1 A rigid rod with 8 clocks

The first experiment is called clock synchronisation.
Halfway in between clock #4 and #5, there is a light source which emits a reset signal. The setup is such that the length lightpath to each clock is the same. Using rule 1 the light signal will reach all the clocks simultaneous. This is important because all the clocks at any moment will all show the same count.

The second experiment starts with making an exact copy of rod #1. Also attached to each clock there is an engine which can be fired with a standard burst in either the forward or backward direction. Each clock also has an observer.
The second experiment consists that each observer on rod #2 fires his engine with a standard burst in the same direction when his clock is reset. This burst will give the rod a certain speed v.
The now moving observers will perform the next tasks when they reach the next clock at rest: They will write down the reading of the clock at rest and the reading of their own moving clock.
This is the result:
They are the same for all observers. The number of counts of the moving clocks is less than the number of counts of the clocks at rest. This is not so strange because it means that the physical forces which influence the behaviour of each clock are identical. Specific what this means is that all the moving clocks stay synchronised. This is rule 2. You can repeat this experiment, but still, rule 2 applies.

Experiment 3 is almost identical to experiment 2. That means all the engines are fired after the reset signal is received. This defines the starting condition of experiment 3. The starting condition of experiment 3 is a moving rod with the speed v. Experiment 3 involves that a certain moment the light signal between clock #4 and #5 of the moving rod issues a reset signal. Like before the moving observers write down the results when they reach the next clock at rest. This is the result:
All the observers write down the same number of counts for the clocks at rest. For the moving clocks, the results are different. The clock in front will have the lowest count. The clock at the back the highest count. Physical the clock in the back is reset the first.

Experiment 4 is the same as Experiment 3 with the difference that we again make an exact copy of rod #2 before the reset signal is issued. This is rod #3. The extra complication is that in experiment 4 both the moving rod #2 and #3 receive the same reset signal. The next complication is that when each of the clocks of rod #3 receives a reset signal also the engine is fired in the same direction as experiment #2. However, this will also give a physical complication, because the engine in the back will start first and in front of the latest. As such the physical forces will try to compress the rod. The opposite case is also possible. That means physical forces will try to expand the length of the physical rod.

Experiment 2 belongs to what you can call a symmetrical experiment. This is the case if you start from a state at rest than in either direction the results are the same i.e. how higher the speed how slower the moving clock ticks.
What is also the case, after reaching a certain speed and the speed is decreased the clock starts to run faster until the speed reaches zero.

Experiment 4 belongs to what you can call an asymmetrical experiment. This is the case when the starting condition involves a moving rod. In that case, when a clock receives a burst in the same direction as the original speed the clock will start to run slower. In the opposite direction, it is first faster and then slower.

These results are maybe different as what is expected. They challenge the concept of what means at rest.

2 A rigid rod with 8 clocks

3 A rigid rod with 8 clocks

These are inconsistent. Everything following is useless.

Tom Roberts

4 A rigid rod with 8 clocks

>	Consider a rod with 8 clocks, equally spaced, a distance l apart. The rod is considered at rest. This implies that the speed of light c in all directions is the same. We call this rule 1.

What would it be otherwise? And 8 clocks, come on, you can find a better excuse in your defence. Jose Gonzalez

5 A rigid rod with 8 clocks

>

The first experiment is called clock synchronisation. Halfway in between clock #4 and #5, there is a light source which emits a reset signal. The setup is such that the length lightpath to each clock is the same. Using rule 1 the light signal will reach all the clocks simultaneous. This is important because all the clocks at any moment will all show the same count.

You may put the clocks all you want, but will never affect the speed of light and anything. Clocks are not related to light in anyway.

6 A rigid rod with 8 clocks

How do you synchronize four clocks #1, #2, #3 and #4 (in a straight line)? You place a light source halfway between the two clock #2 and #3 at x23. and issue a reset signal in both directions towards two beam splitters at x12 (halfway between the clocks #1 and #2) and at x34 (halfway between the clocks #3 and #4). The rest is the same as above. This same strategy can also be used for eight clocks.

7 A rigid rod with 8 clocks

The starting point of clock synchronization is that all the clocks are at rest and that the speed of light is the same in all directions.
In noway the speed of light is affected.
The clocks involved use light signals. See for example page 12 of the book: "SpaceTime physics" by E.F. Taylor and J.A.Wheeler, second edition. The whole issue is that all clocks at rest behave the same.

A different issue is that clocks which move relative to these clocks at rest behave (physical) differently. They count slower.

Nicolaas Vroom.

8 A rigid rod with 8 clocks

9 A rigid rod with 8 clocks

10 A rigid rod with 8 clocks

It simply is not possible for eight clocks to be equally spaced along the rod, and yet the light paths from the center of the rod to each of them are all equal. Clock #8 is OBVIOUSLY further away than clock #4, etc.

Hint: light travels in straight lines; rods are also straight.

>

[...]

When you change the physical description like that, then everything is changed. Changing in the middle of a discussion just confuses everybody, INCLUDING YOURSELF -- the thread splits with different people following different descriptions, and becomes impossible to follow.

Also: I ignore excessively complicated scenarios. Figure out what is the essence of what you are trying to discuss, and construct a simpler scenario involving just it.

Tom Roberts

11 A rigid rod with 8 clocks

>	On 11/9/19 6:13 AM, Nicolaas Vroom wrote:

>>	On Friday, 8 November 2019 22:55:53 UTC+1, tjrob137 wrote:

>>>	On 11/8/19 9:35 AM, Nicolaas Vroom wrote:

>>>>	Halfway in between clock #4 and #5, there is a light source which emits a reset signal. The setup is such that the length lightpath to each clock is the same.

>>>	These are inconsistent. Everything following is useless.

>>	I do not see any inconsistency in the text.

>	It simply is not possible for eight clocks to be equally spaced along the rod, and yet the light paths from the center of the rod to each of them are all equal. Clock #8 is OBVIOUSLY further away than clock #4, etc.

Your argument rests on your assumption that this was meant. AFAICS, it is a straw man argument. Jose Gonzalez

12 A rigid rod with 8 clocks

>	Tom Roberts wrote:

>>	On 11/9/19 6:13 AM, Nicolaas Vroom wrote:

>>>	On Friday, 8 November 2019 22:55:53 UTC+1, tjrob137 wrote:

>>>>	On 11/8/19 9:35 AM, Nicolaas Vroom wrote:

>>>>>

Halfway in between clock #4 and #5, there is a light source which emits a reset signal. The setup is such that the length lightpath to each clock is the same.

>>>>	These are inconsistent. Everything following is useless.

>>>	I do not see any inconsistency in the text.

>>	It simply is not possible for eight clocks to be equally spaced along the rod, and yet the light paths from the center of the rod to each of them are all equal. Clock #8 is OBVIOUSLY further away than clock #4, etc.

>	Lbhe nethzrag erfgf ba lbhe nffhzcgvba gung guvf jnf zrnag. NSNVPF, vg vf n fgenj zna nethzrag.

You have no tensors to prove any of it. Shut up and repent.

13 A rigid rod with 8 clocks

No, my argument rests on the original description of the physical situation:
"a rod with 8 clocks, equally spaced, a distance l apart" "numbered from #1 to #8."
and
"Halfway in between clock #4 and #5, there is a light source which emits a reset signal. The setup is such that the length lightpath to each clock is the same."

I challenge you to display a physical arrangement that meets both specifications, without invoking magic.

[Vroom later said that he intended to invoke a bunch of beamsplitters, or a bunch of sources, essentially invoking magic.]

14 A rigid rod with 8 clocks

15 A rigid rod with 8 clocks

16 A rigid rod with 8 clocks

Let me call this initial inertial frame K.

>	The first experiment is called clock synchronisation. Halfway in between clock #4 and #5, there is a light source which emits a reset signal. The setup is such that the length lightpath to each clock is the same.

As you subsequently explained, there are additional components involved to make the light paths equal.

It is important to describe the physical situation completely.

>	Using rule 1 the light signal will reach all the clocks simultaneous. This is important because all the clocks at any moment will all show the same count.

By "any moment" you mean "observed simultaneously in K, by observers co-located with each clock".

It is important to describe things precisely.

>	The second experiment starts with making an exact copy of rod #1.

Presumably all of its clocks are synchronized in K, and with all the clocks of the original rod.

It is important to describe things completely.

>

Also attached to each clock there is an engine which can be fired with a standard burst in either the forward or backward direction. Each clock also has an observer. The second experiment consists that each observer on rod #2 fires his engine with a standard burst in the same direction when his clock is reset.

This "when" is ambiguous. I presume the observers are not clairvoyant, so each one actually fires their engine a negligibly short time after their clock receives the reset signal. So they all fire simultaneously in K.

>	This burst will give the rod a certain speed v.

Let me call this second inertial frame K', and we agree not to discuss it before or during the firing of the engines.

>	The now moving observers will perform the next tasks when they reach the next clock at rest: They will write down the reading of the clock at rest and the reading of their own moving clock.

OK. Of course the leading clock at rest in K' never meets a clock at rest in K, so ignore it.

>	This is the result: They are the same for all observers. The number of counts of the moving clocks is less than the number of counts of the clocks at rest.

Yes. The clocks at rest in K' are all synchronized in K -- NOT K'. Seven of them meet the next clock at rest in K at the same time in K, and the same time displayed on their own clocks (which is different from the time indicated by the clocks at rest in K).

Note that an observer at rest in K' would describe the clocks at rest in K as closer together than the clocks at rest in K', and none of the clocks are synchronized in K'. In terms of the coordinates of K', the clocks successively meet in pairs, but when each clock from K' meets the clock in K, all clocks in K indicate the same time, and all clocks in K' indicate the same time (that is different from those in K).

>	This is not so strange because it means that the physical forces which influence the behaviour of each clock are identical.

None of these forces influence the behavior of any clock in any way.

I assume the engines are not so powerful that they damage the clocks of the second rod.

>	Specific what this means is that all the moving clocks stay synchronised. This is rule 2. You can repeat this experiment, but still, rule 2 applies.

Your "rule 2" is VERY LIMITED, and applies to this physical situation only.

>	Experiment 3 is almost identical to experiment 2. That means all the engines are fired after the reset signal is received.

Oh. Then you assumed that the observers were indeed clairvoyant in experiment 2. So take my discussion above and apply it here.

>	This defines the starting condition of experiment 3. The starting condition of experiment 3 is a moving rod with the speed v.

This last sentence is different from what you said before, and inconsistent with the engines being fired AFTER the reset signal is received. One paragraph earlier the starting condition of experiment 3 was the same as experiment 2: both rods at rest in K.

It is important to describe things consistently.

>

Experiment 3 involves that a certain moment the light signal between clock #4 and #5 of the moving rod issues a reset signal. Like before the moving observers write down the results when they reach the next clock at rest. This is the result: All the observers write down the same number of counts for the clocks at rest. For the moving clocks, the results are different. The clock in front will have the lowest count. The clock at the back the highest count. Physical the clock in the back is reset the first.

This is wrong. See above.

>	[... too complicated to bother with.]

You MUST describe the physical situation completely AND PRECISELY AND CONSISTENTLY. Details matter, because relativity is both complicated and subtle. Whenever you say "synchronized" you must also state in which frame it applies. Whenever you say "when", you must reword to state "simultaneously in frame ...". Do not ever say "at any moment", but rather specify which frame you are using and specify values of its time coordinate. And don't assume observers are clairvoyant.

Tom Roberts

17 A rigid rod with 8 clocks

A picture says more than a thousand words:

light source : * * * * v * * * * #1 #2 #3 #4 #5 #6 #7 #8

[You should have asked yourself why there are *8* clocks and why the light source is placed between clock *#4 and #5*.]

As I already indicated, this description is open to INTERPRETATION (“length lightpath” is not a word).

And for whatever reason (actually, from my own experience with you I have a fairly good idea why) you have (again) chosen THE WORST POSSIBLE INTERPRETATION, namely one leading to a setup that cannot be realized.

Honi soit qui mal y pense.

18 A rigid rod with 8 clocks

19 A rigid rod with 8 clocks

> >

Also attached to each clock there is an engine which can be fired with a standard burst in either the forward or backward direction. Each clock also has an observer. The second experiment consists that each observer on rod #2 fires his engine with a standard burst in the same direction when his clock is reset.

>	This "when" is ambiguous. I presume the observers are not clairvoyant, so each one actually fires their engine a negligibly short time after their clock receives the reset signal. So they all fire simultaneously in K.

There is nothing clairvoyant involved. Each of the moving observers uses the same script what to do and when at which specific clock count.

> >	This is the result: They are the same for all observers. The number of counts of the moving clocks is less than the number of counts of the clocks at rest.

>	Yes. The clocks at rest in K' are all synchronized in K -- NOT K'. Seven of them meet the next clock at rest in K at the same time in K, and the same time displayed on their own clocks (which is different from the time indicated by the clocks at rest in K).

Don't use the concept of time. Use clock counts.
All the moving observing observers observe the same clock count of the clocks at rest and all the observers at rest observe the same clock count of the moving clocks (assuming there is a clock)

>	In terms of the coordinates of K', the clocks successively meet in pairs, but when each clock from K' meets the clock in K, all clocks in K indicate the same time, and all clocks in K' indicate the same time (that is different from those in K).

Okay. For simplicity use counts. The issue is that the moving clocks show the lowest count compared with the clocks at rest.

> >	This is not so strange because it means that the physical forces which influence the behaviour of each clock are identical.

>	None of these forces influence the behavior of any clock in any way.

The physical forces, in this case, are the engines involved to give the clock a certain speed in either direction.

> >	Specific what this means is that all the moving clocks stay synchronised. This is rule 2. You can repeat this experiment, but still, rule 2 applies.

>	Your "rule 2" is VERY LIMITED, and applies to this physical situation only.

This rule is very powerful because it means that all the moving clocks stay synchronised if you control the engines using the same script. A specific script could, for example, be: to move from A to B and back to A.

> >	Experiment 3 is almost identical to experiment 2. That means all the engines are fired after the reset signal is received.

>	Oh. Then you assumed that the observers were indeed clairvoyant in experiment 2. So take my discussion above and apply it here.

No, they follow the same script.

> >	This defines the starting condition of experiment 3. The starting condition of experiment 3 is a moving rod with the speed v.

>

This last sentence is different from what you said before, and inconsistent with the engines being fired AFTER the reset signal is received. One paragraph earlier the starting condition of experiment 3 was the same as experiment 2: both rods at rest in K. It is important to describe things consistently.

Experiment 3 involves first Experiment 1 and thereafter Experiment 2. In total you perform the following:
1) You start with 8 clocks at rest. (rod 1)
2) You perform the synchronization procedure: issue a reset signal.
3) You copy all the 8 clocks (rod 2)
4) You give all the engines of rod 2 a boost at a certain clock count. (now you have a moving rod).
In this case, the next time when two observers meet (one at rest and one moving) all the readings of the clocks at rest will be the same. The clock readings of the moving clock will also all be the same.
5) Now experiment 3 starts.
You perform the synchronization procedure with rod 2: issue a reset signal in the same direction as in step 2.
6) In this case, the next time when two observers meet all the readings of the clocks at rest will be the same. The clock readings of the moving clock will all be different.

From a practical point of view rod 1 (at rest) should contain extra clocks.

> >	All the observers write down the same number of counts for the clocks at rest. For the moving clocks, the results are different. The clock in front will have the lowest count. The clock at the back the highest count. Physical the clock in the back is reset the first.

>	This is wrong. See above.