wrote in
:

On Sat, 20 Aug 2005 22:55:42 +0000 (UTC), bz
wrote:

wrote in
:

On Fri, 19 Aug 2005 15:07:03 +0000 (UTC), bz
wrote:

wrote in news:4305d0b7.540887@news-
server.austin.rr.com:

This problem is a combination of several problems I've posted in
this group. When I combine the problems, the answers given to me in
previous posts don't work. Here's the problem.

I have two frames which I will call the stationary frame and the
moving frame. Their relative velocity is 0.866 c. In the
stationary frame, parallel to the x-axis there is a rod and a
rotating cylinder. The end points of the rod and the rotating
cylinder are at the same x coordinates. The diameter of the
cylinder is 10 meters and the cylinder is rotating at 10 revolutions
per second.

As measured in the moving frame, let the length of the rod and the
length of the rotating cylinder be 1 light-second. At time t0 as
measured in the moving frame, each point of the rod is
simultaneously attached to the surface of the rotating cylinder.
(Assume the rod is made of a material that is very malleable).

As viewed in the stationary frame, one end of the rod was attached
to the rotating cylinder 1.73 seconds before the other end.

Ok.

That means
that the rod wrapped around the cylinder about 17 times in a spiral
pattern.

Nope. From the stationary frame, the rod was rotating along with the
line drawn straight along the surface of the cylinder drawn by a laser
level device before the rod was ever joined to the cylinder.
No. The rod develops a rotation because it is attached to the
rotating cylinder. Prior to being attached, the rod is not rotating
and has zero velocity wrt to the longitudinal axis of the cylinder.


You have a slight problem.
you said:
In the stationary
frame, parallel to the x-axis there is a rod and a rotating
cylinder. The end points of the rod and the rotating cylinder are at
the same x coordinates. The diameter of the cylinder is 10 meters
and the cylinder is rotating at 10 revolutions per second.

That puts one end of the rod and some [poorly specified] point on the
rotating cylinder at the same point.

If I assume the point is on the circumference of the cylinder rather
than the center of the cylender [that would make for all kinds of
problems] then you have infinite acceleration of the rod at the moment
of attachment.

Only if the rod is already in motion, can it be attached to the
cylinder.
No. The circumference of the rotating cylinder is about 31 meters.
At 10 revolutions per second, the surface of the cylinder is moving at
about 310 meters / second. Let's say the cylinder contains an
extremely powerful electromagnet, and the rod is steel. When the
magnet is turned on, if the force is strong enough, the magnet will
keep the rod attached to the rotating cylinder. There are thousands
of ways to do this attachment. Surely, you agree that if the rotation
speed is very low, say 0.001 revolutions per second, there would be no
problem attaching the rod to the cylinder - you can do this experiment
with short rod segments. I only picked 10 revolutions per second so
that its easier to envision the rod spiraled completely around the
cylinder as opposed to spiraled over a very small angle.
David

delta v / delta t = acceleration.

you have a finite change in velocity (delta v) taking place in zero time
(delta t). This gives infinite acceleration.

Only if the rod is already in motion, can it be attached to the
cylinder.


The stationary observer is intellegent enough to realize that light
moves in a straight line[in the rotating FoR] and that the optical
delusion of a 17 times wrap is exactly that.
.....

When I look at myself in a funhouse mirror, I know that I really do
NOT get long and thin or short and fat. When I look at something in
another FoR, I know that things look different from that FoR.



--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

remove ch100-5 to avoid spam trap

wrote in message ...
On Fri, 19 Aug 2005 16:27:39 GMT, "Dirk Van de moortel"
wrote:


wrote in message ...
This problem is a combination of several problems I've posted in this
group. When I combine the problems, the answers given to me in
previous posts don't work. Here's the problem.

Another everyday experience problem with 300000 km long
rigid rods, I presume?
http://users.pandora.be/vdmoortel/di.../Everyday.html

Dirk, the link you posted has pandora.be in it, from which I infer
refers to a country different than the United States of America. So
I'm guessing English is not your native language. If you carefully
read my sentence that you refer to in the above link, you will see
that I stated that the 300000 km length IS NOT part of my everyday
experience.

Sure.
I *had* carefully read your sentence and I understood it just
the way you had intended it. It was one of the funniest things
you ever wrote on this group.
In order for you not to think that I had misunderstood you
line, I now have put emphasis on the entire sentence:
| "Other than the rod being light-years in length, the parameters are
| values that occur in our daily experience."
You can check it at:
http://users.pandora.be/vdmoortel/di.../Everyday.html

Hope this helps!

Dirk Vdm



If you carefully read what I posted, you will see that
the sentence begins with the word "Other". "Other" when used in this
context means "with the exception of". The meaning of the sentence I
posted is that the 300000 km length IS NOT in my everyday experience,
but the 3 meter per second velocity is in my everyday experience, and
the accleration from 0 to 3 meters per second in 0.1 seconds is in my
everyday experience.
There are some good dictionaries available online
http://www.m-w. com
for example. If you look up the definition of "other" you will see
that first definition is "being the one not included" So in
everyday English as used in the USA, the sentence I posted means that
the 300000 km rod is the parameter that is NOT part of my everyday
experience.
Hope that helps you're understanding of this common English usage.
David

[snip unread]

Please note: If you don't know the physics answer, please feel free
to put up a post that includes personal attacks of my intelligence and
education. That's the approach used by the vast majority of the
people on the planet when they can't logically explain something, so
why should you be different? Besides, your peers may join in giving
each of you mutual support.

Was I right?

Dirk Vdm

On Mon, 22 Aug 2005 15:48:25 +0000 (UTC), bz
wrote:

wrote in
:

On Sat, 20 Aug 2005 22:55:42 +0000 (UTC), bz
wrote:

wrote in
:

On Fri, 19 Aug 2005 15:07:03 +0000 (UTC), bz
wrote:

wrote in news:4305d0b7.540887@news-
server.austin.rr.com:

This problem is a combination of several problems I've posted in
this group. When I combine the problems, the answers given to me in
previous posts don't work. Here's the problem.

I have two frames which I will call the stationary frame and the
moving frame. Their relative velocity is 0.866 c. In the
stationary frame, parallel to the x-axis there is a rod and a
rotating cylinder. The end points of the rod and the rotating
cylinder are at the same x coordinates. The diameter of the
cylinder is 10 meters and the cylinder is rotating at 10 revolutions
per second.

As measured in the moving frame, let the length of the rod and the
length of the rotating cylinder be 1 light-second. At time t0 as
measured in the moving frame, each point of the rod is
simultaneously attached to the surface of the rotating cylinder.
(Assume the rod is made of a material that is very malleable).

As viewed in the stationary frame, one end of the rod was attached
to the rotating cylinder 1.73 seconds before the other end.

Ok.

That means
that the rod wrapped around the cylinder about 17 times in a spiral
pattern.

Nope. From the stationary frame, the rod was rotating along with the
line drawn straight along the surface of the cylinder drawn by a laser
level device before the rod was ever joined to the cylinder.
No. The rod develops a rotation because it is attached to the
rotating cylinder. Prior to being attached, the rod is not rotating
and has zero velocity wrt to the longitudinal axis of the cylinder.


You have a slight problem.
you said:
In the stationary
frame, parallel to the x-axis there is a rod and a rotating
cylinder. The end points of the rod and the rotating cylinder are at
the same x coordinates. The diameter of the cylinder is 10 meters
and the cylinder is rotating at 10 revolutions per second.

That puts one end of the rod and some [poorly specified] point on the
rotating cylinder at the same point.

If I assume the point is on the circumference of the cylinder rather
than the center of the cylender [that would make for all kinds of
problems] then you have infinite acceleration of the rod at the moment
of attachment.

Only if the rod is already in motion, can it be attached to the
cylinder.
No. The circumference of the rotating cylinder is about 31 meters.
At 10 revolutions per second, the surface of the cylinder is moving at
about 310 meters / second. Let's say the cylinder contains an
extremely powerful electromagnet, and the rod is steel. When the
magnet is turned on, if the force is strong enough, the magnet will
keep the rod attached to the rotating cylinder. There are thousands
of ways to do this attachment. Surely, you agree that if the rotation
speed is very low, say 0.001 revolutions per second, there would be no
problem attaching the rod to the cylinder - you can do this experiment
with short rod segments. I only picked 10 revolutions per second so
that its easier to envision the rod spiraled completely around the
cylinder as opposed to spiraled over a very small angle.
David

delta v / delta t = acceleration.
Okay, I see what you are saying, I think. I think you are saying
because I said the attachment for each point of the rod takes place at
the same time, t0, you think that means delta t = 0. I guess, I
should have been more precise and pedantic. Let's do that and say the
acceleration time for the rod to equal the rotational speed of the
surface of the rotating rod is 0.1 second and the acceleration starts
at each point at time t0 as measured in the moving frame.
David

you have a finite change in velocity (delta v) taking place in zero time
(delta t). This gives infinite acceleration.

Only if the rod is already in motion, can it be attached to the
cylinder.


The stationary observer is intellegent enough to realize that light
moves in a straight line[in the rotating FoR] and that the optical
delusion of a 17 times wrap is exactly that.
....

When I look at myself in a funhouse mirror, I know that I really do
NOT get long and thin or short and fat. When I look at something in
another FoR, I know that things look different from that FoR.



--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

remove ch100-5 to avoid spam trap

On Mon, 22 Aug 2005 16:19:22 GMT, "Dirk Van de moortel"
wrote:


wrote in message ...
On Fri, 19 Aug 2005 16:27:39 GMT, "Dirk Van de moortel"
wrote:


wrote in message ...
This problem is a combination of several problems I've posted in this
group. When I combine the problems, the answers given to me in
previous posts don't work. Here's the problem.

Another everyday experience problem with 300000 km long
rigid rods, I presume?
http://users.pandora.be/vdmoortel/di.../Everyday.html

Dirk, the link you posted has pandora.be in it, from which I infer
refers to a country different than the United States of America. So
I'm guessing English is not your native language. If you carefully
read my sentence that you refer to in the above link, you will see
that I stated that the 300000 km length IS NOT part of my everyday
experience.

Sure.
I *had* carefully read your sentence and I understood it just
the way you had intended it. It was one of the funniest things
you ever wrote on this group.
Well, with the velocity being only 3 meters / second, and the
acceleration being only 1 g, I can experience how objects change (on a
local level) when they move from one reference frame to another. For
example, some posters in this group believe if the rod is made long
enough, a person holding one end of the rod will be accelerated to a
velocity approaching the speed of light. But with parameters like 3
meters / second and a 1 g acceleration it is easy for me to see that
that notion is incorrect. You may think of that as being "an
immortal fumble of David Seppala" but actually it helps me understand
things easier. You're not one of those people who think one end of
the rod travels at a speed close to the speed of light when it is
placed on a conveyer belt moving at 3 meters / second, are you? Or is
that why you label my approach as an immortal fumble?
David
In order for you not to think that I had misunderstood you
line, I now have put emphasis on the entire sentence:
| "Other than the rod being light-years in length, the parameters are
| values that occur in our daily experience."
You can check it at:
http://users.pandora.be/vdmoortel/di.../Everyday.html

Hope this helps!

Dirk Vdm



If you carefully read what I posted, you will see that
the sentence begins with the word "Other". "Other" when used in this
context means "with the exception of". The meaning of the sentence I
posted is that the 300000 km length IS NOT in my everyday experience,
but the 3 meter per second velocity is in my everyday experience, and
the accleration from 0 to 3 meters per second in 0.1 seconds is in my
everyday experience.
There are some good dictionaries available online
http://www.m-w. com
for example. If you look up the definition of "other" you will see
that first definition is "being the one not included" So in
everyday English as used in the USA, the sentence I posted means that
the 300000 km rod is the parameter that is NOT part of my everyday
experience.
Hope that helps you're understanding of this common English usage.
David

[snip unread]

Please note: If you don't know the physics answer, please feel free
to put up a post that includes personal attacks of my intelligence and
education. That's the approach used by the vast majority of the
people on the planet when they can't logically explain something, so
why should you be different? Besides, your peers may join in giving
each of you mutual support.

Was I right?

Dirk Vdm

wrote in
:

On Mon, 22 Aug 2005 15:48:25 +0000 (UTC), bz
wrote:

wrote in
:

On Sat, 20 Aug 2005 22:55:42 +0000 (UTC), bz
wrote:

wrote in
:

On Fri, 19 Aug 2005 15:07:03 +0000 (UTC), bz
wrote:

wrote in news:4305d0b7.540887@news-
server.austin.rr.com:

This problem is a combination of several problems I've posted in
this group. When I combine the problems, the answers given to me
in previous posts don't work. Here's the problem.

I have two frames which I will call the stationary frame and the
moving frame. Their relative velocity is 0.866 c. In the
stationary frame, parallel to the x-axis there is a rod and a
rotating cylinder. The end points of the rod and the rotating
cylinder are at the same x coordinates. The diameter of the
cylinder is 10 meters and the cylinder is rotating at 10
revolutions per second.

As measured in the moving frame, let the length of the rod and the
length of the rotating cylinder be 1 light-second. At time t0 as
measured in the moving frame, each point of the rod is
simultaneously attached to the surface of the rotating cylinder.
(Assume the rod is made of a material that is very malleable).

As viewed in the stationary frame, one end of the rod was attached
to the rotating cylinder 1.73 seconds before the other end.

Ok.

That means
that the rod wrapped around the cylinder about 17 times in a
spiral pattern.

Nope. From the stationary frame, the rod was rotating along with the
line drawn straight along the surface of the cylinder drawn by a
laser level device before the rod was ever joined to the cylinder.
No. The rod develops a rotation because it is attached to the
rotating cylinder. Prior to being attached, the rod is not rotating
and has zero velocity wrt to the longitudinal axis of the cylinder.


You have a slight problem.
you said:
In the stationary
frame, parallel to the x-axis there is a rod and a rotating
cylinder. The end points of the rod and the rotating cylinder are
at the same x coordinates. The diameter of the cylinder is 10
meters and the cylinder is rotating at 10 revolutions per second.

That puts one end of the rod and some [poorly specified] point on the
rotating cylinder at the same point.

If I assume the point is on the circumference of the cylinder rather
than the center of the cylender [that would make for all kinds of
problems] then you have infinite acceleration of the rod at the moment
of attachment.

Only if the rod is already in motion, can it be attached to the
cylinder.
No. The circumference of the rotating cylinder is about 31 meters.
At 10 revolutions per second, the surface of the cylinder is moving at
about 310 meters / second. Let's say the cylinder contains an
extremely powerful electromagnet, and the rod is steel. When the
magnet is turned on, if the force is strong enough, the magnet will
keep the rod attached to the rotating cylinder. There are thousands
of ways to do this attachment. Surely, you agree that if the rotation
speed is very low, say 0.001 revolutions per second, there would be no
problem attaching the rod to the cylinder - you can do this experiment
with short rod segments. I only picked 10 revolutions per second so
that its easier to envision the rod spiraled completely around the
cylinder as opposed to spiraled over a very small angle.
David

delta v / delta t = acceleration.
Okay, I see what you are saying, I think. I think you are saying
because I said the attachment for each point of the rod takes place at
the same time, t0, you think that means delta t = 0. I guess, I
should have been more precise and pedantic. Let's do that and say the
acceleration time for the rod to equal the rotational speed of the
surface of the rotating rod is 0.1 second and the acceleration starts
at each point at time t0 as measured in the moving frame.
David

ok.

So now, we, like the viewer of a reflection in a funhouse mirror, see an
optical illusion as we see the 0.1 second moment move away from us
[presumably we have a very powerful telescope with zoom capability that
has been programmed to focus on that moment, as it appears to move away
from us.

We see the optical equivalent of a thunder roll, as the sound from
different portions of the path reach our ears.

We recognize that sight and sound can be missleading and that no wrapping
actually occurs.

you have a finite change in velocity (delta v) taking place in zero time
(delta t). This gives infinite acceleration.

Only if the rod is already in motion, can it be attached to the
cylinder.


The stationary observer is intellegent enough to realize that light
moves in a straight line[in the rotating FoR] and that the optical
delusion of a 17 times wrap is exactly that.
....

When I look at myself in a funhouse mirror, I know that I really do
NOT get long and thin or short and fat. When I look at something in
another FoR, I know that things look different from that FoR.



--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is
an infinite set.

remove ch100-5 to avoid spam trap







--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

remove ch100-5 to avoid spam trap

On Tue, 23 Aug 2005 09:41:49 +0000 (UTC), bz
wrote:

wrote in
:

On Mon, 22 Aug 2005 15:48:25 +0000 (UTC), bz
wrote:

wrote in
:

On Sat, 20 Aug 2005 22:55:42 +0000 (UTC), bz
wrote:

wrote in
:

On Fri, 19 Aug 2005 15:07:03 +0000 (UTC), bz
wrote:

wrote in news:4305d0b7.540887@news-
server.austin.rr.com:

This problem is a combination of several problems I've posted in
this group. When I combine the problems, the answers given to me
in previous posts don't work. Here's the problem.

I have two frames which I will call the stationary frame and the
moving frame. Their relative velocity is 0.866 c. In the
stationary frame, parallel to the x-axis there is a rod and a
rotating cylinder. The end points of the rod and the rotating
cylinder are at the same x coordinates. The diameter of the
cylinder is 10 meters and the cylinder is rotating at 10
revolutions per second.

As measured in the moving frame, let the length of the rod and the
length of the rotating cylinder be 1 light-second. At time t0 as
measured in the moving frame, each point of the rod is
simultaneously attached to the surface of the rotating cylinder.
(Assume the rod is made of a material that is very malleable).

As viewed in the stationary frame, one end of the rod was attached
to the rotating cylinder 1.73 seconds before the other end.

Ok.

That means
that the rod wrapped around the cylinder about 17 times in a
spiral pattern.

Nope. From the stationary frame, the rod was rotating along with the
line drawn straight along the surface of the cylinder drawn by a
laser level device before the rod was ever joined to the cylinder.
No. The rod develops a rotation because it is attached to the
rotating cylinder. Prior to being attached, the rod is not rotating
and has zero velocity wrt to the longitudinal axis of the cylinder.


You have a slight problem.
you said:
In the stationary
frame, parallel to the x-axis there is a rod and a rotating
cylinder. The end points of the rod and the rotating cylinder are
at the same x coordinates. The diameter of the cylinder is 10
meters and the cylinder is rotating at 10 revolutions per second.

That puts one end of the rod and some [poorly specified] point on the
rotating cylinder at the same point.

If I assume the point is on the circumference of the cylinder rather
than the center of the cylender [that would make for all kinds of
problems] then you have infinite acceleration of the rod at the moment
of attachment.

Only if the rod is already in motion, can it be attached to the
cylinder.
No. The circumference of the rotating cylinder is about 31 meters.
At 10 revolutions per second, the surface of the cylinder is moving at
about 310 meters / second. Let's say the cylinder contains an
extremely powerful electromagnet, and the rod is steel. When the
magnet is turned on, if the force is strong enough, the magnet will
keep the rod attached to the rotating cylinder. There are thousands
of ways to do this attachment. Surely, you agree that if the rotation
speed is very low, say 0.001 revolutions per second, there would be no
problem attaching the rod to the cylinder - you can do this experiment
with short rod segments. I only picked 10 revolutions per second so
that its easier to envision the rod spiraled completely around the
cylinder as opposed to spiraled over a very small angle.
David

delta v / delta t = acceleration.
Okay, I see what you are saying, I think. I think you are saying
because I said the attachment for each point of the rod takes place at
the same time, t0, you think that means delta t = 0. I guess, I
should have been more precise and pedantic. Let's do that and say the
acceleration time for the rod to equal the rotational speed of the
surface of the rotating rod is 0.1 second and the acceleration starts
at each point at time t0 as measured in the moving frame.
David

ok.

So now, we, like the viewer of a reflection in a funhouse mirror, see an
optical illusion as we see the 0.1 second moment move away from us
[presumably we have a very powerful telescope with zoom capability that
has been programmed to focus on that moment, as it appears to move away
from us.

We see the optical equivalent of a thunder roll, as the sound from
different portions of the path reach our ears.

We recognize that sight and sound can be missleading and that no wrapping
actually occurs.
Wrapping actually does occur. In the rest frame of the rod and of the
rotating cylinder, we are attaching one end of the rod to the cylinder
a second before we attach the other end. The cylinder rotates 10
times before the other end is attached. Since the speeds are everyday
values can actually do this experiment over a much shorter length.
The short rod will attach to the short segment of the rotating disk,
and if we attach one end at a different time then we attach the other
end (the stationary frame view), the attached rod will spiral about
the cylinder. In the problem I posted because of the lengths involved
the spiral and wrapping occur over large distances, but it still
occurs.
David

you have a finite change in velocity (delta v) taking place in zero time
(delta t). This gives infinite acceleration.

Only if the rod is already in motion, can it be attached to the
cylinder.


The stationary observer is intellegent enough to realize that light
moves in a straight line[in the rotating FoR] and that the optical
delusion of a 17 times wrap is exactly that.
....

When I look at myself in a funhouse mirror, I know that I really do
NOT get long and thin or short and fat. When I look at something in
another FoR, I know that things look different from that FoR.



--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is
an infinite set.

remove ch100-5 to avoid spam trap







--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

remove ch100-5 to avoid spam trap

wrote in news:430b11f5.38471559@news-
server.austin.rr.com:

We see the optical equivalent of a thunder roll, as the sound from
different portions of the path reach our ears.

We recognize that sight and sound can be missleading and that no wrapping
actually occurs.
Wrapping actually does occur. In the rest frame of the rod and of the
rotating cylinder, we are attaching one end of the rod to the cylinder
a second before we attach the other end. The cylinder rotates 10
times before the other end is attached. Since the speeds are everyday
values can actually do this experiment over a much shorter length.
The short rod will attach to the short segment of the rotating disk,
and if we attach one end at a different time then we attach the other
end (the stationary frame view), the attached rod will spiral about
the cylinder. In the problem I posted because of the lengths involved
the spiral and wrapping occur over large distances, but it still
occurs.
David


Not if the attachment is done simultaniously all along the length using
sync'd clocks.

We could sync it another way:
At a great distance, we have a signal source. The signal from that source
approximates a plane wave all along the length of our cylinder.

BTW, at that distance, we have a powerful telescope and we watch the
joining take place. No twisting is observed.


--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

remove ch100-5 to avoid spam trap

wrote in message ...
On Mon, 22 Aug 2005 16:19:22 GMT, "Dirk Van de moortel"
wrote:


wrote in message ...
On Fri, 19 Aug 2005 16:27:39 GMT, "Dirk Van de moortel"
wrote:


wrote in message ...
This problem is a combination of several problems I've posted in this
group. When I combine the problems, the answers given to me in
previous posts don't work. Here's the problem.

Another everyday experience problem with 300000 km long
rigid rods, I presume?
http://users.pandora.be/vdmoortel/di.../Everyday.html

Dirk, the link you posted has pandora.be in it, from which I infer
refers to a country different than the United States of America. So
I'm guessing English is not your native language. If you carefully
read my sentence that you refer to in the above link, you will see
that I stated that the 300000 km length IS NOT part of my everyday
experience.

Sure.
I *had* carefully read your sentence and I understood it just
the way you had intended it. It was one of the funniest things
you ever wrote on this group.
Well, with the velocity being only 3 meters / second, and the
acceleration being only 1 g, I can experience how objects change (on a
local level) when they move from one reference frame to another. For
example, some posters in this group believe if the rod is made long
enough, a person holding one end of the rod will be accelerated to a
velocity approaching the speed of light. But with parameters like 3
meters / second and a 1 g acceleration it is easy for me to see that
that notion is incorrect. You may think of that as being "an
immortal fumble of David Seppala" but actually it helps me understand
things easier. You're not one of those people who think one end of
the rod travels at a speed close to the speed of light when it is
placed on a conveyer belt moving at 3 meters / second, are you? Or is
that why you label my approach as an immortal fumble?

Just compare your
| "Other than the rod being light-years in length, the parameters are
| values that occur in our daily experience."
with
"Your Honour, other than that bitchy wife of mine, I would never
kill anyone, so surely you're not going to put me behind bars?"

Dirk Vdm


David
In order for you not to think that I had misunderstood you
line, I now have put emphasis on the entire sentence:
| "Other than the rod being light-years in length, the parameters are
| values that occur in our daily experience."
You can check it at:
http://users.pandora.be/vdmoortel/di.../Everyday.html

Hope this helps!

Dirk Vdm

wrote:

We recognize that sight and sound can be missleading and that no wrapping
actually occurs.

Wrapping actually does occur. In the rest frame of the rod and of the
rotating cylinder, we are attaching one end of the rod to the cylinder
a second before we attach the other end. The cylinder rotates 10
times before the other end is attached. Since the speeds are everyday
values can actually do this experiment over a much shorter length.
The short rod will attach to the short segment of the rotating disk,
and if we attach one end at a different time then we attach the other
end (the stationary frame view), the attached rod will spiral about
the cylinder. In the problem I posted because of the lengths involved
the spiral and wrapping occur over large distances, but it still
occurs.
David

Right. If either of the two observers can be said to be measuring an
illusion, it is the non-local observer, who measures the rod to be
straight on a moving, length contracted, rotating cylinder.

The geometry and forces which are actually holding the rod to the
cylinder are local effects, and the rigidity of the coiled rod in the
stationary frame.

Aside: The nonlocal observer will only "see" the rod on the cylinder
as straight if and when the rod passes directly in front of him, on a
path perpendicular to his line of sight. Otherwise, differences in
light propagation times between the front and back of the rotating
cylinder will result in an image that does not perfectly represent the
"present" in his frame of reference.

When removing the rod/coil from the cylinder, you want to have a clamp
that comes down on all portions of the rod at once in the nonlocal
frame, and pulls it away from the cylinder with an instantaneous YOINK!

What the clamp will look like from the rest frame is more like a
zipper. In the stationary frame, the two edges of the clamp will not
come down toward each other parallel, but at an angle, meeting at a
point on the rod, gripping it, pulling it loose. The point would roll
up the clamp edges as it passed by, pulling the rod loose as it goes.

Since we have stiffened the rod, it will take considerably more force
to remove the coiled rod than it took to put it on there. Quite
possibly the clamp would simply fail to remove the the rod from the
rotating cylinder, slipping off the rod instead of grabbing hold of it.

I think your conundrum is that the rod appears to be straight in the
nonlocal frame, and it has not been glued to the cylinder; it has not
been increased in mass--it has only been stiffened. Why would
stiffening a straight rod cause it to be harder to remove from a
cylinder?


wrote:

We recognize that sight and sound can be missleading and that no wrapping
actually occurs.

Wrapping actually does occur. In the rest frame of the rod and of the
rotating cylinder, we are attaching one end of the rod to the cylinder
a second before we attach the other end. The cylinder rotates 10
times before the other end is attached. Since the speeds are everyday
values can actually do this experiment over a much shorter length.
The short rod will attach to the short segment of the rotating disk,
and if we attach one end at a different time then we attach the other
end (the stationary frame view), the attached rod will spiral about
the cylinder. In the problem I posted because of the lengths involved
the spiral and wrapping occur over large distances, but it still
occurs.
David

Right. If either of the two observers can be said to be measuring an
illusion, it is the non-local observer, who measures the rod to be
straight on a moving, length contracted, rotating cylinder.

The geometry and forces which are actually holding the rod to the
cylinder are local effects, and the rigidity of the coiled rod in the
stationary frame.

Aside: The nonlocal observer will only "see" the rod on the cylinder
as straight if and when the rod passes directly in front of him, on a
path perpendicular to his line of sight. Otherwise, differences in
light propagation times between the front and back of the rotating
cylinder will result in an image that does not perfectly represent the
"present" in his frame of reference.

When removing the rod/coil from the cylinder, you want to have a clamp
that comes down on all portions of the rod at once in the nonlocal
frame, and pulls it away from the cylinder with an instantaneous YOINK!

What the clamp will look like from the rest frame is more like a
zipper. In the stationary frame, the two edges of the clamp will not
come down toward each other parallel, but at an angle, meeting at a
point on the rod, gripping it, pulling it loose. The point would roll
up the clamp edges as it passed by, pulling the rod loose as it goes.

Since we have stiffened the rod, it will take considerably more force
to remove the coiled rod than it took to put it on there. Quite
possibly the clamp would simply fail to remove the the rod from the
rotating cylinder, slipping off the rod instead of grabbing hold of it.

I think your conundrum is that the rod appears to be straight in the
nonlocal frame, and it has not been glued to the cylinder; it has not
been increased in mass--it has only been stiffened. Why would
stiffening a straight rod cause it to be harder to remove from a
cylinder?

Am I obligated to insult you now since I don't know the exact answer?
Just kidding. I think the answer lies in the nature of the
collisions--where the rubber meets the road, so to speak. If you look
closely at the interactions and forces between the particles in the
rod/coil, and in the clamp/zipper (in either frame), you'll find that
they are more tightly bound to the cylinder after the rod has been
stiffened.

The analysis of exactly how the apparently straight rope attaches
itself in the moving frame is still probably a fairly intricate
problem.

Sorry about the double-post there. The first 7 paragraphs got repeated.