And I ask what makes B's rod measurements any different to Earths Rod measurements when at all times both are at rest when using those rods?
B's rod's measurements do not change from its perspective. What changes is the Earth's rod, which contracts compared to B's rod from B's perpsective becuase the Earth's rod is moving relative to B.
So, just to be sure I understand your point: What does the observer on B record as elapsed time for HIMSELF? and What does the observer on Earth record as elapsed time for HIMSELF? When they come together and compare notes what would they show?
I'll try to tabulate what I am seeing: >>>>>>>A<<<<<<<<>>>>>>>>B<<<<<<<<<< >>12.5 ////7.5<<<<<>>>>>7.5////12.5<<<<<< Where A records 12.5 but SHOULD record 7.5 according to B Where B records 12.5 but SHOULD record 7.5 according to A Not withstanding the SHOULD's both will record 12.5 anyway.
7.5 years. Because that is how long it takes the Earth to Reach him at .8c from 6 ly away. B 7.5 years Earth 12.5 years. Assuming that B starts his clock when he passes the 10 ly marker on Earth's rod ( 6 ly distant according his own rod), and that The Earth observer also starts his clock when B passes 10 ly marker of Earth's rod as determined by the Earth Observer.
Here you seem to be saying that B's measurements do not change from its perspective. Is B's meter the same as a meter from Earth's AT REST original meter? No, it is not, it has already changed despite what you state. In B's frame of reference, it's meter has already changed despite B considering himself at rest and the meter attached to the moving Earth in this frame is the THIRD change of the meter. quote by Janus58: "Assuming that B starts his clock when he passes the 10 ly marker on Earth's rod ( 6 ly distant according his own rod), and that The Earth observer also starts his clock when B passes 10 ly marker of Earth's rod as determined by the Earth Observer." ======================================================== You state the fact that B's meter has already changed yourself right here, ( 6 ly distant according his own rod). The additional change to the meter wrt B's 'view' of the rod attached to the moving Earth in his frame is the third change to the meter.
based on Earths RF and not B's RF. This is obviously assuming Earth to be a preferred RF, an absolute RF and is LR and not SR. The question is why we have chosen earths RF as being the preferred frame to calculate B's recording. Why not the other way round? Maybe B keeps two record books , One for Earths perspective and one for his own. His earth perspective book will declare he is at velocity determined by Earth. His B perspective book will declare he has no velocity as he is at rest unto himself and earth has the veloicty instead. Janus and JAmesR is there a reason for selecting Earth as the preferred RF?
as this is such an important fundamental issue I have drawn the following diagram. <img src=http://www.paygency.com/Diagrams/8.jpg> Now I ask what would Earth and B actually record and if you say B will record 7.5 years I would like to ask what velocity is B travelling at when he records that 7.5 years. And then I would ask how can he knows what that velocity is when according to SR he can only be at rest when he does his recording. The logic problem is simply that for B to show a time of 7.5 years it would have to calculte it's velocity as 0.8c and of course he can't do that because he sees himself at rest. So where am I going wrong Guys????????
by Quantum Quack: "This is obviously assuming Earth to be a preferred RF, an absolute RF and is LR and not SR." ================================================================ This is where both you and Mac make a mistake. In Lorentz Relativity, the Earth or wherever the exercise started is the preferred reference frame. Earth is not an absolute reference frame in LR, ONLY if the Earth is the point of origin of the exercise. For instance, if an exercise started on a distant planet, THAT planet would be the preferred reference frame, not Earth. In SR, you can choose to work from either reference frame, say the Earth or the moving object. But the Earth is almost always chosen as the preferred reference frame, just as in LR. If results of an exercise are to be interpreted by an Earth observer, the Earth is the chosen reference frame in SR just as in LR. Using the Earth as a reference frame does not 'make it LR.'
Correct except for the very first statement. If we apply SR as Janus has suggested we are applying it in a way that makes the Earth the preferred RF. THus LR is being applied as a logic sub routine in a situation that requires SR in total. For the ship to record 7.5 years means that Earth is the preferred RF. For the ship to record 12.5 years as at rest an unresolvable SRT logic conflict becomes evident. And this is the reason for posting this question in this thread. Of course bringing LR into the topic may only confuse the issue.
Read it again, QQ. There is absolutely nothing wrong with using Earth as a reference frame in SR. ONE reference frame HAS to be chosen, even in SR, to get the results IN THAT FRAME. You know I believe SR to be based on a false concept, but what Mac is stating about reference frames does not discredit SR in any way.
If you want to show a mistake in LR, simply start and stop your exercise in the moving frame of reference. For example, use Earth as one point in the reference frame and the moving spacecraft approaching Earth as the other point. Work from the moving spacecraft's point of view, LR doesn't allow you to 'switch' frames. In LR, the moving spacecraft would assume the position of rest when working from that frame of reference, just as SR would. End result would be the Earth observer ages less than the spacecraft observer in LR. Is that the right answer? Of course not, LR is not an accurate discription of reality either.
The problem is the crossing of purposes in the logic. What is actually happening is the distance of separation is diminishing at a velocity of 0.8c. It could be just as equally valid to assume that each RF has a velocity of -0.4 and both are dilated equally thus no difference in their recordings. But this is not SRT. SRT takes a single frame and attempts to extrapolate a single frames dilation and contraction. But SRT demands that both RF can have equal treatment. If both frames are treated identically it is always the other frame that has dilation and contraction. The only solution I can see that is valid is that the over-all dilation of 2.5 years is shared equally between the Frames. But this is not SRT. The question is not about what is calculated for the other frame but what that other frame actually records from it's perspective. And I simply don't see how a frame at rest can record dilation and contraction effects. So when it is said that the ship will record 7.5 years the ship must assume that earth is at rest and the ship is moving. So I guess that is what SR demands then that for some reason the ship has to take Earths perpsective on it's own velocity. And if that's it then that's it. How it works if you swap frames I can not fathom.
A question simply put that ends this discussion: Does a RF consider itself at rest when making a recording of distance/time relative to the other RF or not? If the answer is yes then SR is in trouble. If the answer is no then RF treatment is an absolute preference and RF swapping is not allowed.
another approach would be to say both RF are at rest, no velocity happening, They are deciding to get together, they are 10 lys apart, They have a decision to make, which one gets to travel for the less time,.......don't sound to good to me, I would always take the less time.....so both of them fight over who gets to be dilated.....ha Look out guys I am goin' to dilate you.....ha
If one wants to come as close to 'reality' as possible, an 'absolute' reference frame needs to be chosen. But that reference frame would not be based on relative velocities between two objects. That is the problem. It would have to be based on something like the Milky Way's motion in the universe. The Milky Way galaxie rotates within the universe, the reference frame could be chosen based on this movement which would keep everything WITHIN the Milky Way in an absolute frame of reference. All movement would be relative to this frame. Movement within the galaxie itself is where time dilation would occur, because such variations in time are actually due to movement through the vacuum itself, not just relative to another object. But, my God, how complicated it would be to actually calculate such movement based on an absolute reference frame. Think of all the motions that would have to be taken into account, from Earth's rotation to the movement of the solar system within the Milky Way. Special Relativity is very simple in comparison, and it is unlikely it will be replaced because anything better would be very complicated. (Disclaimer) This is just my humble opinion and does not reflect mainstream science, of course. HeHe.
