On Sunday, June 6, 2021 at 4:42:42 AM UTC-6, Rob Acraman wrote:
>
> On Sunday, June 6, 2021 at 11:25:08 AM UTC+10, hit...@yahoo.com wrote:
> >
> > On Saturday, June 5, 2021 at 3:45:18 PM UTC-6, Rob Acraman wrote:
> > >
> > > > 3c. Communication between frames is always possible by Method I, which never violates causality.
> > >
> > > We have already agreed that communication between frames is ALWAYS possible with RULE 1 and
> > > RULE 2, so Method 1 is basically irrelevant (since if it disagrees, then that's a contradiction) ;->
> >
> > Method I NEVER disagrees and NEVER violates causality when frame-dependent energy is applied.
> > It is NOT irrelevant because every Method I thought experiment inflicted by "great lights" of relativity
> > have completely ignored it and falsely concluded that Method I "proves" that tachyons violate
> > causality. Tachyons don't violate causality, "great lights" do.
>
> Again, RULE 1 and RULE 2 together mean that any message can be transmitted to any individual anywhere.
> Method 1 may mean that direct tachyon transmission from one individual to another in relative motion is
> impossible under certain conditions, but that doesn't stop the INDIRECT transmission via a stationary
> individual (as per RULE 1) who then hands off the message (as per RULE 2)..

The fact that a round-trip signal by Method I is limited to ∆t > vL/c² should give one pause before proposing
another method that presumes to not only beat that, but even causes time to go backwards. We both agree
that time can't go backwards, at least at the classical level where we live..

IF tachyons CAN exist, then something is obviously wrong with Method II. The finger points to the sleight-
of-hand practice of mixing frames when determining what speed S' may use. You and PCH claim it's just
fine to do that, but others disagree:

"An extremely important strategy in solving relativity problems is to plant
yourself in a frame and stay there. The only thoughts running through your head
should be what you observe. That is, don’t try to use reasoning along the lines
of, 'Well, the person I’m looking at in this other frame sees such-and-such.'
This will almost certainly cause an error somewhere along the way, because you
will inevitably end up writing down an equation that combines quantities that
are measured in different frames, which is a no-no. -- David Morin, "Introduction
to Classical Mechanics," p. 522.

Of course, Morin violated his strategy in his book, "Relativity for the Enthusiastic Beginner." That, of course,
spoiled PCH's claim that beginners should obey the strategy :-)

"one should never mix together the descriptions of one phenomenon yielded by different
observers, otherwise--even in ordinary physics--one would immediately meet contradictions"

E. Recami, "Classical Tachyons and Possible Applications," Rivista Del Nuovo Cimento, 9:6 (1986), p. 66.

So Morin's strategy isn't all that new, and Recami never wavered about it (Recami has an impressive tachyon
bibliography). And then there's my little contribution, viXra 2011.0076: "Tachyons from a Laboratory
Perspective" which advocates the same cautionary prescription. We discussed a more rigorous rule
hare a while back:

RULE 4) Morin's strategy should be used to analyze the situation completely in S and then
analyzed completely in S', and the two analyses must agree.

> > > > So choose your poison and we'll discuss it.
> > > >
> > > > Let me start with 3a, and this has nothing to do with tachyons. Take a diagram we are both familiar
> > > > with:
> > > >
> > > > t = 0:
> > > > C --> v _________ D --> v
> > > > A __________________ B
> > > >
> > > > A and C are co-located but D and B are not at the instant t = 0.
> > > >
> > > > t = vL/c²:
> > > > ____ C --> v _________ D --> v
> > > > A __________________ B
> > > >
> > > > D and B are co-located but A and C are not at the instant t = vL/c².
> > > >
> > > > t' = 0:
> > > > v <-- A __________________ v <-- B
> > > > ____ C _______________________ D
> > > >
> > > > A and C are co-located when B and D are co-located at the instant t' = 0.
> > > > Do you agree that this is because of RoS?
> > > Of course. It is a single reality seen from the viewpoint of two frames.
> > >
> > > Clearly A and C are co-located at one instant - that is an event, let's call it E1.
> > > B and D are also colocated at another instant - that is another event, let's call it E2.
> > >
> > > I say that those are rigorously defined, that "co-located" and "instant" completely "rigorously"
> > > define each event E1 and E2 (though clearly not the relation between them, like "are the t
> > > coordinates of E1 and E2 equal for some frame", which is obviously a different topic)
> > >
> > > I say that :
> > > * everything that happens at E1 happens at E1 in EVERY frame; it MUST share the same
> > > coordinates (ie be "co-located" at that "instant").
> > > * everything that does NOT happen at E1 does not happen at E1 in EVERY frame; it CANNOT
> > > share the same coordinates.
> > >
> > > * everything that happens at E2 happens at E2 in EVERY frame; it MUST share the same
> > > coordinates.
> > > * everything that does NOT happen at E2 does not happen at E2 in EVERY frame; it CANNOT
> > > share the same coordinates.
> > >
> > > That means "co-located" and "instant" are rock-solid definitions, including under RoS . Anything
> > > denying that (such as tachyons) is IMHO busted by definition ;-)
> >
> > So let's see. Your E1 = (0,0) in S and [0.0] in S'. Your E2 = (L,vL/c²), [L/γ,0]. These co-ordinates
> > aren't in question. What I question is your insistence that E1 is the same event for the launch of
> > a signal (A to B) as the reception of a signal (D to C), which we may call E3. IOW, you're claiming
> > that E3 = E1.
> >
> > From the perspective of S, C is at xC = v²L/c² when D launches the second signal, u'. You claim
> > that u' can be -∞, thus it is received at E1 = [0,0], which means that time goes backward in S.
>
> Which means that you are declaring that D *CANNOT* emit tachyons at -(near-)∞ - in other words,
> that given D has his tachyon speed dial, he can never hit that EMIT button - right ?

Not at all. I'm saying that from the perspective of S', D MUST emit the tachyon at u' = -∞ in order to
complete the loop. I'm also saying that we must believe what we see in S: C has already passed A
when D emits the signal, so we must disbelieve what S' sees. Contradiction, therefore the configuration
proposed cannot complete a message loop, and any claim that it "proves" tachyons can't exist must be
discounted.

> > I claim that E3 = (vL/c²,v²L/c²) [0,vL/γc²], at LEAST, which means that u' = (0 - L/γ)/(vL/γc²) = -c²/v,
> > and, therefore u = (v²L/c² - L)/(vL/c² - vL/c²) = -∞.
>
> NO.
>
> D setting his tachyon-speed-dial to (near-)∞ and hitting EMIT is ** OBVIOUSLY ** an entirely different
> scenario (a different reality) from D setting his tachyon-speed-dial to -c²/v and hitting EMIT.

Ergo, as I said, this configuration can only promulgate baloney.

> Let's say A,B,C and D perform this experiment repeatedly, with D changing the setting of his speed dial
> on different days. On Monday, he sets it to -(near-)∞, on Tuesday to -c²/v.
>
> So basically you're saying is : "On Monday, D emits -(near-)∞, and we can see the view from the CD frame
> and compare it with .... oh wait, that's impossible for the AB frame, so let's pull a big switcheroo and
> instead consider the view from the AB frame on Tuesday. So the view of the CD frame on Monday doesn't
> have a contradiction with the view of the AB frame on Tuesday, so no contradiction, so Ta Da, Tachyons are
> possible ! "

Wrongo, Rob. I'm saying that the configuration under consideration says nothing about the existence or
nonexistence of tachyons.

> As I said : No ;-> I'm looking for you to address what I said earlier :
>
> What I said earlier still applies :
> ====> 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.".

Gary Harnagel wrote:

> On Sunday, June 6, 2021 at 4:42:42 AM UTC-6, Rob Acraman wrote:
>> Again, RULE 1 and RULE 2 together mean that any message can be
>> transmitted to any individual anywhere.
>> Method 1 may mean that direct tachyon transmission from one individual
>> to another in relative motion is impossible under certain conditions,
>> but that doesn't stop the INDIRECT transmission via a stationary
>> individual (as per RULE 1) who then hands off the message (as per RULE
>> 2).
>
> The fact that a round-trip signal by Method I is limited to ∆t > vL/c²
> should give one pause before proposing another method that presumes to
> not only beat that, but even causes time to go backwards. We both agree
> that time can't go backwards, at least at the classical level where we
> live.

you still incapable to capisce a target at c its length becomes ZERO,
whereafter above c, logically, it has to go negative. You are imbecilicly
promoting negative lengths. Want me to say more?

On Sunday, June 6, 2021 at 7:33:33 AM UTC-6, Gary Harnagel wrote:
>
> I've already given you the configuration that satisfies all the rules:
>
> t = 0:
> C --> v _________________ D --> v
> ____ A ----> w _______________ B
> w = c²/v, w' = ∞
>
> t = vL/c²:
> ____ C --> v ___________ u' <---- D
> ____ A _______________ ----> w B
> tC' = γvL/c², tD' = 0; u' = -c²/v, u = -∞.
> t' = 0:
> v <-- A __________________ v <-- B
> ____ C ______________________ D
>
> tA = 0, tB = vL/c², therefore w = c²/v, w' = ∞.
> u' = -∞, u = -c²/v

Oops! Brain brlwarp! Got mixed up with the other config. This should be:

t' = 0:
____ v <-- A ----> w ______ v <-- B
____ C ________________u' <---- D
tA = 0, tB = vL/c², w = c²/v, w' = ∞

t' = γvL/c²
v <-- A _____________ v <-- B
____ C u' <---- ___________ D
u' = -c²/v, u = -∞

> No causality violation, all the rules are obeyed, but ... um ... the values of u and u' have

not been switched! Perfect agreement with method I.

> [rest deleted]

On Sunday, June 6, 2021 at 12:48:13 PM UTC-7, hit...@yahoo.com wrote:
>
> tA = 0, tB = vL/c², w = c²/v, w' = ∞
>
> t' = γvL/c²
> v <-- A _____________ v <-- B
> ____ C u' <---- ___________ D
> u' = -c²/v, u = -∞
> > No causality violation, all the rules are obeyed, but ... um ... the values of u and u' have
> not been switched! Perfect agreement with method I.
>
Actually, they ARE switched. In your OWN writing, crook.

On Sunday, June 6, 2021 at 2:55:36 PM UTC-6, Dono. wrote:
> On Sunday, June 6, 2021 at 12:48:13 PM UTC-7, hit...@yahoo.com wrote:
> >
> > tA = 0, tB = vL/c², w = c²/v, w' = ∞
> >
> > t' = γvL/c²
> > v <-- A _____________ v <-- B
> > ____ C u' <---- ___________ D
> > u' = -c²/v, u = -∞
> > > No causality violation, all the rules are obeyed, but ... um ... the values of u and u' have
> > not been switched! Perfect agreement with method I.
> >
> Actually, they ARE switched. In your OWN writing, crook.

Nope. Here's the correct entire sequence of diagrams:

t = 0:
C --> v _________________ D --> v
____ A ----> w _______________ B
w = c²/v, w' = ∞

t = vL/c²:
____ C --> v ___________ u' <---- D
____ A _______________ ----> w B
tC' = γvL/c², tD' = 0; u' = -c²/v, u = -∞.

t' = 0:
____ v <-- A ----> w ______ v <-- B
____ C ________________u' <---- D
tA = 0, tB = vL/c², w = c²/v, w' = ∞

t' = γvL/c²
v <-- A _____________ v <-- B
____ C u' <---- ___________ D
u' = -c²/v, u = -∞

View from S:
w = c²/v, u' = -c²/v; w' = ∞, u = -∞
View from S':
w = c²/v, u' = -c²/v, w' = ∞, u = -∞

This is also consistent with Method I: A must send the signal at w <= c²/v because energy is
frame-dependent and D receives it at w' <= ∞. Then D must send it back to A at u' >= -c²/v for
the same reason and A receives it at u > -∞.

Calling people names with no justification does seem to be your modus operandi.

"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 Sunday, June 6, 2021 at 3:44:26 PM UTC-7, hit...@yahoo.com wrote:
>
> tA = 0, tB = vL/c², w = c²/v, w' = ∞
>
> t' = γvL/c²
> v <-- A _____________ v <-- B
> ____ C u' <---- ___________ D
> u' = -c²/v, u = -∞
> View from S:
> w = c²/v, u' = -c²/v; w' = ∞, u = -∞
> View from S':
> w = c²/v, u' = -c²/v, w' = ∞, u = -∞
>

Lying crank,

You are just trying to snow everybody, you are simply contradicting yourself.

On Sunday, June 6, 2021 at 5:24:29 PM UTC-6, Dono. wrote:
>
> On Sunday, June 6, 2021 at 3:44:26 PM UTC-7, hit...@yahoo.com wrote:
> >
> > tA = 0, tB = vL/c², w = c²/v, w' = ∞
> >
> > t' = γvL/c²
> > v <-- A _____________ v <-- B
> > ____ C u' <---- ___________ D
> > u' = -c²/v, u = -∞
> > View from S:
> > w = c²/v, u' = -c²/v; w' = ∞, u = -∞
> > View from S':
> > w = c²/v, u' = -c²/v, w' = ∞, u = -∞
> >
> Lying crank,
>
> You are just trying to snow everybody, you are simply contradicting yourself.

I, and everyone else who reads your vituperation, have no idea what you're bloviating about.
You seem to be choleric most of the time, for some reason ... but most likely, for no reason
at all. Your cantankerousness will not have a good outcome in the end.

On Sunday, June 6, 2021 at 4:37:03 PM UTC-7, hit...@yahoo.com wrote:
> On Sunday, June 6, 2021 at 5:24:29 PM UTC-6, Dono. wrote:
> >
> > On Sunday, June 6, 2021 at 3:44:26 PM UTC-7, hit...@yahoo.com wrote:
> > >
> > > tA = 0, tB = vL/c², w = c²/v, w' = ∞
> > >
> > > t' = γvL/c²
> > > v <-- A _____________ v <-- B
> > > ____ C u' <---- ___________ D
> > > u' = -c²/v, u = -∞
> > > View from S:
> > > w = c²/v, u' = -c²/v; w' = ∞, u = -∞
> > > View from S':
> > > w = c²/v, u' = -c²/v, w' = ∞, u = -∞
> > >
> > Lying crank,
> >
> > You are just trying to snow everybody, you are simply contradicting yourself.
> I have no idea

0f course you don't . you are trying to snow and you are being exposed

On Sunday, June 6, 2021 at 6:05:00 PM UTC-6, Dono. wrote:
>
> On Sunday, June 6, 2021 at 4:37:03 PM UTC-7, hit...@yahoo.com wrote:
> >
> > On Sunday, June 6, 2021 at 5:24:29 PM UTC-6, Dono. wrote:
> > >
> > > On Sunday, June 6, 2021 at 3:44:26 PM UTC-7, hit...@yahoo.com wrote:
> > > >
> > > > tA = 0, tB = vL/c², w = c²/v, w' = ∞
> > > >
> > > > t' = γvL/c²
> > > > v <-- A _____________ v <-- B
> > > > ____ C u' <---- ___________ D
> > > > u' = -c²/v, u = -∞
> > > > View from S:
> > > > w = c²/v, u' = -c²/v; w' = ∞, u = -∞
> > > > View from S':
> > > > w = c²/v, u' = -c²/v, w' = ∞, u = -∞
> > > >
> > > Lying crank,
> > >
> > > You are just trying to snow everybody, you are simply contradicting yourself.
> > I have no idea
>
> 0f course you don't . you are trying to snow and you are being exposed

This "response" has null content. Just like his brain.

"If what you don't know can't hurt you, you're practically invulnerable." --- Anon.

I think zeroing in on the crux is this :

On Sunday, June 6, 2021 at 11:33:33 PM UTC+10, hit...@yahoo.com wrote:
> On Sunday, June 6, 2021 at 4:42:42 AM UTC-6, Rob Acraman wrote:
> >
> > On Sunday, June 6, 2021 at 11:25:08 AM UTC+10, hit...@yahoo.com wrote:
> > > From the perspective of S, C is at xC = v²L/c² when D launches the second signal, u'. You claim
> > > that u' can be -∞, thus it is received at E1 = [0,0], which means that time goes backward in S.
> >
> > Which means that you are declaring that D *CANNOT* emit tachyons at -(near-)∞ - in other words,
> > that given D has his tachyon speed dial, he can never hit that EMIT button - right ?
> Not at all. I'm saying that from the perspective of S', D MUST emit the tachyon at u' = -∞ in order to
> complete the loop. I'm also saying that we must believe what we see in S: C has already passed A
> when D emits the signal, so we must disbelieve what S' sees. Contradiction, therefore the configuration
> proposed cannot complete a message loop, and any claim that it "proves" tachyons can't exist must be
> discounted.

Right : Contradiction. It is THIS contradiction that I have been trying to get you to explore ;-)

So to be clear : in the S' frame, Dave has his tachyon speed dial set to -(near-)∞, and at t'D = 0 fires those tachyons to Carol, who receives them at t'C = 0, and at that instant he is co-located with Alice.

However that contradicts the S frame, since viewed from that frame, Carol passed Alice some time ago.

So yes, contradiction. The important thing is this : This contradiction is NOT completing message loop itself, since the contradiction happened BEFORE any communication (eg tachyons) from A to B. Yes, what is described is how the message loop STARTS - but what you have described above (correctly) as a contradiction does NOT require the message loop to be completed. Indeed, this is pretty much the point of the Nailgun scenario - the nail finishes up at A's feet viewed from one frame, but not from the other : Contradiction.

Therefore, it's not (only) "cannot complete a message loop", but rather "Dave -> Carol -> Alice (or Dave -> Carol -> Nail) is already totally impossible just as it stands (and by the way, that also means cannot complete a message loop)"

Agree ?

Now, you also say :
> I'm also saying that we must believe what we see in S: C has already passed A
> when D emits the signal, so we must disbelieve what S' sees.

Of course, by PoR, then equally "we must believe what we see in S' , C is with A when D emits the signal, so we must disbelieve what S sees." - yes ?

Hmmmmm, is this where your interpretation of Morin's strategy comes in ? Do you believe :
- Sticking in the CD frame, we believe what S' sees, so Carol receives the tachyons just as she is adjacent to Alice
- Sticking in the AB frame, we believe what S sees, so Carol receives the tachyons long after she passed Alice

...... and that believing both of these are valid is Morin's strategy ???????

I sure hope the answer to that is "no", because IMHO that's not "strategy" nor "acknowledging RoS", but just plain contradictions, impossible to believe both (segue to mandatory HHGTTG quote : “If you've done 6 impossible things this morning, why not round it off with breakfast at Milliways, the Restaurant at the End of the Universe?” :-D )

And where does this leave the nailgun scenario - given that Carol fires the nailgun immediately upon receiving the tachyons, then :

- Sticking in the CD frame, the nail ends up at A's feet - yes?

- Sticking in the AB frame, then ..... what ? Is it (a) impossible situation, so even considering CD frame is impossible, or (b) Impossible situation from AB frame's view, so Carol never received the tachyons, so never fired the nailgun, or (c) Nailgun fired but nail ends up some distance away from A ? or something else ????

So far as I'm concerned, a single reality means that every observer must agree every event (as I said, co-located and instant do rigorously define every event). For example, the Pole-Barn scenario : As the tip of the pole is at the exit of the barn, the view from pole frame is that the rear of the pole has yet to reach the barn, and from the barn frame, the rear of the pole is inside the barn. RoS yes - but importantly still a single reality - every event (eg, every physical event happening along the pole) is rigorously defined - all frames will agree where that physical event happens (either all agree inside the barn, or all agree outside the barn).

Basically, A and B pass C and D, yes, but they can always turn around and compare experiences afterwards - and ALL experiences MUST agree. We cannot have Carol saying that she waited, but Alice saying "No you didn't" (or vice-versa). In the lab setting, this is equivalent to collating images from the various cameras - the single reality means that all images from both S and S' MUST agree in showing that single reality (eg, C not waiting).

Agree ?

> > Again, RULE 1 and RULE 2 together mean that any message can be transmitted to any individual anywhere.
> > Method 1 may mean that direct tachyon transmission from one individual to another in relative motion is
> > impossible under certain conditions, but that doesn't stop the INDIRECT transmission via a stationary
> > individual (as per RULE 1) who then hands off the message (as per RULE 2).
> The fact that a round-trip signal by Method I is limited to ∆t > vL/c² should give one pause before proposing
> another method that presumes to not only beat that, but even causes time to go backwards. We both agree
> that time can't go backwards, at least at the classical level where we live.

Nope, so far as Method 1 goes, absolutely no need to pause about Method 2 ;-P

This is because you specified the reason why certain messages are impossible to be received with Method 1 - energy drops to below-zero when velocity between emitter and receiver > 0. However, when velocity = 0, that reason no longer exists, therefore there is zero basis for thinking that the result of that reason (ie that impossibility) should exist.

I don't have the energy to swim across the pacific. That doesn't give me pause before proposing another method to cross the pacific ;-)

On Sunday, June 6, 2021 at 11:31:28 PM UTC-6, Rob Acraman wrote:
>
> I think zeroing in on the crux is this :
> On Sunday, June 6, 2021 at 11:33:33 PM UTC+10, hit...@yahoo.com wrote:
> >
> > On Sunday, June 6, 2021 at 4:42:42 AM UTC-6, Rob Acraman wrote:
> > >
> > > On Sunday, June 6, 2021 at 11:25:08 AM UTC+10, hit...@yahoo.com wrote:
> > > >
> > > > From the perspective of S, C is at xC = v²L/c² when D launches the second signal, u'. You claim
> > > > that u' can be -∞, thus it is received at E1 = [0,0], which means that time goes backward in S.
> > >
> > > Which means that you are declaring that D *CANNOT* emit tachyons at -(near-)∞ - in other words,
> > > that given D has his tachyon speed dial, he can never hit that EMIT button - right ?
> >
> > Not at all. I'm saying that from the perspective of S', D MUST emit the tachyon at u' = -∞ in order to
> > complete the loop. I'm also saying that we must believe what we see in S: C has already passed A
> > when D emits the signal, so we must disbelieve what S' sees. Contradiction, therefore the configuration
> > proposed cannot complete a message loop, and any claim that it "proves" tachyons can't exist must be
> > discounted.
> >
> Right : Contradiction. It is THIS contradiction that I have been trying to get you to explore ;-)

What's there to "explore"? It's a contradiction, therefore it can never be a reality.

> So to be clear : in the S' frame, Dave has his tachyon speed dial set to -(near-)∞, and at t'D = 0
> fires those tachyons to Carol, who receives them at t'C = 0, and at that instant he is co-located with Alice.

You mean. "she" don't you?

> However that contradicts the S frame, since viewed from that frame, Carol passed Alice some time ago.
>
> So yes, contradiction. The important thing is this : This contradiction is NOT completing message loop itself,
> since the contradiction happened BEFORE any communication (eg tachyons) from A to B.
>
> Yes, what is described is how the message loop STARTS - but what you have described above (correctly) as
> a contradiction does NOT require the message loop to be completed. Indeed, this is pretty much the point
> of the Nailgun scenario - the nail finishes up at A's feet viewed from one frame, but not from the other :
> Contradiction.
>
> Therefore, it's not (only) "cannot complete a message loop", but rather "Dave -> Carol -> Alice (or Dave ->
> Carol -> Nail) is already totally impossible just as it stands (and by the way, that also means cannot complete
> a message loop)"
>
> Agree ?

Sure looks that way, doesn't it? But don't you want to "explore" this some more? :-)

> Now, you also say :
> >
> > I'm also saying that we must believe what we see in S: C has already passed A
> > when D emits the signal, so we must disbelieve what S' sees.
>
> Of course, by PoR, then equally "we must believe what we see in S' , C is with A when
> D emits the signal, so we must disbelieve what S sees." - yes ?
>
> Hmmmmm, is this where your interpretation of Morin's strategy comes in ? Do you believe :
> - Sticking in the CD frame, we believe what S' sees, so Carol receives the tachyons just as
> she is adjacent to Alice - Sticking in the AB frame, we believe what S sees, so Carol
> receives the tachyons long after she passed Alice
>
> ..... and that believing both of these are valid is Morin's strategy ???????

Yes, my enhancement of Morin's strategy is that it must be applied to both frames.

> I sure hope the answer to that is "no", because IMHO that's not "strategy" nor "acknowledging
> RoS", but just plain contradictions, impossible to believe both (segue to mandatory HHGTTG
> quote : “If you've done 6 impossible things this morning, why not round it off with breakfast
> at Milliways, the Restaurant at the End of the Universe?” :-D )

“Only those who attempt the absurd will achieve the impossible. I think it's
in my basement... let me go upstairs and check.” – M. C. Escher

> And where does this leave the nailgun scenario - given that Carol fires the nailgun immediately
> upon receiving the tachyons, then :
>
> - Sticking in the CD frame, the nail ends up at A's feet - yes?
>
> - Sticking in the AB frame, then ..... what ? Is it (a) impossible situation, so even considering CD
> frame is impossible, or (b) Impossible situation from AB frame's view, so Carol never received
> the tachyons, so never fired the nailgun, or (c) Nailgun fired but nail ends up some distance away
> from A ? or something else ????
>
> So far as I'm concerned, a single reality means that every observer must agree every event (as
> I said, co-located and instant do rigorously define every event). For example, the Pole-Barn scenario:
> As the tip of the pole is at the exit of the barn, the view from pole frame is that the rear of the pole
> has yet to reach the barn, and from the barn frame, the rear of the pole is inside the barn. RoS yes -
> but importantly still a single reality - every event (eg, every physical event happening along the pole)
> is rigorously defined - all frames will agree where that physical event happens (either all agree inside
> the barn, or all agree outside the barn).
>
> Basically, A and B pass C and D, yes, but they can always turn around and compare experiences
> afterwards - and ALL experiences MUST agree. We cannot have Carol saying that she waited, but
> Alice saying "No you didn't" (or vice-versa). In the lab setting, this is equivalent to collating images
> from the various cameras - the single reality means that all images from both S and S' MUST agree
> in showing that single reality (eg, C not waiting).
>
> Agree ?

I think that's correct, but I'd have to see an event analysis of it.

> > > Again, RULE 1 and RULE 2 together mean that any message can be transmitted to any individual anywhere.
> > > Method 1 may mean that direct tachyon transmission from one individual to another in relative motion is
> > > impossible under certain conditions, but that doesn't stop the INDIRECT transmission via a stationary
> > > individual (as per RULE 1) who then hands off the message (as per RULE 2).
> >
> > The fact that a round-trip signal by Method I is limited to ∆t > vL/c² should give one pause before proposing
> > another method that presumes to not only beat that, but even causes time to go backwards. We both agree
> > that time can't go backwards, at least at the classical level where we live.
>
> Nope, so far as Method 1 goes, absolutely no need to pause about Method 2 ;-P

Absolutely incorrect.

> This is because you specified the reason why certain messages are impossible to be received with Method 1 -
> energy drops to below-zero when velocity between emitter and receiver > 0..

Well, not BELOW zero. It goes "through" a "singularity" in the mathematics.. Since the energy equation has
u² in it, it doesn't matter what the sign of u is. Taking a square root for E leaves some ambivalence about
its sign, of course, but choosing the right one requires more thought than just plug in a number, turn the
crank, and out plops the answer.

> However, when velocity = 0, that reason no longer exists, therefore there is zero basis for thinking that the
> result of that reason (ie that impossibility) should exist.

Since RoS is at the base of the limitation of Method I, and since RoS applies in Method II, the "reason" STILL
exists.

> I don't have the energy to swim across the pacific. That doesn't give me pause before proposing another method
> to cross the pacific ;-)

But I think you're trying to apply tardyon thought to tachyons. There ARE problems with time in the LT where
tachyons are concerned. One is that time and space are treated alike: x is allowed to extend for -∞ to +∞, and
so is time. In our real world, time doesn't go backwards. Along come tachyons and negative time becomes a
possibility - in the mathematics. In order to do that; however, velocity goes through a "singularity." You can't
just plug, crank, plop with impunity.

Part of the problem may be that you're too "faithful to your Rules 1 and 2. I've pointed out two more rules that
perhaps should be Rules 1 and 2 and your rules should be 3 and 4, and modified by provisos:

RULE 1) Analyses must be performed completely in one frame and then completely in the
other frame, and they MUST be in agreement.

RULE 2) When performing each analysis, "what you see is what you get." There' SHOULD
NOT be a conflict between the two analyses specified in RULE 1,

RULE 3) given two individuals who are at rest relative to each other 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 [provided that Rules 1 or 2 are obeyed].

On Monday, June 7, 2021 at 10:57:44 PM UTC+10, hit...@yahoo.com wrote:
> On Sunday, June 6, 2021 at 11:31:28 PM UTC-6, Rob Acraman wrote:

> > Therefore, it's not (only) "cannot complete a message loop", but rather "Dave -> Carol -> Alice (or Dave ->
> > Carol -> Nail) is already totally impossible just as it stands (and by the way, that also means cannot complete
> > a message loop)"
> >
> > Agree ?
> Sure looks that way, doesn't it? But don't you want to "explore" this some more? :-)

Great - so "exploring more" ;-) means that we can scrap the idea that "limitations refer ONLY to completing a message loop" . Here we have a straight out blatant contradiction as you admit yourself, and that from a SINGLE near-∞ speed tachyon transmission.

So again, there are 4 factors involved in this contradiction / impossibility - so which is that is impossible (phrasing as per the nailgun 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)

Has to be one of them ;->

> > Hmmmmm, is this where your interpretation of Morin's strategy comes in ? Do you believe :
> > - Sticking in the CD frame, we believe what S' sees, so Carol receives the tachyons just as she is adjacent to Alice
> >- Sticking in the AB frame, we believe what S sees, so Carol receives the tachyons long after she passed Alice
> >
> > ..... and that believing both of these are valid is Morin's strategy ???????
> Yes, my enhancement of Morin's strategy is that it must be applied to both frames.
> > I sure hope the answer to that is "no"

Sigh .... my hopes are dashed. As I said :

> > , because IMHO that's not "strategy" nor "acknowledging RoS", but just plain contradictions

Let's up the ante. Let's say that D is evil - the message that D sends with those tachyons is not just a bit of text, but a self-destruct command to a bomb in Carol's receiver that, when it goes off, everything and everyone nearby will be blown to smithereens.

So unfortunately, it's good-bye to Carol 8-O but what about Alice ? Well, from your "enhancement of Morin's strategy" above, that means :
- sticking in the CD frame, Carol receives the tachyons just as she is adjacent to Alice , so Alice was blown to smithereens as well, but
- sticking in the AB frame, Carol was away from everyone else at reception, so Alice is fine, seeing the explosion from a safe distance away

To me, Frames of Reference are simply coordinate systems that give different measurements for the one single-reality that happens in 4-D space-time. I have never read anything from any professional physicist that even even so much as implies anything else - and since that includes Morin's quotes, I personally have absolutely no doubt that he would agree with me. This was actually also my point with the nailgun scenario - the frames do not exist only for the period of the scenario being described, but continue to exist after that, and therefore consistency demands that the views from different frames MUST perfectly describe that same reality.

That was why "I sure [hoped your] answer to that is "no"" . However, your "enhancement of Morin's strategy" means we fundamentally disagree about what I wrote in the previous paragraph. If I understand you right, you think that different frames are not simply different measurements, but RoS means they are effectively different realities - they may start each scenario the same, but they develop independently with no requirement for continuing consistency between them. Alice is fine in AB frame, blown to smithereens in CD frame - fine, that happens in those frames, and each frame continues with it's reality - right ?

> > Basically, A and B pass C and D, yes, but they can always turn around and compare experiences
> > afterwards - and ALL experiences MUST agree. We cannot have Carol saying that she waited, but
> > Alice saying "No you didn't" (or vice-versa). In the lab setting, this is equivalent to collating images
> > from the various cameras - the single reality means that all images from both S and S' MUST agree
> > in showing that single reality (eg, C not waiting).
> >
> > Agree ?
> I think that's correct, but I'd have to see an event analysis of it.

Errr, no ;-)

That paragraph is the direct opposite of that to which you said "Yes, my enhancement of Morin's strategy".

> Part of the problem may be that you're too "faithful to your Rules 1 and 2. I've pointed out two more rules that
> perhaps should be Rules 1 and 2 and your rules should be 3 and 4, and modified by provisos:
>
> RULE 1) Analyses must be performed completely in one frame and then completely in the
> other frame, and they MUST be in agreement.

You haven't said how you define "in agreement". To me, "in agreement" means every event happens exactly the same when viewed from either frame.

>
> RULE 2) When performing each analysis, "what you see is what you get." There' SHOULD
> NOT be a conflict between the two analyses specified in RULE 1,

So there MAY be a conflict, and that's OK ????? That means RULE 1 is NOT a rule by definition.

>
> RULE 3) given two individuals who are at rest relative to each other 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 [provided that Rules 1 or 2 are obeyed].

"provided that Rules 1 or 2 are obeyed" ?????? I reckon that, some someone who believes that (near-)infinity speed tachyons are possible, that scenario will always be possible - but that "provided" clause means you must reckon there are exceptions.

So let's start with a fresh example :

Let's say Oliver and Peter are at rest wrt eachother, separated by distance M, and have synchronised their clocks. Oliver sets his tachyon speed dial to (near-)infinity, and as his clock ticks to 0 emits those tachyons toward Peter, who will receive them as his clock also reads (near-)0. All as per my original statement of the rule.

So can you give a concrete example where this Oliver/Peter scenario is impossible ?