# Is time universal? NO (and its proof)

Discussion in 'Physics & Math' started by Billy T, Aug 12, 2005.

1. ### RaphaelRegistered Senior Member

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If there is no mathematical difference, why do proponents of SR get bent out of shape when a "quack" says that time dilation does not modify time but only the tick rate of the clock?

3. ### AerRegistered Senior Member

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They are naturally bent out of shape - possibly from years and years of mental abuse.

Anyway, if you are talking about SR, then you must say "the tick rate as seen by such and such frame...". You cannot talk in terms of absolutes.

5. ### RaphaelRegistered Senior Member

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Given that philosophy may be considered mental abuse and physics without mathematics is philosophy, there may be some truth in your statement.

I have no problem talking about relative tick rates. It's not counter-intuitive.

7. ### Billy TUse Sugar Cane Alcohol car FuelValued Senior Member

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It follows and I mean no offense by in it at points where I say your ideas are naive. Perhaps inocent would have been a better word. All I mean is that there are many things that you are not considering that corrupt your simple ideas about comparing "accumulated times" in two different frames. (You never even mention some of the most important factors and that certainly is "naive."

But first a few words about your reply: I have only just read it without a lot of thought. I think I tend to agree with you that "time dilation" is on much more solid basis that "length contraction." perhaps length contraction is only "illusion." (I am not well versed in SRT and don't really know what I think about "length contraction." I also admit that you are much better informed than me about of the evidence for and and against SRT, especially GPS, etc.)

Ok here my thought and arguments about measuring/comparing "accumulations of time" in two different inertial frames:

This post is long, so I’ll give the conclusion derived in it first. The conclusion is developed in a chain of small logical steps. My statements about the basis of MacM’s views are probably not exactly what he would like, but he only states that “reciprocity of SRT” leads to a “physical impossible” result, without giving any basis for this claim. (To him, it is obvious.) More importantly, he makes no attempt to describe how the period in which the two clocks accumulate time in their respective frames is to be defined. This omission is naive as the distance between the start and stop clock events, not SRT, usually determines the most of the difference in accumulated time measured.

CONCLUSION: MacM’s idea that “reciprocity” destroys SRT is naïve nonsense. I think he bases his claim on the plausible, but wrong, idea that in the two different frames, there must be the same amount of proper time between a “clock start event” and a “clock stop event”, if both frames use the same pair of events and there are no “perception delays.” That is, MacM thinks non accelerating clocks accumulating their own proper time between these same two events should accumulate the same proper time interval and certainly can not both record less elapsed time than each other, as he claims SRT predicts. It does not. SRT claims only that time is dilated (not that time is “perceived” to be dilated or that the dilation is only “illusion.“). I.e. SRT claims that all physical processes in the other frame take more of this frame’s proper time than the same process requires in this frame, but says nothing about the proper time accumulated between start and stop events common to both frames. There is nothing in SRT about clocks accumulating time intervals both smaller than the other. (MacM‘s “reciprocity“ is a “strawman” he set up to knock down.)

I started this thread with a “twist” to the standard "moving train" examples because trying to compare clocks (or time intervals between the occurrence of events) that are not adjacent easily confuses the facts with “perceptions.” This is because time is required for light (or signals) to travel between two separated points so events can be perceived after they have actually happened. In at least one of the two frames moving wrt each other, the “start clock” and “stop clocks” events must be physically separated, if the same events are used in both frames. This space like separation will be shown to be very important to the amount of time accumulated and can not be ignored as MacM does.

A brief summary of first post’s “twist“ follows in this paragraph: Two small bombs on side of a train, one at each end, are exploded simultaneously by flash of flashbulb, also mounted onside of train, midway between bombs. A long line of men, standing shoulder-to shoulder next to track, all have their noses just grazed by passing bombs. An unlucky pair get killed but not simultaneously in their frame as train advanced a little while light from flashbulb was traveling. (Bomb at front of train explodes after one at end of train.) No problems exist in this example with “perception delays” - dead men, with explosion stopped clocks, exist in both frames who were adjacent to the explosions when they occurred.

Step 0: An initial statement, which I hope (and expect) all can accept as “true fact.” (If you think the conclusion is not true, tell why and in which step the first error is made.):
102 units of proper time (time in the clock’s rest frame) are not the same as 1 or 2, or 3 or 4 units of proper time and physically-identical, well-made, non-accelerating clocks in different frames do measure proper time, if they are not broken. (Their physical processes are identical, require the same amount of proper time, etc. because all physics is identical in all inertial frames.)

Step1: Simultaneous explosions in train frame are not simultaneous in the station frame and this is “fact“, not "illusion". (See proof in first post of this thread.)

I express this fact as follows: “Event "F" occurrs after event "R" in the station frame, (“Event F" is the explosion at Front of train and “event R", the explosion at the train‘s Rear) but events F&R were simultaneous in the train’s frame. (Train time of event “x” will be indicated by "Tx" and station time of this same event will be designated by "Sx".)

Step 2:To be specific, lets say the temporal difference Sf - Sr = 100 units of time in the Station frame. Note that if the train were twice as long, it would be 200 units of time. I.e. grant me that some combination of train length and speed does result in Sf - Sr = 100 time units even though Tf -Tr = 0, regardless of train length or speed. (For real trains, one time unit would be much less than a second, but I will never specify the size of a “time unit” in this presentation.)

Step 3: Now I want to slightly modify the location of the flashbulb, moving it closer to the rear of the train, by approximately the distance light travels in one unit of proper train time, so that even in the train's frame the explosion at the front is slightly later than the one at the rear. I.e. Tf > Tr. Thus, Tf-Tr is approximately 2 units of train time.

Step 4: I said “approximately” in step 3 because after the move, Sr -Sr is exactly 102 units of station time. I will continue to use “Tf-Tr = 2” units of train time, but if because of “time dilation” or “length contraction” effects you think Tf - Tr should be only 0.1, or 1, or 3, or 4, etc. units of time, I will not argue with any choice you like, so long as you agree that (Sf - Sr) >> (Tr -Tr.)
If you can not agree that these two observed time intervals differ greatly, then let me increase the train length so that Sr -Sr = 100,000,000,002 units of station time, noting that Tf - Tr remains essentially 2 units regardless of train length. Them perhaps you will agree that (Sf - Sr) >> (Tr -Tr.).

Step 5: I don‘t give either the train’s speed or the exact value of (Tf - Tr) as, in the latter case, MacM would not agree I computed (Tf -Tr) correctly as I would use only the relative velocity and not MacM’s "two components of velocity" that make up the relative velocity. (Main reason why I don’t use MacM’s method is that I don’t have the slightest idea what these two velocity components are.)

Now lets state what have we have thus far. (I think everyone still agrees.):
Step 6: Sf-Sr =102 exactly and Tf-Tr = 2 or something close to 2.

Now lets get to MacM's two clocks accumulating time, using the two explosions as the “start stopwatch/clock” and “stop stopwatch/clock” events. MacM claims SRT's "reciprocity" will cause each clock accumulate less time than the other - a "physical impossibility." Because it is even a logically impossible for both A to be less than B and B to be less than A, I agree it is also a “physical impossibility“, but, as noted earlier, SRT does not claim this occurs. That claim is only MacM’s “strawman.”

What MacM consistently fails to do is describe in any detail how the two clocks, in different frames are started “at the same time” (I.e. by the same “start event”) and “stopped at the same time“ (I.e. by the same “stop event”). He appears to be naively unaware of the fact that the time accumulated by each clock between these common start and stop event depends very strongly on the distance separating the start and stop events, as is clearly demonstrated above by fact (not illusion) that (Sf -Sr)>>(Tf -Tr). In the case of the extra long train mentioned at the end of Step 4, the difference in the accumulated times, due mainly to spatial separation of the start and stop events, was 100,000,000,002 proper time units vs. essentially 2 proper time units! Also note that even if the start and stop events are collocated in one frame, they are physically separated in the other. That is, the “distance effect” upon the amount of time accumulated by at least the stopwatch/clock in one frame can never be ignored, but MacM always does.

Step 7: I hope everyone agrees that the “distance effect” upon the amount of time accumulated (demonstrated numerically above) is "true fact", not "illusion." The big difference in accumulated times observed in this numerical example is due mainly to the fact that the start and stop events were almost simultaneous on the train but well separated in time on the ground and has little or nothing to due with SRT. I also note that to avoid “perception delays” the time of the event must be measured at the site of the event. Because at least in one frame the start and stop event are physically separated, this means that synchronized clocks must be available through out the frame and at least one time accumulation period must be computed by subtracting the time displayed on the clock collocated with the start event from the time later displayed on the clock collocated with the stop event.

Step 8: Now lets bring in MacM's "reciprocity" more directly into the discussion (by noting that this "train" was a "space train" passing galactic station "z483" with a relativistic speed) such that SRT theory predict a 1 to 2 time dilation, both ways. (MacM‘s "reciprocity" problem or proof that SRT is wrong)

Now lets hear what information is exchanged between station and train observers, but please recall from the proof in first post of this thread that synchronized clocks correctly keeping proper time at different locations in one frame can not be synchronized with those correctly keeping proper time in another frame:

9a: The station observers say to the train observers:
"Your clocks are running slow by a factor of two and not synchronized. When our properly synchronized ones all show noon, each of yours, which is next to one of ours showing noon, is showing a different time at each different location."
and:
9b: The train observers say to the station observers:
"Your clocks are running slow by a factor of two and not synchronized. When our properly synchronized ones all show noon, each of yours, which is next to one of ours showing noon, is showing a different time at each different location."
then:
10a: The station observers say to the train observers: "The correct time accumulation between start and stop events R & F is 102 units, but in your frame it is 51 units, as time is passing more slowly there. Because events R &F did not take place at the same point and you computed it by the time difference between local clocks that were not synchronized you got only 2 units - nonsense."
and:
10b; The train observers say to the station observers: "The correct time accumulation between start and stop events R & F is 2 units, but in your frame it is 1 unit, as time is passing more slowly there. Because these events did not take place at the same point and you computed it by the time difference between local clocks that were not synchronized you got 102 units - nonsense. There is another reason for your error which we think you will admit. You let the time accumulate much too long before stopping your clock. More about this will follow later.”

Note that 9a, 9b, 10a & 10b are not part of the conclusion derivation. Hence the word “Step” has been omitted but the paragraph numbering has been continued for ease of reference if anyone wants to comment on the exchange between the two frame‘s observers.

Step 11: Summary of the facts: The time accumulated on the train between the start and stop events is observed to be essentially 2 units. The time accumulated in the station frame between the same start and stop events is observed to be 102 units, both using identical clocks that are synchronized correctly through out their own frame. (This was confirmed by flashing a strobe light located mid way between various pairs and seeing that all pairs displayed identical time under the strobe flash.)

Step 12: This large difference is not due to either correct or erroneous application of SRT‘s “time dilation“. It is due to the effects demonstrated in the first post of this thread. (Events simultaneous in one frame are not in another and clocks can not both keep proper time correctly and be synchronized with those through out another frame that are keeping its proper time correctly. (Thus far no one has challenged the first post demonstration of this.)

Step 13: Fundamentally this great difference in “accumulated time” is due to fact that even two successive events at one location in one frame (purely time separation) are at least partially space like separated in the other frame. (Space and time are mixed differently in the two different frames.) Thus it is nave to think one can make comparisons of time accumulations periods only considering clocks and ignoring the space like separation that must exist between the two events in at least one of the two frames.

Step 14: Thus it is excessive naive to make any statement about the time lapse intervals or “time accumulated” in two different frames even if (1) the same events are used to start and stop the clocks/ accumulators and even if (2) there are no “signal propagation delays” or “perception problems“ without describing how the clocks are started and stopped and where they are when these events occur.

A final note to clarify something that may be troubling some people:
How does the train observer explain that the station observer recorded 102 units as the time accumulated between the two events, when he knows time is progressing more slowly there by a factor of two, and he observed only 2 time units “accumulated“?

15: Superficially, one would think that if the station clocks have “ticked” 102 times while train clocks have only ticked twice, then the station clocks must be running faster, not slower. The answer is simple.

16: First note that the station’s measurement of “accumulated time” (102 units) was computed by subtracting the “time” shown on clocks two at different locations. These “station frame clocks” were not showing the same times at the start and stop instants that all the train observer’s clocks were showing, even though the train frame clocks were sitting immediately beside the station clocks. The train observer “knows” his clock are correctly synchronized, and doubts that the station clocks are. (When the adjoining train clocks all show noon, only one station clock is also showing noon. All the rest are showing different times at the instant of train’s noon.) Obviously subtracting the times shown on two different non synchronized clocks at different locations can produce nonsense.

17: In addition to this “lack of mutual synchronization” problem (The station observers also claim that the train clocks all show different times when their clocks are all showing 12 noon and thus it is the train frame’s clocks are not synchronized.), there is also the fact, admitted by the station observers, that the time delay between the flashbulb flash and the front explosion or “stop event’ was increased more than the period between the flashbulb flash and the rear explosion (start event) was reduced by the motion of the train. That is, in the station frame, the total distance light can travel during the interval between explosions is always greater than half the length of the moving train. (See numerical example at end of post if this is not obvious.)

18: In the train’s frame, during the interval between the two explosions, light can travel zero distance if the flash bulb was centered or only tiny fraction of the train’s length when the flashbulb was slightly shifted towards the rear of the train. If light can travel much farther during the interval between start and stop events used in the station‘s measurement of “accumulated time,” clearly the temporal separation of these events in the station’s proper time is much greater than the proper time between these same events in the train’s frame. (Speed of light is the same in both frames, so longer light travel distances imply longer travel intervals.) If the stations observers let their stopwatch /clock accumulate time for a much longer interval, it is not surprising that their measured of the “accumulated time” between these events is much larger, for example 102 time units vs. only 2 time units.

19: I hope it is now clear that because of the inherent conflict about whose clocks in different locations are “synchronized“ and fact that even the same pair of start and stop events can have greatly different amounts of proper time between them in the two frames, it is not possible or meaningful to try to compare “accumulated time” in two different frames. Certainly it is nonsense to make any claim of comparing “accumulated time” in different frames without at least describing how the “stopwatch accumulators” are to be started and stopped. The distance separating the start and stop events must be carefully considered, not ignored, as the above demonstration shows.

Numerical example showing light travels more than half the length of the train according to the station observers:

20: For this example, assume that train speed is 0.8c and the moving train is twenty light units long in the station frame. For convenience, let the flashbulb flash at t=0. During 5 time units, (I.e. between t=0 and t=5) light from the flashbulb moves 5 light units towards the rear of the train and the rear of the train moves 4 light units towards the oncoming light but light wave front and bomb’s optical fuse are still separated by 1 light unit. Half a time unit later (at t=5.5) the gap between bomb’s fuse and advancing light front is only 0.1 light unit. At t = 5.55 this gap is only 0.01light units, etc. That is the rear bomb explodes at time t= 5.5555555... and the distance this rearward light traveled in this interval is (55/10) light units.
The front bomb explodes at t =50 when the light has travel 50 light units and the 20 light unit long train has advanced 40 light units. Thus in this case, the station observers admit that even in their proper time, the interval between the two explosions is 44.4444444... time units. -Much more that the 2 time units available for “accumulating time on the train. This difference could be greater or less depending upon the length of the train, its speed, and how close to the train center the flashbulb is, but if it is a relativistic train this effect can not be ignored.

Last edited by a moderator: Aug 24, 2005
8. ### AerRegistered Senior Member

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If I am ever really bored, I might consider reading the above..

9. ### AerRegistered Senior Member

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<b<a

Nice effect you found Billy T.

10. ### superluminalI am MalcomRValued Senior Member

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We have all many times tried to explain this to Mac using many of the same words. This is exactly his problem. I predict that your entire post will be labeled "rhetoric", "innuendo", or some other combination of Mac's favorite denouncements.

11. ### James RJust this guy, you know?Staff Member

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MacM probably won't bother reading Billy T's post, and if he does read it he will ignore it, especially the part quoted by superluminal.

I agree that the quoted paragraph is a correct description of MacM's views. MacM believes that SRT requires two clocks to "accumulate different times for the same trip", which is not in any way a correct description of SRT.

12. ### Billy TUse Sugar Cane Alcohol car FuelValued Senior Member

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To MacM:
I know you are busy defending your views and fending off personnel attacks and that my step by step logic demonstration of your errors of omission is long. I hope you are not offended by my characterizing these omissions as “naïve.” There is nothing personal in this, I like you and respect you personnally. I continue to think you are the smartest crackpot I know.

You are completely correct that SRT implies “reciprocity” between two inertial frames, but error when you then state that this implies a “physical impossibility” (clocks in the both frames accumulating less time than the other.)

This is not what SRT states. You do not tell how the period of time accumulation is to be initiated nor how it is to be stopped but occasionally at least imply that both use the same event to start the accumulators running and the same subsequent event to stop them.

My long post concluded with a numerical example: Train traveling at 0.8c and 20 length units (20L) long had explosions set off at each end by flash of light originating 1L closer to the rear of train than the mid point of train. Because 1L is the distance light travels in 1 time unit (1T) the explosion at the front of the train (to observers on train) is 2T after the one at rear.

To observers on the ground, if t = 0 is the instant of the flash, then the explosion at rear of the train occurs at t = 5.55555... T units and the one at the front at t = 50 T or 44.44444... T units Later.

If these two explosions are the “start” and “stop” events used for accumulation of time, then without any consideration of SRT effects, the ground accumulator will record the passage of time for more than 22 times longer than the train observers.

Clearly your neglect to consider even the non-SRT effects of the fact that the start and stop event have different separations in the two frames is “naïve.” Certainly both start and stop events could be with zero spatial separation in one frame, but not in both, if they are the same events.

To drive home more clearly the effect of distance, let the train be twice as long - Then the ground accumulator accumulates time almost 45 times longer. When I make these statements I am assuming that both accumulators (clocks with stopwatch function) are identical and thus each “tick” is the same amount of “proper time”. (I think you do agree that physics is the same in all inertial frames. If it were not, it would be easy to discover a unique “absolute rest frame.”)

The unavoidable fact that at least in one frame the start and stop events are physically separated is very important in determining the time accumulated, but naively ignored by you as you never describe how the two accumulations of time are to be done (the operational procedure) but only state that it is “obvious” that both can’t be less than the other (I agree with this but note SRT makes no such claim - only that each frame’s observer find time passing more slowly in the other frame. )

IF YOU WANT TO COMPARE TIMES ACCUMULATED YOU MUST TELL HOW THE COMPARISON IS TO BE DONE. It is neither trivial nor "obvious" as you naively assume.

I made this shorter post to encourage you to go thru the longer one and tell which of the numbered paragraphs in it is the point of error in your view. If you continue to ignore a step by step logical demonstration that your claims that “reciprocity” disproves SRT are at best “naïve” then I will be forced to join others (see James R's & SL's posts below this one) in thinking you “duck and weave” to avoid hard questions.

Last edited by a moderator: Aug 24, 2005
13. ### Neddy BateValued Senior Member

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Case 1
Two space ships are approaching each other in deep space (at relativistic speeds). One has a male in it and the other has a female in it. The male looks at the female through his powerful telescope, and since he understands relativity theory, he is not surprised that she appears to move in slow motion.

Outer space is a lonely place, so the male decides to accelerate to join frames with the female. When he does this, he notices her clock start advancing faster and faster. She is no longer in slow motion, but she is actually in fast motion now. She ages a few years in just the amount of time that it takes for the ships to join frames. They fall in love and live happily ever after.

Case 2
The following variables are identical to Case 1: Same relativistic speed, same age people, same acceleration rate used to join frames.

Except this time the female ages twenty years in the time it takes for the ships to join frames. The reason for this difference is because the ships had been in relative motion for a longer period of time. Since the rate of the female's clock was dilated for a longer period of relative motion, this translated to greater aging during the frame-joining acceleration period.

Questions
Where is the velocity history information stored? How can equal acceleration in the two different cases result in different rates of clock "speeding up" during the acceleration without such velocity history? Or is it more accurate to say that the rate change for the clock will be the same in both cases due to the identical acceleration?

14. ### MacMRegistered Senior Member

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HeHe

You do present a mixed bag of flatery and insult. We have a number of differances of views but nothing you have ever posted has offended. I do tend to see your statement as selfserving and not informative as to this list of omissions you mention.

Here we do disagree. It is not my interpretation but is clearly stated in most literature on relativity. It states in specific terms that given a inertial relative velocity between "A" and "B" that "A" sees himself as at rest and that "B" has ALL motion and "B" IS dilated relative to "A". Likewise at the same time (which it must be to be relative motion) "B" also sees himself as at rest and that it is "A" that has ALL motion and "A" IS dilated relative to "B".

Now I suggest we clear up this issue at this point since anyother issues are moot.

That can be done but is not necessary. The issue is not linked to simultaneity but to the statements of reciprocity from above. Tick rates need not have simultaneous start/stop times but is a comparison of ongoing ticks within the same time period of relative velocity.

Accumulated time, "yes" you must then provide start/stop conditions. But even accumulated time is based on comparative tick rates. So one doesn't need to complicate the issue by evaluating time dilation and reciprocity from the vantage point of accumulated time but merely comparative tick rates.

So do you want to claim that during periods of relative velocity between "A" and "B" that each has a tick rate slower than the other?

Once (if it ever happens) we can agree on the issue of tick rates and reciprocity then I would be more than happy to debate a scenario which includes specific start/stop and simultaneity issues.

15. ### AerRegistered Senior Member

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Haven't you heard of the matrix? I thought people knew these things. :m:

No need to worry, the relativity of simultaneity fixes everything. All is well.

16. ### MacMRegistered Senior Member

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Wrong again. Further more you don't seem to have a clue as to what my view is, or you simply enjoy distorting it and making up crap that you can argue against. You certainly aren't arguing anything to do with my views.

As I said you don't have a clue. From point "A" to point "B" is the same trip but you of course choose to believe it is a different distance; which I have shown is shaear nonsense.

17. ### MacMRegistered Senior Member

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Don't you get tired of being wrong?

18. ### MacMRegistered Senior Member

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Entirely mis-stated. Yes my examples are often simplified because I believe they can and should be. True time dilation has nothing to do with simultaneity or start/stop events. Measureing accumulated time that becomes another matter.

But true time dilation MUST be based on a differential of clock tick rates. That is how time accumulates. If there is no tick rate differentail then there is no time dilation. Tick rates are not subject to simultaneity and require no start/stop synchronizaton. To attempt to debate time dilation interjecting simultaneity, etc is to simply cloud the issue.

Keep it simple. Given an inertial relative velocity between "A" and "B",in accordance with SRT from "A's" frame "B" has ALL motion and "B" is dilated (its tick rate is slower) relative to "A".

Likewise during the SAME absolute period (Which must be the case if the motion is relative) SRT claims that it is equally true that "B" is at rest and "A" has ALL motion and that "A" is dilated relative to "B" (it's tick rate must be lower than "A").

MacM doesn't ignore it. MacM just understands that it is not part of the issue. Only tick rate and not simultaneity of start/stop, etc must be evaluated to determine if reciprocity of time dilation can be reality.

I appreciate the effort you have put into this long scenario, however, I see no justification to chase simultaneity issues. The issue is reciproicty of time dilation which is based on dilated clock tick rates and are not subject to simultaneity.

If you can answer my simple question first and it then merits it I will go through your scenario but I fail to see it's relavance other than to confuse the issue.

19. ### Billy TUse Sugar Cane Alcohol car FuelValued Senior Member

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I will soon reply to MacM but that takes longer.

Neddy Bate states: “…looks at the female through his powerful telescope …” so already he opening the door to confusion between what is real now and what happen long ago.

I started this thread with a scenario that avoids the perception vs. reality problems and hope others who introduce their own scenarios will try to do the same. This subject (SRT) is confusing enough without dragging the problem of “perceptions” in.

None the less I will comment briefly on Neddy’s scenario:

His case 2 differs from case 1, I think, in that initially the two ships are farther apart. This will produce the extra 20 years. I don’t understand his description “the ships had been in relative motion for a longer period of time” - a statement in the past tense but what happened before “now” - the astronaught observing via telescope - would not seem to make any diffence to what will happen. Thus I will assume he means the ships in case 2 were initially farther apart than in case 1 and answer his other points/question.

He states: “…greater aging during the frame-joining acceleration period. …” This leads me to belive he thinks that the “acceleration” is responsible for the aging effect. If so this is an error. Except for the fact their bodies could not withstand the forces, the entire acceleration could only last a few seconds, by anyone’s clock. It is the relative velocity over an extended period that causes the differential aging effects.
This apparent belief in acceleration as the cause is restated in:
“How can equal acceleration in the two different cases result in different rates of clock "speeding up" during the acceleration without such velocity history? Or is it more accurate to say that the rate change for the clock will be the same in both cases due to the identical acceleration?

As far as where the “velocity history is stored” - It is not stored anywhere. I was once, a long time ago, passing a year between ages 5 & 6. There is much more stored about that year (compared to zero) than any storage of “velocity history.” To show how strange this “velocity history” storage concept is, I ask Neddy: Is the velocity history stored in English text, binary numbers, stone tabulates, etc. - his concern was only as to where it is stored, so I can ask about the format.

Last edited by a moderator: Aug 25, 2005
20. ### Billy TUse Sugar Cane Alcohol car FuelValued Senior Member

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First, MacM, let me congratulate you on a fine reply, in the two posts defending your position, but of course I think it fails to do so. (You really are smart and I greatly enjoy discussion with you.) Some might now be forced to admit that you did not “duck” my attack, but would say you did “weave” by transferring it to a concern over “tick rates”, but I do not say that, nor believe that.

“So do you want to claim that during periods of relative velocity between "A" and "B" that each has a tick rate slower than the other? ”

Yes I do. To you this is “obviously impossible” and my long post (Only for you would I have spent several hours drafting it off line.) is an introduction of irrelevant information/ concern about “simultaneity problems” when the fundamental “impossibility” is two tick rates, both slower than the other.

I won’t comment more on your statements about frames A & B as I agree with what you said and never claimed it was your “interpretation“ That is I agree that what you said is the SRT view. I understand how it is troubling you, leads you to think that SRT must be wrong, etc. (I think) but these SRT facts do not trouble me. There is no logical (and hence no physical) “impossibility” that you infer and think “obvious” inherent in these facts. Let to try to show this:

You state in one of your two posts:
“Tick rates need not have simultaneous start/stop times but is a comparison of ongoing ticks within the same time period of relative velocity.”

In this, IMHO, you error, and once again by letting your intuition or simple view (dare I use the word “naïve“ again?) control your thoughts without thinking carefully about what is “tick rate“ and how is it measured and then compared in two different frames.

There are even two hints about where you need deeper thought in your own statement: (“comparison” & “the same time period.”)
(1) If two things are to be compared in a thought experiment, one must fully describe the operational procedure to be used. (More on this later.)

(2) One must also carefully indicate how one knows it is “the same time period.” I always have been assuming your answer to this was in essence:
“Use the “same event” in both frames to start the time period and a subsequent “same event” in both frames to stop it, being very careful not to confuse “delayed perception” of an event with when “it actually happened.” Thus, the scenario that started this thread postulated two explosions as the start and stop event, both being observed in each frame by observers collocated with the events. (actually clocks stopped by the explosions, not by dead men, as I first suggested.) If I am wrong in this assumption, tell me what procedure you prefer, but I think you agree that this is the most reasonable way to assure that the two frames are indeed using “the same time period” so I will now turn to discussion of (1) above:

First I think we agree on what “tick rate” is, but just to be clear I will give a definition:
Tick rate is the difference between the tick numbers divide by the time interval that elapsed between the ticks. For example, if tick number 3600 occurred one second later than tick number 2600, the tick rate is 1000 ticks per second or one millisecond potential error always exists with this clock.

No clock actually measures time. All use some discrete steps of some physical processes and the time interval they “measure” has an error equal to the time between successive discrete steps or “ticks.”
(I bet a smart guy like you already sees where I am going, but let me beat this dead horse a little longer.)

For example, one can conceive of a very high resolution clock using electroplating copper with large DC current of exactly known amperage (not possible actually as current comes in discrete packages we call “electrons“). Also postulate there is a scale of infinite precision. This clock “measures” time intervals between start current and stop current events by weighing the copper deposited. The precision of this clock is the time it takes to deposit one copper atom. (neglecting electrical inductance and the associated non step function of current switching, etc.)

Again: No clock measures time. All clocks use a start and stop event. (Call these events “tick m” and “tick n” or assign specific integers etc. but note they are discrete events.)

(I think that horse is surely dead now.) and that you will agree with the fact the difference in tick numbers is not a measure of time, but only an approximate measure of the time elapsed between a “start event” and a “stop event.” My point has nothing to do with “clock precession,” but that that all clocks involve start and stop events.

Yes that is right. “Tick rate” does inherently involve a start event (tick number 2600) and a stop event (tick number 3600 in my numerical example above). You can not escape this fact.

If you like, you can assign “tick numbers” to my two explosions, but you can not escape the fact that comparing tick rates inherently requires a start event and a stop event.

Thus it is “naïve” to think that “simultaneity questions” are not inherently involved in a comparison of “tick rates.” If the tick rate in one frame is to be compared to that in another, one must carefully describe how one selects the start and stop events associated regardless of whether the “start event” is the sound of a tick (precisely recorded) or the sound of an explosion (precisely recorded). I.e. my “explosions” are no different in principle than your “ticks.” - Both are conceptually discrete physical events, used as start and stop events but as you use “clock ticks” you are more subject to error than me because all clocks only approximately measure time intervals. In contrast, I define the time interval by the period between explosions. I admit that the two clocks I use to measure this defined interval have error but it is very small compared to the difference 102 T vs. 2 T I exhibited in my numerical example.

SUMMARY: It is only “intuitively plausible“, but not true, that one can compare tick rates in two different frames without worrying about the “simultaneity” of the start and stop events required for the comparison. Thus you are wrong in the other post when you said:

“Tick rates are not subject to simultaneity and require no start/stop synchronization. To attempt to debate time dilation interjecting simultaneity, etc is to simply cloud the issue.”

That is too naïve a view. Support your claim by telling me how tick rates are first measured in a single frame and then how they are to be compared between two frames without, for example, the use of a “simultaneous start event“ common to both frames. I think one compares tick rates by counting a large number (for better accuracy) of ticks that occur between some “start event“ and some “stop event“ and that both frames should use the same pair of events to start and stop the counting of ticks.
If you do not agree, how do you first measure tick rates in either frame and then compare the measured results between frames?

PS I want to note (for the benefit of others) that MacM and I have both defended our views strongly by sticking to physical arguments, without resorting to the more common personal attacks some substitute for physics arguments. I.e. a high standard of behavior is possible, even in strong conflicts.

21. ### Billy TUse Sugar Cane Alcohol car FuelValued Senior Member

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Sorry MacM you lost me here. "absolute period" ??? and the following parenthical note??? But not much if any problem on what SRT is reported to claim - Note my "Yes i do." in loger post just made.
I'll try, but did not see any question here, please restate it.

22. ### Neddy BateValued Senior Member

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1,677
Thank you for responding to my scenario, BillyT. I am genuinely trying to learn where I must be going wrong with my understanding of STR.
I introduced the telescope for one reason: to show that the female is time dilated ("in slow motion") relative to the male. Is this strictly a 'perception' issue?

That last line is important. You do not deny that case 1 could yield 3 years and case 2 could yield 20 years.

I agree that what happened before would not seem to make any difference to what will happen in the future. That is why it becomes a paradox.

Yes, I meant that the ships would have started farther apart. So the different tick rates of the two clocks has had more time to accumulate to a larger difference in clock readings. This is a reciprocal effect, I might add.

I specifically state that the acceleration in both cases is equal, so that would not be a very good explanation for the two different aging effects. I do believe that SRT requires that it is during acceleration that the clock readings re-align themselves to fit the final outcome. Perhaps I am in error there?

But isn't 'changing frames' the period when all of the time dilation is supposed to accumulate to one clock or the other? Remember, in STR thought experiments, the two clocks are reciprocally dilated. Wouldn't it be very bad for reality if at least one of the clocks did not speed up radically during the acceleration phase?

This is what causes the male to be younger than the female, and the female to be younger than the male. Even more so in case 2 where the ships started farther apart. Perhaps this is where I am getting lost? Please help.

I was pointing out the apparent paradox that equal acceleration is causing two different shifts in clock readings, one 3 the other 20. I entertained the question of whether it would be more appropriate for the equal acceleration to cause equal shifts in time readings for both cases, but that is my own idea, and not what SRT advocates (if I understand correctly).

Where is the information stored is something of a hypothetical question. I agree that it seems a silly concept which would lead to your hypothetical question as to what format it would be stored in. Aer said in previous post that it was stored in "the matrix" which was aptly humorous if you've seen the movie.

So, please explain to me how the different accelerations can create different shifts in clock readings. You seem to imply that the difference was there all along, essentially being 'stored' in the dilated clocks themselves. In that you seem to have forgotten the problem of reciprocal time dilation. Until acceleration occurs, it is not known which clock is going to end up ahead of which. If the female had accelerated instead of the male, it would be the male who ended up either 3 or 20 years older. The paradox remains...

23. ### Billy TUse Sugar Cane Alcohol car FuelValued Senior Member

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23,198
No it is real, but I am not speaking of what he sees via the telescope. I don't want (or have time) to think carefully about his view. If she is raisng her arm, the lower part of the movement was imaged by lght that traveled a longer distance to his scope (if he was not moving) than the top of the arm movement, so his perception would be even slower motion that the facts due to time passing more slowly. I try to avoid talking about the perceptions.

It is a paradox only if true and strange. (I am not saying it is not, only that I don't understand exactly what you are saying.)

Good, I guessed correctly what you were trying to state. And yes it is a reciprocal effect - the biological processes of both are proceeding more slowly than if they were in the same frame. - this is the paradox MacM and I have been disputing here (He may say it is not a paradox as SRT is false on this.) I suggest you read our exchanges, I defend what seems "impossible" and MacM believes it is impossible that time can be passing more slowly in each frame than in the other. I bet it seems very clear to you that MacM must be correct on this. Again read our exchanges.

A better way to remove acceleration as an explanation of the change in aging rates is to just let it last very short period by anybody's clock compared to the time "drifting in inertial frames". SRT predicts that the cummulated aging effects is linear in this drift time and can say nothing about the accelerating periods as SRT only applies to inertial frames (GR is much more complex and I don't generally comment on it as I am likely to be wrong.)

Yes you are wrong in your focus on the aceleration periods - forget about the accelerations.
I bet you have heard that the "twin paradox" is not symetric as only one twin experience "acceleration" and he is the one that comes home young. That is all true, but his period of acceleration does not cause his youthful state upon return.

Last edited by a moderator: Aug 25, 2005