# Is relativity of simultaneity measurable?

In $$S$$, both the rail clocks and the ground clocks are $$L$$ units apart,

No, they are not, you just need to use the reciprocal Lorentz transforms to prove that your claim is false.

so the A clocks line up at the same time as the B clocks,

No, they don't , see above.

I challenged you on this very issue when we started talking about the setup for detecting the "rod bending". You never answered.
Didn't I? Probably because it's trivial in principle (although complex in practice, particularly if you want femtosecond precision.)
Try a photocell and light source on each clock, with an aligned mirror on the clock it passes. The photocell is activated when the passing mirror reflects the light source.

No, they are not, you just need to use the reciprocal Lorentz transforms to prove that your claim is false.
You are wrong. We specifically set up the experiment to make the passing events simultaneous in $$S$$; ie in $$S$$, both the rail clocks and the ground clocks are $$L$$ units apart.

The rail clocks are $$L\gamma$$ units apart in $$S'$$, and $$L$$ units apart in $$S$$.
The ground clocks are $$L/\gamma$$ units apart in $$S'$$, and $$L$$ units apart in $$S$$.
This is basic length contraction.

No, they don't , see above.
Yes, they do. In $$S$$, the A clocks line up at the same time as the B clocks. Your equations:
$$t_A=t_B=t_0$$

This is basic length contraction.

Yes, you get this type of error every time you use the dumbed down approach of length contraction. You need to use the complete Lorentz transforms and you will realize your mistake.

Didn't I?

No, you didn't. Because you couldn't.

Try a photocell and light source on each clock, with an aligned mirror on the clock it passes. The photocell is activated when the passing mirror reflects the light source.

This is nonsense.

Yes, you get this type of error
What error?
The rail clocks are $$L\gamma$$ units apart in $$S'$$, and $$L$$ units apart in $$S$$.
The ground clocks are $$L/\gamma$$ units apart in $$S'$$, and $$L$$ units apart in $$S$$.

You need to use the complete Lorentz transforms and you will realize your mistake.
$$t_B - t_A = 0$$
$$t'_B - t'_A = Lv\gamma/c^2$$

The events happen at the same time in $$S$$, as measured by $$S$$ clocks.
They happen at different times in $$S'$$, as measured by $$S'$$ clocks.
We've measured relative simultaneity.

This is nonsense.
No, it's pretty straightforward.

Poor Tach.

What error?
The rail clocks are $$L\gamma$$ units apart in $$S'$$, and $$L$$ units apart in $$S$$.
The ground clocks are $$L/\gamma$$ units apart in $$S'$$, and $$L$$ units apart in $$S$$.

$$t_B - t_A = 0$$
$$t'_B - t'_A = Lv\gamma/c^2$$

Like I said, when you use the dumbed down approach of length contraction, you get errors in return.
Using the full Lorentz transforms, you get the correct answers:

In $$S'$$:

$$x'_A=0$$
$$x'_B=L$$
$$x'_B-x'_A=L$$

In $$S$$:

$$x_A=\gamma(x'_A-vt'_A)=-\gamma v t'_A$$
$$x_B=\gamma(x'_B-vt'_B)=\gamma L - \gamma v t'_B$$
$$x_B-x_A=\gamma L -\gamma v (t'_B-t'_A)=\gamma L-\gamma v \gamma Lv / c^2=\frac{L}{\gamma}$$

So, obviously, the pairs of clocks don't line up in either frame, exactly as I told you. No matter how you twist and turn, your setup is invalid and you will never be able to run a "Ros detection" test, despite your disrespect of the mainstream physics community.

Like I said, when you use the dumbed down approach of length contraction, you get errors in return.
Using the full Lorentz transforms, you get the correct answers:

In $$S'$$:

$$x'_A=0$$
$$x'_B=L$$
$$x'_B-x'_A=L$$
Wrong starting condition.
$$x'_B=L\gamma$$

Wrong starting condition.
$$x'_B=L\gamma$$

This only make your explanation even more invalid: when the clocks at the A endpoint coincide, the B endpoints are at respectively $$L\gamma$$ and $$\frac{L}{\gamma}$$. You will never be able to come up with a workable experimental setup capable of measuring RoS. Never.

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This only make youe explanation even more invalid: when the clocks at the A endpoint coincide, the B endpoints are at respectively $$L\gamma$$ and $$\frac{L}{\gamma}$$. You will never be able to come up with a workable experimental setup capable of measuring RoS. Never.

Tach, are you saying that there is no experimental set up that with today's technology RoS can be measured?

Tach, are you saying that there is no experimental set up that with today's technology RoS can be measured?

The opposite, the technology is available , as I demonstrated to Pete. What Pete cannot do is to put together a coherent theory for the experiment. He simply fumbles from one theoretical mistake to another, as shown above.

The opposite, the technology is available , as I demonstrated to Pete. What Pete cannot do is to put together a coherent theory for the experiment. He simply fumbles from one theoretical mistake to another, as shown above.

If I understand your objection, it is because the train is moving relativistically.., so from either frame—the train's or the embankment's—the other is length contracted and their respective points A and B do not line up when their midpoints M and M' line up. Correct?

If I understand your objection, it is because the train is moving relativistically.., so from either frame—the train's or the embankment's—the other is length contracted and their respective points A and B do not line up when their midpoints M and M' line up. Correct?
...and the misalignment happens no matter how Pete tries to fiddle the spatial separations of the clocks.

If I understand your objection, it is because the train is moving relativistically.., so from either frame—the train's or the embankment's—the other is length contracted and their respective points A and B do not line up when their midpoints M and M' line up. Correct?

...and the misalignment happens no matter how Pete tries to fiddle the spatial separations of the clocks.

...and you are saying that the only way to measure RoS would be if the ends could somehow align simultaneously in both frames, at which time you would measure what? Lack of RoS?

...and you are saying that the only way to measure RoS would be if the ends could somehow align simultaneously in both frames, at which time you would measure what? Lack of RoS?
I can see you are still struggling with the setup.

...and you are saying that the only way to measure RoS would be if the ends could somehow align simultaneously in both frames, at which time you would measure what? Lack of RoS?

I can see you are still struggling with the setup.

Actually I'm just pointing out that if there were no misalignment in either frame, then there would be no RoS to measure. But that's okay, keep digging.

Actually I'm just pointing out that if there were no misalignment in either frame, then there would be no RoS to measure. But that's okay, keep digging.

I think what Tach is saying is that since A and B do not line up in either frame any measurements made in the two frames could not be compared directly.

I'm not sure that is really necessisary though. It seems if you can establish that the flashes occur simultaneously in one frame and sequentially in the other, you have proof of RoS. Einstein's hypothetical goes further than that but it was a teaching tool. You don't really need to know anything about what parts of the train were aligned with the embankment points A and B, or even that the flashes were simutaneous in the embankment frame, or even simutaneous at all. All you need to know is that the event(s) were measured to occurr with a different timing when measured from the two frames.

All Pete needed was the embankment frame, a rest frame for the simultaneous measurement of two events, and an observer in motion relative to the embankment frame. One observer measures the events as simutaneous (whether they are in fact or not) and the other measures them as sequential = RoS.

I think what Tach is saying is that since A and B do not line up in either frame any measurements made in the two frames could not be compared directly.

I'm not sure that is really necessisary though. It seems if you can establish that the flashes occur simultaneously in one frame and sequentially in the other, you have proof of RoS. Einstein's hypothetical goes further than that but it was a teaching tool. You don't really need to know anything about what parts of the train were aligned with the embankment points A and B, or even that the flashes were simutaneous in the embankment frame, or even simutaneous at all. All you need to know is that the event(s) were measured to occurr with a different timing when measured from the two frames.

All Pete needed was the embankment frame, a rest frame for the simultaneous measurement of two events, and an observer in motion relative to the embankment frame. One observer measures the events as simutaneous (whether they are in fact or not) and the other measures them as sequential = RoS.

That sounds a lot like your earlier post:

Two observers separated by some distance during a thunder storm. Each with synchronized clocks. They don't even have to be ideally synchronized for this, government work standard is close enough. They each record when they see a flash of lightning and how llong between the flash and the clap of thunder that follows. When the compare their measurements they find that they disagree on the time of both when and how long between.

Seems doable to me!

That's not relative simultaneity.

Do you understand why Pete said your earlier post was not RoS? If so, can you tell me what you have changed in your newer post that resolves the problem?

When the clocks at the A endpoint coincide, the B endpoints are at respectively $$L\gamma$$ and $$\frac{L}{\gamma}$$.
This is the situation in $$S'$$.
Now check in $$S$$:
When the clocks at the A endpoint coincide, the B endpoints are at respectively $$L$$ and $$L$$.

Tach, this is really simple - the experiment is arranged so that the clocks line up simultaneously in the lab frame.
Is that impossible?