Spin Counter: Can a train's length really dilate?

[James S Saint]

If we get on a train and time the train’s travel over 1000 meters, we can calculate the train’s velocity;

v = dx/dt

But if our watch is running slow, we will measure incorrectly and think the train was going faster than it really was.

v’ = dx/dt’

We know that when something moves very quickly, its clocks will run slower. So we know that we don’t have to have a broken watch for us to measure the wrong velocity. But the equation v’ = dx/dt’ requires that we make a choice that either our velocity measured, v’ is wrong or the length of the track has shortened, dx’, just because we were moving.

Lorentz
The Lorentz equations seem to have chosen to say that our distance has “really” shortened rather than say that we are merely experiencing the effects of a slower clock thus not measuring the “real” velocity. Why is that?

The result of this choice is that we have “relativity of simultaneity” saying that someone will think that 2 events happened at the same time while another thinks they happened at different times rather than having someone think he was going at one speed and another thinks that he was going at a different speed.

The Lorentz equations assume there is a "real" velocity thus there cannot be a "real" length.

Is there some reason for that Lorentz/Einstein choice?

Transverse Spin Counter
If we mount a transverse spin counter on the train and count the number of transverse spins during the train’s 1000 meter run, the Lorentz equations will yield the same number of spins as anyone at the station would count for that same length of time, especially if it is optic, because transverse time isn’t effected by linear motion and certainly optic time isn't. The spin counter would correct for the time dilated slower clock and measure the correct velocity.

So can we say that if a train has a spin counter on it, its length, “dx’ “ doesn’t dilate and thus when it believes things are simultaneous they really will be?

Our other choice is to say that due to Lorentz equations we must accept “relativity of count” wherein our otherwise unaffected count of anything will have to change merely because we were moving (maybe now we know where that missing passenger went?).

 

[Doc Al]

We know that when something moves very quickly, its clocks will run slower.

That's not true. Unless your clocks are broken, they run just fine. Relativity says that when you observe a moving clock you will measure it to run slow according to your clocks. With respect to the train, your clocks are not moving. If you on the train measure the rate of a clock that is stationary with the track, then you will find that the track clock runs slow according to your train clocks.

So we know that we don’t have to have a broken watch for us to measure the wrong velocity. But the equation v’ = dx/dt’ requires that we make a choice that either our velocity measured, v’ is wrong or the length of the track has shortened, dx’, just because we were moving.

If you on the train are doing the measurements, you would of course use your own clocks and measuring rods. You wouldn't measure time using clocks in some other frame, since you know they run slow.

You seem to be thinking that the train is 'really' moving. Which misses the point of relativity.

 

[Passionflower]

It is possible for a traveler to have a clock show coordinate time or maximum aging. The rate of those clocks would be adjusted dynamically based on the proper acceleration in all directions. Adjusting clock rates is not uncommon, even the GPS clocks in satellites are adjusted although their adjustments are not dynamic.

 

[James S Saint]

That's not true. Unless your clocks are broken, they run just fine. Relativity says that when you observe a moving clock you will measure it to run slow according to your clocks. With respect to the train, your clocks are not moving. If you on the train measure the rate of a clock that is stationary with the track, then you will find that the track clock runs slow according to your train clocks.


If you on the train are doing the measurements, you would of course use your own clocks and measuring rods. You wouldn't measure time using clocks in some other frame, since you know they run slow.

You seem to be thinking that the train is 'really' moving. Which misses the point of relativity.

So are you saying that the train "really" isn't moving? Or are you restoring the Twin Clocks paradox? I thought we had that one resolved. Or are you saying that neither twin aged differently?

You can of course reverse the "mover", but how does that change the situation?

 

[Passionflower]

You seem to be thinking that the train is 'really' moving. Which misses the point of relativity.

I fully agree.

But, practically speaking, the train accelerated and not the Earth right? So if a traveler goes on the train and then takes the next train back, his age is in fact less than the observer who saw the train leave.

 

[James S Saint]

You seriously don't want to get into rotational relativity.

And btw,

That's not true.

"True"? What does "true" mean? True relative to whom?

When we speak of such situations, we have to speak of one frame of reference or the other. If we assume both are moving, things get really hard to verbalize and the situation doesn't change.

The transverse spin counter let's us ignore time dilation due to the linear motion. But according to each time dilation affected observer, the counts will be different for the same section of track, thus "relativity of count". Pick your poison.

 

[Doc Al]

So are you saying that the train "really" isn't moving?

I'm saying that when you're on the train, the train is at rest with respect to you. That's all that matters.

Everything is moving! Train, tracks, earth, sun... But uniform motion is relative, not absolute.

Or are you restoring the Twin Clocks paradox? I thought we had that one resolved. Or are you saying that neither twin aged differently?

How is the 'twin paradox' relevant here?

You can of course reverse the "mover", but how does that change the situation?

With respect to your frame, whatever it is, the other frame is the one moving. (Relative to you, of course, which is all that matters.)

 

[James S Saint]

I'm saying that when you're on the train, the train is at rest with respect to you. That's all that matters.

Everything is moving! Train, tracks, earth, sun... But uniform motion is relative, not absolute.


How is the 'twin paradox' relevant here?


With respect to your frame, whatever it is, the other frame is the one moving. (Relative to you, of course, which is all that matters.)

That is all excessively elementary. How does it address the problem?

 

[Doc Al]

Transverse Spin Counter
If we mount a transverse spin counter on the train and count the number of transverse spins during the train’s 1000 meter run, the Lorentz equations will yield the same number of spins as anyone at the station would count for that same length of time, especially if it is optic, because transverse time isn’t effected by linear motion and certainly optic time isn't. The spin counter would correct for the time dilated slower clock and measure the correct velocity.

Please define:

(a) transverse spin counter
(b) transverse time
(c) optic time

 

[James S Saint]

Please define:

(a) transverse spin counter
(b) transverse time
(c) optic time

I'm sorry. I thought that was obvious enough.

A traverse spin counter is just what the name implies. It is a device that counts the spins of something spinning transverse (90 degrees) to the linear motion. An optic spin counter is one counting the spins of an optical spinning, perhaps a photon stream racing around a reflective track, or merely the spins of an electron or any particle.

"Transverse time" refers to time as measured considering the transverse, 90 degree, motion. A station-train scenario has no transverse motion, thus there is no transverse time dilation to be concerned about.

"Optic time" merely refers to the consistency of the speed of light and thus of an optical traveler, anything traveling the speed of light. Any observer will measure a photon to travel the same length within the same time. Thus an optic spin counter doesn't need to worry about length dilation issues. Any length involved is certain to be consistent with its fixed consistent speed. An entirely optic spin is not effected by length dilation issues, such as the spin of an electron and its circumference.

The Lorentz for v = c, (1-(v/c)²)^1/2, becomes trivially = 0

 

[Doc Al]

So you claim that some device mounted on the train, your 'transverse spin counter', will enable you to determine that the train is 'actually' moving and will allow you to determine its 'correct' velocity?

Yes or no?

 

[James S Saint]

So you claim that some device mounted on the train, your 'transverse spin counter', will enable you to determine that the train is 'actually' moving and will allow you to determine its 'correct' velocity?

Yes or no?

I am not claiming any "actuality" at all other than the actual fact that a transverse spin counter will count a different number of spins according to either observer (according to Lorentz anyway).

 

[Doc Al]

I am not claiming any "actuality" at all other than the actual fact that a transverse spin counter will count a different number of spins according to either observer (according to Lorentz anyway).

Please try to be precise. A train travels from point A to point B. A 'transverse spin counter' is mounted on the train. Are you claiming that the train-mounted spin counter will record a different number of spins during the trip from A to B depending on who observes it?

 

[Mentz114]

I am not claiming any "actuality" at all other than the actual fact that a transverse spin counter will count a different number of spins according to either observer (according to Lorentz anyway).

Your 'actual fact' is a falsehood. Counting events gives the same number in all frames.

 

[James S Saint]

Your 'actual fact' is a falsehood. Counting events gives the same number in all frames.

How so?

According to Lorentz, the time dilation will cause the train passenger to think that the section of track was traversed in perhaps 9 seconds rather than 10 from the station's perspective (assuming a Japanese train going 1/10^th the speed of light).

Time dilation isn't really in question and has been proven both rationally as well as experimentally. That is why the GPS systems must track their acceleration and adjust their clocks to "Earth time".

But if they didn't adjust their clocks, their spin count would have to be less in less time. The spin counter doesn't experience any dilation of any kind.

 

[Doc Al]

The spin counter doesn't experience any dilation of any kind.

There's your problem.

Your 'spin counter' will behave just like any other clock.

 

[James S Saint]

There's your problem.

Your 'spin counter' will behave just like any other clock.

So you are saying that Lorentz says that clocks mounted above each other on the train with be seen by the station as reading differently? That isn't in his equations nor in any diagrams relating to them. z-axis concerns are ignored because there is no relative motion in that direction.

But if you want to claim that, you better realize that not only will you be arguing with 100 years of Science, but will also create quite a number of paradoxes, including the impossibility of the consistency of the speed of light.

 

[Doc Al]

So you are saying that Lorentz says that clocks mounted above each other on the train with be seen by the station as reading differently?

Now you have two clocks both on the train?

But if you want to claim that, you better realize that not only will you be arguing with 100 years of Science, but will also create quite a number of paradoxes, including the impossibility of the consistency of the speed of light.

Give me a break.

 

[Mentz114]

So you are saying that Lorentz says that clocks mounted above each other on the train with be seen by the station as reading differently? That isn't in his equations nor in any diagrams relating to them. z-axis concerns are ignored because there is no relative motion in that direction.

But if you want to claim that, you better realize that not only will you be arguing with 100 years of Science, but will also create quite a number of paradoxes, including the impossibility of the consistency of the speed of light.

If a disc spins, and rings a bell on each revolution, say, all frames will agree that on the number of times the bell rang. They may disagree on the time between rings.

... you better realize that not only ...

I think it's time you realized you don't know what you're talking about.

 

[James S Saint]

Now you have two clocks both on the train?


Give me a break.

So, I take it that you can't resolve the problem and instead propose that Lorentz was wrong about transverse motion?

So you don't have to take my word for it, here's link - http://galileo.phys.virginia.edu/classes/252/lorentztrans.html"

If a disc spins, and rings a bell on each revolution, say, all frames will agree that on the number of times the bell rang. They may disagree on the time between rings.

If they disagree on the time between the rings, then they have said that the spinner took less or more time to rotate. That is simple arithmetic. But Lorentz says that doesn't happen.

I think it's time you realized you don't know what you're talking about.

Well without giving the same kind of smartass response, I have to say that apparently one of us doesn't.

 

[Doc Al]

So, I take it that you can't resolve the problem and instead propose that Lorentz was wrong about transverse motion?

The only problem is your lack of understanding.

If they disagree on the time between the rings, then they have said that the spinner took less or more time to rotate. That is simple arithmetic. But Lorentz says that doesn't happen.

Apparently, you think that your 'spin counter' is exempt from relativity. Lorentz would not agree.

Well without giving the same kind of smartass response, I have to say that apparently one of us doesn't.

You've made it abundantly clear.

 

[James S Saint]

So you don't have to take my word for it, here is a link - http://galileo.phys.virginia.edu/classes/252/lorentztrans.html"

Let us now suppose that O′ and her crew observe a small bomb to explode in S′ at (x′, 0, 0, t′). In this section, we shall find the space coordinates and time (x, y, z, t) of this event as observed by O in the frame S. (As above, S′ moves relative to S at speed v along the x-axis). In other words, we shall derive the Lorentz transformations—which are just the equations giving the four coordinates of an event in one inertial frame in terms of the coordinates of the same event in another inertial frame. We take y′ ,z′ zero because they transform trivially—there is no Lorentz contraction perpendicular to the motion, so y = y′ and z = z′ .

 

[James S Saint]

There is no "relative motion" between the counter on the station and that of the train in the direction of their spin. Thus they spin equally.

 

[Doc Al]

So you don't have to take my word for it, here is a link - http://galileo.phys.virginia.edu/classes/252/lorentztrans.html"

What is your point in quoting that site? Perhaps you are confusing "there is no length contraction transverse to the motion" with "there is no time dilation transverse to the motion".

 

[James S Saint]

What is your point in quoting that site? Perhaps you are confusing "there is no length contraction transverse to the motion" with "there is no time dilation transverse to the motion".

Read more carefully, "There is no Lorentz contraction" - no change in relative distances.

For time dilation to occur, there has to relative motion. The spinners move identically in there spin directions, There is no relative motion between them, thus there can be time dilation.

You are arguing with Lorentz AND me.

But if you have some equation that supports your idea, then let's have it. Else it would help if you leave these kinds of questions up to those who understand the concepts involved.

 

[James S Saint]

If a bee crosses the tracks, both the station and the train will measure it going the same velocity, because it is in the transverse direction to both train and station, as are the spinners.

 

[Doc Al]

Read more carefully, "There is no Lorentz contraction".

That is length contraction!

For time dilation to occur, there has to relative motion. The spinners move identically in there spin directions, There is no relative motion between them, thus there can be time dilation.

You are arguing with Lorentz AND me.

Nonsense. If you have two 'spin counters', one on the train and one on the tracks, then they of course will record different counts, just like any other clocks. They are in relative motion.

But if you have some equation that supports your idea, then let's have it. Else it would help if you leave these kinds of questions up to those who understand the concepts involved.

I think we're done here. (Once again.)

If a bee crosses the tracks, both the station and the train will measure it going the same velocity, because it is in the transverse direction to both train and station, as are the spinners.

And you can add 'relative velocity' to the list of things you do not understand.