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So I've been doing a lot of reading about the twin paradox and have encountered several different explanations that strive to resolve it. First off let me start by saying general relativity is not an adequate explanation and in fact has nothing to do with resolving the paradox. (That much has been made clear to me from what I have read, as it has been pointed out that believing general resolves the paradox is a common misconception) To drive that point home let me propose a slight variation on the twin paradox that removes acceleration all together.

Some ancient race of aliens long ago set up an experiment for us without our knowledge to help us understand space time. The experiment contains two space craft with clocks on board separated by a very large distance. The first clock, clock A, was accelerated to .866 speed of light millions of years ago (Thus time runs at half speed) and is set on a trajectory to fly past earth. As it flies past earth it resets its clock to 0 and continues on its way. (The aliens also left behind a clock on Earth, clock C, that starts ticking the moment Clock A passes earth and resets itself to 0) The other clock, clock B, was also accelerated to .866 the speed of light long ago and is on the same trajectory as clock A but in the opposite direction so that it heads towards Earth. The two ships and their respective clocks pass each other at a distance of four light years away from earth at which point clock A transfers its time reading to Clock B. Clock B flies past earth and relays its time measurement so as to be compared to Clock C. The time reads half the time elapsed by Clock C, but how could this be possible if time dilation is always symmetrical?

John Rennie
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Krel
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1 Answers1

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The idea of "proper time", is a fudge-factor appended to the Special Theory in an attempt to get it to seem to work. In Einstein's original presentation, the phenomenon of time-dilatation is derived purely as a function of (relative) speed, and owes nothing to a geometrical account, such as that offered a few years later by his former tutor, Herman Minkowski; but this leads to the obvious contradictions discussed above.

Initially sceptical of Minkowski's spacetime, Einstein later felt obliged to accept his argument as a matter of expediency. However, it is not possible to derive or postulate such a model without undermining supposedly fundamental objections to simultaneity as an a priori concept. That is because "spacetime" presupposes a uniquely fixed standard of simultaneity with respect to a nominally "stationary" frame, (see David Malament, 1977, "Causal Theories of Time and the Conventionality of Simultaneity"). On the other hand, and in any case, it is impossible to think of a physical criterion to justify one's use of the epithet "stationary" as though this referred to a property of some sort, of a reference frame, such as the privilege of using synchronized clocks. Thus the supposed standard required by Minkowski spacetime becomes "unfixed".

Stuart G
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