Merely by assuming the self-consistency and reciprocity of the "barn-
pole paradox", we can form some estimates on the velocities necessary
to observe a given degree of length contraction, without any prior
knowledge of the Lorentz transformation.

Assume that lengths in fact contract with velocity, that the effect is
reciprocal between relatively moving observers, and that no signals
can travel faster than c.

In the rest frame of a 40m barn, say a pole of rest length 80m is
approaching at a velocity sufficient so that doors on both sides of
the barn can just be closed before there is a collision. Since the
tail end of the pole makes it in the door in this frame, we know this
event must happen in any frame.

Now look at the rest frame of the pole, which is being approached by a
hyper-velocity barn of apparent length 20m, by reciprocity of the
effect! Assuming the far door is shut, and strikes the pole, we know
that no effect, even one traveling at c, can prevent the tail of the
pole from making it inside the other door. Any impulse from the
collision has 80m to travel to the end of the pole, whereas the near
end of the barn only has 60m. So assuming the impulse and the nearer
barn door just make it to the end of the pole simultaneously, we would
say the relative closing speed is .75c.

The relative speed is actually faster than that, since we know in the
rest frame of the barn that the tail end of the pole crosses the
threshold of the door and meets any light speed impulse traveling from
the impact somewhere inside the barn. We could refine our estimate,
or even possibly derive the exact relation, from similar
considerations, but merely by assuming the consistency of special
relativity and not knowing much else, we can immediately say that an
object must be traveling greater than 3/4 c in order to display a 50%
length contraction.

I think that's kind of neat.

Am Tue, 02 Sep 2008 19:13:06 -0700 schrieb Edward Green
in
:

[...]
Assume that lengths in fact contract with velocity, that the effect is

This was the Fitzgerald assumption. He based it on the fact that at the
time nobody really knew the true nature of atoms. So maybe they shrunk
in the direction of movement. As it turned out though, Einstein's reason
stood up better than Fitzgerald's even though both had the same equation.

reciprocal between relatively moving observers, and that no signals can
travel faster than c.

In the rest frame of a 40m barn, say a pole of rest length 80m is
approaching at a velocity sufficient so that doors on both sides of the
barn can just be closed before there is a collision. Since the tail end
of the pole makes it in the door in this frame, we know this event must
happen in any frame.

The point to the Fitzgerald postulate was that it could *not* happen in
any frame, only the rest frame. Since the rest frame was the preferred
frame, it was the one that the aether was at rest in. The concept of no
preferred frames was automatically built into Einstein's view. That is
why, as an aside, there was no need for aether under Einstein's view.


Now look at the rest frame of the pole, which is being approached by a

Under the Fitzgerald view, the rest frame is the barn frame. The pole
frame is the moving frame.

[...]
I think that's kind of neat.

You're not the first one to come up with this sort of scenario. However,
like Fitzgerald's view, you can not be sure of what is really a rest
frame, since even though the barn is not moving, it's on Earth and the
Earth is moving. Einstein cut through this by saying that you can not
say that something is at rest in the absolute. Things are only at rest
with respect to themselves and moving with respect to other objects.
That is the main reason the Einstein won out over Fitzgerald.

--
// The TimeLord says:
// Pogo 2.0 = We have met the aliens, and they are us!

Edward Green wrote in message

Merely by assuming the self-consistency and reciprocity of the "barn-
pole paradox", we can form some estimates on the velocities necessary
to observe a given degree of length contraction, without any prior
knowledge of the Lorentz transformation.

Assume that lengths in fact contract with velocity, that the effect is
reciprocal between relatively moving observers, and that no signals
can travel faster than c.

In the rest frame of a 40m barn, say a pole of rest length 80m is
approaching at a velocity sufficient so that doors on both sides of
the barn can just be closed before there is a collision. Since the
tail end of the pole makes it in the door in this frame, we know this
event must happen in any frame.

Now look at the rest frame of the pole, which is being approached by a
hyper-velocity barn of apparent length 20m, by reciprocity of the
effect! Assuming the far door is shut, and strikes the pole, we know
that no effect, even one traveling at c, can prevent the tail of the
pole from making it inside the other door. Any impulse from the
collision has 80m to travel to the end of the pole, whereas the near
end of the barn only has 60m. So assuming the impulse and the nearer
barn door just make it to the end of the pole simultaneously, we would
say the relative closing speed is .75c.

The relative speed is actually faster than that, since we know in the
rest frame of the barn that the tail end of the pole crosses the
threshold of the door and meets any light speed impulse traveling from
the impact somewhere inside the barn. We could refine our estimate,
or even possibly derive the exact relation, from similar
considerations, but merely by assuming the consistency of special
relativity and not knowing much else, we can immediately say that an
object must be traveling greater than 3/4 c in order to display a 50%
length contraction.

I think that's kind of neat.

I don't want to spoil the fun, but if I understand correctly, you
have found that for every gamma g 1, the "real" velocity
v/c = sqrt( 1 - 1/g^2 )
is always greater than your estimate
v/c = 1 - 1/g^2
:-)

Dirk Vdm

On Sep 4, 7:11*am, "Dirk Van de moortel"
wrote:
Edward Green wrote in message

*





Merely by assuming the self-consistency and reciprocity of the "barn-
pole paradox", we can form some estimates on the velocities necessary
to observe a given degree of length contraction, without any prior
knowledge of the Lorentz transformation.

Assume that lengths in fact contract with velocity, that the effect is
reciprocal between relatively moving observers, and that no signals
can travel faster than c.

In the rest frame of a 40m barn, say a pole of rest length 80m is
approaching at a velocity sufficient so that doors on both sides of
the barn can just be closed before there is a collision. *Since the
tail end of the pole makes it in the door in this frame, we know this
event must happen in any frame.

Now look at the rest frame of the pole, which is being approached by a
hyper-velocity barn of apparent length 20m, by reciprocity of the
effect! *Assuming the far door is shut, and strikes the pole, we know
that no effect, even one traveling at c, can prevent the tail of the
pole from making it inside the other door. *Any impulse from the
collision has 80m to travel to the end of the pole, whereas the near
end of the barn only has 60m. *So assuming the impulse and the nearer
barn door just make it to the end of the pole simultaneously, we would
say the relative closing speed is .75c.

The relative speed is actually faster than that, since we know in the
rest frame of the barn that the tail end of the pole crosses the
threshold of the door and meets any light speed impulse traveling from
the impact somewhere inside the barn. *We could refine our estimate,
or even possibly derive the exact relation, from similar
considerations, but merely by assuming the consistency of special
relativity and not knowing much else, we can immediately say that an
object must be traveling greater than 3/4 c in order to display a 50%
length contraction.

I think that's kind of neat.

I don't want to spoil the fun, but if I understand correctly, you
have found that for every gamma g 1, the "real" velocity
* * * * v/c = sqrt( 1 - 1/g^2 )
is always greater than your estimate
* * * * v/c = 1 - 1/g^2
:-)

Oh yes, if you want to put some actual _equations_ in the thing, my
insight looks pretty stupid! But I'd prefer not to think of it that
way. I'd prefer to think of it as a half-assed and incomplete
rederivation of the Lorentz transformation. I still think it's
interesting, even with half an ass. ;-)

Edward Green wrote in message

On Sep 4, 7:11 am, "Dirk Van de moortel"
wrote:
Edward Green wrote in message







Merely by assuming the self-consistency and reciprocity of the "barn-
pole paradox", we can form some estimates on the velocities necessary
to observe a given degree of length contraction, without any prior
knowledge of the Lorentz transformation.

Assume that lengths in fact contract with velocity, that the effect is
reciprocal between relatively moving observers, and that no signals
can travel faster than c.

In the rest frame of a 40m barn, say a pole of rest length 80m is
approaching at a velocity sufficient so that doors on both sides of
the barn can just be closed before there is a collision. Since the
tail end of the pole makes it in the door in this frame, we know this
event must happen in any frame.

Now look at the rest frame of the pole, which is being approached by a
hyper-velocity barn of apparent length 20m, by reciprocity of the
effect! Assuming the far door is shut, and strikes the pole, we know
that no effect, even one traveling at c, can prevent the tail of the
pole from making it inside the other door. Any impulse from the
collision has 80m to travel to the end of the pole, whereas the near
end of the barn only has 60m. So assuming the impulse and the nearer
barn door just make it to the end of the pole simultaneously, we would
say the relative closing speed is .75c.

The relative speed is actually faster than that, since we know in the
rest frame of the barn that the tail end of the pole crosses the
threshold of the door and meets any light speed impulse traveling from
the impact somewhere inside the barn. We could refine our estimate,
or even possibly derive the exact relation, from similar
considerations, but merely by assuming the consistency of special
relativity and not knowing much else, we can immediately say that an
object must be traveling greater than 3/4 c in order to display a 50%
length contraction.

I think that's kind of neat.

I don't want to spoil the fun, but if I understand correctly, you
have found that for every gamma g 1, the "real" velocity
v/c = sqrt( 1 - 1/g^2 )
is always greater than your estimate
v/c = 1 - 1/g^2
:-)

Oh yes, if you want to put some actual _equations_ in the thing, my
insight looks pretty stupid! But I'd prefer not to think of it that
way. I'd prefer to think of it as a half-assed and incomplete
rederivation of the Lorentz transformation. I still think it's
interesting, even with half an ass. ;-)

Well, anyway... the higher gamma, the closer your lower bound
estimate to the real thing :-)

Dirk Vdm

On Sep 3, 3:41*pm, The TimeLord wrote:
Am Tue, 02 Sep 2008 19:13:06 -0700 schrieb Edward Green
in
:

[...]

Assume that lengths in fact contract with velocity, that the effect is

This was the Fitzgerald assumption. He based it on the fact that at the
time nobody really knew the true nature of atoms. So maybe they shrunk
in the direction of movement. As it turned out though, Einstein's reason
stood up better than Fitzgerald's even though both had the same equation.

reciprocal between relatively moving observers, and that no signals can
travel faster than c.

In the rest frame of a 40m barn, say a pole of rest length 80m is
approaching at a velocity sufficient so that doors on both sides of the
barn can just be closed before there is a collision. *Since the tail end
of the pole makes it in the door in this frame, we know this event must
happen in any frame.

The point to the Fitzgerald postulate was that it could *not* happen in
any frame, only the rest frame. Since the rest frame was the preferred
frame, it was the one that the aether was at rest in. The concept of no
preferred frames was automatically built into Einstein's view. That is
why, as an aside, there was no need for aether under Einstein's view.



Now look at the rest frame of the pole, which is being approached by a

Under the Fitzgerald view, the rest frame is the barn frame. The pole
frame is the moving frame.

[...]

I think that's kind of neat.

You're not the first one to come up with this sort of scenario. However,
like Fitzgerald's view, you can not be sure of what is really a rest
frame, since even though the barn is not moving, it's on Earth and the
Earth is moving. Einstein cut through this by saying that you can not
say that something is at rest in the absolute. Things are only at rest
with respect to themselves and moving with respect to other objects.
That is the main reason the Einstein won out over Fitzgerald.

I think you are reading too much into my simple thought experiment: I
had no intention of contrasting some "Fitzgerald" point of view with
an "Einstein" point of view. I simply applied some well accepted
results of relativity: A sees B as length contracted, and B sees A as
length contracted, where "sees" means under notions of simultaneity in
their proper frames (when A and B are in relative motion).

I also think you are reading too much into the into the alleged
triumph of the Einstein view over the Fitzgerald (or Lorentz) view,
which I will venture to express that "objects in motion really
contract because of physical processes". I would prefer to see the
result as a concept-splitting on "really". You may be focusing on the
reciprocity of the effect: since anything A can say of B, B can say of
A, then you may conclude that length contraction cannot be "real". On
the other hand, length contraction is as "real" in a fixed frame of
reference as any physical effect: it enables objects to momentarily
fit inside (at least brief simultaneous enclosure without any
mechanical interference) spaces where they would not ordinarily be
able to fit, and it causes strings to break which other wise would be
long enough to span a certain distance (Bell space ship paradox), and
it introduces mechanical stresses into rotating objects (Ehrenfest
disk).

All these effects are certainly "real", and easy to understand,
provided we hold onto the idea that length contraction is a real
physical effect of motion as seen in any fixed inertial frame -- as
real as Fitzgerald or Lorentz could have wished. If we focus on the
apparent complete reciprocity of the effect among inertial frames, and
conclude that since it is not "real" in this sense it cannot be "real"
in the sense of being a physical effect we can deal with as a peer
among other physical effects in a given inertial frame, then we create
confusion for ourselves.

As far as a fixed inertial observer is concerned, atoms, and
structures built out of them, really become shorter in their direction
of motion.

On Sep 5, 12:20 pm, Edward Green wrote:
[...]

As far as a fixed inertial observer is concerned, atoms, and
structures built out of them, really become shorter in their direction
of motion.


Ahem...
You think if I put my watch on big bottle rocket and
blast is off, your watch is going to change shape ?


A relativistic particle is a

-- subatomic --

particle moving at relativistic speed.
http://en.wikipedia.org/wiki/Relativistic_speed

Such a particle is characterised by the
*probability* of some length or time not
the certainty that some time associates
with some length.

http://en.wikipedia.org/wiki/Uncertainty_principle

Sue...

On Sep 5, 1:35*pm, "Sue..." wrote:
On Sep 5, 12:20 pm, Edward Green wrote:
[...]



As far as a fixed inertial observer is concerned, atoms, and
structures built out of them, really become shorter in their direction
of motion.

Ahem...
You think if I put my watch on big bottle rocket and
blast is off, your watch is going to change shape ?

That's a vague question. But if you mean, that if you are
sufficiently equivalent to an inertial observer, as can be judged by
bench top experiments in your rest frame, and if your watch is
traveling at a substantial fraction of c in your rest frame, then,
yes, I expect your watch to change shape, in the narrowly defined
sense of special relativity, in so much that it will be shortened in
the direction of motion as measured by any instruments or method in
your rest frame which establish simultaneous locations of front and
back surfaces, and that this shortening will have all the normal
physical consequences of "size" in your frame, including but not
limited to, entrapment in barns, tightening of strings, and stress in
larger objects of which your watch may form a composite part, not all
of which composite parts are simultaneously traveling with identical
velocity, as will be observed in a rotating object.

That's hardly controversial, being a normal consequence of special
relativity, except, therefore, among those people who do not
understand special relativity, and those people who like to affect
that they understand a lot about a large number of things, by
stringing together references and ideas domino fashion, so that some
part of each moiety matches but that no larger patterns is formed,
such class of persons possibly, but not necessarily, including the
contributor to various internet groups who signs itself as "Sue".

A relativistic particle is a

* *-- * * *subatomic * *--

particle moving at relativistic speed. http://en.wikipedia.org/wiki/Relativistic_speed

Such a particle is characterised by the
*probability* of some length or time not
the certainty that some time associates
with some length.

http://en.wikipedia.org/wiki/Uncertainty_principle

That's vintage "Sue". I am talking of the consequences of special
relativity for macroscopic objects, and you try to shift the topic to
microscopic objects, implying, along the way, that special relativity
only applies to subatomic particles, which is simply nonsense.

You are an enigma, it may give you pleasure to read, for remaining an
enigma is at least compatible with the unknown set comprising your
motivations, which are somewhere enclosed in the convex hull whose
vertices include "trolling", "random association of scientific ideas",
and "scientifically flavored experiment in AI, with a strong
resemblance to ELIZA or PARRY".

I've allowed myself to become annoyed by a SUEBOT!

On Sep 5, 9:15 pm, Edward Green wrote:
On Sep 5, 1:35 pm, "Sue..." wrote:

On Sep 5, 12:20 pm, Edward Green wrote:
[...]

As far as a fixed inertial observer is concerned, atoms, and
structures built out of them, really become shorter in their direction
of motion.

Ahem...
You think if I put my watch on big bottle rocket and
blast is off, your watch is going to change shape ?

That's a vague question. But if you mean, that if you are
sufficiently equivalent to an inertial observer, as can be judged by
bench top experiments in your rest frame, and if your watch is
traveling at a substantial fraction of c in your rest frame, then,
yes, I expect your watch to change shape, in the narrowly defined
sense of special relativity, in so much that it will be shortened in
the direction of motion as measured by any instruments or method in
your rest frame which establish simultaneous locations of front and
back surfaces, and that this shortening will have all the normal
physical consequences of "size" in your frame, including but not
limited to, entrapment in barns, tightening of strings, and stress in
larger objects of which your watch may form a composite part, not all
of which composite parts are simultaneously traveling with identical
velocity, as will be observed in a rotating object.

That's hardly controversial, being a normal consequence of special
relativity, except, therefore, among those people who do not
understand special relativity, and those people who like to affect
that they understand a lot about a large number of things, by
stringing together references and ideas domino fashion, so that some
part of each moiety matches but that no larger patterns is formed,
such class of persons possibly, but not necessarily, including the
contributor to various internet groups who signs itself as "Sue".

A relativistic particle is a

-- subatomic --

particle moving at relativistic speed. http://en.wikipedia.org/wiki/Relativistic_speed

Such a particle is characterised by the
*probability* of some length or time not
the certainty that some time associates
with some length.

http://en.wikipedia.org/wiki/Uncertainty_principle

That's vintage "Sue". I am talking of the consequences of special
relativity for macroscopic objects, and you try to shift the topic to
microscopic objects, implying, along the way, that special relativity
only applies to subatomic particles, which is simply nonsense.

Today the "special theory" exists only
(aside from its historical importance) as a
convenient set of widely applicable formulas
for important limiting cases of the general
theory, but the phenomenological justification
for those formulas can only be found in the
general theory.
http://www.mathpages.com/rr/s4-07/4-07.htm

Relativistic particle dynamics
http://farside.ph.utexas.edu/teachin...s/node126.html

Sue...



You are an enigma, it may give you pleasure to read, for remaining an
enigma is at least compatible with the unknown set comprising your
motivations, which are somewhere enclosed in the convex hull whose
vertices include "trolling", "random association of scientific ideas",
and "scientifically flavored experiment in AI, with a strong
resemblance to ELIZA or PARRY".

I've allowed myself to become annoyed by a SUEBOT!

On Sep 5, 10:25 pm, "Sue..." wrote:
On Sep 5, 9:15 pm, Edward Green wrote:





On Sep 5, 1:35 pm, "Sue..." wrote:

You think if I put my watch on big bottle rocket and
blast is off, your watch is going to change shape ?

…

That's hardly controversial, being a normal consequence of special
relativity, except, therefore, among those people who do not
understand special relativity, and those people who like to affect
that they understand a lot about a large number of things, by
stringing together references and ideas domino fashion, so that some
part of each moiety matches but that no larger patterns is formed,
such class of persons possibly, but not necessarily, including the
contributor to various internet groups who signs itself as "Sue".

A relativistic particle is a

-- subatomic --

particle moving at relativistic speed. http://en.wikipedia.org/wiki/Relativistic_speed

Such a particle is characterised by the
*probability* of some length or time not
the certainty that some time associates
with some length.

http://en.wikipedia.org/wiki/Uncertainty_principle

Today the "special theory" exists only
(aside from its historical importance) as a
convenient set of widely applicable formulas
for important limiting cases of the general
theory, but the phenomenological justification
for those formulas can only be found in the
general theory. http://www.mathpages.com/rr/s4-07/4-07.htm

Yet another random citation. That doesn't change anything. As a
"limiting case" of general relativity, the "widely applicable"
formulas of special relativity apply to macroscopic assemblages of
particles, provided, obviously, they transverse regions of spacetime
which may be taken as approximately flat. This is true regardless
whether we take the "limiting case" to be of general relativity, or of
macroscopic objects as opposed to quantum objects.

That includes your watch.

Relativistic particle dynamicshttp://farside.ph.utexas.edu/teaching/em/lectures/node126.html

Which has precisely what to do with your apparent claim that the
equations of special relativity are inapplicable to macroscopic
objects?