I'm posting this problem in simpler form. I haven't found how
observers in a moving frame explain what occurs using Einstein's
notions of space and time.

There is a circular disk rotating in the X-Y plane of the rest frame.
The disk is centered at x=0, y=0. As measured in the rest frame
there is an iron rod positioned along a diameter of the disk.

There is a moving frame with velocity V moving along the x-axis
relative to the rest frame. For observers in this frame, according to
Einstein, when one end of the iron rod is at x=R, where R is the
radius of the disk, the coordinate of the other end is not on the
x-axis (These events are not simultaneous events in the moving frame
since they are separated by 2R and are simultaneous events in the rest
frame). The moving frame observers do not measure this iron rod to be
a straight line.

Let this iron rod be weakly glued to the disk. And let there be two
weak magnets in the rest frame. These magnets cannot pick up the iron
rod from the rotating disk unless all segments of the magnet are
aligned with the iron rod. One magnet is a straight line the length
of the diameter of the disk. The other magnet is shaped to be
identical to what the moving observer measures the shape of the iron
rod to be when one end of the rod is at x=R.

If the moving observer is instructed to use one of these rest magnets
to remove the iron rod from the rotating disk, and at least one end of
the magnet must be on the x-axis at x=R (as measured in the rest
frame), and the the magnet must have zero velocity relative to the
rest frame, should the moving frame observer choose the magnet shape
where all segments of the magnet are simultaneously aligned with the
iron rod as he has measured it in the moving frame, or should he
choose the straight magnet which he measures to be only partially
aligned to the iron rod?

Since the only magnet that works per the given information in the
problem is the straight magnet, how does the moving observer explain
the fact that if less points of the magnet are aligned with the
rotating iron rod, the iron rod can be removed from the disk? And
also if all points of the magnet (as per the shape of the other
magnet) are simultaneously aligned with the iron rod, the magnet is
not strong enough to remove the iron rod from the disk?

Dave Seppala

I'm posting this problem in simpler form. I haven't found how
observers in a moving frame explain what occurs using Einstein's
notions of space and time.

There is a circular disk rotating in the X-Y plane of the rest frame.
The disk is centered at x=0, y=0. As measured in the rest frame
there is an iron rod positioned along a diameter of the disk.

There is a moving frame with velocity V moving along the x-axis
relative to the rest frame. For observers in this frame, according to
Einstein, when one end of the iron rod is at x=R, where R is the
radius of the disk, the coordinate of the other end is not on the
x-axis (These events are not simultaneous events in the moving frame
since they are separated by 2R and are simultaneous events in the rest
frame). The moving frame observers do not measure this iron rod to be
a straight line.

Let this iron rod be weakly glued to the disk. And let there be two
weak magnets in the rest frame. These magnets cannot pick up the iron
rod from the rotating disk unless all segments of the magnet are
aligned with the iron rod. One magnet is a straight line the length
of the diameter of the disk. The other magnet is shaped to be
identical to what the moving observer measures the shape of the iron
rod to be when one end of the rod is at x=R.

If the moving observer is instructed to use one of these rest magnets
to remove the iron rod from the rotating disk, and at least one end of
the magnet must be on the x-axis at x=R (as measured in the rest
frame), and the the magnet must have zero velocity relative to the
rest frame, should the moving frame observer choose the magnet shape
where all segments of the magnet are simultaneously aligned with the
iron rod as he has measured it in the moving frame, or should he
choose the straight magnet which he measures to be only partially
aligned to the iron rod?

Since the only magnet that works per the given information in the
problem is the straight magnet, how does the moving observer explain
the fact that if less points of the magnet are aligned with the
rotating iron rod, the iron rod can be removed from the disk? And
also if all points of the magnet (as per the shape of the other
magnet) are simultaneously aligned with the iron rod, the magnet is
not strong enough to remove the iron rod from the disk?

Dave Seppala

I'm posting this problem in simpler form.

observers in a moving frame explain what occurs using Einstein's
notions of space and time.

There is a circular disk rotating in the X-Y plane of the rest frame.
The disk is centered at x=0, y=0. As measured in the rest frame
there is an iron rod positioned along a diameter of the disk.

There is a moving frame with velocity V moving along the x-axis
relative to the rest frame. For observers in this frame, according to
Einstein, when one end of the iron rod is at x=R, where R is the
radius of the disk, the coordinate of the other end is not on the
x-axis (These events are not simultaneous events in the moving frame
since they are separated by 2R and are simultaneous events in the rest
frame). The moving frame observers do not measure this iron rod to be
a straight line.

Let this iron rod be weakly glued to the disk. And let there be two
weak magnets in the rest frame. These magnets cannot pick up the iron
rod from the rotating disk unless all segments of the magnet are
aligned with the iron rod. One magnet is a straight line the length
of the diameter of the disk. The other magnet is shaped to be
identical to what the moving observer measures the shape of the iron
rod to be when one end of the rod is at x=R.

If the moving observer is instructed to use one of these rest magnets
to remove the iron rod from the rotating disk, and at least one end of
the magnet must be on the x-axis at x=R (as measured in the rest
frame), and the the magnet must have zero velocity relative to the
rest frame, should the moving frame observer choose the magnet shape
where all segments of the magnet are simultaneously aligned with the
iron rod as he has measured it in the moving frame, or should he
choose the straight magnet which he measures to be only partially
aligned to the iron rod?

Since the only magnet that works per the given information in the
problem is the straight magnet, how does the moving observer explain
the fact that if less points of the magnet are aligned with the
rotating iron rod, the iron rod can be removed from the disk? And
also if all points of the magnet (as per the shape of the other
magnet) are simultaneously aligned with the iron rod, the magnet is
not strong enough to remove the iron rod from the disk?

Dave Seppala

David wrote:
I'm posting this problem in simpler form.

:)

I haven't found how
observers in a moving frame explain what occurs using Einstein's
notions of space and time.

They "explain" what occurs in the same way that observers in non-moving
frames do, since all observe the *same occurences*, albeit from
different perspectives.

How do the American football spectators whose seats are in-line with the
goal posts, explain field goals?

David wrote:
I'm posting this problem in simpler form.

:)

I haven't found how observers in a moving frame explain what
occurs using Einstein's notions of space and time.

They "explain" what occurs in the same way that observers in non-moving
frames do, since all observe the *same occurences*, albeit from
different perspectives.

How do the American football spectators whose seats are in-line with the
goal posts, explain field goals?

I'm posting this problem in simpler form. I haven't found how
observers in a moving frame explain what occurs using Einstein's
notions of space and time.

There is a circular disk rotating in the X-Y plane of the rest frame.
The disk is centered at x=0, y=0. As measured in the rest frame
there is an iron rod positioned along a diameter of the disk.

There is a moving frame with velocity V moving along the x-axis
relative to the rest frame. For observers in this frame, according to
Einstein, when one end of the iron rod is at x=R, where R is the
radius of the disk, the coordinate of the other end is not on the
x-axis (These events are not simultaneous events in the moving frame
since they are separated by 2R and are simultaneous events in the rest
frame). The moving frame observers do not measure this iron rod to be
a straight line.

Let this iron rod be weakly glued to the disk. And let there be two
weak magnets in the rest frame. These magnets cannot pick up the iron
rod from the rotating disk unless all segments of the magnet are
aligned with the iron rod.

One magnet is a straight line the length
of the diameter of the disk. The other magnet is shaped to be
identical to what the moving observer measures the shape of the iron
rod to be when one end of the rod is at x=R.

If the moving observer is instructed to use one of these rest magnets
to remove the iron rod from the rotating disk, and at least one end of
the magnet must be on the x-axis at x=R (as measured in the rest
frame), and the the magnet must have zero velocity relative to the
rest frame, should the moving frame observer choose the magnet shape
where all segments of the magnet are simultaneously aligned with the
iron rod as he has measured it in the moving frame, or should he
choose the straight magnet which he measures to be only partially
aligned to the iron rod?

Since the only magnet that works per the given information in the
problem is the straight magnet, how does the moving observer explain
the fact that if less points of the magnet are aligned with the
rotating iron rod, the iron rod can be removed from the disk? And
also if all points of the magnet (as per the shape of the other
magnet) are simultaneously aligned with the iron rod, the magnet is
not strong enough to remove the iron rod from the disk?

Dave Seppala

On Feb 21, 9:56 am, David <dsepp...@austin.rr.com> wrote:
I'm posting this problem in simpler form. I haven't found how
observers in a moving frame explain what occurs using Einstein's
notions of space and time.

There is a circular disk rotating in the X-Y plane of the rest frame.
The disk is centered at x=0, y=0. As measured in the rest frame
there is an iron rod positioned along a diameter of the disk.

There is a moving frame with velocity V moving along the x-axis
relative to the rest frame. For observers in this frame, according to
Einstein, when one end of the iron rod is at x=R, where R is the
radius of the disk, the coordinate of the other end is not on the
x-axis (These events are not simultaneous events in the moving frame
since they are separated by 2R and are simultaneous events in the rest
frame). The moving frame observers do not measure this iron rod to be
a straight line.

Let this iron rod be weakly glued to the disk. And let there be two
weak magnets in the rest frame. These magnets cannot pick up the iron
rod from the rotating disk unless all segments of the magnet are
aligned with the iron rod. One magnet is a straight line the length
of the diameter of the disk. The other magnet is shaped to be
identical to what the moving observer measures the shape of the iron
rod to be when one end of the rod is at x=R.

If the moving observer is instructed to use one of these rest magnets
to remove the iron rod from the rotating disk, and at least one end of
the magnet must be on the x-axis at x=R (as measured in the rest
frame), and the the magnet must have zero velocity relative to the
rest frame, should the moving frame observer choose the magnet shape
where all segments of the magnet are simultaneously aligned with the
iron rod as he has measured it in the moving frame, or should he
choose the straight magnet which he measures to be only partially
aligned to the iron rod?

Since the only magnet that works per the given information in the
problem is the straight magnet, how does the moving observer explain
the fact that if less points of the magnet are aligned with the
rotating iron rod, the iron rod can be removed from the disk? And
also if all points of the magnet (as per the shape of the other
magnet) are simultaneously aligned with the iron rod, the magnet is
not strong enough to remove the iron rod from the disk?

Dave Seppala

Simple. Just use the Lorentz transformations for EM fields.

On Feb 21, 9:56 am, David <dsepp...@austin.rr.com> wrote:
I'm posting this problem in simpler form. I haven't found how
observers in a moving frame explain what occurs using Einstein's
notions of space and time.

There is a circular disk rotating in the X-Y plane of the rest frame.
The disk is centered at x=0, y=0. As measured in the rest frame
there is an iron rod positioned along a diameter of the disk.

There is a moving frame with velocity V moving along the x-axis
relative to the rest frame. For observers in this frame, according to
Einstein, when one end of the iron rod is at x=R, where R is the
radius of the disk, the coordinate of the other end is not on the
x-axis (These events are not simultaneous events in the moving frame
since they are separated by 2R and are simultaneous events in the rest
frame). The moving frame observers do not measure this iron rod to be
a straight line.

Let this iron rod be weakly glued to the disk. And let there be two
weak magnets in the rest frame. These magnets cannot pick up the iron
rod from the rotating disk unless all segments of the magnet are
aligned with the iron rod.

Do you mean all segments of the magnet are aligned with the iron rod
*at the same time*, or do you mean that one small segment of the
magnet can pick up one small segment of the rod if the small segments
are aligned?

You see, the first constraint on the magnet (that the global shape of
the magnet and rod must be the same) is impossible, given Maxwell's
equations. Each part of the magnet and rod must act locally, without
influences faster than the speed of light.

What will happen is that, in the rest frame, an observer will see the
magnet pick up the entire rod at the same time, but will note that due
to speed of light constraints each part of the rod must have been
picked up by a local interaction.

In the other frame, the observers will see each small segment of the
rod get attracted to each small segment of the magnet, as the rod
rotates under the magnet. They will stick when they get aligned, non-
simultaneously.
Why doesn't this moving frame think the magnet (of the rest frame)

The details of the magnetic field really have no relevance beyond a
discussion of the details of which field actually causes the
attraction.

Relativity of simultaneity saves the day again! (As well as rejecting
the notion of absolutely rigid bodies.)

One magnet is a straight line the length
of the diameter of the disk. The other magnet is shaped to be
identical to what the moving observer measures the shape of the iron
rod to be when one end of the rod is at x=R.

If the moving observer is instructed to use one of these rest magnets
to remove the iron rod from the rotating disk, and at least one end of
the magnet must be on the x-axis at x=R (as measured in the rest
frame), and the the magnet must have zero velocity relative to the
rest frame, should the moving frame observer choose the magnet shape
where all segments of the magnet are simultaneously aligned with the
iron rod as he has measured it in the moving frame, or should he
choose the straight magnet which he measures to be only partially
aligned to the iron rod?

Since the only magnet that works per the given information in the
problem is the straight magnet, how does the moving observer explain
the fact that if less points of the magnet are aligned with the
rotating iron rod, the iron rod can be removed from the disk? And
also if all points of the magnet (as per the shape of the other
magnet) are simultaneously aligned with the iron rod, the magnet is
not strong enough to remove the iron rod from the disk?

Dave Seppala

David wrote:
I'm posting this problem in simpler form.

:)

I haven't found how
observers in a moving frame explain what occurs using Einstein's
notions of space and time.

They "explain" what occurs in the same way that observers in non-moving
frames do, since all observe the *same occurences*, albeit from
different perspectives.

How do the American football spectators whose seats are in-line with the
goal posts, explain field goals?
The spectators can take in all the information. They actually have a

There is a circular disk rotating in the X-Y plane of the rest frame.
The disk is centered at x=0, y=0. As measured in the rest frame
there is an iron rod positioned along a diameter of the disk.

There is a moving frame with velocity V moving along the x-axis
relative to the rest frame. For observers in this frame, according to
Einstein, when one end of the iron rod is at x=R, where R is the
radius of the disk, the coordinate of the other end is not on the
x-axis (These events are not simultaneous events in the moving frame
since they are separated by 2R and are simultaneous events in the rest
frame). The moving frame observers do not measure this iron rod to be
a straight line.

Let this iron rod be weakly glued to the disk. And let there be two
weak magnets in the rest frame. These magnets cannot pick up the iron
rod from the rotating disk unless all segments of the magnet are
aligned with the iron rod. One magnet is a straight line the length
of the diameter of the disk. The other magnet is shaped to be
identical to what the moving observer measures the shape of the iron
rod to be when one end of the rod is at x=R.

If the moving observer is instructed to use one of these rest magnets
to remove the iron rod from the rotating disk, and at least one end of
the magnet must be on the x-axis at x=R (as measured in the rest
frame), and the the magnet must have zero velocity relative to the
rest frame, should the moving frame observer choose the magnet shape
where all segments of the magnet are simultaneously aligned with the
iron rod as he has measured it in the moving frame, or should he
choose the straight magnet which he measures to be only partially
aligned to the iron rod?

Since the only magnet that works per the given information in the
problem is the straight magnet, how does the moving observer explain
the fact that if less points of the magnet are aligned with the
rotating iron rod, the iron rod can be removed from the disk? And
also if all points of the magnet (as per the shape of the other
magnet) are simultaneously aligned with the iron rod, the magnet is
not strong enough to remove the iron rod from the disk?

Dave Seppala

I'm posting this problem in simpler form. I haven't found how
observers in a moving frame explain what occurs using Einstein's
notions of space and time.

There is a circular disk rotating

On Thu, 22 Feb 2007 09:21:17 -0500, jem <xxx@xxx.xxx> wrote:


David wrote:

I'm posting this problem in simpler form.

:)

I haven't found how

observers in a moving frame explain what occurs using Einstein's
notions of space and time.

They "explain" what occurs in the same way that observers in non-moving
frames do, since all observe the *same occurences*, albeit from
different perspectives.

How do the American football spectators whose seats are in-line with the
goal posts, explain field goals?

The spectators can take in all the information. They actually have a
three dimensional view of the field, albeit in your analogy they
cannot determine by one point in space whether or not there was a
field goal. But if they are aligned with the goal posts, they can
view the football's trajectory, the three dimensions of the field,
etc, the location of the players and officials, their reaction and the
crowd's reaction and come to a valid conclusion based on all aspects
of the problem.

But why do the moving frame observers think that a magnet that is
simultaneously aligned with all points of an iron rod exerts less
force on the rod than a magnet that is not-simultaneously aligned with
all points of the iron rod?

David

There is a circular disk rotating in the X-Y plane of the rest frame.
The disk is centered at x=0, y=0. As measured in the rest frame
there is an iron rod positioned along a diameter of the disk.

There is a moving frame with velocity V moving along the x-axis
relative to the rest frame. For observers in this frame, according to
Einstein, when one end of the iron rod is at x=R, where R is the
radius of the disk, the coordinate of the other end is not on the
x-axis (These events are not simultaneous events in the moving frame
since they are separated by 2R and are simultaneous events in the rest
frame). The moving frame observers do not measure this iron rod to be
a straight line.

Let this iron rod be weakly glued to the disk. And let there be two
weak magnets in the rest frame. These magnets cannot pick up the iron
rod from the rotating disk unless all segments of the magnet are
aligned with the iron rod. One magnet is a straight line the length
of the diameter of the disk. The other magnet is shaped to be
identical to what the moving observer measures the shape of the iron
rod to be when one end of the rod is at x=R.

If the moving observer is instructed to use one of these rest magnets
to remove the iron rod from the rotating disk, and at least one end of
the magnet must be on the x-axis at x=R (as measured in the rest
frame), and the the magnet must have zero velocity relative to the
rest frame, should the moving frame observer choose the magnet shape
where all segments of the magnet are simultaneously aligned with the
iron rod as he has measured it in the moving frame, or should he
choose the straight magnet which he measures to be only partially
aligned to the iron rod?

Since the only magnet that works per the given information in the
problem is the straight magnet, how does the moving observer explain
the fact that if less points of the magnet are aligned with the
rotating iron rod, the iron rod can be removed from the disk? And
also if all points of the magnet (as per the shape of the other
magnet) are simultaneously aligned with the iron rod, the magnet is
not strong enough to remove the iron rod from the disk?

Dave Seppala

David wrote:

On Thu, 22 Feb 2007 09:21:17 -0500, jem <xxx@xxx.xxx> wrote:


David wrote:

I'm posting this problem in simpler form.

:)

I haven't found how

observers in a moving frame explain what occurs using Einstein's
notions of space and time.

They "explain" what occurs in the same way that observers in non-moving
frames do, since all observe the *same occurences*, albeit from
different perspectives.

How do the American football spectators whose seats are in-line with the
goal posts, explain field goals?

The spectators can take in all the information. They actually have a
three dimensional view of the field, albeit in your analogy they
cannot determine by one point in space whether or not there was a
field goal. But if they are aligned with the goal posts, they can
view the football's trajectory, the three dimensions of the field,
etc, the location of the players and officials, their reaction and the
crowd's reaction and come to a valid conclusion based on all aspects
of the problem.

Which is the point. The spectators don't "explain" the occurence of a
field goal any differently than the referees do (i.e. the ball travels
between a pair of goal posts), despite the fact that they describe the
occurence differently.

But why do the moving frame observers think that a magnet that is
simultaneously aligned with all points of an iron rod exerts less
force on the rod than a magnet that is not-simultaneously aligned with
all points of the iron rod?

Here's a simpler problem.

Assume there's a theory T which indicates that if tall observers measure
a particular collection of events E as m, then short observers will
measure E as m+4.

Now suppose a tall observer O happens to measure that particular
collection of events E as 7. Then, according to theory T, a short
observer O' will measure E as 11. How does O' /explain/ that the
measurement is 11?

Got an answer for that?
Jem, I am not asking how does someone in one frame explain the

Then here's a generalized version of your problem.

Suppose a non-moving observer O views a series of events E and makes a
collection of measurements M based on E. Then, according to the theory
of Relativity, an observer O', who's moving relative to O, will make a
corresponding set of measurements M' upon viewing E. How does O'
/explain/ M'?

Did you notice that the two problems are essentially the same?

And the "explanation", in each case, is that the measurement(s)
logically follow(s) from the given information using the applicable
theory, which is the only sort of explanation that's possible in Physics.

Now perhaps you think that there may be some current theory other than
Relativity that could indicate the measurement(s) of O' will be
different than M'. However, that simply can't be the case as long as
the /given/ measurements of O (i.e. M) are consistent with current
theory, since Relativity is the *only* current theory that relates the
measurements of relatively moving observers.

David

There is a circular disk rotating in the X-Y plane of the rest frame.
The disk is centered at x=0, y=0. As measured in the rest frame
there is an iron rod positioned along a diameter of the disk.

There is a moving frame with velocity V moving along the x-axis
relative to the rest frame. For observers in this frame, according to
Einstein, when one end of the iron rod is at x=R, where R is the
radius of the disk, the coordinate of the other end is not on the
x-axis (These events are not simultaneous events in the moving frame
since they are separated by 2R and are simultaneous events in the rest
frame). The moving frame observers do not measure this iron rod to be
a straight line.

Let this iron rod be weakly glued to the disk. And let there be two
weak magnets in the rest frame. These magnets cannot pick up the iron
rod from the rotating disk unless all segments of the magnet are
aligned with the iron rod. One magnet is a straight line the length
of the diameter of the disk. The other magnet is shaped to be
identical to what the moving observer measures the shape of the iron
rod to be when one end of the rod is at x=R.

If the moving observer is instructed to use one of these rest magnets
to remove the iron rod from the rotating disk, and at least one end of
the magnet must be on the x-axis at x=R (as measured in the rest
frame), and the the magnet must have zero velocity relative to the
rest frame, should the moving frame observer choose the magnet shape
where all segments of the magnet are simultaneously aligned with the
iron rod as he has measured it in the moving frame, or should he
choose the straight magnet which he measures to be only partially
aligned to the iron rod?

Since the only magnet that works per the given information in the
problem is the straight magnet, how does the moving observer explain
the fact that if less points of the magnet are aligned with the
rotating iron rod, the iron rod can be removed from the disk? And
also if all points of the magnet (as per the shape of the other
magnet) are simultaneously aligned with the iron rod, the magnet is
not strong enough to remove the iron rod from the disk?

Dave Seppala

On Sat, 24 Feb 2007 08:41:58 -0500, jem <xxx@xxx.xxx> wrote:


David wrote:


On Thu, 22 Feb 2007 09:21:17 -0500, jem <xxx@xxx.xxx> wrote:



David wrote:


I'm posting this problem in simpler form.

:)

I haven't found how


observers in a moving frame explain what occurs using Einstein's
notions of space and time.

They "explain" what occurs in the same way that observers in non-moving
frames do, since all observe the *same occurences*, albeit from
different perspectives.

How do the American football spectators whose seats are in-line with the
goal posts, explain field goals?

The spectators can take in all the information. They actually have a
three dimensional view of the field, albeit in your analogy they
cannot determine by one point in space whether or not there was a
field goal. But if they are aligned with the goal posts, they can
view the football's trajectory, the three dimensions of the field,
etc, the location of the players and officials, their reaction and the
crowd's reaction and come to a valid conclusion based on all aspects
of the problem.

Which is the point. The spectators don't "explain" the occurence of a
field goal any differently than the referees do (i.e. the ball travels
between a pair of goal posts), despite the fact that they describe the
occurence differently.


But why do the moving frame observers think that a magnet that is
simultaneously aligned with all points of an iron rod exerts less
force on the rod than a magnet that is not-simultaneously aligned with
all points of the iron rod?

Here's a simpler problem.

Assume there's a theory T which indicates that if tall observers measure
a particular collection of events E as m, then short observers will
measure E as m+4.

Now suppose a tall observer O happens to measure that particular
collection of events E as 7. Then, according to theory T, a short
observer O' will measure E as 11. How does O' /explain/ that the
measurement is 11?

Got an answer for that?

Jem, I am not asking how does someone in one frame explain the
measurement in another frame. I am asking how does someone in an
inertial frame measure that when all points of a magnet simutlaneously
align with all points of an iron rod as measured in his own frame that
magnet exerts less force on the iron rod then when all points of the
magnet are not simultaneously aligned with the iron rod as measured in
the same frame.
In your responses, you keep asking how does one frame explain the
measurements of another's frame - that is not what I am asking.

David

Then here's a generalized version of your problem.

Suppose a non-moving observer O views a series of events E and makes a
collection of measurements M based on E. Then, according to the theory
of Relativity, an observer O', who's moving relative to O, will make a
corresponding set of measurements M' upon viewing E. How does O'
/explain/ M'?

Did you notice that the two problems are essentially the same?

And the "explanation", in each case, is that the measurement(s)
logically follow(s) from the given information using the applicable
theory, which is the only sort of explanation that's possible in Physics.

Now perhaps you think that there may be some current theory other than
Relativity that could indicate the measurement(s) of O' will be
different than M'. However, that simply can't be the case as long as
the /given/ measurements of O (i.e. M) are consistent with current
theory, since Relativity is the *only* current theory that relates the
measurements of relatively moving observers.


David


There is a circular disk rotating in the X-Y plane of the rest frame.
The disk is centered at x=0, y=0. As measured in the rest frame
there is an iron rod positioned along a diameter of the disk.

There is a moving frame with velocity V moving along the x-axis
relative to the rest frame. For observers in this frame, according to
Einstein, when one end of the iron rod is at x=R, where R is the
radius of the disk, the coordinate of the other end is not on the
x-axis (These events are not simultaneous events in the moving frame
since they are separated by 2R and are simultaneous events in the rest
frame). The moving frame observers do not measure this iron rod to be
a straight line.

Let this iron rod be weakly glued to the disk. And let there be two
weak magnets in the rest frame. These magnets cannot pick up the iron
rod from the rotating disk unless all segments of the magnet are
aligned with the iron rod. One magnet is a straight line the length
of the diameter of the disk. The other magnet is shaped to be
identical to what the moving observer measures the shape of the iron
rod to be when one end of the rod is at x=R.

If the moving observer is instructed to use one of these rest magnets
to remove the iron rod from the rotating disk, and at least one end of
the magnet must be on the x-axis at x=R (as measured in the rest
frame), and the the magnet must have zero velocity relative to the
rest frame, should the moving frame observer choose the magnet shape
where all segments of the magnet are simultaneously aligned with the
iron rod as he has measured it in the moving frame, or should he
choose the straight magnet which he measures to be only partially
aligned to the iron rod?

Since the only magnet that works per the given information in the
problem is the straight magnet, how does the moving observer explain
the fact that if less points of the magnet are aligned with the
rotating iron rod, the iron rod can be removed from the disk? And
also if all points of the magnet (as per the shape of the other
magnet) are simultaneously aligned with the iron rod, the magnet is
not strong enough to remove the iron rod from the disk?

Dave Seppala