# Is time universal? NO (and its proof)

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

1. ### Neddy BateValued Senior Member

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You make a good point that we should avoid talking about perceptions. I guess I just assumed everyone knows to disregard doppler effect and delay-effects caused by c being finite. That way it does not have to be stipulated for every scenario. For example, if the female's ship is approaching at relativistic speed, she would appear in fast-motion not slow motion, but I referred to the slow motion because I already disredarded the doppler effect.

I have been following your exchanges with MacM, and I am hoping that you or someone can finally explain away the reciprocal time dilation problem. I don't think it has been explain satisfactorily yet, but that does not mean that I reject SRT outright.

Very well, I will try not to focus on the acceleration. I knew it was not supposed to be the cause but I did think that it was during this time that the clocks changed radically.

In closing, let me ask one thing that might help me to finally grasp this:

Is there supposed to be such thing as 'real' motion which induces time dilation and 'real' rest which does not induce time dilation? I thought relativity theory forbids a preferred frame of reference. Because if I cannot focus on acceleration in the twin paradox, then how can I possibly detect which twin will be younger unless I choose a preferred frame?

Oh no, now I am totally confused. Check out this website.

http://www.phys.vt.edu/~jhs/faq/twins.html
(Scroll down to the short section at the bottom.)

This is a pretty good explanation of the twin paradox, but there is one short section at the bottom of the page that treats the twin paradox without acceleration. What the #\$^&*? ...Oh lord, now it looks like there is a preferred reference frame. Someone please tell me this is wrong!

3. ### MacMRegistered Senior Member

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10,104
NeddyBate,

Don't fret. Notice it is just the typical slight of hand used by relativists. He has deliberately excluded reciprocity which is inherent in SRT. That is if O' is in inertial velocity and O is at rest. According to SRT it is equally valid to claim O has the velocity and O' is at rest.

Taking that fact into consideration the twin paradox vanishes and the reciprocity paradox arises. Now each twin is younger than the other.

5. ### superluminalI am MalcomRValued Senior Member

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Neddy,

What problem?

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

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dear Neddy:
You have (if I may include myself) three smart guys trying to help you!

Unfortunately we don't agree, but generally I think SL and I are singing the same tune, but that does not that proves MacM is wrong. SL says "What problem?" - I am a little more generious with MacM. I see his problem very clearly. MacM put it to me very well when he asked if I really believed that clocks in both frames A & B were ticking more slowly than in the other. (I think they do, but this is not the logical impossibility it seems to be with only superficial consideration. - As stated in some detail in my posts, one must describe how they are to be compared very completely, including the "simultaneity issues" )
Now my take on your closing question:

All motion is relative. There is no preferred rest frame. In the standard twin paradox, only one twin experiences acceleration and that one is the one who is younger when they stand side by side after his round trip thru space. No problem knowing which is the younger one, but it was the high speed traveling time that caused him to be younger than his now older brother (not the mid-trip, turn-arround, acceleration itself) when they joinly celebrate his safe return to Earth.

I think SL agrees with this, but MacM I am almost sure does not.

PS by edit: I forgot to correct your wrong comments about Doppler Effect: The DE has nothing to do with time dilation, the lady being or appearing younger or older etc. All the DE can do is make her look sad (bluer) or embarissed (red faced). DE changes the frequency of the photons, not the time for them to travel.

Last edited by a moderator: Aug 26, 2005
8. ### Neddy BateValued Senior Member

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I'll try to summarize the problem(s) with SR in the case of uniform translational motion:

1. Time dilation results in two clocks which are each ticking slower than the other clock
2. The slower rate (of each clock with respect to the other) causes time dilation to accumulate more and more time descrepency depending on how long the journey of translational motion
3. Acceleration is required to join the clocks in the same frame, and during this acceleration the clocks will have to reconsile their differences
4. Equal acceleration can cause unequal time shifts depending on how much accumulated time descrepency
5. No one knows where the information required to acheive the appropriate time shift would be stored
6. Some claim that acceleration is not even required to acheive this (see link in above post)

9. ### Neddy BateValued Senior Member

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1,590
And I thank you for your help. I am not being stubborn here. If I could genuinely understand this, I would gladly say so and be on my merry way.

I think I should consider the simultaneity issues more closely. This is probably where I am going off-track.

I tend to agree with you, but did you see the link I provided where acceleration was not considered?

Time dilation was the only thing I was considering when I said that she appeared in slow motion. I agree it is a totally different concept to the doppler effect (DE). However, I think you underestimate the capability of DE to make someone appear in 'fast' or 'slow' motion. Don't you agree that DE is more than just a color shift? I consider it to be the accumulation of light information that is in transit between the source and the receptor. So an approaching source would be sped up and a receding source would be slowed down.

10. ### MacMRegistered Senior Member

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10,104
Well you would lose your bet. It is indeed the only answer. That is the onc that accelerates is the only one that has had an energy level change and is the one that will dilate.

That is precisely my view. Reciprocity grants to the twin (clock) that had no change the same dilation affects and that is the error in SRT.

11. ### AerRegistered Senior Member

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2,250
Yes, the relativity of simultaneity fixes almost every intuitive problem one may have with SR. Until you understand the relativity of simultaneity, you shouldn't really be trying to understand relativity problems without just doing the lorentz transformation and trusting the results that pop out - at least that is the advice I would give for anyone who justs wants to understand how relativity works.

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

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No, it is "just a color shift" or more correctly stated a "frequency shift/change effect." - "color" is not a property of light frequency alone, but the joint effect of the light frequency and the eye's photo receptors. This is expecially obvious if one of the three types of photo receptors is missing (I.e. a "color blind" person) or the observer is normal, but non human. (E.g. Most of the "white" flowers you see are highly colored to the bee. We can tell by measuring their UV reflectivity and also noting bees see (respond to) UV light.)

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

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I am surprized by your first paragraph quoted above, but not the second. I could swear that you had several times in prioor posts denyed the SRT claim that they are different ages when reunited.
The statement that "reciprocity" makes both dialated is true (and not the logical conflict you think it is as I tried to show in post that ends with: "ball in your court now") but the SRT claim about the twin paradox is that the astronaught twin is younger when he gets home again than this twin brother. SRT does not claim both are younger or have the same age when reunited because they have relative motion when one was making the round trip thru space at high speed. As I read/understand you last paragraph above, that is what you say SRT claims and it does not. ("Reciprocity grants...the same dialations effects...")

14. ### MacMRegistered Senior Member

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Unfortunently, you do not seem to realize I have many times crossed the aisle to argue the point from a different vantage point. When I have claimed "No" differance in age it was based on strictly velocity (no GR) and included the issue of reciprocity advocated by SRT.

You should keep in mind the original "Twin Paradox" did not consider acceleration as a factor and simply argued the affect was due to time dilation due to velocity of the twin that had accelerated.

The issue of reciprocity made that claim null and void and the next solution was then to claim age differance due to acceleration of the one twin.

That explanation I do not believe is totally correct but is enough so (disallowing reciprocity) that I won't argue the issue.

******************************************************
http://www.mathpages.com/home/kmath307/kmath307.htm

Given this definition of inertial reference frames, the principle of relativity asserts that for any material particle in any state of motion there exists an inertial reference frame - called the rest frame of the particle - with respect to which the particle is instantaneously at rest (i.e., the change of the spatial coordinates with respect to the time coordinate is zero). This principle is usually extended to include reciprocity, meaning that for any two systems S1 and S2 of inertial coordinates, if the spatial origin of S1 has velocity v with respect to S2, then the spatial origin of S2 has velocity -v with respect to S1. The existence of this class of reference frames, and the viability of the principles of relativity and reciprocity, are inferred from experience. Once these principles have been established, the relationship between relatively moving inertial coordinate systems can then be considered.
*****************************************************

My statements are consistant with all text descriptions of SR and reciprocity.

Last edited: Aug 27, 2005
15. ### Billy TUse Sugar Cane Alcohol car FuelValued Senior Member

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If Ifail to get back to this remind me - going to bed now. See post I just made in the uniKEF thread. You will like two parts of it (More Oscom razor support for uniKEF.)

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

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If there is no period of acceleration, it is impossible for the astronaught twin to return to Earth. He can not stand beside his brother again on Earth, but is still traveling fast and far away. Thus, you have the fact, well demonstrated in first post of this thread, that the brothers in two different frames do not agree that the other made a "simultaneous" comparison of their ages.

For example, from astronaught's POV, at the instant he turned 30 his brother was only 25 and likewise from the POV of the Earth bound twin, when he turned 30, at that instant his astronaght brother was only 25. This is not a perception delay. It does not mean the "physical impossibility "of one calendar (or clock) being able to display both 30 and 25 at the same time in any one frame (Your "reciprocity" that "disprooves" SRT argument.) It only means, and is due to, the fact that what is a simultaneous comparison of ages for one brother is not done at the same time from the other one's POV. The other one, from his POV send msg to his brother saying: "Have you gone crazy? You are "comparing" our age at two different times, which are years apart!"

PS - I have noticed that you were a moving target, "crossing aisles" as you put it, but perhaps my interpretations of this admission is not what you really intended to state.

velocity is limited by c, but there is no limit on acceleration, in principle, but human bodies do have a limit, but ths is a thought experiments so lets make the entire turn arround period be completed in one second. (If you worry that on the other guys clock it is 10 seconds, then accelerate 10 times faster so on the clock with the greatest measure of time in the turn arround, the turn arround time is only one second.) Let there be 25 years of earth time from launch til turn arround and the trip back is also 25 years so except for a second (or less) the Earth bound brother is 50 years older than he was at launch. (I believe that SRT is correct that the astronaught is younger when standing by is brother on Earth again.) You may call this the "earlier SRT view", I don't care. It is still the SRT view. The fact is that the period of acceleration can be neglected if the acceleration is very forceful/ rapid/ short duration on everyone's clocks compared to much longer travel in inertial frames times.

Last edited by a moderator: Aug 28, 2005
17. ### MacMRegistered Senior Member

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What do you mean can't return. He never left.

Just kidding. The point wasn't that there wasno acceleration but that it was not specified or argued as part of the scenario. The claim was that the twin was younger due to his time spent at a relative velocity. No acceleration of one twin and not the other was made.

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

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Don't include me in this "we" (now bold above.) In recent post I considered the case of one twin not returning, but maintaining steady speed away form Earth. The Earth bound brother, correctly allowed/corrected for the time delay of messages (big telescope views etc.) and was so surprized to find that when he was 30 his distant traveling twin was only 25. He had arranged with his brother before launch the the traveling brother would do the same on his thirth birthday. The traveling brothe got the smae result - his Earth bound brother was only 25.
A few years later when each had learnd the results of their prearranged observation, each sent messages to the other saying: "Are you crazy? you must compare our ages at the same time aws I did."

SUMMARY: Turn arround acceleration has nothing to due the SRT prediction in the twin paradox. It is useful only in that (1) I breaks the symetry - let one know which of the two twins standing side by side after a round trip by one is the younger. and (2) avoids the Simultanity conflict that makes each think the other did not observe his age at the same time that he turned 30. (both believe the did the necessary corrections to compensate for "perceptual delays" AND THEY DID. - It is true that when T1 was 30 T2 was only 25 as "simultanious" is defined in T1's reference frame, and also true that when T2 was 30, T1 was only 25 as "simultanious" is defined in T2's reference frame.

The fact is, as clearly demonstrated in first post this thread (no one has said other wise yet) that events that are simultaneous in one frame are not simultaneous in the other. Thus both are correct in their own frames the other is younger. Their is not conflict in a local clock showing noon when (simultaneously in that frame) one in another frame is only showing 11AM, Even thought is also true that thaking the point of view of the other frame it is only 11AM when the local clock shows noon. You think clock "A" can not show both noon and 11 AM "at the same time" and this is true in any one frame, but if you consider both frames, clock A can show 11AM "at the same time" (frame B's "at the same time") that the local frame B clock is showing noon and yet at "the same time" (frame A's "at the same time") clock A is showing noon clock b is showing only 11 AM. - no problem if your realize "at the same time" is frame dependant, or as title of this thread states Time is not universal.

19. ### MacMRegistered Senior Member

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10,104
If you continue to increase your tone "Are you crazy", I may return the favor.

I think you should slow down and realize that your traveling twin is only traveling because he accelerated. Your scenario fails to consider reciprocity as advocated by SRT such that the traveling twin can equally claim to be at rest and it is his brother that has the motion and would in that case be the younger.

That is the flaw in SRT (reciprocity), not the fact that a twin in motion due to acceleration will age slower.

You once again move from physics to perception when you start to include simultaneity affects. I don't care what you see at a distance or during motion. I am only concerned about actual time diation which is recorded by accumulated time on two clocks when compared in a common frame. That is the only actual time dilation that occurs. All else is illusion.

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

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That was message from one twin to the other, not intended for you. read again and it is clear.

He was not necesarily accelerated, but it is complex to show how. (uses artificial fertizalation, cloning etc to get both twins born in different frames. Just as you are passenger on planet Earth and hence traveling at high speed wrt distant stars field but you never experience more than a few "Gs", they could be born already moving fast and never have acceleration,even their "parents" could have been, on different planets etc.)

How can you say I neglect reciprocity? In one post when you asked if I though both clocks were slower that the other, I said "Yes I do." even if it is superficially "crazy" and went on to defend that it is not. Also in same post I think you are responding to, I said each accurately measures the other to be 25 on his 30th birthday. - If I have the guts to state what is superficially impossible, you should not deny that I do by saying I neglect "reciprocity."

Not a flaw if one one understand the simultaneity problem, which you don't. See next responce also.

Not true. Have you read the first post of this thread? Their is no "preception delay" in that proof that simultaneous events in one frame are not simultneous in another - the explosions at ends of train are locally timed /observed etc in Both frames! No delays!, No illusions! No Perception. Only facts, as they exist.

Please read first post and them tell me if you agree that "simultaneous events in one frame are not simultneous in another." or not. If you ignore the first post proof, and/or continue to not to show any error in it, then we can't discuss SRT becuase you fail to be responsive to a logical proof.

I.e. show me where there is error in the derivation that "simultaneous events in one frame are not simultneous in another" or accept this as fact. As it is now, you reject this fact and then argue that SRT is wrong as it uses the this fact and conculudes that: yes one twin brother is 30 and his brother is only 25 and conversely etc., which I admit is superficially nonsense and remains such for one who does not understand that "simultaneous events in one frame are not simultneous in another."

Last edited by a moderator: Aug 29, 2005
21. ### Billy TUse Sugar Cane Alcohol car FuelValued Senior Member

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to MacM:

A further thought: I don't think you are in a position to state SRT facts as you reject SRT, as either internally inconsisten or inconsistent with observable facts or both (not sure which of these, perhaps all).

I defend SRT. I am even willing to defend its claims that seem superficially "crazy". Rather than you tell me what SRT states (because in MY view you don't fully understand it) why not you tell me where my defense of "simultaneous events in one frame are not simultneous in another" (first post this thread) is in error.

In analogy: I don't completely understand cricket, but know there are batters, a ball fielders, runs, sides get put out etc so I am not entirely ignorant of it either.
Do you think I am in a position to tell others what the rules of cricket imply about the game? Or would it not be better to let a cricket authority/ unpire etc, who sees no selfcontradictions in the cricket rules or result of the game state what is implied and me attack his statement (using ony them, not some I had made up) to try to expose inconsistencies?

It annoys me that you say I ignore "reciprocity" (especially when it is clear I don't). SRT has both reciprocity and the appearant nonsense of the twin paradox is a direct result of this "reciprocity", but it is not nonsense, because SRT also denys the existance of universal time. - I.e. simultaneous events in one frame are not simultneous in another. So each twin in his own frame's simultanity is simultaneously 30 when his brother in another frame is 25 etc.

Last edited by a moderator: Aug 29, 2005
22. ### Neddy BateValued Senior Member

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I like the above version of the twin paradox. It is simpler than the version where one twin turns around and returns home. Plus, I see that you have specifically allowed/corrected for the time delay of messages.

However, I want to be 100% sure that the reciprocal nature of time dilation is not being caused by an incorrect allowance/correction for the time delay of messages.

So, could we please turn the situation around so that the twins start very far apart with synchronized clocks and then travel toward each other? The correction for time delay must be included in the synchronization process, but this can be done accurately because there is no length contraction of the distance between them while they are at rest.

Next, one or both of them accelerate toward each other. (If I understand correctly, it does not matter which twin accelerates?!?) When they meet again, simply passing very close to each other in space, would you still say that they are each younger than each other due to lack of simultanaety?

And finally, if one of the clocks accelerates to join the other in its frame, could someone describe the behavior of both clocks during the time when the clocks join frames? Here is an example of what I mean:

According to TwinA, just before acceleration to join frames:
TwinA = 30
TwinB = 25

According to TwinB, just before acceleration to join frames:
TwinA = 25
TwinB = 30

And this is where the paradox kicks in every time... Let's say that TwinB accelerates and joins the reference frame of TwinA (in a negligible amount of time):

According to both Twins, just after joining frames:
TwinA = ?
TwinB = ?

23. ### AerRegistered Senior Member

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It does matter which one accelerates. I think there have been some on this forum that have incorrectly lead people to believe that it doesn't matter.

Your setup is ill-posed, we know not which one has accelerated. If neither accelerated, they would never meet as they started at rest far away from each other.

Nope. The relativity of simultaneity makes no sense