There is an obvious theoretical deficiency when a high speed traveller can only measure clocks in other inertial frames as running slower than their own, even if the interval as recorded by that traveller is much shorter than the non-traveller.
To test this we can consider a simple thought experiment that can not be interpreted in any other way than the way we present it. All Special Relativity text books agree that if a rocket takes off from, say, Earth, and travels at very high speed and then returns then the interval recorded on the rocket clocks for the journey will be shorter than the interval recorded on the clocks here on Earth and that difference can be calculated using Special Relativity math. Gravitational time dilation also has to be considered for very accurate calculations.
This phenomenon has been tested numerous times, navigation and GPS satellites must take Special Relativistic time dilation into account in order for their clocks to keep pace with Earth bound clocks and Neutrons created by decaying particles entering Earth’s atmosphere have a longer than the expected 15 minute decay interval due to relativistic time dilation.
So here is our thought experiment to test the ‘never faster clock’ hypothesis implicit in Special Relativity: Consider a space station laboratory (the lab) floating in space so that gravitational time dilation is small enough to be ignored. From there an android Rocketeer (who can handle the acceleration) leaves and travels at 0.865c (86.5% of the speed of light) to Pluto to see if its demotion from planet status was justified. It returns immediately and so we only need to consider the two high speed legs of the journey. At 0.865c the Rocketeer will record around half the interval for the journey than the lab observer.
The interval recorded on the Android Rocketeer’s clocks will be half that of the observers back at the lab. That is agreed Special Relativity. If you disagree with the essay thus far then take it up with the authors of standard text books, not me, it is simply assumed that they are right.
Now we consider a pulsar at a great distance orthogonal to the plane of the Solar system (‘orthogonal’ is more or less the 3D version of ‘at right angles to’). The pulses of the Pulsar are measured by both lab observers and the Android Rocketeer. Let the frequency of the pulses be one per second by the measure of the lab. The total number of pulses recorded by both the Rocketeer and the lab Observer will be the same. Due to time dilation of the Android Rocketeer, the same number of pulses will have been received in half the time, a doubling of the frequency by the Rocketeer’s measure.
It is said that pulsars are even more accurate as time keepers than atomic clocks here on Earth so it is fair to say that pulsars can be thought of as celestial clocks and the Rocketeer records the frequency of pulses as double that of the lab observer’s measure.
The Pulsar is so far away that the angle between the ends of the journey (parallax) is insignificant as is the change in distance between rocket and pulsar as the rocket travels between the lab and Pluto. If it was significant for an actual pulsar that we might consider we can just place our hypothetical pulsar further away, say five or ten billion light years away. From a theoretical perspective the practical considerations are irrelevant.
How might we interpret this result?
Length contraction only occurs in the direction of travel and not orthogonal to the direction of travel, could time dilation also have a directional component? That seems unlikely.
Another consideration is the possibility that time has wavelength and frequency analogues such that each burst from the Pulsar is redshifted but the frequency of individual pulses is quicker by the Rocketeer’s measure. We discussed a case such as this two essays ago (Special Relativistic Changes as a Rocket approaches the Speed of Light) and showed that there was a condition in which clocks appeared to pass by quicker whilst each one appeared also to be slower as the rocket passed over it. The theoretical model that could account for this from the perspective of time does not exist. All we have in the earlier case is the Relativity of Simultaneity which only tells us that the clocks (in the earlier thought experiment) are not synchronise in the rocket frame, but falls far short of a comprehensive account of the condition.
We don’t see any way out of this simple thought experiment: As the interval to be measured starts and ends where the lab and rocket are adjacent then there are no simultaneity issues. If the interval recorded by the Rocketeer is shorter for the lab-Pluto-lab journey than measured by the lab observers then the Pulsar (as a clock) pulses quicker by the Rocketeer’s measure than lab observer’s measurements.
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