Minguizzi's Simultaneity Method

[Halc]

That last line is incorrect.

OK, I actually don't know if the last line is true or not. I've not seen the method enough to know it, but if it's not true, then the method is A) not symmetrical. B) cannot be used to compute the age of anything else, and C) Cannot be used by the twin that stays home.
This seem unituitively wrong to me, and I lay odds that if his paper is read in detail, that I got it right. It is a way of mapping every event in that light cone, and it is self-inconsistent if it cannot be applied to any other object except inertial ones.

But after [turnaround], the traveler and the imaginary twin who passes him when he's asking his question AREN'T the same age when they are momentarily co-located.

The method is actually quite simple and I don't think of it in the complicated terms of an imaginary twin at all. Where's the paper? I looked through ON THE CONVENTIONALITY OF SIMULTANEITY and didn't find it described. Maybe it's elsewhere.

After the velocity change, there is a DIFFERENT imaginary twin for each instant in the traveler's life. All of the imaginary twins are zero years old when they leave the home twin (when she is zero years old).

This is the same thing as saying the (square of the age of the other twin) plus the (square of the interval between this twin and the reference event) is zero. No need for an imaginary twin, or a bunch of them.

 

[Halc]

Are you saying that Minguzzi uses an imaginary twin co-moving with the traveling twin, and from that concludes that the resolution to the twin 'paradox' is that they are both the same age upon being reunited?

Not sure. Looking for what he actually says. Yes, the method, if implemented by either twin, results in them the same age, but the one appears younger because he's dilated from the motion. It's kind of the same answer as the absolutists, except one doesn't need to know or posit the absolute frame. If you read the guy's paper, it reads like he's got absolutist blood in him. But the paper I read didn't describe this method, or if it did, I didn't recognize it as it went by.

By the way, here is the link I found after Googling Mike_Fontenot's 0411233v1 reference:
https://arxiv.org/abs/physics/0411233

Maybe that's it. Haven't read that one yet. I'm basing my bit about the imaginary twin from Mike's page.

 

[Halc]

OK, that link has it, section II A.
It seems it is meant as Mike puts it, an asymmetrical method that can only be used by one person, and only if they're twins and the other twin remains perpetually inertial. So yes, when he turn around and starts going home, his age begins to fall behind hers. The method only seems to assure that her age is forever increasing, but it isn't commutative. So when he's 20, she's 20, but when she's 20, he's not 20. Ouch. What possible use is that??

 

[Mike_Fontenot]

Are you [Halc] saying that Minguzzi uses an imaginary twin co-moving with the traveling twin, and from that concludes that the resolution to the twin 'paradox' is that they are both the same age upon being reunited?

That's not what Minguzzi says. ALMOST all of his paper is about determining the ages of the twins at the reunion, supposedly using the traveler's (his) perpective, not the home twin's (her) perspective. WHY anyone would want to do that escapes me ... the situation at the reunion is trivial to get from her: it only requires the use of the time dilation equation (TDE). I don't think Minguzzi was maintaining that she ISN'T twice as old as he is at the reunion ... i.e., I don't think Minguizzi was disagreeing with her perspective and the TDE.

By the way, here is the link I found after Googling Mike_Fontenot's 0411233v1 reference:
https://arxiv.org/abs/physics/0411233

I don't see where any imaginary twins are mentioned, and I don't understand anything the paper is trying to say. [...]

Minguzzi introduces and discusses the imaginary twins only in his short Section A on page 3. It's the ONLY part of the whole paper that deals with simultaneity at a distance. I'm convinced that what Minguzzi MEANT to say in that short comment is that when an imaginary twin ("it") is co-located (usually only momentarily) with the traveler (him) and tells him "it's" age at that instant, he concludes that her current age is equal to "it's" age then. (So in my numerical example, the ages of he, "it", and she are all EQUAL on the entire outbound leg ... so the age correspondence diagram (ACD) for Minguzzi's method has a slope of 1.0 on the first segment). But that ISN'T what Minguizzi LITERALLY said ... Minguzzi literally said that her current age is the DIFFERENCE in "it's" age and his age. So what Minguzzi LITERALLY said implies that in my numerical example, her age is zero during the entire outbound leg ... obviously nonsensical.

Minguzzi NOW denies that his paper has ANYTHING to do with simultaneity at a distance! It's amazing that he would argue that, given that his imaginary twins play NO role WHATSOEVER whenever the traveler and the home twin are co-located. I don't know WHY he is now denying what he clearly said in his paper.

 

[phyti]

Mike;

I recently ended an exchange with a poster who has spent the last 13 yr attempting to resolve the 'twin scenario', his way (whatever that is). He has ignored all help, on different forums, even involving spacetime graphics. I thought, what a waste of his time. Then you make an appearance with CADO. How many people have you convinced in those 20 yrs, that it works?

He didn't understand the theory at the foundational level of relativity principle and the two postulates. You are attempting to derive instantaneous information within the framework of SR, which has removed absolute universal time, absolute rest, and instantaneous light speed.

Any information you accumulate, by known physical processes is historical.

 

[Halc]

I'm convinced that what Minguzzi MEANT to say in that short comment is that when an imaginary twin ("it") is co-located (usually only momentarily) with the traveler (him) and tells him "it's" age at that instant, he concludes that her current age is equal to "it's" age then.

He does say that, but in somewhat more precise language. A better wording yet would ditch the imaginary twin and just talk about the imaginary interval between the two events.

... so the age correspondence diagram (ACD) for Minguzzi's method has a slope of 1.0 on the first segment. But that ISN'T what Minguizzi LITERALLY said ... Minguzzi literally said that her current age is the DIFFERENCE in "it's" age and his age.

He doesn't say that. He talks about her age differential, not her age. The differential is zero while he's inertial, but becomes nonzero thereafter.

Minguzzi NOW denies that his paper has ANYTHING to do with simultaneity at a distance!

You really need to stop putting words into his mouth. Nowhere does it say that. I suspect you're talking about this: "This definition has the advantage of avoiding conventions for distant simultaneity", which talks about avoiding conventions, but doesn't go so far as to assert the paper has nothing to do with simultaneity at a distance. Anyway, I agree that quote is nonsense since a different convention is still a convention, so it isn't avoiding conventions.

 

[Mike_Fontenot]

He talks about her age differential, not her age.

That's one of his ambiguities: he never defines what he means by "the age differential". I think he just means that the two twins have different ages during the trip (from either of their perspectives).

Nowhere does it say that.

The above quote was in response to my statement "Minguzzi NOW denies that his paper has ANYTHING to do with simultaneity at a distance!" you said:

I suspect you're talking about this: "This definition has the advantage of avoiding conventions for distant simultaneity"

That WAS a bizarre comment from him, that seems to directly contradict what he said immediately before. But that wasn't what I was referring to in my statement above. I was referring to the fact that a guy I've been corresponding with has traded a few emails with Minguzzi recently, and that denial I quoted came just recently from Minguzzi himself. (I've also sent Minguzzi a couple of emails, but he has never responded to me).

 

[Halc]

That's one of his ambiguities: he never defines what he means by "the age differential".

It's not a scientific term in need of explicit definition. In the English language, that just means the difference in their ages.

I was referring to the fact that a guy I've been corresponding with has traded a few emails with Minguzzi recently, and that denial I quoted came just recently from Minguzzi himself. (I've also sent Minguzzi a couple of emails, but he has never responded to me).

OK. If he said that, then I don't know what he thinks his paper is about. It certainly doesn't provide a generic rule to use in any situation, and there are plenty of conventions that do, so I find it impractical. Why publish a convention with no practical uses?

 

[Mike_Fontenot]

It's not a scientific term in need of explicit definition. In the English language, that just means the difference in their ages.

Whose ages? One of Minguzzi's communications said that it DIDN'T refer to the home twin. But he uses the term right at the beginning of the paper, LONG before he said anything about the imaginary twins. He should have been clear what the meaning of the term was. He may be using the same term to mean different things in different parts of his paper. I thought his whole paper was very sloppy.

 

[phyti]

Mike;

If there was an award for making something simple appear complicated, Minguzzi could win it!

The clocks in the A static frame and the B moving frame, are running at constant rates for the inertial portions of the speed profiles (the simple triangle). If B reverses to reunite with A, the td factor of 2 is the same for both out and back, since gamma is a function of speed.
If B does not reverse, and continues outbound, there cannot be a comparison for age.
The age correspondence would look like the graphic, when the B course is closed.
For the B frame, the A clock switches from 10 to 70, since the account involves segments from two different frames.
The td effects are reciprocal, as required by SR.

 

[phyti]

Mike;
Here is a pdf that is similar to the Minguzzi example, but in a much simpler manner. It follows the more realistic profile (C in fig.1), with short intervals of acceleration.
It only shows the dependence of accumulated time on the velocity of a clock.

I don't understand his ideas in the remainder of his paper.

 

[Mike_Fontenot]

If B does not reverse, and continues outbound, there cannot be a comparison for age.

I don't understand why you said that. For two perpetually-inertial observers, they each will say the other is ageing slower than they themselves are. They don't agree with each other, but that's OK.

 

[Mike_Fontenot]

The age correspondence would look like the graphic, when the B course is closed.
For the B frame, the A clock switches from 10 to 70, since the account involves segments from two different frames.
The td effects are reciprocal, as required by SR.

I didn't understand the above. And I don't understand your two diagrams. The larger diagram seems to say that B says that A is ageing twice as fast on the entire trip (and I think B is the one who accelerates). WHO's simultaneity model is that? It's not any of the 4 methods I know about (CMIF, mine, D&G, and Minguzzi). And I don't understand what you meant by reciprocity ... two perpetually-inertial observers will each think that the other is ageing more slowly, but when one accelerates, their conclusions about the correspondence between their ages are not at all alike. Have I misunderstood you?

 

[Jonathan Doolin]

I see in the earlier paper, https://arxiv.org/pdf/gr-qc/0506127.pdf that Minguzzi uses the word "foliation" five times. The implication is that he believes, for any arbitrarily accelerating observer, that the whole of spacetime can be sliced into instants, one following another. This would be consistent with Dolby and Gull's "Radar Time" which I wrote an unpublished critique of, a few years ago. It's available here, if anyone cares to read it: https://www.researchgate.net/public..._Facing_A_Distinction_of_Two_Compatible_Ideas

Dolby and Gull's main concern seemed to be that for an accelerating observer, distant events would be swinging forward and backward in time, and they were completely determined to HIDE that fact, by introducing a great deal of unnecessary mathematics. In particular, they used what I call the HERPT DERPD method, or "Half emission Reflection Perception Time" "Defference Emission Reflection Perception Distance". Such a process does, in fact foliate the spacetime into isoclines of consecutive events, but it does not change the fact that the distant events are truly swinging forward and backward in time. It only hides the fact, by requiring the accelerating twin to only acknowledge the time on her own clock.

Near the beginning of Minguzzi's paper, he says "However, here we should take into account that before making any statement on the value of the one-way (i.e. from one point to another) speed of light, and thus even before the formulation of the constancy postulate, a global time variable to make sense of expressions such as ∆x/∆t is needed. In most special relativity textbook this important conceptual point is not explained, and the existence of a global time variable such that the one-way speed of light is a constant c is assumed without further explanations."

I think Minguzzi misses the point. The existence of a global time variable is assumed. But more importantly Time Homogeneity, Symmetry, and Transitivity, simply CANNOT BE MET by accelerating clocks. Nor can it be met by clocks that are traveling at different speeds. To a certain extent the GPS clocks and Universal Standard Time manages to meet these criteria, but they are calibrated and updated as needed to stay synched up.

Yes, global x, global t, global x' and global t' are assumed, but only for bodies that are moving at constant velocity. What often fails to be explained is that (∆t'/∆t|x' held constant)=(∆t/∆t'|x held constant) is a smaller than 1, while (∆t'/∆t|x held constant)=(∆t/∆t'|x' held constant) is a number larger than 1. In other words, if you watch a single clock as it goes by, that clock is running slowly in your reference frame. But if you keep looking at each new clock as it passes by your position, the consecutive readings are going faster than your clock.

 

[phyti]

This is a quote from the D&G paper, following fig.2.

"Although this period of acceleration can indeed fix the gap between G and H, it cannot resolve the more serious problem (mentioned also in Marder[7] and in Misner et al.[8]) which occurs to Barbara’s left. Here her hypersurfaces of simultaneity are overlapping, and she assigns three times to every event!"

Not true. Every intersecting aos (green) is not necessarily a reflection event. As the graphic shows, using the radar method, B sends signals in an ordered sequence, which return in the same order. B assigns a B time, forming an aos that rotates during acceleration. Each C event still has only one B time of perception.
If the aos are extended, obviously they intersect on the far side of C, but not necessarily
at a single point. If C was more distant from A, the signals would be sent earlier and return later, forming a different set of aos. There is no absence of causality.
You can't accept everything on internet sources as true.

 

[phyti]

Mike;

Here's the inertial motion only scenario, with
blue-light signals, green-aos, red-time dilation.
left:
A observes B events from B0 to B80 in the interval A0 to A100.
B observes A events from A0 to A64 in the interval B0 to B80.
Each concludes .80 time dilation for the other in agreement with SR.
right:
A observes C events from C0 to C80 in the interval A-20 to A80.
C observes A events from A16 to A80 in the interval B0 to B80.
Each concludes .80 time dilation for the other in agreement with SR.

If the initial triangle is divided at the reversal point, the B observation is reduced to A0 to A16, and the C observation is reduced to A64 to A80. The interval A16 to A64 is not covered, and the analysis is incomplete, and in that sense the time is missing. Any attempt to patch a variable speed profile onto the linear ones distorts the results. No surprise since the aos is only defined for SR and inertial frames.

You, D&G, Minguzzi, have not discovered anything new, just tried to fit a square peg into a round hole!

 

[Mike_Fontenot]

This is a quote from the D&G paper, following fig.2.

"Although this period of acceleration can indeed fix the gap between G and H, it cannot resolve the more serious problem (mentioned also in Marder[7] and in Misner et al.[8]) which occurs to Barbara’s left. Here her hypersurfaces of simultaneity are overlapping, and she assigns three times to every event!"

Not true.

You've misunderstood. In that quote, he was talking about a serious problem with the co-moving inertial frames (CMIF) simultaneity method, NOT with his D&G simultaneity method. Another way of stating that serious problem is that the CMIF method says that the home twin (she) suddenly gets YOUNGER when the traveling twin (he) instantaneously changes his velocity in the direction AWAY from her (when their separation is sufficiently great). That's a characteristic that many physicists find repugnant.

 

[Neddy Bate]

You've misunderstood. In that quote, he was talking about a serious problem with the co-moving inertial frames (CMIF) simultaneity method, NOT with his D&G simultaneity method. Another way of stating that serious problem is that the CMIF method says that the home twin (she) suddenly gets YOUNGER when the traveling twin (he) instantaneously changes his velocity in the direction AWAY from her (when their separation is sufficiently great). That's a characteristic that many physicists find repugnant.

Yes, the hypersurfaces of simultaneity overlapping to Barbara's left mean that the CMIF method allows the home twin to get younger. But it is not "suddenly," that is an artifact that you impose by neglecting the very small but non-zero time required for velocities to change.

However, even worse than that, D&G seem to think it means that Barbara "assigns three times to every event" in that region. That is not correct. That is like saying that the traveling twin (he) thinks the stay home twin (she) is both younger than himself and older than himself at the same time. This is a fundamental error, in that the earlier age he assigned to her is replaced by the later age he assigned to her. He does not retain both, and say she is both! That is a sign that D&G seem to be tilting at windmills, imagining a problem where there is none.

On the other hand, if people find it repugnant that he can think she can get younger, that is up the their own aesthetics. It is not a problem for SR, which must always use the CMIF method, contrary to your (and D&G's) beliefs to the contrary.

By the way, here is a link to the Dolby & Gull paper, in case anyone else wants a laugh.
https://arxiv.org/pdf/gr-qc/0104077.pdf

 

[Mike_Fontenot]

On the other hand, if people find it repugnant that he can think she can get younger, that is up the their own aesthetics. It is not a problem for SR, which must always use the CMIF method,[...]

Re: your statement I've highlighted in red:

There is NO requirement that SR use the CMIF method for the accelerating observer's perspective about the home twin's current age. SR is completely silent on the subject.

The CMIF method ASSUMES that an observer who is not currently accelerating will always agree with the perpetually-inertial observer (PIO) with whom he is currently co-located and c0-stationary. In other words, the assumption is that whenever an accelerating observer stops accelerating, he will IMMEDIATELY agree with the PIO about the home twin's current age. That's an ASSUMPTION, not something handed down on tablets to Moses, or from Einstein. In fact, I don't believe that Einstein ever talked about an accelerating observer in special relativity.

By the way, here is a link to the Dolby & Gull paper, in case anyone else wants a laugh.
https://arxiv.org/pdf/gr-qc/0104077.pdf

I'm not a fan of the Dolby & Gull simultaneity method, purely because it is non-causal. But Steve Gull is no slouch ... he's an emeritus professor at Cambridge, and still teaches special and general relativity there.

 

[Neddy Bate]

The CMIF method ASSUMES that an observer who is not currently accelerating will always agree with the perpetually-inertial observer (PIO) with whom he is currently co-located and c0-stationary. In other words, the assumption is that whenever an accelerating observer stops accelerating, he will IMMEDIATELY agree with the PIO about the home twin's current age. That's an ASSUMPTION, not something handed down on tablets to Moses, or from Einstein. In fact, I don't believe that Einstein ever talked about an accelerating observer in special relativity.

You have it backwards. SR, (and Einstein himself), begins with definitions and postulates that are known to be supported by physics experiments. From the definitions and postulates, the predictions of SR theory are derived.

The definition of an inertial frame is a frame of reference in which the laws of Newton hold good, (i.e. a body at rest will remain at rest). That means the frame is not currently accelerating or in a gravitational field. It is a postulate that the speed of light is a constant relative to that type of inertial frame. It does not allow for certain people at rest in that frame to disagree, just because they accelerated in the past. It also does not require that the frame was perpetually inertial for all time in the past, which is something you made up completely.

From those definitions and postulates, reciprocal time dilation is derived to have a mathematical value, due to relative motion alone. This is all that is needed to establish that the traveling twin, during both inertial legs of his journey, must measure the rate of the stay-home twin's clock to be time dilated to a slower rate, by the same factor that the stay-home twin finds the traveling twin's clock to be time dilated to a slower rate. That is what the theory says.

If you or Gull want to make your own theory, you also need to start with definitions and postulates that are known to be supported by physics experiments. You should be saying that, since physics experiments show that the speed of light is only constant relative to an inertial frame which has been perpetually inertial for all time in the past, that is one of your postulates. Even more illogically, you should also be saying that, since physics experiments show that the speed of light is only constant relative to an inertial frame which has been perpetually inertial for all time in the past, FOR PEOPLE IN THAT FRAME WHO HAVE, THEMSELVES, NEVER ACCELERATED, that is also one of your postulates.

If either of those were true, then there would be a need for a new theory, because SR does not say either of those things, nor is it compatible with them. But no experimental evidence exists for either of those things. Maybe you should describe an experiment where you can obtain evidence that the speed of light only constant in inertial frames which have been perpetually inertial. Or, since that is probably impossible, maybe you should at least describe an experiment where you can obtain evidence that the speed of light is different for different people who have no motion relative to each other, just because of their prior acceleration history. Short of that, you guys are just demonstrating that you can make up something different than SR, but sort of like it, which anyone can do.

By the way, there is a logical fallacy in your paper. You assume the CMIF method is valid at the very beginning of the paper, and yet you conclude that the CMIF method is not always valid. How do you know it is valid at the beginning but not at the end? Maybe you should be saying that, since the traveling twin accelerated at the very beginning, that he thinks her clock ticks faster than his own right away? How do you know that is not true? Because SR tells you he finds her clock rate to be time dilated to a slower rate. Well, if that is the case, then you should also be using that principal for the return leg of the trip, but you don't. The CMIF method does though, because the CMIF method is SR.