On Saturday, May 29, 2021 at 11:52:19 PM UTC-6, Rob Acraman wrote:
>
> On Sunday, May 30, 2021 at 1:04:24 AM UTC+10, hit...@yahoo.com wrote:
> >
> > Hmmm, that's still not making sense to me. If EF is heading west, then it's going the same
> > direction as CD, but faster.
>
> Errr, not according to the diagrams we've been posting, which have AB travelling WEST relative
> to CD ;-) (and of course CD travelling EAST relative to AB )

Why not just say left or right? Of course, motions depend upon who's observing them.

> So, with WEST to the LEFT, and with the view from the Emitter's frame (ie, CD frame is "stationary"),
> the diagrams we have been using are these :
>
> t' = 0:
> v <-- A_________________ v <-- B
> ____ C ________________u' <---- D
>
> D is the emitter, so with the emitter's frame "stationary" and the tachyon travelling to the left (West),
> and AB moving relative to CD to the LEFT - to the WEST, as I stated.
>
> If B is emitting that tachyon instead (so same tachyon, so tachyon is still travelling to the west), therefore :
>
> B is the emitter, so with the emitter's frame "stationary" and the tachyon travelling to the left (West), and
> EF moving relative to AB to the LEFT - to the WEST.
>
> So we have this :
>
> t = 0:
> v <-- E_________________ v <-- F
> ____ A ________________u <---- B
>
> Other than the simple scaling factor (the ratio of the proper distances CD/AB = AB/EF by construction), the
> scenario is EXACTLY THE SAME.

The "same" as what? Certainly not the same as AB/CD.

> That means that since D cannot emit a (near-)∞ tachyon because of the "hurling back in time" of AB, then
> neither can B emit a (near-)∞ speed tachyon because of the "hurling back in time" of EF.

You're over-simplifying. Tachyons between EF or CD cannot affect time in any frame, even their own. If it
appears to "hurl a frame back in time," it represents a pathological situation, an impossible configuration.
This only happens when passing messages.

Now, you appear to have given up on the "simple" AB/CD configurations. Why is that? Do you agree that they
can't violate causality and you believe that adding more complications will change that? OTOH, are you saying
that EF/AB from AB's perspective is the same as AB/CD from CD's perspective? It's not. I'm still quite confused
about your stratagem.

Let's take the end bit first :)

> > That means that since D cannot emit a (near-)∞ tachyon because of the "hurling back in time" of AB, then
> > neither can B emit a (near-)∞ speed tachyon because of the "hurling back in time" of EF.
> You're over-simplifying. Tachyons between EF or CD cannot affect time in any frame, even their own. If it
> appears to "hurl a frame back in time," it represents a pathological situation, an impossible configuration.
> This only happens when passing messages.

In other words, if D were able to emit (near-)∞ tachyons when passing a message to C, that would lead to the impossible situation of the time in AB being affected ("hurled back in time"). Therefore, D emitting (near-)∞ tachyons must be an impossibility - right ?

>
> Now, you appear to have given up on the "simple" AB/CD configurations. Why is that? Do you agree that they
> can't violate causality and you believe that adding more complications will change that? OTOH, are you saying
> that EF/AB from AB's perspective is the same as AB/CD from CD's perspective? It's not. I'm still quite confused
> about your stratagem.

My focus on the "simple" AB/CD configurations (D emitting a (near-)∞ tachyon to C) is exactly what I stated above - that with those 2 frames, you agree that D emitting (near-)∞ tachyons must be an impossibility. This is due to the mere fact that (near-)∞ tachyons from D to C leads to the impossibility of the AB frame's time being affected (even without considering anything about message loops).

Now personally, I reckon that since the AB/CD configuration does not constrain either v or L, that it is a GENERAL case configuration - ie, given ANY (near-)∞ tachyon from one individual to another in the same frame, that emitting individual could be labelled D, the receiver C, and appropriate A and B individuals introduced in a passing frame that would therefore be "hurled back in time" by that tachyon, so rendering that (near-)∞ tachyon impossible.

In other words, since ANY (near-)∞ tachyon fits our "D emitting (near-)∞ tachyons must be an impossibility" scenario, therefore means ALL (near-)∞ tachyons must be equally impossible by defintion.

Now, you have said that although it is impossible for D to emit a (near-)∞ tachyon, it is perfectly possible for B to do so presumably without affecting any other frame the same way that D emitting a (near-)∞ tachyon would have affected the AB frame.

Again, I reckon that, since neither v nor L are constrained, that B emitting a (near-)∞ tachyon falls foul of the GENERAL case as stated above..

On Sunday, May 30, 2021 at 10:38:33 PM UTC+10, hit...@yahoo.com wrote:
> On Saturday, May 29, 2021 at 11:52:19 PM UTC-6, Rob Acraman wrote:
> >
> > On Sunday, May 30, 2021 at 1:04:24 AM UTC+10, hit...@yahoo.com wrote:
> > >
> > > Hmmm, that's still not making sense to me. If EF is heading west, then it's going the same
> > > direction as CD, but faster.
> >
> > Errr, not according to the diagrams we've been posting, which have AB travelling WEST relative
> > to CD ;-) (and of course CD travelling EAST relative to AB )
> Why not just say left or right? Of course, motions depend upon who's observing them.
> > So, with WEST to the LEFT, and with the view from the Emitter's frame (ie, CD frame is "stationary"),
> > the diagrams we have been using are these :
> >
> > t' = 0:
> > v <-- A_________________ v <-- B
> > ____ C ________________u' <---- D
> >
> > D is the emitter, so with the emitter's frame "stationary" and the tachyon travelling to the left (West),
> > and AB moving relative to CD to the LEFT - to the WEST, as I stated.
> >
> > If B is emitting that tachyon instead (so same tachyon, so tachyon is still travelling to the west), therefore :
> >
> > B is the emitter, so with the emitter's frame "stationary" and the tachyon travelling to the left (West), and
> > EF moving relative to AB to the LEFT - to the WEST.
> >
> > So we have this :
> >
> > t = 0:
> > v <-- E_________________ v <-- F
> > ____ A ________________u <---- B
> >
> > Other than the simple scaling factor (the ratio of the proper distances CD/AB = AB/EF by construction), the
> > scenario is EXACTLY THE SAME.
> The "same" as what? Certainly not the same as AB/CD.

Yes, it is clearly exactly the same as AB/CD.

Since the proper distances CD/AB = AB/EF by construction, we can simply rescale and rename everything relating to AB to EF, and also everything relating to CD to AB. That means we can take EVERY diagram of AB/CD, EVERY equation from AB/CD, and therefore EVERY conclusion of AB/CD, and by simple renaming apply them to EF/AB.

A simple case-in-point of that is that the two diagrams above are exactly the same (other than the simple rescaling and renaming).

Bottom line Gary :-) Since you agree it is impossible for one individual to emit (near-)∞ tachyons in a GENERAL case with no constraint on v nor L, I do not see how you reckon it could be possible for any individual.

On Sunday, May 30, 2021 at 8:36:18 AM UTC-6, Rob Acraman wrote:
> Let's take the end bit first :)
> > >
> > > That means that since D cannot emit a (near-)∞ tachyon because of the "hurling back in time" of AB, then
> > > neither can B emit a (near-)∞ speed tachyon because of the "hurling back in time" of EF.
> >
> > You're over-simplifying. Tachyons between EF or CD cannot affect time in any frame, even their own. If it
> > appears to "hurl a frame back in time," it represents a pathological situation, an impossible configuration.
> > This only happens when passing messages.
>
> In other words, if D were able to emit (near-)∞ tachyons when passing a message to C, that would lead to the
> impossible situation of the time in AB being affected ("hurled back in time"). Therefore, D emitting (near-)∞
> tachyons must be an impossibility - right ?

That's not what I said, Rob. I said essentially time doesn't get hurled back in ANY frame. Not in the REAL world,
anyway. My motto is, "Tachyons don't violate causality, people do."

> > Now, you appear to have given up on the "simple" AB/CD configurations. Why is that? Do you agree that they
> > can't violate causality and you believe that adding more complications will change that? OTOH, are you saying
> > that EF/AB from AB's perspective is the same as AB/CD from CD's perspective? It's not. I'm still quite confused
> > about your stratagem.
>
> My focus on the "simple" AB/CD configurations (D emitting a (near-)∞ tachyon to C) is exactly what I stated above
> - that with those 2 frames, you agree that D emitting (near-)∞ tachyons must be an impossibility.

Not so, Rob. It's only an impossibility when creating a loop.

> This is due to the mere fact that (near-)∞ tachyons from D to C leads to the impossibility of the AB frame's time being
> affected (even without considering anything about message loops).

Tachyons sent between stationary observers don't affect other frames. If an analysis says they do, then that
configuration is untenable for the purpose of creating a loop.

> Now personally, I reckon that since the AB/CD configuration does not constrain either v or L, that it is a GENERAL
> case configuration - ie, given ANY (near-)∞ tachyon from one individual to another in the same frame, that emitting
> individual could be labelled D, the receiver C, and appropriate A and B individuals introduced in a passing frame that
> would therefore be "hurled back in time" by that tachyon, so rendering that (near-)∞ tachyon impossible.

That's not clear thinking, Rob. See above.

> In other words, since ANY (near-)∞ tachyon fits our "D emitting (near-)∞ tachyons must be an impossibility" scenario,
> therefore means ALL (near-)∞ tachyons must be equally impossible by defintion.

Non sequitur.

> Now, you have said that although it is impossible for D to emit a (near-)∞ tachyon, it is perfectly possible for B to do
> so presumably without affecting any other frame the same way that D emitting a (near-)∞ tachyon would have affected
> the AB frame.

You're going way off the beam, Rob.

> Again, I reckon that, since neither v nor L are constrained, that B emitting a (near-)∞ tachyon falls foul of the GENERAL
> case as stated above.

You're completely ignoring the fact that these limitations refer ONLY to completing a message loop.
PCH and I have been "cussing and discussing" the PWD (Paddle Wheel Device) which bears on the mistakes you and he
are making: (near) infinite-speed tachyons do NOT violate causality! Period!
See the "Manuscript submission" thread.

I'm not going to address your new scenario because it perpetuates the errors in your thinking. You assume you can
just reverse directions without adjusting other parameters and go merrily making assertions without critical analysis.
If you want to discuss

v <-- E _____________ u' <---- F
____ A ___________________ B

then let's do so without the unfounded assertions about what you think I believe..

Hi Gary, and sorry for the delay.

Before we get started, this is still outstanding, and I think it's important to confirm the logistics :

At the instant that one individual ("Peter") is colocated-with while being passed by another ("Paul") with v < c, then at that instant Peter can always successfully hand off to Paul any information (a "message") that Peter has available (ie that he received previously or at that instant). For example, we can imagine that Peter could attach that information as a text file to an email that is sent by radio, so always perfectly capable of being received by Paul. Naturally, how Peter originally got the information (eg mode of transmission, such as radio or tachyons) is totally irrelevant to this.

IOTTMCO - Agreed ? :-)

On Monday, May 31, 2021 at 1:17:41 AM UTC+10, hit...@yahoo.com wrote:
> On Sunday, May 30, 2021 at 8:36:18 AM UTC-6, Rob Acraman wrote:
> > Let's take the end bit first :)
> > > >
> > > > That means that since D cannot emit a (near-)∞ tachyon because of the "hurling back in time" of AB, then
> > > > neither can B emit a (near-)∞ speed tachyon because of the "hurling back in time" of EF.
> > >
> > > You're over-simplifying. Tachyons between EF or CD cannot affect time in any frame, even their own. If it
> > > appears to "hurl a frame back in time," it represents a pathological situation, an impossible configuration.
> > > This only happens when passing messages.
> >
> > In other words, if D were able to emit (near-)∞ tachyons when passing a message to C, that would lead to the
> > impossible situation of the time in AB being affected ("hurled back in time"). Therefore, D emitting (near-)∞
> > tachyons must be an impossibility - right ?
> That's not what I said, Rob. I said essentially time doesn't get hurled back in ANY frame. Not in the REAL world,
> anyway. My motto is, "Tachyons don't violate causality, people do."

Yes - "hurled back in time" is, as I said, an "impossible situation" (so always an impossible situation for any frame), so I'm not sure what point you're making.

> > > Now, you appear to have given up on the "simple" AB/CD configurations.. Why is that? Do you agree that they
> > > can't violate causality and you believe that adding more complications will change that? OTOH, are you saying
> > > that EF/AB from AB's perspective is the same as AB/CD from CD's perspective? It's not. I'm still quite confused
> > > about your stratagem.
> >
> > My focus on the "simple" AB/CD configurations (D emitting a (near-)∞ tachyon to C) is exactly what I stated above
> > - that with those 2 frames, you agree that D emitting (near-)∞ tachyons must be an impossibility.
> Not so, Rob. It's only an impossibility when creating a loop.

Not so Gary ;-) You have already agreed that the Nailgun scenario is also "an impossible situation" (that you have yet to resolve ;-> ), and that stands completely independent of message loops. To recap :
=====At the instant that D is co-located with B, D sets his tachyon-speed-dial to (near-)∞ and so emits tachyons at that speed to C, who at the instant she receives them will fire a nail into the ground of the AB frame.
=====So what renders this so impossible ? Well, IMHO there are 4 principle factors in this scenario :
1) SR's PoR (which is clearly not impossible)
2) SR's RoS (which is clearly not impossible)
3) D emitting (near-)∞ tachyons
4) C firing a nailgun (which is clearly not impossible)

So what factor do you reckon renders this scenario impossible ? ;-)

> > This is due to the mere fact that (near-)∞ tachyons from D to C leads to the impossibility of the AB frame's time being
> > affected (even without considering anything about message loops).
> Tachyons sent between stationary observers don't affect other frames. If an analysis says they do, then that
> configuration is untenable for the purpose of creating a loop.

You earlier said : "Actually it was Bob -> Dave -> Carol -> Alice -> Bob. Logistics are important."

The point about that ordering is that Alice is DEFINED as the person who is co-located with Carol at the instant she receives (and hands off) the message. So CD is not affecting the AB frame at all, other than simply handing off the message.

Let's imagine that CD is a train, with D at the front, and with passengers all the way down its length. Likewise, AB is a (segment of a REALLY long) platform, that is also fully lined all along its length with people.

That means at the instant that C receives the tachyons, she WILL be co-located with SOMEONE on the platform. That SOMEONE might be Alice, or it might be someone else (let's say "Anna") but it WILL be SOMEONE - even Morin's Principle would agree with that - Agree ?

(Of course, this has direct similarities to the nailgun scenario above ;-) )

>
> I'm not going to address your new scenario because it perpetuates the errors in your thinking. You assume you can
> just reverse directions without adjusting other parameters and go merrily making assertions without critical analysis.
> If you want to discuss
>
> v <-- E _____________ u' <---- F
> ____ A ___________________ B
>
> then let's do so without the unfounded assertions about what you think I believe..

For the EF/AB scenario, I didn't reverse directions (EF is moving in the same direction and speed relative to AB as AB is moving relative to CD), and the parameters were adjusted (the EF/AB scenario is a "scaled replica" of AB/CD, so consequently all the equivalent ratios and equations - and therefore conclusions - exactly match).

But I agree, let's concentrate on one issue - and the simplest issue is the nailgun scenario, and I'm still very interested in what factor you reckon makes it so impossible ;-)

On Thursday, June 3, 2021 at 7:46:29 AM UTC-6, Rob Acraman wrote:
>
> Hi Gary, and sorry for the delay.
>
> Before we get started, this is still outstanding, and I think it's important to confirm the logistics :
>
> At the instant that one individual ("Peter") is colocated-with while being passed by another ("Paul")
> with v < c, then at that instant Peter can always successfully hand off to Paul any information (a
> "message") that Peter has available (ie that he received previously or at that instant). For example,
> we can imagine that Peter could attach that information as a text file to an email that is sent by
> radio, so always perfectly capable of being received by Paul. Naturally, how Peter originally got the
> information (eg mode of transmission, such as radio or tachyons) is totally irrelevant to this.
>
> IOTTMCO - Agreed ? :-)

Yes. as an experimental physicist, I think of the "message" as an electromagnetic pulse emitted
at the proper time as one passes the other. At speeds relativistic, that's about all that CAN be done
practically. One could set up an automatic system: a photocell loses light from a source because
the passing body shadows it for an instant. That's a message.

> > > In other words, if D were able to emit (near-)∞ tachyons when passing a message to C, that would lead to the
> > > impossible situation of the time in AB being affected ("hurled back in time"). Therefore, D emitting (near-)∞
> > > tachyons must be an impossibility - right ?
> >
> > That's not what I said, Rob. I said essentially time doesn't get hurled back in ANY frame. Not in the REAL world,
> > anyway. My motto is, "Tachyons don't violate causality, people do."
>
> Yes - "hurled back in time" is, as I said, an "impossible situation" (so always an impossible situation for any frame),
> so I'm not sure what point you're making.

Our diagreement is over what "causes" time to be hurled back. You claim it's the existence of tachyons that
causes it, but I claim it's refusal to acknowledge RoS.

> > > My focus on the "simple" AB/CD configurations (D emitting a (near-)∞ tachyon to C) is exactly what I stated above
> > > - that with those 2 frames, you agree that D emitting (near-)∞ tachyons must be an impossibility.
> >
> > Not so, Rob. It's only an impossibility when creating a loop.
>
> Not so Gary ;-) You have already agreed that the Nailgun scenario is also "an impossible situation" (that you have yet
> to resolve ;-> ),

Not so, Rob. It's resolved by:

t = 0: (S frame)
C --> v _________________ D --> v
____ A ----> w _______________ B
Figure 1.

A sends a signal to B at w = c²/v. To C and D it's velocity is w' = ∞ since it's launched at t = tC' = 0 and it arrives at
tD' = 0. Then D sends it to C at u' = -c²/v. To A and B it's velocity is u = -∞.

> and that stands completely independent of message loops. To recap :
> ======
> At the instant that D is co-located with B, D sets his tachyon-speed-dial to (near-)∞ and so emits tachyons at that
> speed to C, who at the instant she receives them will fire a nail into the ground of the AB frame.
> ======

Which is not possible in my diagram.

> So what renders this so impossible ? Well, IMHO there are 4 principle factors in this scenario :
> 1) SR's PoR (which is clearly not impossible)
> 2) SR's RoS (which is clearly not impossible)
> 3) D emitting (near-)∞ tachyons
> 4) C firing a nailgun (which is clearly not impossible)
>
> So what factor do you reckon renders this scenario impossible ? ;-)

The fact that in your presumed scenario:

t = 0: (S frame)
C --> v _________________ D --> v
A _____________________ B
Figure 2.

According to AB, D CANNOT send an infinitely-fast signal to C because tC' = 0 and tD' = -γvL/c².
If D sent an infinitely-fast signal to C, it would look like this:

i = -vL/c²: (S frame)
C --> v _________________ D --> v
____ A _____________________ B
Figure 3.

Look familiar? This is just Figure 1 with a different time stamp. The REAL fabricated argument
is:

t = 0: (S frame)
C --> v _________________ D --> v
A _________________________ B
Figure 4.

t = vL/c²:
____ C --> v __________ u' <---- D --> v
A _________________________ B
Figure 5.

In this scenario, AB says C can't pass the message to A. OTOH, CD says they can:

t' = 0: (S' frame)
v <-- A _________________v <-- B
____ C _____________________ D
tA = 0, tB = vL/c²
Figure 6.

but it would require that time go backward for AB. As I'm sure we agree, a signal in S' CANNOT
make time go backward in S. And CD would say that A couldn't send a signal to B faster than
c²/v. It's all about RoS.

> > Tachyons sent between stationary observers don't affect other frames. If an analysis says they do, then that
> > configuration is untenable for the purpose of creating a loop.
>
> You earlier said : "Actually it was Bob -> Dave -> Carol -> Alice -> Bob. Logistics are important."
>
> The point about that ordering is that Alice is DEFINED as the person who is co-located with Carol at the instant
> she receives (and hands off) the message. So CD is not affecting the AB frame at all, other than simply handing
> off the message.

Correct. The dastardly dirty work has already been done at that point. It's caused by D sending the message
at u' = -∞. Look at Figure 4. It is claiming that C received the message before B passed it to D. Figure 5
claims that C and A aren't adjacent. This is RoS. Only by denying RoS can you make a loop "work," but you
destroy causality in the process. And it's all because you ignore Morin's strategy and combine what you
believe D can do in S' while standing with your feet planted infirmly in S.

> Let's imagine that CD is a train, with D at the front, and with passengers all the way down its length. Likewise,
> AB is a (segment of a REALLY long) platform, that is also fully lined all along its length with people.
>
> That means at the instant that C receives the tachyons, she WILL be co-located with SOMEONE on the platform.
> That SOMEONE might be Alice, or it might be someone else (let's say "Anna") but it WILL be SOMEONE - even
> Morin's Principle would agree with that - Agree ?

Sure, but you're still forgetting about RoS, and it's going to bite you. Since you'reversed the normal nomenclature
and you haven't specified which way the train is moving, I'm going back to Figure 5, but with another observer, E,
inserted adjacent to C:

t = vL/c²:
____ C --> v __________ u' <---- D --> v
A __ E _____________________ B
Figure 7.

But C is still at x = v²L/c² and tC' is still γvL/c²(1 - v²/c²). It's NOT at tC' = 0.

> But I agree, let's concentrate on one issue - and the simplest issue is the nailgun scenario,

This has ALWAYS been identical to the nailgun. The nail is a message.

> and I'm still very interested in what factor you reckon makes it so impossible ;-)

As always, it's RoS.

Tachyons obey RoS, people don't.

On Friday, June 4, 2021 at 9:35:30 AM UTC+10, hit...@yahoo.com wrote:
> On Thursday, June 3, 2021 at 7:46:29 AM UTC-6, Rob Acraman wrote:
> >
> > Hi Gary, and sorry for the delay.
> >
> > Before we get started, this is still outstanding, and I think it's important to confirm the logistics :
> >
> > At the instant that one individual ("Peter") is colocated-with while being passed by another ("Paul")
> > with v < c, then at that instant Peter can always successfully hand off to Paul any information (a
> > "message") that Peter has available (ie that he received previously or at that instant). For example,
> > we can imagine that Peter could attach that information as a text file to an email that is sent by
> > radio, so always perfectly capable of being received by Paul. Naturally, how Peter originally got the
> > information (eg mode of transmission, such as radio or tachyons) is totally irrelevant to this.
> >
> > IOTTMCO - Agreed ? :-)
> Yes. as an experimental physicist, I think of the "message" as an electromagnetic pulse emitted
> at the proper time as one passes the other. At speeds relativistic, that's about all that CAN be done
> practically. One could set up an automatic system: a photocell loses light from a source because
> the passing body shadows it for an instant. That's a message.

Great - Thanks Gary, and again, always happy when we agree :-)

So to summarise, we agree the following rules are ALWAYS true :

RULE 1) given two individuals who are at rest relative to eachother and whose clocks have been synchronised (such as C and D), then one can always emit near-infinite-speed tachyons that the other can always receive, and the receiver's clock at reception will be (near-)exactly the same time as the emitter's clock at emission.

RULE 2) At the instant that one individual ("Peter") is colocated-with while being passed by another ("Paul") with v < c, then at that instant Peter can always successfully hand off to Paul any information (a "message") that Peter has available (ie that he received previously or at that instant). For example, we can imagine that Peter could attach that information as a text file to an email that is sent by radio, so always perfectly capable of being received by Paul. Naturally, how Peter originally got the information (eg mode of transmission, such as radio or tachyons) is totally irrelevant to this.

> > > > In other words, if D were able to emit (near-)∞ tachyons when passing a message to C, that would lead to the
> > > > impossible situation of the time in AB being affected ("hurled back in time"). Therefore, D emitting (near-)∞
> > > > tachyons must be an impossibility - right ?
> > >
> > > That's not what I said, Rob. I said essentially time doesn't get hurled back in ANY frame. Not in the REAL world,
> > > anyway. My motto is, "Tachyons don't violate causality, people do."
> >
> > Yes - "hurled back in time" is, as I said, an "impossible situation" (so always an impossible situation for any frame),
> > so I'm not sure what point you're making.
> Our diagreement is over what "causes" time to be hurled back. You claim it's the existence of tachyons that
> causes it, but I claim it's refusal to acknowledge RoS.

Well, I actually claim it's the existence of tachyons WITH acknowledging RoS. ;-) Tachyons without RoS (ie, against a background of Galilean transformation instead of SR) would not have any problem.
You claim that an individual can, for example, always emit (near-)∞ tachyons, but then also say that is impossible due to RoS considerations. I say that it must be one or the other - always possible, or not always possible. You can't have it both ways.

> > > > My focus on the "simple" AB/CD configurations (D emitting a (near-)∞ tachyon to C) is exactly what I stated above
> > > > - that with those 2 frames, you agree that D emitting (near-)∞ tachyons must be an impossibility.
> > >
> > > Not so, Rob. It's only an impossibility when creating a loop.
> >
> > Not so Gary ;-) You have already agreed that the Nailgun scenario is also "an impossible situation" (that you have yet
> > to resolve ;-> ),
> Not so, Rob. It's resolved by:
>
> t = 0: (S frame)
> C --> v _________________ D --> v
> ____ A ----> w _______________ B
> Figure 1.
>
> A sends a signal to B at w = c²/v. To C and D it's velocity is w' = ∞ since it's launched at t = tC' = 0 and it arrives at
> tD' = 0. Then D sends it to C at u' = -c²/v. To A and B it's velocity is u = -∞.

Which is not the nailgun scenario, which I state below.

For example, I explicitly state "D sets his tachyon-speed-dial to (near-)∞ and so emits tachyons at that speed to C" . The resolution to that is NOT to say "Let's forget that, and instead talk about a different scenario where D sets his tachyon-speed-dial to -c²/v.".

I want to know what you think happens when D sets his tachyon-speed-dial to -(near-)∞, OR agree that it is impossible for him to do so (ie, that (near-)∞ speed tachyons are impossible).

> > and that stands completely independent of message loops. To recap :
> > ======
> > At the instant that D is co-located with B, D sets his tachyon-speed-dial to (near-)∞ and so emits tachyons at that
> > speed to C, who at the instant she receives them will fire a nail into the ground of the AB frame.
> > =====> Which is not possible in my diagram.

Yes, your diagram is not the nailgun scenario I stated.

> > So what renders this so impossible ? Well, IMHO there are 4 principle factors in this scenario :
> > 1) SR's PoR (which is clearly not impossible)
> > 2) SR's RoS (which is clearly not impossible)
> > 3) D emitting (near-)∞ tachyons
> > 4) C firing a nailgun (which is clearly not impossible)
> >
> > So what factor do you reckon renders this scenario impossible ? ;-)
> The fact that in your presumed scenario:
>
> t = 0: (S frame)
> C --> v _________________ D --> v
> A _____________________ B
> Figure 2.
>
> According to AB, D CANNOT send an infinitely-fast signal to C because tC' = 0 and tD' = -γvL/c².

Firstly : You stated above "Tachyons sent between stationary observers don't affect other frames. ". The reverse must IOTTMCO be equally true : "Other frames don't affect (including they can't dictate speeds of) Tachyons sent between stationary observers" ... except here you are saying they can.

Secondly, according to our agreed (RULE 1) above, "one can always emit near-infinite-speed tachyons that the other can always receive, and the receiver's clock at reception will be (near-)exactly the same time as the emitter's clock at emission." That fits perfectly well with frames not affecting/being-affected by other frames, but now at the first discussion you want to discard (RULE 1), saying D CANNOT emit those tachyons ???

Finally, you made the statement earlier "You're completely ignoring the fact that these limitations refer ONLY to completing a message loop."

So is this limitation " D CANNOT send" only a limitation when completing a message loop ? Because, as I have repeatedly stressed, this nailgun scenario is a scenario in its own right WITHOUT completing a message loop. It starts at the instant when D (co-located with B) emits the tachyon, and it ends when C fires the nail (and so the nail is embedded in the AB ground). Note that A sending to B (completing the loop) is emphatically NOT part of this current scenario.

So are you saying that "D CANNOT send " limitation ("ONLY to completing a message loop.") still stands even where there is no message loop ? >:->

Just some important extra points to my earlier post, which I have deleted.

On Friday, June 4, 2021 at 9:35:30 AM UTC+10, hit...@yahoo.com wrote:
> On Thursday, June 3, 2021 at 7:46:29 AM UTC-6, Rob Acraman wrote:
> >
> > Hi Gary, and sorry for the delay.
> >
> > Before we get started, this is still outstanding, and I think it's important to confirm the logistics :
> >
> > At the instant that one individual ("Peter") is colocated-with while being passed by another ("Paul")
> > with v < c, then at that instant Peter can always successfully hand off to Paul any information (a
> > "message") that Peter has available (ie that he received previously or at that instant). For example,
> > we can imagine that Peter could attach that information as a text file to an email that is sent by
> > radio, so always perfectly capable of being received by Paul. Naturally, how Peter originally got the
> > information (eg mode of transmission, such as radio or tachyons) is totally irrelevant to this.
> >
> > IOTTMCO - Agreed ? :-)
> Yes. as an experimental physicist, I think of the "message" as an electromagnetic pulse emitted
> at the proper time as one passes the other. At speeds relativistic, that's about all that CAN be done
> practically. One could set up an automatic system: a photocell loses light from a source because
> the passing body shadows it for an instant. That's a message.

Great - Thanks Gary, and again, always happy when we agree :-)

So to summarise, we agree the following rules are ALWAYS true :

RULE 1) given two individuals who are at rest relative to eachother and whose clocks have been synchronised (such as C and D), then one can always emit near-infinite-speed tachyons that the other can always receive, and the receiver's clock at reception will be (near-)exactly the same time as the emitter's clock at emission.

RULE 2) At the instant that one individual ("Peter") is colocated-with while being passed by another ("Paul") with v < c, then at that instant Peter can always successfully hand off to Paul any information (a "message") that Peter has available (ie that he received previously or at that instant). For example, we can imagine that Peter could attach that information as a text file to an email that is sent by radio, so always perfectly capable of being received by Paul. Naturally, how Peter originally got the information (eg mode of transmission, such as radio or tachyons) is totally irrelevant to this.

> > > > In other words, if D were able to emit (near-)∞ tachyons when passing a message to C, that would lead to the
> > > > impossible situation of the time in AB being affected ("hurled back in time"). Therefore, D emitting (near-)∞
> > > > tachyons must be an impossibility - right ?
> > >
> > > That's not what I said, Rob. I said essentially time doesn't get hurled back in ANY frame. Not in the REAL world,
> > > anyway. My motto is, "Tachyons don't violate causality, people do."
> >
> > Yes - "hurled back in time" is, as I said, an "impossible situation" (so always an impossible situation for any frame),
> > so I'm not sure what point you're making.
> Our diagreement is over what "causes" time to be hurled back. You claim it's the existence of tachyons that
> causes it, but I claim it's refusal to acknowledge RoS.

Well, I actually claim it's the existence of tachyons WITH acknowledging RoS. ;-) Tachyons without RoS (ie, against a background of Galilean transformation instead of SR) would not have any problem.

You claim that an individual can, for example, always emit (near-)∞ tachyons, but then also say that is impossible due to RoS considerations. I say that it must be one or the other - always possible, or not always possible. You can't have it both ways.

> > > > My focus on the "simple" AB/CD configurations (D emitting a (near-)∞ tachyon to C) is exactly what I stated above
> > > > - that with those 2 frames, you agree that D emitting (near-)∞ tachyons must be an impossibility.
> > >
> > > Not so, Rob. It's only an impossibility when creating a loop.
> >
> > Not so Gary ;-) You have already agreed that the Nailgun scenario is also "an impossible situation" (that you have yet
> > to resolve ;-> ),
> Not so, Rob. It's resolved by:
>
> t = 0: (S frame)
> C --> v _________________ D --> v
> ____ A ----> w _______________ B
> Figure 1.
>
> A sends a signal to B at w = c²/v. To C and D it's velocity is w' = ∞ since it's launched at t = tC' = 0 and it arrives at
> tD' = 0. Then D sends it to C at u' = -c²/v. To A and B it's velocity is u = -∞.

Which is not the nailgun scenario, which I state below.

For example, I explicitly state "D sets his tachyon-speed-dial to (near-)∞ and so emits tachyons at that speed to C" . The resolution to that is NOT to say "Let's forget that, and instead talk about a different scenario where D sets his tachyon-speed-dial to -c²/v.".

I want to know what you think happens when D sets his tachyon-speed-dial to -(near-)∞, OR agree that it is impossible for him to do so (ie, that (near-)∞ speed tachyons are impossible).

> > and that stands completely independent of message loops. To recap :
> > =====> > At the instant that D is co-located with B, D sets his tachyon-speed-dial to (near-)∞ and so emits tachyons at that
> > speed to C, who at the instant she receives them will fire a nail into the ground of the AB frame.
> > =====> Which is not possible in my diagram.

Yes, your diagram is not the nailgun scenario I stated.

> > So what renders this so impossible ? Well, IMHO there are 4 principle factors in this scenario :
> > 1) SR's PoR (which is clearly not impossible)
> > 2) SR's RoS (which is clearly not impossible)
> > 3) D emitting (near-)∞ tachyons
> > 4) C firing a nailgun (which is clearly not impossible)
> >
> > So what factor do you reckon renders this scenario impossible ? ;-)
> The fact that in your presumed scenario:
>
> t = 0: (S frame)
> C --> v _________________ D --> v
> A _____________________ B
> Figure 2.
>
> According to AB, D CANNOT send an infinitely-fast signal to C because tC' = 0 and tD' = -γvL/c².

My presumed scenario does have a (near-)∞ speed signal - so this diagram with tC' = 0 and tD' = -γvL/c² is NOT my presumed scenario.

> If D sent an infinitely-fast signal to C, it would look like this:
>
> i = -vL/c²: (S frame)
> C --> v _________________ D --> v
> ____ A _____________________ B
> Figure 3.
>
> Look familiar?

Still not my presumed scenario, which is explicitly that D is co-located with B as the tachyons are emitted.

>
> t = vL/c²:
> ____ C --> v __________ u' <---- D --> v
> A _________________________ B
> Figure 5.

Right, so tB=vL/c² and t'D = 0.

>
> In this scenario, AB says C can't pass the message to A.

To be clear : the "scenario" is the single reality that I described above (within the "===="). This diagram is NOT a "scenario", but simply a view of that scenario - of that single reality - from the viewpoint of the AB frame.

So from this viewpoint of AB, the nail will end up far from A in that single reality.

OTOH, CD says they can:
>
> t' = 0: (S' frame)
> v <-- A _________________v <-- B
> ____ C _____________________ D
> tA = 0, tB = vL/c²
> Figure 6.

Yes, in this a view of that same single reality I referred to above, but this time from the viewpoint of the CD frame,
So from this viewpoint of CD, the nail will end up at A's feet in that single reality.

>
> but it would require that time go backward for AB. As I'm sure we agree, a signal in S' CANNOT
> make time go backward in S. ... It's all about RoS.

Firstly : You stated above "Tachyons sent between stationary observers don't affect other frames. ". The reverse must IOTTMCO be equally true : "Other frames don't affect (including they can't dictate speeds of) Tachyons sent between stationary observers" ... except here you are saying they can - CD is being affected by AB.

Secondly, according to our agreed (RULE 1) above, "one can always emit near-infinite-speed tachyons that the other can always receive, and the receiver's clock at reception will be (near-)exactly the same time as the emitter's clock at emission." That fits perfectly well with frames not affecting/being-affected by other frames, but now at the first discussion you want to discard (RULE 1), saying D CANNOT emit those tachyons ???

Finally, you made the statement earlier "You're completely ignoring the fact that these limitations refer ONLY to completing a message loop."

On Friday, June 4, 2021 at 12:12:32 AM UTC-6, Rob Acraman wrote:
>
> On Friday, June 4, 2021 at 9:35:30 AM UTC+10, hit...@yahoo.com wrote:
> >
> > Yes. as an experimental physicist, I think of the "message" as an electromagnetic pulse emitted
> > at the proper time as one passes the other. At speeds relativistic, that's about all that CAN be done
> > practically. One could set up an automatic system: a photocell loses light from a source because
> > the passing body shadows it for an instant. That's a message.
>
> Great - Thanks Gary, and again, always happy when we agree :-)
>
> So to summarise, we agree the following rules are ALWAYS true :
>
> RULE 1) given two individuals who are at rest relative to eachother and whose clocks have
> been synchronised (such as C and D), then one can always emit near-infinite-speed tachyons
> that the other can always receive, and the receiver's clock at reception will be (near-)exactly
> the same time as the emitter's clock at emission.
>
> RULE 2) At the instant that one individual ("Peter") is colocated-with while being passed by
> another ("Paul") with v < c, then at that instant Peter can always successfully hand off to Paul
> any information (a "message") that Peter has available (ie that he received previously or at that
> instant). For example, we can imagine that Peter could attach that information as a text file to
> an email that is sent by radio, so always perfectly capable of being received by Paul. Naturally,
> how Peter originally got the information (eg mode of transmission, such as radio or tachyons)
> is totally irrelevant to this.

RULE 3) "Co-located" and "instant" may not have rigorous definitions because of RoS. Analyses
performed completely in one frame and then completely in the other frame MUST be in agreement
IF Method II communication between the frames is possible. ( Communication between frames is
always possible by Method I, which never violate causality).

> > Our disgreement is over what "causes" time to be hurled back. You claim it's the existence of
> > tachyons that causes it, but I claim it's refusal to acknowledge RoS.
>
> Well, I actually claim it's the existence of tachyons WITH acknowledging RoS. ;-) Tachyons without
> RoS (ie, against a background of Galilean transformation instead of SR) would not have any problem.
>
> You claim that an individual can, for example, always emit (near-)∞ tachyons, but then also say that
> is impossible due to RoS considerations. I say that it must be one or the other - always possible, or
> not always possible. You can't have it both ways.

Well, I just ate my cake ... and I still have some left :-))

Obeying RoS can be subtle. Following simple high school algebra where, for example, xC = vt and
xT = L/γ² + u(t - vL/c²) and we set xC = xT and solve for t: t = (1 - v²/c² + uv/c²)L/(u + v), where u is
a negative number and u < -c. Clearly, any value for u > -∞ results in t > vL/c², thus no causality violation.

The problem comes when we fold in u = (u' + v)/(1 + u'v/c²) and u' < -c²/v. This where RULE 3 is
violated.

> > > Not so Gary ;-) You have already agreed that the Nailgun scenario is also "an impossible situation"
> > > (that you have yet to resolve ;-> ),
> >
> > Not so, Rob. It's resolved by:
> >
> > t = 0: (S frame)
> > C --> v _________________ D --> v
> > ____ A ----> w _______________ B
> > Figure 1.
> >
> > A sends a signal to B at w = c²/v. To C and D it's velocity is w' = ∞ since it's launched at t = tC' = 0 and it
> > arrives at tD' = 0. Then D sends it to C at u' = -c²/v. To A and B it's velocity is u = -∞.
>
> Which is not the nailgun scenario, which I state below.
>
> For example, I explicitly state "D sets his tachyon-speed-dial to (near-)∞ and so emits tachyons at that
> speed to C" . The resolution to that is NOT to say "Let's forget that, and instead talk about a different
> scenario where D sets his tachyon-speed-dial to -c²/v.".
>
> I want to know what you think happens when D sets his tachyon-speed-dial to -(near-)∞, OR agree that it
> is impossible for him to do so (ie, that (near-)∞ speed tachyons are impossible).

I think I've already explained that: The nail doesn't get driven at A's feet.

> > > and that stands completely independent of message loops. To recap :
> > > ======
> > > At the instant that D is co-located with B, D sets his tachyon-speed-dial to (near-)∞ and so emits
> > > tachyons at that speed to C, who at the instant she receives them will fire a nail into the ground
> > > of the AB frame.
> > > ======
> >
> > Which is not possible in my diagram.
>
> Yes, your diagram is not the nailgun scenario I stated.

Your diagram violates RULE 3 and is, therefore, impossible. My diagram obeys RULE 3.

> > > So what renders this so impossible ? Well, IMHO there are 4 principle factors in this scenario :
> > > 1) SR's PoR (which is clearly not impossible)
> > > 2) SR's RoS (which is clearly not impossible)
> > > 3) D emitting (near-)∞ tachyons
> > > 4) C firing a nailgun (which is clearly not impossible)
> > >
> > > So what factor do you reckon renders this scenario impossible ? ;-)
> >
> > The fact that in your presumed scenario:
> >
> > t = 0: (S frame)
> > C --> v _________________ D --> v
> > A _____________________ B
> > Figure 2.
> >
> > According to AB, D CANNOT send an infinitely-fast signal to C because tC' = 0 and tD' = -γvL/c².
>
> My presumed scenario does have a (near-)∞ speed signal - so this diagram with tC' = 0 and
> tD' = -γvL/c² is NOT my presumed scenario.

It's a difference between fantasy and reality.

> > If D sent an infinitely-fast signal to C, it would look like this:
> >
> > i = -vL/c²: (S frame)
> > C --> v _________________ D --> v
> > ____ A _____________________ B
> > Figure 3.
> >
> > Look familiar?
>
> Still not my presumed scenario, which is explicitly that D is co-located with B as the tachyons are emitted.

I was getting there ...

> > t = vL/c²:
> > ____ C --> v __________ u' <---- D --> v
> > A _________________________ B
> > Figure 5.
>
> Right, so tB=vL/c² and t'D = 0.
>
> > In this scenario, AB says C can't pass the message to A.
>
> To be clear : the "scenario" is the single reality that I described above (within the "===="). This diagram
> is NOT a "scenario", but simply a view of that scenario - of that single reality - from the viewpoint of the
> AB frame.
>
> So from this viewpoint of AB, the nail will end up far from A in that single reality.
> OTOH, CD says they can:
>
> > t' = 0: (S' frame)
> > v <-- A _________________v <-- B
> > ____ C _____________________ D
> > tA = 0, tB = vL/c²
> > Figure 6.
>
> Yes, in this a view of that same single reality I referred to above, but this time from the viewpoint
> of the CD frame,
> So from this viewpoint of CD, the nail will end up at A's feet in that single reality.

But both Figure 5 and 6 are supposed to refer to a SINGLE reality. But they don't, hence RULE 3 is
violated.

> > but it would require that time go backward for AB. As I'm sure we agree, a signal in S' CANNOT
> > make time go backward in S. ... It's all about RoS.
>
> Firstly : You stated above "Tachyons sent between stationary observers don't affect other frames. ".
> The reverse must IOTTMCO be equally true : "Other frames don't affect (including they can't dictate
> speeds of) Tachyons sent between stationary observers" ... except here you are saying they can - CD
> is being affected by AB.

Nope. I'm saying that if you, in one frame, want to affect another frame, then you MUST pay attention
to logistics and RULE 3.

> Secondly, according to our agreed (RULE 1) above, "one can always emit near-infinite-speed tachyons
> that the other can always receive, and the receiver's clock at reception will be (near-)exactly the same
> time as the emitter's clock at emission." That fits perfectly well with frames not affecting/being-affected
> by other frames, but now at the first discussion you want to discard (RULE 1), saying D CANNOT emit
> those tachyons ???
>
> Finally, you made the statement earlier "You're completely ignoring the fact that these limitations refer
> ONLY to completing a message loop."
>
> So is this limitation " D CANNOT send" only a limitation when completing a message loop ?
> Because, as I have repeatedly stressed, this nailgun scenario is a scenario in its own right
> WITHOUT completing a message loop.

On Friday, June 4, 2021 at 6:52:50 AM UTC-7, hit...@yahoo.com wrote:

> RULE 3) "Co-located" and "instant" may not have rigorous definitions because of RoS.

Crank Gary,

"Colocated" means the following:

1. In frame F, \Delta x =0 and \Delta t=0
2. In frame F', point 1 implies \Delta x'=0
3. RoS plays no role, colocated in frame F means colocated in frame F'.

On Friday, June 4, 2021 at 12:45:55 PM UTC-6, Dummkopf Dono. wrote:
>
> On Friday, June 4, 2021 at 6:52:50 AM UTC-7, hit...@yahoo.com wrote:
> >
> > RULE 3) "Co-located" and "instant" may not have rigorous definitions because of RoS.
>
> Crank Gary,
>
> "Colocated" means the following:
>
> 1. In frame F, \Delta x =0 and \Delta t=0
> 2. In frame F', point 1 implies \Delta x'=0
> 3. RoS plays no role, colocated in frame F means colocated in frame F'.

You are wrong, Dummkopf-breath. Anyone with a modicum of brain matter
can see that the INSTANT when D is CO-LOCATED with B, C is NOT co-located
with A:

> > t = vL/c²:
> > ____ C --> v __________ u' <---- D --> v
> > A _________________________ B
> > Figure 5.

But, from the S' frame, A and C ARE so co-located when D and B are co-located:

> > t' = 0: (S' frame)
> > v <-- A _________________v <-- B
> > ____ C _____________________ D
> > tA = 0, tB = vL/c²
> > Figure 6.

Contrary to your dishonest babbling, this CLEARLY shows that RoS has a significant
role. If you had any brains and any honesty, you wouldn't have deleted this obvious
clarification that I had to reinstate. You did because you have neither.

“You are mean because inside you’re tiny. So tiny you cannot hold up the weight of
your own body. You must inflate your ego just to fill the skin. You float around like a
helium balloon. Blown up and bloated and gassy and empty.” ― Rivers Solomon

“Some people are in such utter darkness that they will burn you just to see a light.”
― Kamand Kojouri

But go ahead and be a stupid ass, because:

“I will never grow thick skin so that you don't have to feel bad about being a jerk to me.”
― Dan Pearce

"Attack me again with your sticks and your stones,
And, yes, you just may end up breaking my bones.
But name-calling earns you the hapless disgrace
Of failing to logically argue your case." -- David Morin

On Friday, June 4, 2021 at 2:08:04 PM UTC-7, hit...@yahoo.com wrote:
> On Friday, June 4, 2021 at 12:45:55 PM UTC-6, Dummkopf Dono. wrote:
> >
> > On Friday, June 4, 2021 at 6:52:50 AM UTC-7, hit...@yahoo.com wrote:
> > >
> > > RULE 3) "Co-located" and "instant" may not have rigorous definitions because of RoS.
> >
> > Crank Gary,
> >
> > "Colocated" means the following:
> >
> > 1. In frame F, \Delta x =0 and \Delta t=0
> > 2. In frame F', point 1 implies \Delta x'=0
> > 3. RoS plays no role, colocated in frame F means colocated in frame F'.
> You are wrong,

Keep digging yourself, crank