Re: So... Lerentz Contractions are *physical* not observered?

<gehgehtester@xxxxxxxxx> wrote in message
news:1183460924.374645.265380@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On Jul 3, 6:01 am, Tom Roberts <tjroberts...@xxxxxxxxxxxxx> wrote:

[...]
Lorentz "length contraction" is similar: the invariant length of an
object is GEOMETRICALLY PROJECTED onto a coordinate system, and
depending on orientation the projected value of that length can be less
than the invariant length of the object (the invariant length of an
object is its length in its own rest frame).

So the object does not get "physically" any shorter (i.e. its invariant
length remains constant), but the orientation between object and
coordinates used for measurement can have "physical" consequences (i.e.
one obtains a different value for the length, the pole can fit into the
barn in a famous gedanken, etc.).

[..]

Greetings, apologies for my indiscriminate snipping.

I have a semantic argument with this claim that an object does not get
"physically" any shorter (why the quotes?).

If I measure an object to be 80m, using the physical definition of
length, isn't that object physically 80m? Am I incorrect to say the
physical length of the train as measured from the rest frame of the
tracks is 80m?

Of course we agree the object remains 100m as measured in its own rest
frame, but does that mean that Lorentz contraction is somehow not
physical?

Perhaps the answer is similar to the reason why the Coriolis force is
often called "fictional", despite the very real physical effects.

Thanks -

I think the point is whether the proper length of the object changes or not.
In SR it doesn't change .. its projection in other frames of references is
shorter .. but the object itself isn't.

I think also "physical" implies some change to the object itself.

For example in Lorentz theory, there is physical contraction (objects get
physically shorter .. ie their proper length changes) when objects move in
the absolute ether frame .. but because all the rulers comoving with the
object change by the same amount, the measurement of it in its rest frame
appears to be the same. That's pretty much the opposite to what SR says
happens.



.

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