On Saturday, June 19, 2021 at 7:39:47 AM UTC-5, sep...@yahoo.com wrote:
> On Saturday, June 19, 2021 at 1:05:34 AM UTC-5, Al Coe wrote:
> > On Friday, June 18, 2021 at 8:25:42 PM UTC-7, sep...@yahoo.com wrote:
> > > > > In F0, after a steady state condition is reached, the piece of rubber as viewed
> > > > > in F0 is basically parallel to the x-axis at any point in time but now the piece of
> > > > > rubber has 10 twists in it along this parallel line. Describe how F1 observers view
> > > > > the piece of rubber and how F1 observers explain where the 10 twists came from.
> > > >
> > > > If in terms of F0 you attach one end of a ribbon to one spindle, and then after 10 turns you attach the other end to the other spindle, the ribbon will have 10 net twists in it in terms of F0, but it will have 0 net twists in terms of F1 (in which you attached the ends of the ribbon simultaneously). Understand?
> > >
> > > I understand that's how the transform works, but I don't understand how that is
> > > physically possible. If for example, the top side of the piece of rubber is white and
> > > the other side is red, if F1 says that the piece of rubber has zero twists then the
> > > red side is never at a coordinate that has a radius greater than the white side.
> > As always, you are trivially mistaken. You didn't ask in the previous post about the radial position of the band, you asked about the twists, and the trivial answer is as given above, independent of the radial positions. Now you are asking yet another question, namely, how the radial position of the band is described in terms of F1. Again, the answer is trivial:
> >
> > Since you are forcing the centerline of the band to be straight and parallel to the plate's axis of rotation in terms of F0, it is in a helical shape with ten loops in terms of F1, with the band maintaining a fixed orientation relative to the plates. Thus the band is not twisted, but the red side is alternately on the side closer to the plate axis and on the side further from the plate axis, alternating ten times along the length.
> >
> > In summary: In terms of F0, the band is straight and twisted; in terms of F1 the band is helical and untwisted. These are just two different descriptions of the same thing, in terms of two different coordinate systems. All of this has been covered many times previously. Now do you finally understand?
> > > Describe how F1 observers view the piece of rubber and how F1 observers explain
> > > where the 10 twists came from.
> > Again, the band is not twisted in terms of F1, the centerline of the band has a helical shape around the plate axis. See above. If there is something about this that you still don't understand, just go ahead and ask.
> Its unclear to me how you define the helical shape of the centerline in terms of F1. If the piece of rubber has a small hole along the length L along the centerline as viewed in F0, when the steady-state condition is reached, a very small object could be fired along the x-axis and travel from A to B through this hole without hitting the piece of rubber. The speed of this object could be any speed and the result would be the same. Please explain how that would work with a helical shaped centerline in terms of F1.
> Thanks,
> David Seppala
> Bastrop TX

I should clarify that in the last question the piece of rubber was initially along the x-axis (y=0, z=0) before it was attached to the spinning plates at the center of each plate.
Regards,
David Seppal
Bastrop TX

On Sunday, June 20, 2021 at 11:47:58 AM UTC-5, Al Coe wrote:
> On Saturday, June 19, 2021 at 5:56:30 AM UTC-7, sep...@yahoo.com wrote:
> > I should clarify that in the last question the piece of rubber was initially along the x-axis (y=0, z=0) before it was attached to the spinning plates at the center of each plate.
> No, you said in F0 the two sides of the band in their end state are alternately closer to the plate axis and further away, which can only be true if the centerline of the band is *not* on the axis. In that case the centerline has a helical shape in terms of F1. If you're now proposing yet another scenario, in which the centerline is on the plate axis in terms of F0, then it's obviously on the plate axis in terms of F1 as well (axial positions are unaffected), in which case it's just a band with 10 twists in terms of F0 and 0 twists in terms of F1.
>
> > It's unclear to me how you define the helical shape of the centerline in terms of F1.
>
> Again, this refers to your scenario in which the band in terms of F0 has centerline straight and parallel to the plate axis, but *not* on the axis, so it is revolving around the axis, and hence the twists imply that alternate faces of the band are closer to the plate axis. In terms of F1, the centerline of the band is therefore obviously a helical shape at the same distance from the plate axis, winding ten times around, but not twisted. Hence alternate faces are closer to the plate axis.
>
> > [If I propose yet another scenario, with the band centerline on the plate axis,
> > and] if the piece of rubber has a small hole along the length L along the centerline as
> > viewed in F0, a very small object could be fired along the x-axis and travel from A to B
> > through this hole without hitting the piece of rubber. The speed of this object could be
> > any speed and the result would be the same. Please explain how that would work with
> > a helical shaped centerline in terms of F1.
> Again, if the centerline of the band is straight on the plate axis in terms of F0, then it is straight on the plate axis in terms of F1 as well (radial positions are unaffected), so your claim about sides of the band being alternately closer to and further away from the plate centerline does not apply. In this case there are 10 twists in terms of F0 and 0 twists in terms of F1, both along the plate axis, and your little bullet along the plate axis passes through just fine in terms of both descriptions. On the other hand, if you stipulate the centerline is not on the plate axis, then the bullet will not pass through in terms of either description. Merely changing the system of coordinates does not change what actually happens, it just changes the terms of description.
>
> Do you have any unresolved questions remaining? [Time capsule: The next time you raise this question, I'll point back to this message, and remind you that all your questions were answered and you ran away. If you had any unresolved questions about any of this, the time to ask them would have been now, not waiting 6 months and starting over at square zero.]

If I do a single wire or piece of rubber problem where the wire starts off parallel to the x-axis at some radius R and I have a fixed rod sitting along on x-axis at rest in frame F0 I cannot see how the parallel wire can wrap around the rod unless one plate makes more revolutions than the other. So if the center of the rod is at x=0, and before the wire is attached to the rotating plates, lets say there are two points P1 at (-1meter,0,R) and the other point P2 at (1 meter, 0, R) with the ends of the wire at (-L/2,0,R) and (L/2,0,R), can you tell me the coordinates of P2, and plates A and B just before P1's coordinates reach almost touch the rod at x = - 1 meter + delta, as viewed in frame F1?
David Seppala
Bastrop TX

On Monday, June 21, 2021 at 12:13:04 PM UTC-5, Al Coe wrote:
> On Monday, June 21, 2021 at 7:12:29 AM UTC-7, sep...@yahoo.com wrote:
> > If I do a single wire or piece of rubber problem where the wire starts off parallel to the
> > x-axis at some radius R and I have a fixed rod sitting along on x-axis....
>
> Now you are jumping back to the previous scenario with a rod on the x axis. The answer for that scenario has not changed. Remember, with a central rod (and/or with two wires) it is not possible to continuously deform the wire so that it is straight (and twisted) parallel to the axis in terms of F0, because there are 10 "turns" around the rod or other wire in that case. With a rod or second wire present, the subject wire with minimized spatial length in terms of F0 must wrap around the other entity, so at minimum you have a linear ramp, windings, and linear ramp, with the corresponding -q, +2q, -q shape (zero net turns around the other entity) in terms of F1, as explained to you countless times times before.
>
> Then you ran away from those scenarios, and proposed to have just a single wire with no central post, in which case it *is* possible to continuously deform the wire to be straight and parallel -- and twisted -- in terms of F0, and in terms of F1 this has no twists but is a helical shape, still with zero "turns" because there is nothing to "turn" around. In this case nothing prevents us from continuously deforming the wire into this helical shape in terms of F1, which corresponds to the straight shape in terms of F0.
>
> Then you proposed yet another scenario, with no post and with the wire residing on the x axis in terms of both F0 and F1, and there are 10 twists in the former and none in the latter, with a little bullet passing through a tunnel along the x axis.
>
> > Lets say there are two points P1 at (-1meter,0,R) and the other point P2 at (1 meter, 0, R) ...
> > can you tell me the coordinates of P2...as viewed in frame F1?
>
> Sure. The event at x,y,z,t in terms of F0 occurs at (x-vt)g, y, z, (t-vx/c^2)g in terms of F1, where g=1/sqrt(1-v^2/c^2).
>
> You are constantly confusing different scenarios. You need to stop mixing them up, and think about each scenario clearly. Each scenario has been fully and correctly described. Do you finally understand this now?

You said,
> Lets say there are two points P1 at (-1meter,0,R) and the other point P2 at (1 meter, 0, R) ...
> can you tell me the coordinates of P2...as viewed in frame F1?
Sure. The event at x,y,z,t in terms of F0 occurs at (x-vt)g, y, z, (t-vx/c^2)g in terms of F1, where g=1/sqrt(1-v^2/c^2).

Tell me the coordinates, not the transform equation. When plate A is at (-L/2',0,R) and plate B is at (L/2',0,R) and point P1 is at (-1+delta meter, 1 meter, 1 meter), tell me what the coordinates of P2 are at that instant of time as observed in frame F1. I'm trying to understand if P2 is still above the rod just when P1 is just above the rod.
David Seppala
Bastrop TX

On Tuesday, June 22, 2021 at 12:58:53 AM UTC-5, Al Coe wrote:
> On Monday, June 21, 2021 at 8:40:22 PM UTC-7, sep...@yahoo.com wrote:
> > [ Barnpole Dave ignores the thorough explanation of each scenario, and the
> > incisive diagnosis of his misconceptions about each one...]
>
> You forgot to acknowledge that you now (finally) understand all the scenarios that I've carefully and patiently explained to you, with and without a central rod, with one wire or two, with the wire on the axis or off, with and without a clay cylinder, etc., etc. Every single scenario has been thoroughly explained... so ... you're welcome.
> > > > Lets say there are two points P1 at (-1meter,0,R) and the other point P2 at (1 meter, 0, R) ...
> > > > can you tell me the coordinates of P2...as viewed in frame F1?
> > >
> > > Sure. The event at x,y,z,t in terms of F0 occurs at (x-vt)g, y, z, (t-vx/c^2)g in terms of F1, where g=1/sqrt(1-v^2/c^2).
> >
> > Tell me the coordinates, not the transform equation.
> Those *are* the coordinates. The event with coordinates x,y,z,t in terms of F0 has coordinates (x-vt)g, y, z, (t-vx/c^2)g in terms of F1. Do you understand this?
> > When plate A is at (-L/2',0,R) and plate B is at (L/2',0,R) and point P1 is at
> > (-1+delta meter, 1 meter, 1 meter)...
>
> Irrelevant information (and ambiguous use of the word "when").
> > tell me what the coordinates of P2 are at that instant of time as observed in frame F1.
> You failed to provide the one piece of information that is relevant: The coordinates of event P2 in terms of F0. Given that information, the coordinates of P2 in terms of F1 are as stated above. Also, when you say "at that instant", you must surely know that since P1 and P2 are at different x values they are not simultaneous in terms of both F0 and F1.
> > I'm trying to understand if P2 is still above the rod just when P1 is just above the rod.
> The points of the wire are wherever you specify them to be. Remember, there are infinitely many degrees of freedom for the positions of the particles of the wire on this spatial and temporal scale. Specifying the positions of the end points does not suffice to specify the positions of the other points. Also, you left "L" generic but specified x values of 1 meter, so the situation is even more underspecified. If you're telling me that you don't know the coordinates of the event in terms of either system of coordinates, then your question is under-specified. It's equivalent to asking "If Bob is 2 meters tall, how many centimeters tall is Sam?"

Okay, here's what I'm trying to understand. I will try to make things clearer. Let's say in F0 and F1, the distance between plate A and plate B is such that simultaneous events at the two plates as measured in F1 occur 1 second apart as measured in F0. Let's have a piece of rubber 1 cm wide in the y-direction, 1 mm thick in the z direction extend in the x direction from A to B but not connected to the plates yet. The wire is flat relative to the y axis (no twists). The top of the piece of rubber is white (direction farthest away from the x-axis) and the bottom of the piece of rubber (nearest to the x-axis) is red. The piece of rubber is initially at the top of the plates with z coordinate = R + delta. At the middle of the piece of rubber, which I'll call point P0, a line is drawn parallel to the y-axis across the white part of the piece of rubber. The plates, as measured in F0 are rotating 1 revolution per second. In F1 each end of the piece of rubber is simultaneously attached to the top of the each of the plates. The piece of rubber had been stretched as a result of this but the piece of rubber shortens itself.
As observed in F0, the piece of rubber tries to become a straight line as it shortens. When the point P0 on the piece of rubber initially reaches the x-axis in this shortening process, when this occurs lets say that both ends of the piece of rubber have the same y and z coordinates as measured in frame F1 as they had when the piece of rubber was initially attached to the plates.
In terms of F1, at the instant the piece of rubber reaches the x-axis is the line that was drawn at P0 (midpoint of the piece of rubber) parallel to the y axis? Is the red side of the piece of rubber touching the x-axis or is the white side of the piece of rubber touching the x-axis? In terms of F1, do they observe that the piece of rubber has twists in it going from plate A to P0, if so, how many?
Giving simple answers to those questions in terms of F1 will help me understand things.
Thanks,
David Seppala
Bastrop TX

On Thursday, June 24, 2021 at 12:25:09 AM UTC-5, Al Coe wrote:
> On Tuesday, June 22, 2021 at 6:25:43 AM UTC-7, sep...@yahoo.com wrote:
> > > > [ Barnpole Dave ignores the thorough explanation of each scenario, and the
> > > > incisive diagnosis of his misconceptions about each one...]
> Since Dave has fled the scene (again), let's tidy up the answers to his latest batch of questions, so they will be a ready reference when he re-surfaces in 6 months with the same question(s).
>
> > When the point P0 on the piece of rubber initially reaches the x-axis.... lets say that both
> > ends of the piece of rubber have the same y and z coordinates as measured in frame F1
> > as they had when the piece of rubber was initially attached to the plates.
> This sentence can charitably be taken to imply that the intersection event is simultaneous in terms of F1 with the attachment points on the disk being at the top. As explained in the previous post, this is not the same as being simultaneous in terms of F0 with the attachment points on the disk being at the top. (This is Dave's crucial misunderstanding.)
>
> As with all of his statements, Dave's statement above is ambiguous, since the phrase "the ends of the piece of rubber" could refer to the lateral ends attached to the plates, or it might be trying to refer to the edges of the band on the cross-sectional slice through the axial midpoint. With the first interpretation his questions are grossly under-specified, so let's suppose that he is specifying that the orientation of the band is held fixed along the length of the band in terms of F1, i.e., even during the transient process of re-configuring the band it never has any twists in terms of F1.
>
> > In terms of F1, at the instant the piece of rubber reaches the x-axis, is the line that
> > was drawn at P0 (midpoint of the piece of rubber) parallel to the y axis?
> Given the most charitable interpretation of the previous statements, the answer to this is tautologically yes, since it has been explicitly stipulated, i.e., the band has been stipulated to be untwisted in terms of F1 (not just 0 net twists, but continuously untwisted along it's length), and the crossing event is simultaneous in terms of F1 with the attachment points being in their original (top) positions.
> > Is the red side of the piece of rubber touching the x-axis or is the white side of
> > the piece of rubber touching the x-axis?
> Again the scenario as stated is grossly underspecified, since Dave is tacitly assuming the band's centerline is deformed from being straight in terms of F1 to being straight in terms of F0, which implies that the centerline becomes a helix with one turn in terms of F1, and there are infinitely many sequences of intermediate configurations the band can undergo to proceed from the initial shape to the final shape. One simple way would involve the band simply "descending" straight through the axis (without turning) from the top to the bottom (relative to the disk orientation) in terms of F1. For this scenario the red surface touches the axis first. But, again, this is underspecified.
> > In terms of F1, do they observe that the piece of rubber has twists in it going from plate A to P0, if so, how many?
> This too is underspecified, but we can (as noted above) stipulate that there are no twists at any point of the band in terms of F1.
> > Giving simple answers to those questions in terms of F1 will help me understand things.
> That statement is false, as Dave has demonstrated countless times. Note that he has not claimed any inconsistency, but he clearly intends to insinuate some inconsistency, which would be motivated by his failure to recognize that the crossing event is not simultaneous with the attachment points being at the top in terms of F0. That event is 180 degrees out of phase, but Dave does not understand this.

Al, tell me what happens in the following scenario.
There are two massive plates, A and B, separated a distance L in frame F0. Both plates are rotating at 10 revolutions per second as measured in F0. The radius of each plate is R. Just above each plate is a piece of metal or rubber initially at rest in F0 extending parallel to the x-axis from plate A to plate B. The piece of metal is 1 millimeter thick (z direction) and 1 centimeter wide (y direction) as measured in F0. In F0 there is also a rod 1 millimeter in diameter that extends from A to B parallel to the x axis at z coordinate R. This rod is fixed at that location in F0 so that it is always stationary as the two plates rotate in the y-z plane just beyond each end of the rod.
There is an inertial reference frame F1 that has a velocity V relative to F0 along the x-axis. V and L are such that simultaneous events that occur at plate A and plate B as measured in frame F1 occur one second apart as measured in F0.
At time t0' observers in F1 attach the piece of metal simultaneously to the top of each rotating plate and simultaneous rest it along the top of the stationary rod that extends from plate A to plate B. With each rotation of plate A and plate B, the piece of metal that extends from plate A to plate B is stretched when it is at the top of each plate (z=R) by pulling it at plate A one centimeter in the negative x direction, and by pulling it one centimeter in the positive x at plate B. This causes the midway position along the 1 cm width of the piece of metal to approach a straight line as viewed in F0.
This scenario causes the piece of metal to tangle with the rod. How do the observers in F1 explain how the piece of metal that was initially parallel to the rod became entangled with the rod when each plate rotates at the same rate and the same number of rotations as measured in F1 after the observers in F1 simultaneously attached each end of the metal to each plate at the same y and z coordinates? Your previous explanations have talked about external "forces" on the piece of metal without defining what they were.. How many places along the rod do the rod and piece of metal interact at?
David Seppala
Bastrop TX

On Thursday, June 24, 2021 at 4:01:07 PM UTC-5, Al Coe wrote:
> On Thursday, June 24, 2021 at 11:44:25 AM UTC-7, sep...@yahoo.com wrote:
> > Al, tell me what happens in the following scenario.
> So, now you propose yet another scenario. Have you understood all the explanations of previous scenarios?
> > This rod is fixed at that location in F0 so that it is always stationary as the two plates rotate
> That makes no sense. The ribbon will wind 10 times around that rod, but the attachment points of the ribbon rotate with the disks whereas the rod is in a fixed position, so the ribbon will be ripped apart from the ends on every rotation.
>
> > .. by pulling it at plate A one centimeter in the negative x direction, and by pulling it one
> > centimeter in the positive x at plate B. This causes the midway position along the 1 cm
> > width of the piece of metal to approach a straight line as viewed in F0..
> Nope, for two reasons. First, simply pulling on the ends of the ribbon does not determine the shape because you have already acknowledge that the ribbon must stretch, so it can continue to stretch and maintain any shape. (You've not specified elasticity, brittleness, bulk modulus, etc.) Second, the ribbon will wind 10 times around the rod, so even if you fix your scenario by stipulating that the rod is attached to the disks and rotates with them, it will still prevent the wire from being straight in terms of F0. And witgout fixing your scenario, the ribbon will be ripped apart with every rotation (barring a limit cycle with near infinite elasticity). We've covered all the possible scenarios before.
> > Your previous explanations have talked about external "forces" on the piece of metal
> > without defining what they were.
> Not true. The forces are defined as whatever they need to be to configure the ribbon into the shape that you specify. In general the ribbon would not assume the shapes you are imagining without the application of external forces to the particles of the ribbon. But you don't really need to specify these forces, you just need to specify the shape (or sequence of shapes leading from the initial to the final). Once you have specified the shape(s) in terms of (say) F0, I can then tell you the shape(s) in terms of any other system of coordinates, such as F1.
> > How many places along the rod do the rod and piece of metal interact at?
> They interact at the molecular and atomic and sub-atomic level, at a virtually infinite number of "places". As explained before, any influence can propagate along the ribbon only at the speed of sound in the ribbon, whereas you need deformations in your scenario that occur between space-like separated particles (e.g., when the first end of the ribbon is attached to one disk and the ribbon begins to deform, the opposite end of the ribbon is spacelike separated, so it can't possibly have any influence, and likewise for most other particles of the ribbon, but to maintain a coherent unbroken shape you will need to apply forces to the particles to keep the ribbon in the shape you want. There are infinitely many continuous patterns you could impose. For purposes of your questions, you just need to specify a shape in terms of (say) F0, and then I can tell you the shape in terms of F1. But the shape you specify has to be logically coherent to begin with, e.g., you need to fix your scenario as explained above, because your current scenario rips the ribbon apart on each rotation.

You wrote:
> > This rod is fixed at that location in F0 so that it is always stationary as the two plates rotate
> That makes no sense. The ribbon will wind 10 times around that rod, but the attachment points of the ribbon rotate with the disks whereas the rod is in a fixed position, so the ribbon will be ripped apart from the ends on every rotation.

Explain that from the F1 point of view. When did the piece of metal or ribbon wind 10 times around that rod from the point of view of F1 observers? I clearly see how that occurs from the F0 observers point of view, but I don't see how the F1 observers explain how that happens when the rod and piece of metal (or ribbon) were initially parallel to each other. How do the F1 observers explain how the piece of metal or ribbon wraps around the rod 10 times? I see how that occurs from the F0 point of view, but how do the F1 observers explain how that occurred when the rod and piece of metal (or ribbon) started out parallel and attached simultaneously to the top of each plate? Please provide the details from the F1 point of view, and not simply say that's what occurs in the F0 frame so if we use the transform equations that is what F1 must see. Let the relative velocity between F0 an F1 be sqrt(3)/2 * c. In that case, from the F1 point of view, each plate is rotating at a rate of 5 revolutions per second. What caused the piece of metal or ribbon to wrap around the rod 10 times?
Thanks,
David Seppala
Bastrop TX

On Thursday, June 24, 2021 at 9:28:43 PM UTC-5, Al Coe wrote:
> On Thursday, June 24, 2021 at 3:54:15 PM UTC-7, sep...@yahoo.com wrote:
> > > > This rod is fixed at that location in F0 so that it is always stationary as the two plates rotate
> > >
> > > That makes no sense. The ribbon will wind 10 times around that rod, but the attachment points of the ribbon rotate with the disks whereas the rod is in a fixed position, so the ribbon will be ripped apart from the ends on every rotation.
> >
> > I clearly see how that occurs from the F0 observers point of view [but] explain that from the F1 point of view.
>
> The radial positions of the ribbon are the same in terms of F1 as in terms of F0, so if you clearly see how it occurs in terms of F0 you must also clearly see how it occurs in terms of F1. As the parts of the ribbon move to radii less than R, they would collide with the stationary rod on every rotation, tearing the ribbon apart.
> > When did the piece of metal or ribbon wind 10 times around that rod from the point of
> > view of F1 observers?
> Huh? The ribbon has zero net turns around the rod in terms of F1, and it has 10 in terms of F0. Remember?
>
> > Please provide the details from the F1 point of view...
>
> The detailed sequence of shapes that the ribbon has at various times depends on what forces are applied to it, which you have not specified. (Specifying some movements of the ends of the ribbon is grossly insufficient for such spacelike-separated events.) To help you understand, I can give a specific example: At the moment of attachment in terms of F1 we could stipulate a distribution of forces such that the parts of the ribbon continue being straight in terms of F1, in which case they become a helix with 10 turns and radius R in terms of F0. Since all parts of the wire are at radius R, they do not hit the rod as they rotate, so all is well... until...
>
> You then begin superimposing on whatever other forces are being applied a process of pulling on the ends of the ribbon each time the connection points "are at the top of each plate", but you need to specify if this sequence of coupled pulls start simultaneously in terms of F0 or in terms of F1. If the pulls start simultaneously in terms of F0, then they start 360 deg out of phase in terms of F1, and the ribbon at the mid event is 180 deg out of phase (i.e., on the bottom), and hence that part of the ribbon has a radial pull upward (inward). If the sequence of pulls commence simultaneously in terms of F1, then no radial deflection occurs in terms of F1, and the shape remains straight at radius R in terms of F1 and helical at radius R in terms of F0. Remember, the effect of each pull propagates at the speed of sound along the ribbon, so when the displacement reaches the intermediate points of the ribbon it may have transverse components, and these are superimposed on whatever other forces are being applied.
>
> The point is that, no matter what we do, a part of the wire is forced radially in terms of F0 if and only if it is forced radially in terms of F1. For example, if in terms of F0 a ribbon centerline is a helix with radius varying gradually from R down to r and then back to R, it is described as a bow shape from R to r and back to R in terms of F1. And vice versa. The complexity you are introducing are due solely to the range of possible behaviors -- strictly in terms of (say) F0, depending on the material properties, accelerations, and so on. That's why it's so ironic that you are hung up on the description in terms of F1, when you can't even describe a scenario correctly in terms of F0 (even though you repeatedly claim you understand it in terms of F0 perfectly well.... No, you do not.)
>
> > [Don't] simply say that's what occurs in the F0 frame so if we use the transform
> > equations that is what F1 must see.
> You habitually fail to completely specify the description of "what occurs" in terms of F0, but for any specified description, the corresponding description in terms of F1 is indeed simply given by transforming from one coordinate system to the other (including the transformations of forces). Your problem seems to be that you can't visually grasp the effect of such transformations, especially the twist due to the relativity of simultaneity, and how a given sequence of shapes in terms of F0 maps to a sequence of shapes in terms of F1, and vice versa (differing purely by the uniform 10-turn twist of the axial slices), so you want someone to describe it verbally -- as I have done for you many times (including in this post above). But for some reason, when I provide the detailed verbal description, you ignore it and ask again, claiming that no one has ever described it to you. It's also ironic that you implicitly accept the relativistic transformation when you specify that the ribbon is attached simultaneously in terms of F1 but not in terms of F0. Once you have accepted this, everything else is just math.
>
> Now do you understand this?

In reponset to:
> > > This rod is fixed at that location in F0 so that it is always stationary as the two plates rotate
> >
You wrote:
> > That makes no sense. The ribbon will wind 10 times around that rod, but the attachment points of the ribbon rotate with the disks whereas the rod is in a fixed position, so the ribbon will be ripped apart from the ends on every rotation.

In terms of F1, how many rotations of Plate A occur before the ribbon (or piece of metal) will be ripped apart from the ends on every rotation? If the ribbon is ripped apart from the ends you state that occurs on every rotation. If the ribbon is ripped apart from the ends it is no longer attached to the rotating plates, so that will only happen one time at each plate. The ribbon will eventually stop rotating due to friction with the rod. How many twists will the ribbon (or piece of metal) have when the rotation stops?
David Seppala
Bastrop TX

On Friday, June 25, 2021 at 10:19:57 AM UTC-5, Al Coe wrote:
> On Friday, June 25, 2021 at 5:51:48 AM UTC-7, sep...@yahoo.com wrote:
> > In terms of F1, how many rotations of Plate A occur before the ribbon (or piece of
> > metal) will be ripped apart from the ends on every rotation?
> Seven rotations. Note that you failed to specify how many rotations would occur before you begin to force parts of the ribbon to a radial position less than R, so I will assist you by providing the specification: Seven. Of course, if you want to consider a scenario in which you begin to force parts of the wire to a radial position less than R after just six rotations, then the answer would be six. And likewise for any other number of rotations you specify. You could even choose to leave the ribbon straight in terms o F1, in which case it would never clash with the rod at all (being then a helix of radial R in terms of F0).
>
> Remember, in previous scenarios you talked about cooling the wire, and it was explained that the resulting response depended on whether the temperature is uniform in terms of F0 or in terms of F1. And you've been informed that a pressure wave propagating along a wire that is straight in terms of F1 follows a helical path at the speed of sound in the wire (because the wire is revolving around the axis), and so on.
>
> Now that we've established that your latest scenario makes no sense at all, and we've thoroughly explained all your other scenarios, do you have any remaining questions?
You wrote:
>Seven rotations. Note that you failed to specify how many rotations would occur before you begin to force parts of the ribbon to a radial >position less than R, so I will assist you by providing the specification: Seven. Of course, if you want to consider a scenario in which you >begin to force parts of the wire to a radial position less than R after just six rotations, then the answer would be six. And likewise for any >other number of rotations you specify. You could even choose to leave the ribbon straight in terms o F1, in which case it would never >clash with the rod at all (being then a helix of radial R in terms of F0).
If we choose to leave the ribbon straight in terms of F1, when the ribbon is at the top of each plate observers in F1 pull 1 cm of the ribbon past each plate, one end of the ribbon being pulled in the negative x direction and the other end being pulled in the positive x direction, do the observers in F1 observe that the ribbon remains straight?
David Seppala
Bastrop TX

On Saturday, June 26, 2021 at 10:30:15 PM UTC-5, Al Coe wrote:
> On Saturday, June 26, 2021 at 6:39:11 PM UTC-7, sep...@yahoo.com wrote:
> > If we choose to leave the ribbon straight in terms of F1... do the observers in F1 observe
> > that the ribbon remains straight?
> If the ribbon remains straight in terms of F1 then it remains straight in terms of F1.
>
> > If ... when the ribbon is at the top of each plate observers in F1 pull 1 cm of the ribbon past each plate, one end of the ribbon being pulled in the negative x direction and the other end being pulled in the positive x direction, do the observers in F1 observe that the ribbon remains straight?
>
> For the 100th time, the configuration of the parts of the ribbon is not specifiable purely in terms of what occurs at the ends, for two reasons: First, on this spatial and temporal scale the parts are spacelike-separated and hence mechanically independent, so each particle of the ribbon must be subjected to a suitable force to maintain any desired configuration, resisting centrifugal acceleration, etc. Second, any momentum flux propagating along the ribbon can only propagate at the speed of sound in the material (which you have not specified), and hence as the wire rotates a pressure wave will convey transverse momentum (both circumferential and radial) to the parts of the ribbon. So, in addition to the external forces you must already have been applying to keep the ribbon straight without the pulls, you must apply additional external forces to keep the ribbon straight when you begin the pulls.
>
> Think of a small tunnel drilled down the centerline of the ribbon, and shoot a tiny pellet of momentum into the tunnel. Even if the ribbon is straight, the pellet must follow a helical path because the ribbon is rotating around the axis, and hence the pellet exerts transverse forces (circumferential and radial) on the walls of the tunnel as it rotates around the axis. Similarly with any pressure pulse transmitted along the ribbon. And how the ribbon responds will depend on the materials properties of the ribbon, etc. along with the external forces, none of which you have specified.
>
> Of course, in addition to the above, if you begin the sequence of pulls at top center simultaneously in terms of F1, you will be starting them non-simultaneously (360 deg out of phase) in terms of F0, so one end will always be one pull ahead of the other. (Same comment appliers if you start them simultaneously in terms of F0 so they are out of phase in terms of F1.) All these factors combined (and several more I could mention) show that you need to specify a huge amount of information to enable a first-principles calculation of the dynamical shape of a rotating ribbon. Fortunately, none of this really matters if you are content to stipulate that you will apply whatever forces are necessary to give the ribbon some specified shape in terms of F0 (or F1). Then you can ask for the description of that shape in terms of F1 (or F0).
>
> Now do you understand?
Let's say between plate A and plate B there is a cylinder of soft clay of radius R rotating at the same rate as both massive steel endplates. Now let's say the ribbon or piece of rubber or metal is stretched to its limit before it is attached to the steel plates. Now F1 attaches the ribbon or piece of rubber or metal simultaneously to both end plates. Describe what occurs as viewed in F1.
Thanks,
David Seppala
Bastrop TX

On Sunday, June 27, 2021 at 11:34:34 AM UTC-5, Al Coe wrote:
> On Sunday, June 27, 2021 at 6:00:18 AM UTC-7, sep...@yahoo.com wrote:
> > Let's say between plate A and plate B there is a cylinder of soft clay of radius R rotating at the same rate as both massive steel endplates. Now let's say the ribbon or piece of rubber or metal is stretched to its limit before it is attached to the steel plates. Now F1 attaches the ribbon or piece of rubber or metal simultaneously to both end plates. Describe what occurs as viewed in F1.
> That is still grossly underspecified, as explained above. If you said (for example) that you are going to attach each particle of the ribbon to the (undisturbed) cylinder simultaneously in terms of F1, then the locus of particles would be straight and parallel to the x axis in terms of F1. If you don't stipulate this, then you need to make some other stipulation that suffices to determine how the parts of the ribbon are configured. Remember, "stretching to it's limit" is irrelevant, because the deformations are space-like (e.g., 5 complete revolutions of the end plates occur before even a light signal could reach the middle of the ribbon, so it would obviously be torn to shreds unless you apply coordinated forces to each individual particle of the ribbon to maintain some specified configuration for the locus of particles). Again, the particles of the ribbon are mechanically independent on this time scale.
>
> I say again: You don't even have a scenario until/unless you provide sufficient information to specify the configuration(s) of the ribbon in terms of *some* system of description. Once you have provided that, describing the configuration(s) in terms of other systems is trivial. So, what configuration(s) of the ribbon are you asking about? [To save time, if your response is anything other than a valid specification of the configuration(s), my response will be: That is still underspecified, as explained above.]

Okay,
Between rotating plate A and plate B there is a soft clay cylinder rotating at the same rate as the two plates. The two plates and cylinder have a radius R. Just above the plates and cylinders are two ribbons or pieces of rubber or metal that extend from plate A to plate B. The two pieces are of length L, width 1 cm and thickness 1 mm. One ribbon or piece of rubber or metal has been stretched to its limit as it extends from plate A to plate B, the other ribbon or piece of rubber or metal has not been stretched. The two ribbons or pieces of rubber or metal are initially aligned side by side along the x-axis, just above R. At time t0', frame F1 simultaneously places all points of the two ribbons or pieces of rubber or metal side by side on the clay cylinder and attaches each end of the two pieces side by side on to each rotating plate.
Please explain what the configuration of the two ribbons or pieces of rubber or metal look like initially at time t0' + delta and what they look like after a steady state condition is reached.
David Seppala
Bastrop TX

On Sunday, June 27, 2021 at 7:36:53 PM UTC-5, Al Coe wrote:
> On Sunday, June 27, 2021 at 12:52:12 PM UTC-7, sep...@yahoo.com wrote:
> > Please explain what the configuration of the two ribbons or pieces of rubber or metal look like initially at time t0' + delta and what they look like after a steady state condition is reached.
> Since you seem determined to never actually provide a specification of the configurations, let's just note for the record what a smarter version of you would be asking: If, by the application of suitable external forces, every particle of the ribbon is initially set rotating simultaneously about the x axis in terms of F1 (superimposed on its high translational motion), and the ends of the ribbon are attached to the disk, and then subsequently the ribbon re-configures continuously to minimize its proper length and uniformly distribute any twists, what will be its spatial shape in terms of F1 at constant t' when it reaches the minimal proper length and uniform twist configuration?
>
> Answer (for the 100th time): With nothing in the way (no central bar or opposite ribbon or fixed eccenteric bar, etc.) the minimum proper length of the ribbon moving axially at high speed v and rotating at a given angular speed is a uniform helical shape of radius R with no twists. Note that the integrated proper length of the ribbon is invariant, regardless of what system of coordinates is used to describe it.
>
> If a rod is present on the x axis, or another ribbon on the opposite side, the configurations with minimal proper length are likewise as explained dozens of times before (e.g., -q, 2q, -q).
>
> Needless to say, the normal laws of mechanics in terms of any given system of inertial coordinates (such as F1) entail forces on the parts of the wire to minimize the proper length (and hence energy); we stipulate that any required external forces to resist centrifugal acceleration, etc., are present. Also, note that although the 4-acceleration of a particle is parallel to the applied 4-force, the 3-acceleration is not in general parallel to the applied 3-force, due to the relativity of simultaneity. In any case, precisely the same laws of physics apply in terms of any system of inertial coordinates.

Let a cylinder rotate at 1 revolution per second with a ribbon just above the cylinder and parallel to the cylinder from A to B. If the ribbon attached to the top of the cylinder at side A and then one second later it is attached to top of the cylinder at side B, the helical pattern is not identical to the pattern created if the ribbon is first attached to side B and one second later is attached to the top of the cylinder at side A. So in the rest frame of the cylinder, you can determine which end of the ribbon was attached first by looking at the helical pattern once a steady state condition is reached.
The question for you is, if an inertial reference frame is moving with velocity V parallel to the rest frame of the cylinder, can that frame also determine which end of the ribbon was attached to the cylinder first?
David Seppala
Bastrop TX

On Sunday, July 4, 2021 at 7:07:28 AM UTC-7, sep...@yahoo.com wrote:
> If an inertial reference frame is moving with velocity V parallel to the rest frame of the
> cylinder, can that frame also determine which end of the ribbon was attached to the
> cylinder first?

Of course. In terms of the original system the two cases result in a helix with -1 or +1 turns, and in terms of the moving system this corresponds to 0 or +2 turns.

On Sunday, July 4, 2021 at 1:06:16 PM UTC-5, Al Coe wrote:
> On Sunday, July 4, 2021 at 7:07:28 AM UTC-7, sep...@yahoo.com wrote:
> > If an inertial reference frame is moving with velocity V parallel to the rest frame of the
> > cylinder, can that frame also determine which end of the ribbon was attached to the
> > cylinder first?
> Of course. In terms of the original system the two cases result in a helix with -1 or +1 turns, and in terms of the moving system this corresponds to 0 or +2 turns.
Let's say there is a frame F0 that has a cylinder rotating at two revolutions per second. Let frame F1 that is moving with velocity V along the length of the cylinder attach a ribbon that extends along the x-axis above the cylinder first to one end of the cylinder and then one second later attach the other end of the ribbon to the other end of the cylinder. The ribbon makes a helical pattern around the cylinder as observed by F1. Why can't every frame that has a velocity parallel to the x-axis determine which end of the cylinder the ribbon was attached to first based on the helical pattern?
David Seppala
Bastrop TX

On Monday, July 5, 2021 at 2:01:53 PM UTC-7, sep...@yahoo.com wrote:
> On Sunday, July 4, 2021 at 1:06:16 PM UTC-5, Al Coe wrote:
> > On Sunday, July 4, 2021 at 7:07:28 AM UTC-7, sep...@yahoo.com wrote:
> > > If an inertial reference frame is moving with velocity V parallel to the rest frame of the
> > > cylinder, can that frame also determine which end of the ribbon was attached to the
> > > cylinder first?
> > Of course. In terms of the original system the two cases result in a helix with -1 or +1 turns, and in terms of the moving system this corresponds to 0 or +2 turns.
> Let's say there is a frame F0 that has a cylinder rotating at two revolutions per second. Let frame F1 that is moving with velocity V along the length of the cylinder attach a ribbon that extends along the x-axis above the cylinder first to one end of the cylinder and then one second later attach the other end of the ribbon to the other end of the cylinder. The ribbon makes a helical pattern around the cylinder as observed by F1. Why can't every frame that has a velocity parallel to the x-axis determine which end of the cylinder the ribbon was attached to first based on the helical pattern?

I just explained to you why they can, and now you ask me to explain why they can't? What is wrong with you?

Again (please try to focus): For spacelike-separated attachment events the attachment that occurs first (i.e., at a lesser value of the time coordinate) depends on the system of coordinates. Regardless of which system you use, the number of turns of the ribbon (at a given value of the time coordinate) matches the rotations between the attachment events in terms of the respective system of coordinates. Now do you understand?

On Monday, July 5, 2021 at 4:33:04 PM UTC-5, Al Coe wrote:
> On Monday, July 5, 2021 at 2:01:53 PM UTC-7, sep...@yahoo.com wrote:
> > On Sunday, July 4, 2021 at 1:06:16 PM UTC-5, Al Coe wrote:
> > > On Sunday, July 4, 2021 at 7:07:28 AM UTC-7, sep...@yahoo.com wrote:
> > > > If an inertial reference frame is moving with velocity V parallel to the rest frame of the
> > > > cylinder, can that frame also determine which end of the ribbon was attached to the
> > > > cylinder first?
> > > Of course. In terms of the original system the two cases result in a helix with -1 or +1 turns, and in terms of the moving system this corresponds to 0 or +2 turns.
> > Let's say there is a frame F0 that has a cylinder rotating at two revolutions per second. Let frame F1 that is moving with velocity V along the length of the cylinder attach a ribbon that extends along the x-axis above the cylinder first to one end of the cylinder and then one second later attach the other end of the ribbon to the other end of the cylinder. The ribbon makes a helical pattern around the cylinder as observed by F1. Why can't every frame that has a velocity parallel to the x-axis determine which end of the cylinder the ribbon was attached to first based on the helical pattern?
> I just explained to you why they can, and now you ask me to explain why they can't? What is wrong with you?
>
> Again (please try to focus): For spacelike-separated attachment events the attachment that occurs first (i.e., at a lesser value of the time coordinate) depends on the system of coordinates. Regardless of which system you use, the number of turns of the ribbon (at a given value of the time coordinate) matches the rotations between the attachment events in terms of the respective system of coordinates. Now do you understand?

Let frame F0 have a cylinder of length sqrt(3)/3 light-seconds along the x-axis rotating at 2 revolutions per second. Let frame F1 have a velocity along the x-axis of sqrt(3)/2*c relative to F0. At time t0, F1 observers attach the ribbon to the top of the cylinder on the left side of the cylinder and then one second later F1 observers attach the ribbon to the top of the cylinder on the right side.
Now if we have another inertial reference frame F2, moving along the x-axis with velocity -sqrt(3)/2*c relative to F0, observers in that frame disagree as to which end of the ribbon was attached first, right?
Thanks,
David Seppala
Bastrop TX

On Monday, July 5, 2021 at 4:15:47 PM UTC-7, sep...@yahoo.com wrote:
> Let frame F0 have a cylinder of length sqrt(3)/3 light-seconds along the x-axis rotating at 2 revolutions per second. Let frame F1 have a velocity along the x-axis of sqrt(3)/2*c relative to F0. At time t0, F1 observers attach the ribbon to the top of the cylinder on the left side of the cylinder and then one second later F1 observers attach the ribbon to the top of the cylinder on the right side. Now if we have another inertial reference frame F2, moving along the x-axis with velocity -sqrt(3)/2*c relative to F0, observers in that frame disagree as to which end of the ribbon was attached first, right?

Nope, as stated previously, the order of attachment events can be different in terms of different inertial coordinate systems only if those events are spacelike-separated. You have now jumped to a scenario with a long enough duration between attachment events (compared with cylinder length) such that those events are time-like separated, and hence occur in the same temporal order in terms of every system of inertial coordinates. In this case the spatial ordering of the events differs between F1 and the others.

[Note: When you refer to "left" and "right" I'm charitably substituting lesser and greater x values, with the speed of F1 in the positive x direction, and when you refer to "observers" doing various things I'm charitably substituting "in terms of the respective inertial coordinates", and so on.]

So, now that every one of your nitwit scenarios has been thoroughly explained (you're welcome), and all your confusions have been shown to be based on nothing but trivial misunderstandings, do you have any remaining questions?

On Monday, July 5, 2021 at 7:38:23 PM UTC-5, Al Coe wrote:
> On Monday, July 5, 2021 at 4:15:47 PM UTC-7, sep...@yahoo.com wrote:
> > Let frame F0 have a cylinder of length sqrt(3)/3 light-seconds along the x-axis rotating at 2 revolutions per second. Let frame F1 have a velocity along the x-axis of sqrt(3)/2*c relative to F0. At time t0, F1 observers attach the ribbon to the top of the cylinder on the left side of the cylinder and then one second later F1 observers attach the ribbon to the top of the cylinder on the right side. Now if we have another inertial reference frame F2, moving along the x-axis with velocity -sqrt(3)/2*c relative to F0, observers in that frame disagree as to which end of the ribbon was attached first, right?
> Nope, as stated previously, the order of attachment events can be different in terms of different inertial coordinate systems only if those events are spacelike-separated. You have now jumped to a scenario with a long enough duration between attachment events (compared with cylinder length) such that those events are time-like separated, and hence occur in the same temporal order in terms of every system of inertial coordinates. In this case the spatial ordering of the events differs between F1 and the others.
>
> [Note: When you refer to "left" and "right" I'm charitably substituting lesser and greater x values, with the speed of F1 in the positive x direction, and when you refer to "observers" doing various things I'm charitably substituting "in terms of the respective inertial coordinates", and so on.]
>
> So, now that every one of your nitwit scenarios has been thoroughly explained (you're welcome), and all your confusions have been shown to be based on nothing but trivial misunderstandings, do you have any remaining questions?

When I asked if frame F1 and F2 disagree on which end of the ribbon was attached first, you replied "Nope". With your great insight I'm sure your realize that in terms of F0 in this scenario, F0 observers see that the all points of the ribbon were attached to the top of the rotating cylinder simultaneously. So if F1 is moving with velocity V along the x-axis relative to F0, and F2 is moving with velocity -V along the x-axis relative to F0, and observers in F0 attach all points of the ribbon simultaneously to the top of the rotating cylinder, which end of the ribbon is attached to the cylinder first as you say both F1 and F2 agree to?
David Seppala
Bastrop TX

On Tuesday, July 6, 2021 at 5:12:19 AM UTC-7, sep...@yahoo.com wrote:
> When I asked if frame F1 and F2 disagree on which end of the ribbon was attached first, you replied "Nope".

I did indeed, because for your stated scenario the attachment events are time-like separated.

> With your great insight I'm sure your realize that in terms of F0 in this scenario, F0 observers
> see that the all points of the ribbon were attached to the top of the rotating cylinder simultaneously.

No they do not. You specified that the coordinate system F1 (x',t') is moving in the positive x direction with speed sqrt(3)/2, which implies the cylinder is moving at that speed in the negative x' direction in terms of F1, and hence the attachment events in terms of F0 are (0,0), (1/sqrt(3),1) and in terms of F1 are (0,0), (-1/sqrt(3),1) and in terms of F2 are (0,0), (5/sqrt(3),3).

Now you've revealed that you messed up your specification, and what you meant to say is that F1 is moving in the negative (not positive) x direction at speed sqrt(3)/2. In other words, you got your directions reversed. Sheesh. For this scenario the attachment events in terms of F0 are (0,0), (1/sqrt(3),0) and in terms of F1 are (0,0), (5/sqrt(3),1) and in terms of F2 are (0,0), (2/sqrt(3), -1). Hence the attachments have the opposite temporal order in terms of F1 and F2.

> So if F1 is moving with velocity V along the x-axis relative to F0, and F2 is moving with
> velocity -V along the x-axis relative to F0...

Again, you have your directions reversed. If your intent is for the attachment events to be simultaneous in terms of F0, then F1 must be moving in the negative x direction. Sheesh.

> ...and observers in F0 attach all points of the ribbon simultaneously to the top of the
> rotating cylinder, which end of the ribbon is attached to the cylinder first as you say
> both F1 and F2 agree to?

As always, you are confused. For the scenario you stated, the attachment event at the origin unequivocally occurs prior to the other attachment event, but for the new scenario in which the motions of F1 and F2 are the opposite of what you specified, the attachment event at the origin is prior to the other attachment in terms of F1, and later than the other attachment in terms of F2.

So, now that we've fully explained yet another of your nitwit scenarios, showing that (as always) your confusion was based on nothing but misunderstanding (combined with an inability to even formulate your questions accurately), do you have any remaining questions?

On Tuesday, July 6, 2021 at 8:21:56 AM UTC-5, Al Coe wrote:
> On Tuesday, July 6, 2021 at 5:12:19 AM UTC-7, sep...@yahoo.com wrote:
> > When I asked if frame F1 and F2 disagree on which end of the ribbon was attached first, you replied "Nope".
> I did indeed, because for your stated scenario the attachment events are time-like separated.
> > With your great insight I'm sure your realize that in terms of F0 in this scenario, F0 observers
> > see that the all points of the ribbon were attached to the top of the rotating cylinder simultaneously.
> No they do not. You specified that the coordinate system F1 (x',t') is moving in the positive x direction with speed sqrt(3)/2, which implies the cylinder is moving at that speed in the negative x' direction in terms of F1, and hence the attachment events in terms of F0 are (0,0), (1/sqrt(3),1) and in terms of F1 are (0,0), (-1/sqrt(3),1) and in terms of F2 are (0,0), (5/sqrt(3),3).
>
> Now you've revealed that you messed up your specification, and what you meant to say is that F1 is moving in the negative (not positive) x direction at speed sqrt(3)/2. In other words, you got your directions reversed. Sheesh. For this scenario the attachment events in terms of F0 are (0,0), (1/sqrt(3),0) and in terms of F1 are (0,0), (5/sqrt(3),1) and in terms of F2 are (0,0), (2/sqrt(3), -1). Hence the attachments have the opposite temporal order in terms of F1 and F2.
> > So if F1 is moving with velocity V along the x-axis relative to F0, and F2 is moving with
> > velocity -V along the x-axis relative to F0...
>
> Again, you have your directions reversed. If your intent is for the attachment events to be simultaneous in terms of F0, then F1 must be moving in the negative x direction. Sheesh.
>
> > ...and observers in F0 attach all points of the ribbon simultaneously to the top of the
> > rotating cylinder, which end of the ribbon is attached to the cylinder first as you say
> > both F1 and F2 agree to?
> As always, you are confused. For the scenario you stated, the attachment event at the origin unequivocally occurs prior to the other attachment event, but for the new scenario in which the motions of F1 and F2 are the opposite of what you specified, the attachment event at the origin is prior to the other attachment in terms of F1, and later than the other attachment in terms of F2.
>
> So, now that we've fully explained yet another of your nitwit scenarios, showing that (as always) your confusion was based on nothing but misunderstanding (combined with an inability to even formulate your questions accurately), do you have any remaining questions?

In an early post I thought we agreed any frame can look at one end of the rotating cylinder after the ribbon has been attached and determine which end was attached first. When I do an attachment of a ribbon to a cylinder, if one end is attached first and then the other end is attached later even if the cylinder is moving along the x-axis I can tell which end was attached first since the two patterns are different. That is true even if the cylinder is moving with a positive or negative velocity with respect to my frame. Now are you saying that is no longer the case?
David Seppala
Bastrop TX

On Tuesday, July 6, 2021 at 8:17:53 AM UTC-7, sep...@yahoo.com wrote:
> In an early post I thought we agreed any frame can look at one end of the rotating
> cylinder after the ribbon has been attached and determine which end was attached first.

Of course, merely by looking at whether we have positive or negative (or zero) turns. This was thoroughly explained previously.

> When I do an attachment of a ribbon to a cylinder, if one end is attached first and then
> the other end is attached later ... I can tell which end was attached first since the two
> patterns are different.

Of course, that's what was thoroughly explained to you previously. Sheesh.

> Now are you saying that is no longer the case?

Huh? What is wrong with you? In your latest example, in terms of F0 the attachments are simultaneous and there are zero net turns of the ribbon, and in terms of F1 the attachment event at the origin precedes the other attachment and the result is a helix with positive net turns, and in terms of F1 the attachment event at the origin a later than the other attachment and the result is a helix with negative net turns. Hence merely by examining the net turns at any given value of the time coordinate of a given frame, we can determine the temporal order of the attachment events in terms of that frame.

Now do you finally understand? If not, what part don't you understand?

On Tuesday, July 6, 2021 at 10:46:15 AM UTC-5, Al Coe wrote:
> On Tuesday, July 6, 2021 at 8:17:53 AM UTC-7, sep...@yahoo.com wrote:
> > In an early post I thought we agreed any frame can look at one end of the rotating
> > cylinder after the ribbon has been attached and determine which end was attached first.
> Of course, merely by looking at whether we have positive or negative (or zero) turns. This was thoroughly explained previously.
> > When I do an attachment of a ribbon to a cylinder, if one end is attached first and then
> > the other end is attached later ... I can tell which end was attached first since the two
> > patterns are different.
>
> Of course, that's what was thoroughly explained to you previously. Sheesh..
> > Now are you saying that is no longer the case?
> Huh? What is wrong with you? In your latest example, in terms of F0 the attachments are simultaneous and there are zero net turns of the ribbon, and in terms of F1 the attachment event at the origin precedes the other attachment and the result is a helix with positive net turns, and in terms of F1 the attachment event at the origin a later than the other attachment and the result is a helix with negative net turns. Hence merely by examining the net turns at any given value of the time coordinate of a given frame, we can determine the temporal order of the attachment events in terms of that frame.
>
> Now do you finally understand? If not, what part don't you understand?
I assume you had a typo using F1 twice instead of F1 and F2. I can look at a helix around a cylinder and instead of counting net turns across the cylinder, all I have to do to determine which end was attached first is look at one end of the cylinder and the direction the ribbon leaves that end. It does not matter whether the cylinder and ribbon are traveling in the positive x direction or the negative x direction relative to me when I make that observation.
David Seppala
Bastrop TX

On Tuesday, July 6, 2021 at 9:29:03 AM UTC-7, sep...@yahoo.com wrote:
> I can look at a helix around a cylinder and instead of counting net turns across the
> cylinder, all I have to do to determine which end was attached first is look at one end
> of the cylinder and the direction the ribbon leaves that end.

That's just an abbreviated way of establishing the net turns under the assumption that you attach each part of the wire or ribbon to the cylinder simultaneously in terms of (say) F0, given that the ribbon is forced to be straight in terms of that system of coordinates. The advantage of counting net turns is that we can dispense with that straightness stipulation, so it's completely general. (You don't see the value of this because you erroneously imagine that specifying the end points suffices to specify the other points of the ribbon.)

> It does not matter whether the cylinder and ribbon are traveling in the positive x direction
> or the negative x direction relative to me when I make that observation.

Huh? What is wrong with you? Given that the ribbon is straight and parallel to the axis in terms of F0, it is a helix winding in one direction in terms of F1, and a helix winding in the other direction in terms of F2, consistent with the temporal ordering of the attachment events in terms of the respective coordinate systems.

Now do you finally understand?

On Tuesday, July 6, 2021 at 12:03:12 PM UTC-5, Al Coe wrote:
> On Tuesday, July 6, 2021 at 9:29:03 AM UTC-7, sep...@yahoo.com wrote:
> > I can look at a helix around a cylinder and instead of counting net turns across the
> > cylinder, all I have to do to determine which end was attached first is look at one end
> > of the cylinder and the direction the ribbon leaves that end.
> That's just an abbreviated way of establishing the net turns under the assumption that you attach each part of the wire or ribbon to the cylinder simultaneously in terms of (say) F0, given that the ribbon is forced to be straight in terms of that system of coordinates. The advantage of counting net turns is that we can dispense with that straightness stipulation, so it's completely general. (You don't see the value of this because you erroneously imagine that specifying the end points suffices to specify the other points of the ribbon.)
> > It does not matter whether the cylinder and ribbon are traveling in the positive x direction
> > or the negative x direction relative to me when I make that observation..
> Huh? What is wrong with you? Given that the ribbon is straight and parallel to the axis in terms of F0, it is a helix winding in one direction in terms of F1, and a helix winding in the other direction in terms of F2, consistent with the temporal ordering of the attachment events in terms of the respective coordinate systems.
> Now do you finally understand?
okay, I got it.
David Seppala
Bastrop TX