
Originally Posted by
Max™
No I did not posit an absolute reference frame, I simply stated that the observer who experienced a change in their rate of motion would be able to distinguish they had not been at rest, which is one of the main points of SR.
That the symmetry of physical laws holds while in motion or at rest means if you cannot see outside of your ship, and you are not accelerating, you cannot tell if you are moving or at rest.
If you stop moving and turn around, even without seeing outside of the ship (let's assume it is automated, so you have no control over the path), you could tell that you had stopped moving and reversed course simply by hanging a pendulum in front of you and watching it's behavior.
Nonetheless, you have to recognize that once you change direction, you are no longer in a symmetrical situation or state of uniform velocity.
First, Einstein assumed it is a standard clock, as it is based on a physical principle which has yet to be invalidated: that the speed of light remains constant regardless of the reference frame of any observer.
If you place two mirrors at a distance which light will travel in some specific time, then light WILL travel between them in that time. That is the only assumption Einstein makes regarding SR, and I'm only using his arguments.
If the mirrors are in motion, the distance the light travels will increase, thus the ticks will be further apart, and the clock will measure less time.
Going back to the example where you are in a closed off room in a spaceship with no way to see outside, if you could look at a light clock and determine you were in motion, then SR would be invalidated.
The only way to resolve this dilemma is to have your very ability to perceive time be adjusted, so even though the clock is ticking slower, you still claim it is ticking at the proper time. Thus your motion through time is slower relative to an observer at rest with their own light clock at rest.
You cannot account for the factor in SR. It is not a symmetrical example, if you are in a closed room and the room is following a circular path, you could simply hang a pendulum in front of you and note that it does not hang vertically, simple logic would then say that you were in some state of motion.
You're attempting to apply SR in situations where it breaks down.
It is not a fundamental principle, it is ONLY valid to assume time dilation is symmetrical between two symmetrical frames of reference. That is the only situation where SR holds to be exact, and it is not the description used to explain the actual effect of time dilation in Einstein's very first paper on SR, in which he clearly describes a case of an observer tracing a path which brings it back to the origin, and the resulting time dilation of his clock relative to the clock which remained at rest.
If you are attempting to include anything which violates your hypothetical symmetric situation, the problem is with your example.
Having your observers brought back together is not a symmetrical situation. One of them can clearly state that they underwent acceleration which the other did not, thus the effect you are referring to would only be valid during the parts of the trip when they were in uniform motion relative to each other. It is a different effect from the actual amount of dilation the twin in motion would incur over his trip.
Yes it is an issue, when one observer changes his state of motion you can determine that the symmetry is broken and perform an accurate measurement.