[David Cooper]

My particles move with regard to one another, and they only use the light emitted by the other particle to do so. That light tells them to resist to acceleration, to get speed, to get a direction, and to move at constant speed when acceleration has stopped. Isn't that enough to call it an absolute reference?

...

I've replied to the above post on the simulation thread https://www.thenakedscientists.com/forum/index.php?topic=71122.150 instead of here because your particle-movement simulations are not yet sufficiently close to describing real physics. They need a lot more work done on them before they're ready to display to the public.

[MikeFontenot]

The apparent paradox in the twin "paradox" scenario arises because it would seem that each twin should conclude that the other twin is ageing more slowly, due to the well-known "time-dilation" result, during the entire trip, except for the single instant at the instantaneous turnaround ... "surely" nothing could happen to peoples' ages during a single instant.  But that assumption is wrong: the traveling twin must conclude that the home twin's age instantaneously increases during the instantaneous turnaround.

Double the length of his trip and see what happens. When he turns round, his twin ages not 27 years in an instant, but 54 years. How can an identical acceleration cause double the ageing?

Because the effect of the instantaneous velocity change is directly proportional to the separation of the twins.

[Le Repteux (OP)]

Instantaneous velocity change is not an observable fact whereas force due to resistance to acceleration is, so since all velocities are due to accelerations, why not take the departing velocity as a fact, and the returning one as a fact also? Does relativity prevent us from admitting the facts?

[David Cooper]

Because the effect of the instantaneous velocity change is directly proportional to the separation of the twins.

The reason it's proportional to the separation is that it's the distance covered at a particular speed that determines how much the clock runs slow. The accelerations don't impact on the rate that the clocks tick at other than by changing their speed of travel through space, which then leads to them running at a particular rate until the next acceleration. We see this from the experiment which eliminates the accelerations by having ships pass each other and exchange the time.

[MikeFontenot]

Because the effect of the instantaneous velocity change is directly proportional to the separation of the twins.

[...]

A few years ago, a well-respected physicist named Brian Greene (best known as a string theorist) did a TV show for NOVA, and gave an example that gets the same results that I've given in this thread.  The link below is a short YouTube clip of his example.  Scan to the 6:00 point:

 https://www.youtube.com/watch?v=VYZQxMowBsw

[David Cooper]

A few years ago, a well-respected physicist named Brian Greene (best known as a string theorist) did a TV show for NOVA, and gave an example that gets the same results that I've given in this thread.  The link below is a short YouTube clip of his example.  Scan to the 6:00 point:

 https://www.youtube.com/watch?v=VYZQxMowBsw

Video doesn't get on well with my computer. Have you studied reply #12 to this thread? It reveals that your way of doing things generates contradictions. In the example I give there, it shows that 6=12.

[MikeFontenot]

[...]
So, here we have the twin boys, both apx. 7 years old and right together for a moment at the same Spacetime location, but one of them asserts that their twin sister is 6 while the other asserts that she is 12. They can't both be right.

They ARE both right!   And your example can be generalized: at any instant t in the traveler's trip, it is possible that an arbitrarily large number of inertial observers happen at that instant to be momentarily co-located with the traveler, with each of these observers moving at different velocities relative to the traveler.  They will each come to a different conclusion about the home twin's age at that instant of co-location.  And they are all correct!  This is the well-known "relativity of simultaneity".  Each observer has a different "view" about what "now" is at a distance, and each observer's perspective is equally valid.  The home twin also has her own answer to the question "How old am I when the traveler's age is t?", and she will disagree with the traveler.  And they are each correct.

A similar well-known thing happens in the famous time-dilation result: any two inertial observers moving relative to each other at a constant velocity will each conclude that the other is ageing more slowly.  And they are both correct!  It sounds inconsistent, but it's not.  That's just how special relativity is.

[Le Repteux (OP)]

Each observer has a different "view" about what "now" is at a distance, and each observer's perspective is equally valid.

That's a contradiction. Even if the two twins see the other twin as the one who ages less, once reunited, only one of them will be right, and the easiest way to analyze the problem is to consider that acceleration determines the one who is really traveling. That's what your equation does but in a disguised way. At the turn around point, it uses the speed given by the first acceleration and the distance that speed lasts to compute time dilation, and it attributes it to the right twin. How would it know it is the right twin if each perspective would be equally valid?

[MikeFontenot]

Each observer has a different "view" about what "now" is at a distance, and each observer's perspective is equally valid.

That's a contradiction. Even if the two twins see the other twin as the one who ages less, once reunited, only one of them will be right, [...]

There IS NO contradiction or inconsistency.

Take the case where gamma = 2.0, and where the traveler spends 20 years of his life on the outbound segment of the trip, and 20 years of his life on the inbound segment.

On the outbound (constant velocity) segment, the traveler says that the home twin is ageing at half his own rate, and therefore that she is only 10 years old right before his turnaround.  During his instantaneous turnaround, he says that she instantaneously gets 60 years older.  Finally, during his inbound segment, he says that she is ageing at half his own rate, and so she ages 10 years during that inbound segment.  So he says she is 80 at their reunion.

SHE says that HE is the one who is ageing slowly, during the entire trip.  So she says she is 40 at his turnaround, and is 80 at their reunion.

If you look at their two statements, you will see that they disagree during the entire trip, EXCEPT for the instant of the departure, and the instant of the reunion.  I.e., they agree during the two instants when they are co-located, but they disagree all of the time when they are separated (except halfway through the turnaround, at the instant when their relative velocity is momentarily zero ... they both say she is 40 then).  When they are separated, their disagreements do NOT produce any inconsistency, just like the famous time-dilation produces no inconsistency when it says that both inertial observers moving relative to each other will each say the other is ageing more slowly.

[Le Repteux (OP)]

just like the famous time-dilation produces no inconsistency when it says that both inertial observers moving relative to each other will each say the other is ageing more slowly.

What is not inconsistent is to consider that motion is so relative that we can't tell which one of us is moving, thus considering that I am at rest and you are moving, or any other configuration, is de facto inconsistent. If motion is relative, then there is no way to tell which twin is actually moving with regard to the other, except if we know which one has accelerated.

[Halc]

If motion is relative, then there is no way to tell which twin is actually moving with regard to the other, except if we know which one has accelerated.

Pretty easy to find counterexamples for this claim.

A pair of twins take a trip.  Alice leaves first, accelerating by X amount.  Bob leaves years later, also accelerating by X amount, matching Alice's speed.  The next day Bod accelerates by X amount again, so he starts to gain on Alice.  Years later, they meet and Alice accelerates by X, matching speed with Bob.

They're now in each other's presence again, having both accelerated the same amount each, yet Alice is much older than Bob now.

Another scenario is Alice having an economy model ship that accelerates at 1G, while Bob has the sports model that pulls 2G.  Alice goes to Arcturus and back, while Bob spends the time zipping this way and that around the Solar system, always at 2G, but exploring many local places instead of one distant one.  Alice comes back and is far older again, despite having accelerated half as much.

[Le Repteux (OP)]

Pretty easy to find counterexamples for this claim.

I was talking about the usual mind experiment where only one of the twins accelerates. If both accelerate, then we have to account for the speed and the distance traveled between the accelerations, and it is precisely what Mike's equation does. There is no way to tell which twin is traveling more or less with regard to the other than to account for all the accelerations.

[David Cooper]

[...]
So, here we have the twin boys, both apx. 7 years old and right together for a moment at the same Spacetime location, but one of them asserts that their twin sister is 6 while the other asserts that she is 12. They can't both be right.

They ARE both right!

Fine, but it's important to make sure everyone understands that that only "works" in an eternal static block universe version of SR. It "works" there because the 6=12 bit becomes 6y=12y while y=0 (which is possible because actual time is completely absent from that model). However, for any model with real, running time, y has to be greater than zero and you then run into contradictions if you try to claim that both twins are right. By using y=0 you're restricting yourself to an eternal static block universe model, but so long as you understand that you're doing so (and don't care that all causality then becomes a mere illusion of causation), and so long as you don't mix this with any incompatible models where time runs, then that's fine.

[MikeFontenot]

[...]
So, here we have the twin boys, both apx. 7 years old and right together for a moment at the same Spacetime location, but one of them asserts that their twin sister is 6 while the other asserts that she is 12. They can't both be right.

They ARE both right!

Fine, but it's important to make sure everyone understands that that only "works" in an eternal static block universe version of SR. It "works" there because the 6=12 bit becomes 6y=12y while y=0 (which is possible because actual time is completely absent from that model). However, for any model with real, running time, y has to be greater than zero and you then run into contradictions if you try to claim that both twins are right. By using y=0 you're restricting yourself to an eternal static block universe model, but so long as you understand that you're doing so (and don't care that all causality then becomes a mere illusion of causation), and so long as you don't mix this with any incompatible models where time runs, then that's fine.

I don't understand your comments at all.  Time is certainly not absent from my CADO reference frame, or from my CADO equation.   I'd like to see the contradictions you refer to above.

[David Cooper]

I don't understand your comments at all.  Time is certainly not absent from my CADO reference frame, or from my CADO equation.   I'd like to see the contradictions you refer to above.

I would hope that you agree that 6=12 is a contradiction. 6y=12y is also a contradiction if y>0. In a model with running time, y>0, and that means that in such a model it is not possible for both the twins to be right about the age of their twin sister. The only way you can get away with 6y=12y is if y=0, but that's a model with no time in it - all it has is a static "time dimension". A "time dimension" is not time, but just a special kind of space dimension in which all objects have infinite length. "Past" and "future" in such a model are mere directions like up and down, or left and right. A model only has real time in it if there is change, but in a static block model there is never any change: the entire future is pre-existing and was never generated out of the past.

If you're using a model with real time, you can then run events and see if the girl can be 6 and 12 years old at the same time. I can tell you for free that she can't. You can change the way you run the simulation by slowing clocks in different ways, but you'll find that there's always one age that she has at the point when her twins are arguing about her age. If you go for a model where no clocks run slow, you'll find that the boys get back to the reunion point where they meet her again before she's arrived, so you run into event-meshing failures, but even if you go for a model that erases those failures over Newtonian time, then you find that the girl is actually 7 when her brothers (both 7) are arguing about her age. These models are not compatible with each other and should not be mixed. If you want the girl to be 6 and 12 at the same time, you have to use a static block model where that's possible because it's 6x0 = 12x0 and there is no time in the model. You can take your pick, but please don't mix incompatible models and pretend that the girl can be 6 and 12 at the same time in any model with running time. Mathematics does not allow that.

[yor_on]

I think you're correct Le. a observation of a weight is a sign of gravity. There can be no confusion about who's experiencing it.
=
Spelling

[guest46746]

I would think that changing reference frames would be akin to creating support for a hypothesis by using a probability math function to bolster another probability math function! It's done all the time but it's questionable science! lol

[MikeFontenot]

I don't understand your comments at all.  Time is certainly not absent from my CADO reference frame, or from my CADO equation.   I'd like to see the contradictions you refer to above.

I would hope that you agree that 6=12 is a contradiction. 6y=12y is also a contradiction if y>0. In a model with running time, y>0, and that means that in such a model it is not possible for both the twins to be right about the age of their twin sister. The only way you can get away with 6y=12y is if y=0, but that's a model with no time in it - all it has is a static "time dimension". A "time dimension" is not time, but just a special kind of space dimension in which all objects have infinite length. "Past" and "future" in such a model are mere directions like up and down, or left and right. A model only has real time in it if there is change, but in a static block model there is never any change: the entire future is pre-existing and was never generated out of the past.

If you're using a model with real time, you can then run events and see if the girl can be 6 and 12 years old at the same time. I can tell you for free that she can't. You can change the way you run the simulation by slowing clocks in different ways, but you'll find that there's always one age that she has at the point when her twins are arguing about her age. If you go for a model where no clocks run slow, you'll find that the boys get back to the reunion point where they meet her again before she's arrived, so you run into event-meshing failures, but even if you go for a model that erases those failures over Newtonian time, then you find that the girl is actually 7 when her brothers (both 7) are arguing about her age. These models are not compatible with each other and should not be mixed. If you want the girl to be 6 and 12 at the same time, you have to use a static block model where that's possible because it's 6x0 = 12x0 and there is no time in the model. You can take your pick, but please don't mix incompatible models and pretend that the girl can be 6 and 12 at the same time in any model with running time. Mathematics does not allow that.

The above still just sounds like gibberish to me.  I think you and I will just have to agree to disagree, to keep from wasting any more time and keystrokes.

[David Cooper]

The above still just sounds like gibberish to me.  I think you and I will just have to agree to disagree, to keep from wasting any more time and keystrokes.

The reason it sounds like gibberish to you is that you haven't thought it through carefully. Like most people in this field, you don't apply reason rigorously and keep incompatible models apart. You pretend that you understand time, but you're actually combining a model with no time in it with an incompatible model with running time, and the result is that you end up with a composite model built upon a contradiction. Your solution when confronted with reality is to run away from the truth. With running time, mathematics dictates that there is no possibility of the girl being 6y and 12y at the same time. The only models where she can be 6y and 12y are the models with time removed from them such that y=0. But if you think applying mathematics correctly in physics is a waste of time, then that's up to you.

[Le Repteux (OP)]

I got news for you guys! I found a way to produce the right contraction rate on my simulation of acceleration, and since it is due to a first particle accelerating before the other one has, it supports my OP idea that we can use acceleration to tell which twin is traveling. If I can succeed to apply it to my simulation on opposite acceleration, if contraction becomes stretching when acceleration reverses, there will be no more event meshing failure like David is pointing to, no more instantaneous accelerations like Mike is suggesting, and no more interminable discussions about that. My simulation will be able to solve any problem where any amount of light clocks start from the same point and get to the same other point, providing it has the parameters of their respective accelerations, direction and speed. They will slow down and contract (or speed up and stretch) at the right rates and only because any information takes time to go from one point to the other. That's precisely what relativity is about, nothing else.