Re: Clock synch

Nicolaas Vroom wrote:
"Tom Roberts" <tjroberts137@xxxxxxxxxxxxx> schreef in bericht news:kU9Dg.6016$9T3.619@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Nicolaas Vroom wrote:
"Nicolaas Vroom" <nicolaas.vroom@xxxxxxxxxx> schreef in bericht news:ItWBg.10231$fQ5.270355@xxxxxxxxxxxxxxxxxxxxxxxx
"Tom Roberts" <tjroberts137@xxxxxxxxxxxxx> schreef in bericht news:Z3SAg.3029$kO3.2790@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
There is no "time dilation", in the sense of a clock physically ticking slower, or in the sense of "time moving slower". There is no "shortening/elongating", in the sense of a given object physically getting shorter or longer.

The effects called "time dilation" and "length contraction" in SR are not physical effects, and are due to different measurement procedures used by differently moving observers.
Suppose there are two Observers A and B at the same position P1
which both have identical clocks and which initially show the same value.
How would you call the effect, that, if those two Observers move
from P1 to P2 along a different path, that when they meet,
they realize that the two clocks show a different value ?
What is wrong by calling that a physical effect ?
There is nothing wrong with that, indeed that is what we mean by "physical effect". But that is NOT "time dilation".

Accordingly to the book "Introducing Einstein's relativity" by
Ray d'Inverno at page 33 "Thus moving clocks go slow by a factor
SQR(1- v*v/c*c). This phenomenon is called time dilation."

Yes. That is NOT what you described. <shrug>


IMO this is the situation I have described above.

Then you need to learn how to distinguish different situations better.

Inverno's definition, and mine, involves the comparison of a single moving clock's elapsed time to the coordinate clocks of a specified inertial frame -- this NECESSARILY requires two different clocks in that frame, because the moving clock is MOVING (relative to that frame).

The use of two coordinate clocks of that frame is essential in performing the geometric PROJECTION that is known as time dilation.

Your scenario is completely different from this. <shrug>


As I have said so often, time dilation is the difference in projections onto different coordinates.

How would you describe an experiment that demonstrates above

In inertial frame A an observer arranges for two assistants to be pre-positioned along the path that moving clock B will take relative to frame A. These assistants are given standard clocks, and they are synchronized using Einstein synchronization in frame A. When the clock B passes each assistant, they record the values on their own clock and on clock B. Afterwards, both assistants bring their records to the observer, who then computes the time different on clock B and in frame A.

It is the use of multiple clocks SYNCHRONIZED IN FRAME A that makes this a projection onto the time coordinate of frame A.


In Euclidean geometry, the analogy to time dilation is the fact that a meterstick held at 45 degrees relative to the X axis subtends only .707 meters along the X axis. The analogy to your example is a triangle ABC: the path AB has a different path length than the path ACB.

If you do not understand the difference in these two analogous situations in Euclidean geometry, I don't know how to help you.


Tom Roberts
.

Relevant Pages

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