TWIN PARADOX: EINSTEIN'S 1918 PAPER

Before the advent of Einstein's general relativity, the traveling-twin-is-younger tale was more than vulnerable in an analysis taking into account only the valid conclusions from Einstein's 1905 postulates. The youthfulness of the traveling twin was totally unjustifiable - the stationary twin sees his brother's clock running slow, the traveling twin sees his brother's clock running slow, and changes of direction involving acceleration are immaterial, as Einstein had implicitly assumed in his 1905 paper and explicitly announced in 1911:

http://einsteinpapers.press.princeto...vol3-trans/368
Albert Einstein: "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."

General relativity changed the situation and strenghtened Einstein's position:

http://sciliterature.50webs.com/Dialog.htm
Albert Einstein 1918: "A homogenous gravitational field appears, that is directed towards the positive x-axis. Clock U1 is accelerated in the direction of the positive x-axis until it has reached the velocity v, then the gravitational field disappears again. An external force, acting upon U2 in the negative direction of the x-axis prevents U2 from being set in motion by the gravitational field. (...) 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 is perhaps the most fraudulent text in the history of science but in 1918 general relativity was incomprehensible and opponents were paralyzed - they could not be sure if "the calculation" really existed. Actually there can be no calculation showing that "this speeding ahead constitutes exactly twice as much as the lagging behind during the partial processes 2 and 4". The turning-around "gravitational field" (acceleration) varies with time (from zero to some value, back to zero, then to some other value, back to zero again) and all these variations are arbitrary to some extent - they depend on the preferences of the operator. So no calculation at all based on the turning-around acceleration is possible, let alone one showing that something constitutes "exactly twice as much" as something else.

Nowadays the topic is avoided but still the 1918 hoax does appear in the relativistic literature from time to time:

http://www.people.fas.harvard.edu/~djmorin/chap11.pdf
Introduction to Classical Mechanics With Problems and Solutions, David Morin, Cambridge University Press, Chapter 11, p. 14: "Twin A stays on the earth, while twin B flies quickly to a distant star and back. (...) For the entire outward and return parts of the trip, B does observe A's clock running slow, but enough strangeness occurs during the turning-around period to make A end up older. Note, however, that a discussion of acceleration is not required to quantitatively understand the paradox..."

Pentcho Valev