 U2 happens to be located at a higher GRAVITATIONAL POTENTIAL than U1. The calculation shows that this speeding ahead constitutes exactly twice as much as the lagging behind during the partial processes 2 and 4. This consideration completely clears up the paradox that you brought up."

Pentcho Valev