Re: Distance-dependent time contraction

From: mich (mich_at_efni.com)
Date: 06/13/04 

Date: Sat, 12 Jun 2004 23:30:56 -0400

"Dirk Van de moortel" <dirkvandemoortel@ThankS-NO-SperM.hotmail.com> wrote
in message news:OQDyc.153754$1r7.7547942@phobos.telenet-ops.be...
>
> "mich" <mich@efni.com> wrote in message
news:10cm00m85ai1b6@corp.supernews.com...

...cut

> > Therefore, one can deduce from this that "one of the twin's
> > measurment of time/length was indeed different from the other,and not
only
> > apparent. Therefore, it in this context that I ask the question, was a
> > "true" length contraction experienced, or a length dilation ? We cannot
> > speak in relative terms when we use the twin paradox, in my opinion.
> > It is in this concept, that I would re-enquire the above .
>
> We take "measured" as "true". If you measure something, then it
> is true by definition. Saying that something is *merely measured*,
> does not make sense. Something is measured and then we call it
> "true". If it is not measured (or at least measurable in principle)
> then we don't talk about it.
> Physics is about measuring, and relativity is about the relationship
> between what different observers measure.
> When the experiment with the twins is caried out in reality, the
> age difference is "truly measured". It does happen.

   My thoughts were along, let's say a doppler shift. Let us assume that the
light's velocity was not invariant. We would still "observe" a time dilation
as a frame of reference would move away from us, a red doppler shift. The
events within the moving frame would seem as though they had been slowed
down. In this case, the observed, or measured time dilation could not be
considered as true, but only apparent.

> > >
> > > Can you try to explain what exactly you mean with "time dilation"
> > > in terms of the above?
> >
> > Again, in my opinion, I would apply two terms; relative time dilation,
of
> > which, would be in agreement to your explanation, but I would have to
> > add as well, "true" time dilation as explained specifically by in the
twin
> > experiment.
>
> As I said above, don't think in terms of "true"... If it is measured or
> measurable, then we talk about it, otherwise we don't.
> Try to keep that in mind.

I try, but as for now, do fail to see it as you do.

> > In the latter case, there must be either a "real" change in time
> > rates between two different frames.
>
> Ha, here is another problem. There a three frames:

o.k. you do have a point here.

> 1) The frame in which I (who stays at home) am at rest. I am
> just sitting there, doing nothing, feeling nothing, reading
> books and looking at my clock.

o.k. and you notice my clock is running slower than yours. (let's call this
an event)
...although this in itself is not necessarily due to the invariant speed of
light
as the Newtonian physics would claim the same thing, right?

> 2) The frame in which you are at rest while you are travelling
> away from me, reading books and looking at your own
> clock while it ticks.

...and my clock ticks faster than yours.

> 3) The frame in which you are at rest while you are coming
> back to me.
> You see, you had to do something at the half-way point:
> Either you had to jump from one rocket into another rocket
> already on its way back, or you had to severely decelerate,
> stop, and accelerate again in my direction.
> I just kept on sleeping.

true. So now I will immediatly observe your clock "rate" as going faster
than mine(blue shifted), while you will continue to observe my clock rate as
going slower than yours for another s/c. In this, I think I understand why
one would identify this as an assymetrical situation.

> Under these circumstances we will notice - *measure*,
> when we meet again and are at the same place, and don't
> move anymore with respect to each other, that your clock
> on your wrist had less elapsed time than my clock on my
> wrist.

  O.k.....So, right after I turned around, acceleration/deceleration not
counting, it seemed as though I have travelled the distance s, being simply
v/t,in the direction away from you, whereas you observed me going further, a
distance of s+ (ct).Now, due to the invariant speed of light, the light
shifts (blue/red) would always be the same for both; meaning, overall, that
I had a smaller distance to travel, therefore taking less time for me to
finish the trip than your elapse time observed. Would I be close? If yes,
then, I might understand it better, although it still remains fuzzy,
especially concerning the value of gamma in this case. But I 'll leave it at
that until I read your response.
>
> > The question is which one is it? Time
> > dilation, or time contraction?
>
> Forget these words for a minute. They cause confusion,
> and in this situation, they are meaningless.

o.k...you might be right.Are we talking about Relativity or Quantum
mechanics...because everything seems fuzzy...:}
>
>
> > I would like to specify, as I try to do often, that I am "not" a
> > physicist of any kind, so my questioning is not due to contradict
anyone,
> > only in order to try to understand
> > Relativity a bit better.
>
> Okay then.
> I can say something about time dilation, and when it does make
> (a bit) sense to use the expression, but I'd like to make sure that
> you have understood what I wrote above first.
> As soon as you fully aknowledge that, we'll talk about "time
> dilation".

o.k...it's a deal ;)
.
>
> Dirk Vdm
>
Andre

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