Is time universal? NO (and its proof)

[valich]

Relative = Absolute

I did not suggest, nor in anyway insinuate that. Time is relative to our point of reference, but there is still such a thing as absolute time, else how do universal know the approximate beginnings of the Earth, the sun, our solar sytem, our galaxy, our own age, etc.?

[James R]

valich:

In any case, this endless talk about frames of reference is nothing more than a waste of intellectual argument.

On the contrary, an understanding of frames of reference is the first crucial step to understanding relativity. If you're interested, see my thread titled "What is a reference frame?"

In space/time we have differing frames of reference but in absolute time it is the same. What is the problem?

The problem is that there is no absolute time.

[James R]

Aer:

I think you missed my post to you...

[valich]

Hi Pete,

I know my post sounds frightfully naive, but I think I might actually be making some ground with this.

If systems K and K' are each 'filled' with a network of synchronized notepad-clocks, then you do not have to wait for any clocks to be reunited in order to compare tick rates. This lays bare the notion that SR can predict a dilated tick rate. It cannot because both frames are equally valid. If you disagree then simpy tell me whether it is K or K' that has the slower tick rate recorded on the notepads.

Universal time, and identical tick rates seem to be the only logical conclusion to this non-accelerating, perfectly symmetric and inertial thought experiment.

Of course the real universe might not necessarily have anythng like systems K and K', so SR might be just a theoretical, foundational construct that leads to greater things.

If I might coin a new phrase: "naivity is the mother of truth." Finally someone got it straight. In both reality and theoretical constructs this is just how it is! In theory you can go on-and-on creating more-and-more complex constructs, and I'm assuming that's what you mean by "might theoretically lead to greater things."? What do you mean by "greater things"? More complex? Yes. A greater mental exercise? Yes. Of benefit to our understanding of reality? No.

[Aer]

Aer:

I think you missed my post to you...

Where is it?

[Pete]

Try here
And don't forget about this one either.

And I'm still wondering about this:

1. SR says that if two events happen in the same place at the same time, then they happen in the same place and time in all frames.
2. SR says that when two events simultaneous in one frame are in the same location in the direction of motion of a second frame, then the two events are also simultaneous in the second frame.

The first statement is a consequence of the second.
The second statement is a consequence of the Lorentz transform.

Do you agree with them as they are written? Please don't read anything else into them.

[Aer]

What about "proper time"? Do you think that proper time is the same as "elapsed time"? Do you think it is well defined?

Is this the same question as "tick rates" measure elapsed time? Because the elapsed time will be dependent on the time the clock started ticking which, with the relativity of simultaneity changes.

What about "time as measured by an accelerating clock"? Do you think it is well defined? Do you think it is a meaningful measure of elapsed time for that clock?

Do I think it is meaningful? Of course.. Do I think that the relativity of simultaneity is meaningful? Well that is yet to be seen. I suspect that it is not meaningful.

The first statement is a consequence of the second.
The second statement is a consequence of the Lorentz transform.

Do you agree with them as they are written? Please don't read anything else into them.

You asked me not to read anything into them, so I deleted my response . But since you want to know. I do believe that the relativity of simultaneity forbids any synchronization which has already been shown.

[James R]

In what sense do you believe that the relativity of simultaneity is not meaningful, Aer?

It is a derived consequence of the basic postulates of relativity.

Which one of the basic postulates do you doubt?

[Pete]

Is this the same question as "tick rates" measure elapsed time?

No. Proper Time.

But since you want to know. I do believe that the relativity of simultaneity forbids any synchronization which has already been shown.

Welcome to MacM's world. I wish you all the best.

[Aer]

No. Proper Time.

I think you are stigmatized by MacM's usage of the phrase "tick rate". How is a clock's tick rate not:
proper time is time as measured by the clock for an observer who is traveling through spacetime.

Just sayin..

Welcome to MacM's world. I wish you all the best.

Very well, but I believe your point of view is just as biased. Well, I'll at least admit that I believe either to be possibily correct, but I see no reason for there to be the relativity of simultaneity given the experiments we have to rely on regarding special relativity.

[Aer]

In what sense do you believe that the relativity of simultaneity is not meaningful, Aer?

It's not demonstrated by any experiment. I cannot even think of an experiment that would demonstrate it's existance. Aren't these some of the same arguments against string theory? I admit, the lack of evidence shouldn't be considered a proof of non-existance, but that is why it is just an idea.

It is a derived consequence of the basic postulates of relativity.

I agree that this is true. I can only tell you that the local ether model predicts that c is constant relative to the purported local ether.

Which one of the basic postulates do you doubt?

See above.

[James R]

Aer:

Then, in a nutshell, you don't believe the postulate of relativity which says "The laws of physics are the same in all reference frames."

You believe instead in what I assume is the "local ether" postulate, that the "local ether" frame is special and privileged above other frames of reference. All real physical calculations must be done in the "local ether" frame to avoid incorrect results.

Do I have that correct?

[Aer]

Aer:

Then, in a nutshell, you don't believe the postulate of relativity which says "The laws of physics are the same in all reference frames."

You believe instead in what I assume is the "local ether" postulate, that the "local ether" frame is special and privileged above other frames of reference. All real physical calculations must be done in the "local ether" frame to avoid incorrect results.

Do I have that correct?

I don't believe it is as cut and dry as you make it. Because first of all, I would say that it is the other postulate that would be modified. The speed of light is constant with respect to the local ether frame. But you must remember that the two theories predict much of the same given different interpretations so the laws of physics would still be the same in all frames of references. I am not going to defend the correctness of either theory other than to say that I know of no experiment that invalidates either.

[Billy T]

....I see no reason for there to be the relativity of simultaneity given the experiments we have to rely on regarding special relativity.

Aer we often disagree but I do not think you have actually read the first post of this thread I started. I say this as there I think it proven that simultaneity is relative. You accused me of using relativity to prove relativity, but that is false. I asked you for even one example of my use of relativity in this entire thread. - Never have I used a single equation from relativity here.

I also note that Pete's stamping time clocks is really no different from the concept I set forth in the first post. Both Pete's idea and mine of having a multitude of observers "shoulder-to-shoulder" in a line along the track while a fast moving train passed provide co located with events observers in both frames. I some what humoriously had two explosions on out side of train be the two events and these explosive charges "just grazed the noses" of the line of observers to assure the co-location.

The explosions were photo-electrically trigered by a flash of light originating from the center (outside also) of the train, so simultaneous in the train frame, but the ground observers find that the "end of train explosion" preceeds that "head of train explosion" because while the light is traveling to the "end explosion" the end of the train is advancing to meet the advancing flash of light and like wise the front explosion is delayed as the flash must travel the extra distance the train advanced while flash was in motion.

That is what is simultaneous in one frame, can not be simultaneous in another. (I also considered effect of a slight shift from center of the train of the light flash source and gave several numerical examples.) I have no objection to Pete's clocks stamping paper, but it is really nothing new, not already in the first post conceptually.

I again challenge you to support your claim that I am using SR to prove SR. Give one example.

In some ways, my “trains and explosives” are better than Pete’s “stamping clocks.“ To do any thing with Pete’s clocks, you must calculate the times stamped. (Pete & James have do so using SR theory.) In my example, one shows that two events simultaneous in one frame are not simultaneous in another without any calculation. I do not even need to claim that light has the same speed in both frames! (I do assume this true when making some numerical illisutration, but they are given only to make the point numerically also, not essential to the proof.)

I might also add that my observers do not actually have "noses" - they are blast-proof locally-sychronized in their own frame clocks - the explosion need not be powerful, so no problem for them to stop and record the time of the explosions. Train times recorded have (Tfront -Tend) = 0 but Station times, (Sfront - Send) > 0.

[Aer]

Aer we often disagree but I do not think you have actually read the first post of this thread I started. I say this as there I think it proven that simultaneity is relative.

Simultaneity is relative according to the postulates of special relativity. You cannot say that you've not used the postulates of special relativity in deriving a result of special relativity.

[1100f]

The explosions were photo-electrically trigered by a flash of light originating from the center (outside also) of the train, so simultaneous in the train frame, but the ground observers find that the "end of train explosion" preceeds that "head of train explosion" because while the light is traveling to the "end explosion" the end of the train is advancing to meet the advancing flash of light and like wise the front explosion is delayed as the flash must travel the extra distance the train advanced while flash was in motion.

In your example, you indeed assume that in the train both flash light travel at the speed of light. But you also assume that in the ground frame, the velocities of the flashlights are not c-v and c+v, and you do not have reasons to assume it, unless you say that galilean transformation (which lead to the galilean formula of addition of velocity where the flashlights would have velocities c-v and c+v and would have arrived simultaneously to both ends of the train) is incorrect ==> time is relative. So that in fact your proof of non universality of time goes like that: Time is relative (I don't use galilean transformation) so the train experiment shows that with this assumption time is relative.
According to you, since you do not use the galilean transformation, you should have stated what velocity addition formula you use, because in principle you could have stated that the flashligth going toward the front end of the train travels or a ground observer at, let's say, 2c and the flashlight going backward goes at c/2.
Of course, if you say as SRT says that the speed of light is constant in all frames, the example that you gave is perfectly good to show that time and simultaneity are relative.

Futhermore. I totally agree with you that the relativity of simultaneity is a real effect. People who don't understand SRT sometimes think that this relative simultaneity is just an illusion because we "see" the events by mean of light which has a finite velocity. This effect of "seing" is a Dopplerlike effect which would give different result wether we use SRT ore wether we don't.

Finallt, i would like also to point out that I had the impression that people here think that if simultaneity is relative, then every thing is permitted. Well, this is not.
For example, if two events are simultaneous in some frame at the same location, then they will be simultaneous in all reference frames. This means that if particle 1 reaches point A at some time and particle 2 reaches the point A at the same time (this means that they collide), then in all frames they will reach the point A at the same time.
Another example is that if two events have a timelike separation, in all frames the order of the events will be preserved. If a particle reaches point A and later reaches point B, if this particle goes slower than light (the two events have timelike separation), then in all frames the particle will reach point A before point B

[Billy T]

In your example, you indeed assume that in the train both flash light travel at the speed of light. But you also assume that in the ground frame, the velocities of the flashlights are not c-v and c+v, and you do not have reasons to assume it, unless you say that galilean transformation (which lead to the galilean formula of addition of velocity where the flashlights would have velocities c-v and c+v and would have arrived simultaneously to both ends of the train) is incorrect ==> time is relative. So that in fact your proof of non universality of time goes like that: Time is relative (I don't use galilean transformation) so the train experiment shows that with this assumption time is relative....

I am not sure exactly what you are saying, but let me note for emphases, that my proof does not care what the speed of light is on the ground so long as it is not infinite. Light in the station frame could travel at the speed of sound in air, and the proof is still valid. All I require is that light traveling both ways along the train tracks has the same speed.

The time interval to reach the explosive charge at the end of the train is shorter than the time interval to reach the explosive charge at the head of the train, because during the time of flight of the light the trains moves. In fact, if light were traveling at the speed of sound in air the effect on a train traveling at only 100 mph would be easily observed. Namely "end explosion" preceeds "head explosion" in the ground frame but they are simultaneous in the trains frame.

[Aer]

Futhermore. I totally agree with you that the relativity of simultaneity is a real effect. People who don't understand SRT sometimes think that this relative simultaneity is just an illusion because we "see" the events by mean of light which has a finite velocity.

You should state that you believe the relativity of simultaneity is a real effect. There is no experimental evidence to conclusively conclude that it is. The local ether model which cannot be ruled out by experimental evidence does not say that the relativity of simultaneity is real or perception.

[Aer]

I am not sure exactly what you are saying, but let me note for emphases, that my proof does not care what the speed of light is on the ground so long as it is not infinite.

That is not the point. The point is:

All I require is that light traveling both ways along the train tracks has the same speed.

[1100f]

I am not sure exactly what you are saying, but let me note for emphases, that my proof does not care what the speed of light is on the ground so long as it is not infinite. Light in the station frame could travel at the speed of sound in air, and the proof is still valid. All I require is that light traveling both ways along the train tracks has the same speed.

What I am saying is that you give up galilean transformation (that claims that simultaneity is absolute) to prove that simultaneity is relative.