[General] nature of light particles & theories

[Dr. Albrecht Giese]

Hi Al,

I do not see any conflict if the situation with synchronized clocks is 
obeyed as I explained it in my last mail (see below). Those clock 
assemblies show dilation, but do not present any logical conflict.

When looking at a real situation one has to identify the observed object 
on the one hand with a clock in the example, and on the other hand the 
observer with another clock or a sequence of other clocks. If we observe 
a moving particle (like a muon) in a laboratory, than the muon is 
represented by one clock in the moving system. In this case the observer 
is represented by a line of clocks positioned along the path of the 
muon. Because, if we think in an idealized way, we have first to note 
the time when the muon starts by looking at the clock which is close to 
the muon at start time. When the muon decays we have for the decay time 
to look to the clock which is close to the muon at that moment.

This may look ridiculous as for the observer in the lab all clocks have 
the same indication. But from the "view" of the muon the clock at rest 
at the start looks advanced and the clock at the end looks retarded. So 
the muon has the impression that the time in the lab was slowed down.

As a reminder: The equation for time transformation is:  t' = gamma* (t 
- vx / c^2 )  (i.e. the Lorentz transformation). Here is x the position 
of that clock which is close to the moving object at the time of 
observation. And that position is x = v*t if the observer it at rest. 
So, for this observer there is t' = t/gamma. For a co-moving observer 
there is v = 0, so the result is t' = t*gamma. Both results are covered 
by this equation, and there is no logical conflict.

Best wishes
Albrecht



> Hi Albrecht & Curious:
> Overlooked in my previous responce:
> If, as is done in virtually all text books on SR  (I just checked 
> Rindler, for example) time dilation is discussed in terms of the 
> dialtion happening to a concrete objects (as it must if the Muon story 
> is to make sense) then there is an obvious inconsitency and sever 
> conflict with the relativity principle.  Two entities cannot at once 
> be both be dialted in the other's view and not their own.  The real 
> trick here is explaing how this is not obvious to authors of text 
> books!  Maybe, to paraphrase Weinburg:  That stupid people say dumb 
> things is natural, to get smart people to say dumb things, it takes 
> physics!
> Your explantion (or my prefered version: perspctive) renders the 
> objection both mute and sterile wrt muons, however.
> *Gesendet:* Sonntag, 11. Oktober 2015 um 22:55 Uhr
> *Von:* "Dr. Albrecht Giese" <genmail at a-giese.de>
> *An:* general at lists.natureoflightandparticles.org, "A. F. Kracklauer" 
> <af.kracklauer at web.de>
> *Betreff:* Re: [General] nature of light particles & theories
> Hi Al,
>
> about time dilation.
>
> The problem is that time dilation looks inconsistent at the first 
> glance. But it is not. I shall try to explain. It has to do with clock 
> synchronization. (I try to do it without graphics, which would be 
> easier, but a problem in an email.)
>
> Assume that there are two inertial systems, I call them A and B. Both 
> move in relation to each other at some speed v. Now assume that there 
> are clocks distributed equally over both systems. And of course in 
> both systems the clocks are synchronized. Now there comes a 
> relativistic effect. If the observer in A looks to the clocks in B, he 
> finds them desynchronized. The clocks which are in front with respect 
> to the direction of motion are retarded, the ones in the rear 
> advanced. Similar in the other system. If an observer in B looks to 
> the clocks in A, he finds them also desynchronized in the way that the 
> clocks in the front are retarded and the clocks in the rear advanced. 
> Shall I explain why this happens? If you want, I can do it. But next 
> time to keep it short here.
>
> Now, what is dilation in this case?
>
> If the observer in A takes one of the clocks in B and compares it to 
> those clocks in his own system, which is just opposite in sequence, 
> then the clock in B looks slowed down. But if he takes one clock in 
> his own system, A, and compares it to the clocks in B which are 
> opposite in sequence, the clocks in B look accelerated.
>
> Now it looks in a similar way for the observer in B. If the observer 
> in B does the equivalent to the observer in A just described, he will 
> make just the same experience. No contradiction!
>
> In the case of the muons: The muon which will decay is in the position 
> of a clock in the muon-system, and this clock is slowed down as seen 
> from the observer at rest as described above, and this is no violation 
> of symmetry between the systems. If an observer, who moves with the 
> muon, looks to the clocks of the system at rest, he will find those 
> clocks accelerated. No contradiction. Correct?
>
> Albrecht
>
>     </a>
>



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