Re: Are SR effects real or not? Simplified case.

On Jul 18, 8:36 am, stevendaryl3...@xxxxxxxxx (Daryl McCullough)
wrote:
Uncle Ben says...

Tom Roberts <tjroberts...@xxxxxxxxxxxxx> wrote:
 If you never discussed "physical length", or "real
length", but always said "projected length" or
"measured length", I doubt very much that Einstein
(or anybody else) would object to the result.

What's wrong with being precise in terminology?

Tom Roberts

IMHO, it's not being precise.  It's being wishy-washy.

How is it being wishy-washy?

It is avoiding the concept that relativity is about real things, not
just appearances. (In the Bell's Paradox, the string really does
break, doesn't it. That is as real as it can get.)

Length of a
moving object is perfectly well defined.  You mark the coordinates of
the two ends at the same time.

And how is "at the same time" determined?

I think that you mean that if you have *already* set up
a coordinate system, then the length of an object relative
to that coordinate system is well-defined.

Of course.

What you are trying to do is to preserve a pre-relativistic idea.

How in the world is he doing that? He's *rejecting* the
pre-relativistic idea of "length" as not being meaningful.

Are you sure that is what you meant? It seems to me that he is trying
to preserve the concept that the object has a real physical (proper)
length and the the "measured" lengths are just artifacts. I think that
is a pre-relativistic view. The relativistic view is that objects
moving or not have a (real) length that is related to the proper
length through a Lorentz Transformation. And this is the view that Tom
is rejecting.


The four different concepts are inherently circular
in their definitions. To break out of the circularity,
something has to be true "by definition".

Maybe, but I wouild rather say, by hypothesis. Einstein proposed
postulates for a theory and deduced consequences. The test of truth
or usefulness is experiment.

Cheers, Uncle Ben
.

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