Re: Another Rotating Cylinder Problem - explain from moving frame view
- From: David <dseppala@xxxxxxxxxxxxx>
- Date: Mon, 17 Apr 2006 03:16:54 GMT
On Sat, 15 Apr 2006 11:02:17 +0100, "Martin Hogbin"
<goatREMOVETHIS123@xxxxxxxxxx> wrote:
I cannot demonstrate a clear "understanding" of Einstein's postulates.
"David" <dseppala@xxxxxxxxxxxxx> wrote in message news:2781421lvufjvsa14pmj5fnvk52d3mutdd@xxxxxxxxxx
On Fri, 14 Apr 2006 18:29:50 +0100, "Martin Hogbin"
<goatREMOVETHIS123@xxxxxxxxxx> wrote:
He is none of the above. David's understanding of Einstein's notions
"David" <dseppala@xxxxxxxxxxxxx> wrote in message news:5e5v32hhd167p57ikjfcvnfm82o1thjecu@xxxxxxxxxx
Can anyone explain this rotating disk problem from the point of view
of a moving observer?
Davis Seppala is one of the mysteries of this group. Unlike
Spaceman, for example, he is smart enough to dream up
endless SR puzzles, many of them involving accelerating
reference frames, yet by his own admission he has practically
no understanding of SR.
Is he really an expert on the subject testing posters'
understanding?
Is he a bunch of psychology students performing
some kind of experiment on us all?
Is he just a troll who delights in stirring up discussion
and argument?
Any suggestions?
so far is much like David's comprehension of E. M. Escher's drawings.
He gets to points in problems where there seems to be contradictory
results as in his posting on 4/10/2006 where a moving rigid rod is
always parallel to the x-axis and loops about the x-axis in a circular
pattern at a 10 meter diamter circle yet no forces are applied to the
rod to make it continue in this circular pattern. Or in this posting
where as tension on a straight wire increases the center of the wire
moves away from a straight line. This is opposite to typical
experiences - wires form straight lines when stretched from two points
with nothing in between them to interfere with the straight line. This
does not make sense to David.
Then what David should do, as he has been told many times,
is to make sure he fully understands basic SR _in inertial
frames_ with only _inertial motion_ involved.
If he could demonstrate a sound understanding of Einstein's
postulates,
I know the two main hypotheses stated in relativity are that all
physical laws are the same in any given inertial reference frame and
that the speed of light is constant and independent of the motion of
the emitting source. The translated text I read actually used the
word "velocity" of light instead of speed. We all know the velocity
of light (speed and direction) must vary with the motion of the light
source but the speed can possibly be constant. Although stated as a
definition and not as a hypothesis Einstein states that "time" at two
points cannot be defined at all unless the "time" required to travel
from A to B equals the "time" required to travel from B to A. I
readily admit that this statement of time that Einstein characterizes
as "true by definition" seems to me more like a hypothesis than
something true by definition.
what an inertial frame is,An inertial frame is one in which no accelerations or higher order
changes in position of objects occur. In in a real sense we do not
find inertial frames except in rare situations since any kind of
motion causes the frame to accelerate slightly. But these are
negligible in a practical sense.
the train experiment,I'm not certain which train experiment you are referring to. To
demonstrate that one inertial frame is identical to every other frame
there is a real life experiment where the acceleration of a train is
so small that passengers on either of two trains cannot easily tell
which train is moving out of the station or not. This is not much of
a physics experiment since it merely demonstrates lack of needed
sensitivity in measuring devices, so I don't know if this is the
experiment you are referring to or not.
and the pole and barn paradox the others would be muchThe pole and barn paradox. What am I supposed to do here? Plug in
more willing to help him.
values in the time and length separation formulas to show in one
inertial frame where the two door closings are simultaneous and the
pole just fits gives values that in another inertial frame the two
doors open and close at different times and this is compensated
precisely by the legnth contraction? Maybe you want me to plug in the
length contraction, and then add the product of the time difference &
V (distance traveled) to see if I get the correct number. This only
demonstrates an understanding of algebra.
I suspect this posting still won't result in any physics answers to my
I should point out that is no good his saying, 'Yes, yes, yes,
I know all that', he must clearly demonstrate that he
fully understands basic SR before anyone will accept that
his questions are serious.
two cylinder questions I posted - this one and the one 4/10/2006.
But we'll see.
David
.
Will he make a concerted effort to understand the basics
and show that he has done so or will he continue as
before? We shall see.
Martin Hogbin
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