On 9/23/2003 3:58 AM, Harry wrote:
I doubt that according to most of you, SRT agrees with the consequence of
the above reasoning that a cube is both a cube and a non-cubic box,
depending on the reference frame.

In SR, the "objective reality" is the OBJECT ITSELF, and not any
specific geometrical attribute like "cubic". Whether or not I consider
this particular box to be "cubic" depends upon how I measure it. The
boundaries of the box itself have no such dependence.


In other words, according to SRT, does a cube have a reference-frame
independent physical reality or not?

The BOX does; whether or not it is a "cube" depends on other factors.

But note that the shape of the box it its rest frame is an objective
attribute of the box.


Tom Roberts

Tom Roberts wrote in message ...
On 9/23/2003 3:58 AM, Harry wrote:
I doubt that according to most of you, SRT agrees with the consequence of
the above reasoning that a cube is both a cube and a non-cubic box,
depending on the reference frame.

In SR, the "objective reality" is the OBJECT ITSELF, and not any
specific geometrical attribute like "cubic". Whether or not I consider
this particular box to be "cubic" depends upon how I measure it. The
boundaries of the box itself have no such dependence.


In other words, according to SRT, does a cube have a reference-frame
independent physical reality or not?

The BOX does; whether or not it is a "cube" depends on other factors.

But note that the shape of the box it its rest frame is an objective
attribute of the box.


Tom Roberts

xxein: You are proscribing that SRT(-GRT) define its own reality. I
don't think that's fair!

xxein wrote:

xxein: You are proscribing that SRT(-GRT) define its own reality. I
don't think that's fair!

Could you explain what you mean by this? I read this group mainly to
learn more about how people think and the above statement mystifies me.

Consider this: I by a board at the lumber store, take it home, and use
it for a room addition project. Then I measure it's heigth.. Do I
measure 8 feet or 2 inches? That depends whether I installed the board
in a wall or in the foundation. So even in Euclidian geometery, an
object's measured dimensions depend on the arbitrary choice of a
coorindate system. Doews that create two different realities, one
where the board is 8 feet higha nd one where the board is 2 inches high?

Bruce Seiler

Bruce Seiler wrote;
Consider this: I by a board at the lumber store, take it home, and use
it for a room addition project. Then I measure it's heigth.. Do I
measure 8 feet or 2 inches? That depends whether I installed the board
in a wall or in the foundation. So even in Euclidian geometery, an
object's measured dimensions depend on the arbitrary choice of a
coorindate system. Doews that create two different realities, one
where the board is 8 feet higha nd one where the board is 2 inches high?

Not really. Your example concerns an objects height and width whose meaning
is attributed to context. What SR says is that any length (regardless of
whether it is a height or width) in contracted in the direction of its
motion.

In another part of this thread the idea was presented that the only reality
is what we measure. I do not entirely agree with that position. My
position is one of utility - we can assume things are on;y what we measure
or we can assume things have an intrinsic quality (such as length in a rest
frame) and something (such as motion) caused us to measure it differently.
Each position is just as valid - the one we choose is the one that best
suits the problem at hand - just like your example above of what we consider
height and width depends on context - it is what best suits the problem at
hand.

This is an especially important thing to keep in mind when examining
problems in QM. IMHO failure to context shift appropriately causes all
sorts of problems. For example consider Schrodengers cat. Failure to
realize that the cat is a classical object that obeys classical laws leads
one to the idea it can be alive and dead - a property of quantum objects.
The real problem with Schrogengers cat is determining exactly when we can
count an object as classical and an object as quantum - a cat is obviously
classical - an atom quantum - but where do you draw the line? However that
seems not to be the way most people look at the experiment - they for some
reason want to draw the conclusion that the quantum world has somehow leaked
into the cat - this is an inference I have never understood.

Thanks
Bill


---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.520 / Virus Database: 318 - Release Date: 9/18/2003