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

On Jul 3, 3:24 pm, "Jeckyl" <n...@xxxxxxxxxxx> wrote:
<gehgehtes...@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 ..

I don't think that's accurate. The length of an object as measured
from the ether rest frame changes when that object is in motion, yes.
However, the Lorentz interpretation agrees with standard SR that the
length of an object as measured in its own rest frame does not
change. If this is what we mean by proper length, and what else could
we mean, then the proper length doesn't change.

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.

I don't see much of a difference. Both say the proper length stays
the same. Both say the length of the train as measured by the radio
switch operator will be shorter. Isn't this the same theory we are
talking about?

.

Relevant Pages

  • Re: Proper Frequency
    ... >>> I know there is such a thing as proper length and proper time for an ... >> value of that measurement when taken in the rest frame of the object ... >> no reference frame where the light is at rest. ...
    (sci.physics)
  • Re: Are SR effects real or not? Simplified case.
    ... "The proper length of the object" which is the same in any ... length" as the name for the invariant quantity, ... preferred frame (the rest frame of the object), ... But perhaps this is why there is no such thing as "proper momentum". ...
    (sci.physics.relativity)
  • Re: Are SR effects real or not? Simplified case.
    ... "The proper length of the object" which is the same in any ... length" as the name for the invariant quantity, ... preferred frame (the rest frame of the object), ... separates the invariant quantity from the 3D quantity momentum. ...
    (sci.physics.relativity)
  • Re: SR length contraction - the train example reworked.
    ... If it involves measurement it requires a set of defined ... Do you feel that this has some deeper significance or is velocity what ... running slower than in the embankment rest frame. ... the path of the light WRT the frame on the train. ...
    (sci.physics.relativity)
  • Re: SR Length Contraction - how do physicists explain this
    ... > or proper length". ... > in the rest frame will be smaller than the rest length or proper ... In special relativity, ... > relative to a moving frame the speed becomes zero (relative to ...
    (sci.physics.relativity)
Loading