I will try and reply to each in the order received.
DaleSpam stated: (in regards to symmetrical time dilation)
"LET also shows this feature. It is not unique to relativity."
Yes, it is unique to Special Relativity. LET does not have this feature because LET is based on there being an absolute frame of reference by which all motion can be compared to. The Lorentz/Fitzgerald equation works from the frame of reference that is least in motion towards the frame that is in greater motion. Time dilation is therefore asymmetrical, with the frame that is in greater motion being the only one having a slower time flow rate.
Because SR says there is no valid frame of reference for determining which is actually in motion, time dilation is supposedly therefore symmetrical with both frames seeing the other frame’s clock running more slowly than their own.
Bcrowell stated: (in regards to my poor explanation)
"I see. So by "symmetrical," you mean that the clock readings agree when they're reunited? That is not what SR predicts. Your reasoning about how all motion is relative is not correct; in SR, as in Newtonian mechanics, only inertial motion is relative."
No, that is not what I meant. When in the “twin paradox” scenario, each twin see’s the other’s clock running more slowly than their own,- that is a symmetrical time dilation statement. Both see the others clock running more slowly than their own.
SR says all motion is relative and makes no statement as to whether it is inertial or not. General Relativity makes the distinction between types of motion.
"The Hafele-Keating experiment was consistent with general relativity."
Yes, the H-K is consistent with GR, not SR. General Relativity though is also consistent with LET. It is those two theories that give identical results.
The first statement of SR, that light travels at the same speed for every observer, whether in motion or not, is also consistent with LET, because Lorentz postulated that idea first in his aether theory (1904). The second statement of SR that “there is no absolute frame of reference” has never been proven and appears to not fit with any results so far obtained. No symmetrical time dilation events ever recorded.
Pyzguy stated:
"…no experiment can ever be done which would verify "symmetrical time dilation" in the sense that you are asking.
Do you agree? Or is there a possible experiment that would satisfy you?"
I think experiments have already been done, but no symmetrical time dilation events have ever been recorded.
"Consider two observers in relative motion at constant velocity, each sending out a video signal from a camera pointing at their clock. Each observer will, in fact, see that the other's clock is running slow, as you can easily verify with space-time diagrams. Of course, this is just a thought experiment today. Would a real version of this experiment satisfy you, or don't you consider this "proof" of "symmetrical time dilation"?"
The spacetime diagrams that are given are all based on SR. Thought experiments are not proof either, as you can imagine anything you wish. Let's imagine that the universe is made up of strings vibrating in 11 dimensions. No, thought experiments are not proof. Isn’t the
H-K experiment, and GPS satellites a real version of the twin paradox experiment?
D_H stated:
"Scientific theories cannot be proven to be true. The best that can be done is to show that the logic/mathematics of the theory is sound and that the results of experimental tests of the theory do not falsify the theory. All the experimental evidence in the world will not "prove" the theory to be true."
So the theory that the Earth is round could not be proven? That the sun is the center of our solar system could not be proven? That lightning is actually electricity, that there are more than just one galaxy that make up the universe, and the equivalence of energy to matter could not be proven?
The only theories that cannot be proven are those that are false, and those that offer no evidence in support of themselves. If experimental evidence does not help to prove or discover things, then why perform them? I pretty much disagree with you on that D H.
"That said, once enough evidence has been accumulated the theory is deemed to be "true", or at least close enough to true for all practical purposes. Relativity is one of those. The evidence in favor of it is overwhelming. Arguing that it is not true is tilting at windmills. You don't want to go there."
Yes, I do want to go there. To which Relativity are you referring too. GR has lots of support and evidence in support of it. SR has no evidence to back up it’s statement that there is no valid frame of reference, and in fact atomic clocks show otherwise. By arguing you can learn, and that is what I am doing. Can you prove to me that there is no valid frame of reference for determining motion?
Ghwellsjr stated:
“So as I pointed out, in post #9, since LET and SR are identical in every way except in the philosophical notion of the existence of a preferred reference frame, there can be no experiment to validate one and not the other.”
SR is not identical to LET. General Relativity (1916) is for all practical purposes the same as LET. Here is a quote from Einstein on this point.
"The ether of the general theory of relativity is a medium which is itself devoid of all mechanical and kinematical qualities, but helps to determine mechanical (and electromagnetic) events. …"
Translation: The aether of General Relativity is not moving, but it affects objects moving through it.
"What is fundamentally new in the ether of the general theory of relativity as opposed to the ether of Lorentz consists in this, that the state of the former is at every place determined by connections with the matter and the state of the ether in neighbouring places, which are amenable to law in the form of differential equations; whereas the state of the Lorentzian ether in the absence of electromagnetic fields is conditioned by nothing outside itself, and is everywhere the same."
Translation: My aether of General Relativity deals with physical objects of substance, and Lorentz’ only deals with electromagnetic fields.
"The ether of the general theory of relativity is transmuted conceptually into the ether of Lorentz if we substitute constants for the functions of space which describe the former, disregarding the causes which condition its state. Thus we may also say, I think, that the ether of the general theory of relativity is the outcome of the Lorentzian ether, through relativization."
Translation: Really these two theories are interchangeable in their conceptual workings, so General Relativity and Lorentz Ether Theory are pretty much the same.
You also stated:
"In any case, I think what he is looking for is an experiment that would validate the outbound leg of the Twin Paradox where both twins see the other one's clock as going slower than their own and in which they never come back together. He's apparently thinking that if they forever remained "younger" than each other, then SR would be validated because it would truly be relative but if it turns out that one of them is "really" younger than the other then LET would be validated."
In away you are correct, but really it’s already answered for us when the space bound twin comes back having aged the least. LET is validated (or GR) because it is an asymmetrical time dilation event, and there has never been a recorded symmetrical time dilation event to prove SR.
"Of course, this "interpretation" still would not distinguish between LET and SR (nothing can) but it has the problem that there is no way to compare the absolute times on the two remote clocks. Whatever additional assumption we want to make to evalutate the "absolute" times on the two clocks is itself philosophical and will lead us to whichever answer we want."
SR and LET are completely separate theories with different accounts as to what is happening. GR is a correction of SR by recreating an aether outcome that fits with reality. With increased motion comes a slowdown in the flow rate of time.
This is not a philosophical topic and you cannot pick or choose an answer. There are real ramifications to these theories, and developing evidence that indicates that there are indeed valid frames of reference for determining real motion. Atomic clock tests bear this out.