Re: Length definition in SR - can anyone explain

On Sun, 23 Apr 2006 08:45:57 GMT, "Dirk Van de moortel"
<dirkvandemoortel@xxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:


"David" <dseppala@xxxxxxxxxxxxx> wrote in message news:9ljl42h2ip4t7v9eo6ftm7uaok527v9vjd@xxxxxxxxxx
On Thu, 20 Apr 2006 19:06:36 GMT, "Dirk Van de moortel"
<dirkvandemoortel@xxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:


"Martin Hogbin" <goatREMOVETHIS123@xxxxxxxxxx> wrote in message news:AJadnSbcgbxUKdvZRVny1Q@xxxxxxxxx

"Dirk Van de moortel" <dirkvandemoortel@xxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:8Lx1g.381376$kU7.11025545@xxxxxxxxxxxxxxxxxxxxxxxx

"Martin Hogbin" <goatREMOVETHIS123@xxxxxxxxxx> wrote in message news:-N2dnTAc79tAOtvZRVnyig@xxxxxxxxx

"David" <dseppala@xxxxxxxxxxxxx> wrote in message news:v8lc42dpp731snaggm8eg2me89b5ne4q77@xxxxxxxxxx
I'm trying to understand fundamental concepts of SR like time and
length. In my posting about clocks I got a varied opinions of what
constitutes a clock. This posting is a question about lengths. Can
anyone explain why this is or isn't allowed in SR?

I'm in an inertial frame.

An excellent start.

Since the speed of light is constant I
decide to make my standard unit of length equal to one light-second
(the distance light travels in one second as measured by synchronized
clocks in my inertial frame).

Good idea.

Now let there be an inertial frame moving along the x axis with
velocity V = 0.866c relative to my frame.
At time t0 I fire two lasers for a one second burst. The length of
each pulse is one light-second. The lasers are aligned along the
x-axis. One points in the positive direction, the other points in the
negative direction.

The moving observer measures the length of one pulse to be much less
than the length of the other pulse...

Why?

He properly explained in another message.

OK, I should have looked at his conversation with you first.

Let us see how he goes on this one.

It seems that he just lost interest in it. He already posted a
new problem. It is, as always, a variation of the previous one.
Now he brought probability into the picture again:
http://www.google.com/search?sourceid=navclient&q=seppala+probability
Next step will be an infinitely rigid conveyer belt two
lightyears long. After that we will probably get some new
questions about giant rotating cylinders.
Every time someone answers or solves one of his "questions"
or "problems", he responds with a period of dead silence,
and then he comes with a "new" variation of one of his old
problems.

From yesterday on this very thread he could have learned that
carefully specifying his "problems" with events and coordinates
is the only way to make them crystal clear and understandable
by everyone, including himself - and then the problem solves
itself. Just look at the first reactions of different people to his
opening post.
So he just ignored it and posted a "new" problem, again with
his own classic style. It wouldn't surprise me that he merely
copied it from a few years ago.
I think he once again clearly demonstrated that he is just a (very
patient) troll with the purpose to make you work and test you.
I think he is a *very* dishonest person.

Dirk Vdm

Hey Dirk look at your postings. Here's the summary of your responses
to my question.

Dirk's first reponse - why do you believe that?
David's response - I thought it was well known.
Dirk's second reponse - Try to explain your results using events and
length calculations
David's response - David listed events and calculations so Dirk
could agree with obvious statements in David's original post.
Dirk's third response - I agree with your first statement in first
posting.
Dirk's fourth response - Dirk posted definition of closing speeds.

Right, and this is where the relevance of the list stops. You
fail to take into account your and my simultaneous behaviour
on other threads. Up to this point you were doing just fine,
and from this point I was waiting for you to acknowledge,
and nicely continue using the same style, which you did not.
In stead you ignored the responses and, exactly like you
always have been doing, you started another thread with a
related 'problem'. So it became clear that again you had
merely demonstrated your usual modus operandi, which I
somewhat summarized in my message to Martin.

Think about this, Seppala... Even if, hypothetically speaking,
you *would be* a really honest person with really honest
questions, after all these years your still show the behaviour
of a malicious little troll. So, after been explained how to
avoid it and refusing to do so, you are and will continue to
be treated just like the other malicious little trolls over here.
The only person who can do something against the way you
are treated, is you. The fact that you don't, clearely shows
that you show sings of autism, or plain stupidity at best.
Paul Simon has a song lyric that says "People believe what they want
to believe and disregard all the rest." Not a good quality for a
physicist to have. But you may believe what you want to.

Now, back to business with the answer to your new thread.
You can find it right here:
http://groups.google.com/groups?sourceid=navclient&q=seppala%20probability
Try just a little bit harder.
Well that search just leads me back to a similar but different
question about asteroids. In this problem, this is really a question
about the range of speeds my photon emitting device can have and the
solution given for the asteroid problem doesn't apply. In this
problem, I made the light pulse-photon emitting device independent of
the laser pulse generater which changes the question to that of what
range of velocities can the devices have. The typical SR answer for
this problem is an infinite range and this leads to a probability the
way I calculate it as the same for all pulse widths if I apply
detection limits to the photon emitting devices or the conclusion that
the experiment is not repeatable and no consistent probability exists
if the photon emitter-dectection device of the problem has an infinite
detection bandwidth and ability to detect infinitesmal signals. But
two problems arise from these results.
I find that if there is no absolute limit to velocity - that is
there is only a relative limit to velocity and not an absolute limit
as SR dictates then
1. My length measurement posting in which most posters agree has
different pulse widths for the same pulse implies that if the pulse is
comprised of N photons, then either the spacing between photons must
vary or the length of a photon must vary or the concept of a discrete
number of photons per pulse is flawed. If V has no absolute limit,
some frames can measure a pulse of N photons to have each photon
separated by light-years which doesn't make any sense. So I rejected
the idea of photons being treated like point particles. On the other
hand, the photon length being extended over large distances makes no
sense to me either. The third alternative that the concept of N
photons in a given pulse being flawed makes the most sense. When I
look at Einstein's explanation of the photo-electric effect,
scientists were trying to explain how energy from a point source (a
particle) could be transferred to something spread out (a wave).
Einstein thought things could be explained if light consisted of
particles and then the transfer was a point to point interaction. The
more logical hypothesis would have been that particles really have
wave properties (not the probability notion adopted by physicists)
instead of hypothesizing as Einstein did that light waves have
particle properties - but that's another thread. So all three of my
alternatives lead to concepts that don't seem to work unless the
photon notion is corrected.
So my posting was to determine how others calculate the
probability.
2. The second problem I encountered in doing the problem at home
before posting was that there seemed to be no functional definition
how a moving frame moving with V relative to a laser source measures
pulse width for a pulse not traveling in the direction of V - if you
read my original post you will see that I wanted posters to confirm
the simple concept for pulses traveling in the dirrection of V (only
took you 4 posts to agree) and then define how they measure the pulse
width for the perpendicular case (no one posted a method). When I
look at that problem, in the moving frame, I can create pulses where
no single point in the moving frame encounters more than one point of
the traveling light pulse. So I had no idea how frequency is measured
in that frame, and wasn't clear on how pulse width is defined in that
frame. You can't put a clock and sensor at a single point in the
moving frame and measure pulse width as you can with a single clock
and sensor in the rest frame of the light source. I haven't the
foggiest idea of how to measure frequency of the pulse in the moving
frame. Just know that in the moving frame nothing can be done at a
single point in that frame.
David



Dirk Vdm

.

Relevant Pages

  • Re: Length definition in SR - can anyone explain
    ... I'm in an inertial frame. ... The moving observer measures the length of one pulse to be ... about the range of speeds my photon emitting device can have and the ... how a moving frame moving with V relative to a laser source measures ...
    (sci.physics.relativity)
  • Re: Math/Physics Gurus Help - SR probability problem
    ... traveling in opposite directions along the x-axis. ... and the other pulse B. ... I'll call them wave trains in frame K, ... This emitted photon always crosses the x-axis. ...
    (sci.physics.relativity)
  • Re: Math/Physics Gurus Help - SR probability problem
    ... traveling in opposite directions along the x-axis. ... and the other pulse B. ... I'll call them wave trains in frame K, ... This emitted photon always crosses the x-axis. ...
    (sci.physics.relativity)
  • Re: Length definition in SR - can anyone explain
    ... In my posting about clocks I got a varied opinions of what ... This posting is a question about lengths. ... I'm in an inertial frame. ... The moving observer measures the length of one pulse to be much less ...
    (sci.physics.relativity)
  • Re: Math/Physics Gurus Help - SR probability problem
    ... traveling in opposite directions along the x-axis. ... and the other pulse B. ... I'll call them wave trains in frame K, ... This emitted photon always crosses the x-axis. ...
    (sci.physics.relativity)