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[Phys-L] Re: "moving clock runs slower" (yes)



I hit the save rather than the send button, as offering something too
pretentious, too trite, too obvious, after writing this little response
a day or two ago. But when did those considerations ever stop me
before? And the hand-wringing about reality persists still!

Enjoy?

Brian

At 11:00 AM 9/12/2005, John M., you wrote:
As I see it, this thread is revolving around two semantic concerns:

1. What is the meaning of "real" (length, time, etc.)?
2. What is the meaning of "apparent" (length, time, etc.)?

Arguing, correctly in my opinion, from the perspective of a
sophisticated practitioner of physics, John Denker argues
persuasively that "real" should be essentially synonymous with what
is commonly called "proper," that the "real lengths" of rods and the
"real rates" of clocks are their "proper" lengths and rates. Thus,
moving clocks do NOT "run slow" and moving lengths do NOT "contract."
When we say that they do, we are talking only about "appearances."

///

John Mallinckrodt
Cal Poly Pomona


Ah, how soon we forget: that we are dealing with instances of
the most sophisticated models there are - the latest and greatest, after
a hundred years' development on the Einsteinian theme.

We forget that we have free choice of physics model.
We forget that no matter how difficult the model to grasp, how
satisfying its predictions, it says nothing about Truth with a capital T.
Truth may well subsist in reality, but physics models do not constitute
Truth.

If he wants to use 4-this and 4-that, and she wants to use 3-this
and 3-that, and they want to use 2-this or the other, they are at liberty
to do so, if they can make their usage rational and useful.
I like John's sentiment better, when he talks of what model is
suited to the needs of students at introductory or advanced levels.
That is a worthy question. What is "real" is not a physicist's
proper question in my view [to mangle the specialist vocabulary (!) ]
His purvue is in the weaving together of observables with the
simplest theoretical underpinning that will serve a particular
purpose.



Brian Whatcott Altus OK Eureka!
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