Re: What is the " ACTUAL " length ?

On Jan 12, 9:50 am, kenseto <kens...@xxxxxxxxxx> wrote:
On Jan 10, 8:15 pm, PD <TheDraperFam...@xxxxxxxxx> wrote:





On Jan 10, 9:43 am, kenseto <kens...@xxxxxxxxxx> wrote:

On Jan 9, 1:19 pm, PD <TheDraperFam...@xxxxxxxxx> wrote:

It certainly is. It is a direct comparison of a particle distribution
from a center of mass of a collision between two circumstances: 1) the
rods in the calorimeter and the center of mass of the collision (and
the particle distribution) have no relative motion, and 2) the rods in
the calorimeter and the center of mass of the collision (and the
particle distribution) have relative motion.

Item 1 is based on a wrong assumption....All objects in the
universe are in a state of absolute motion.

Item 1 refers to objects with no *relative* motion.

How can the center of mass of moving particles and the calorimeter
fixed in your frame have no relative motion?

I just gave you an example of how a center of mass of moving objects
can have no relative motion with respect to another anchored object.
Read the part about the two moving billiard balls and how their center
of mass is *stationary* relative to the corner pocket. You do know
what a center of mass is, don't you?


This doesn't say
that anything is at absolute rest. You and your keyboard have no
*relative* motion, even though you and your keyboard are both whipping
around the axis of the Earth at 850 mph. In this case, the calorimeter
and the center of mass of the collision and the calorimeter have no
*relative* motion.

This is a bogus assumption.

It's not a bogus assumption. It's observable. You do know what
relative motion is, don't you? What's your relative motion with
respect to your chair right now? What's the relative motion between
the coffee cup in the cabinet and your computer monitor right now?
(You should be able to tell me a *value* for that quantity.)

In any case, you can't measure length
contraction if length contraction in SR is only a form of geometric
projection.

But you can, and it's been done, and I've explained how. Therefore
what you think about length contraction in SR being only a form of
geometric projection and not measurable must be faulty. Wherever did
you get the idea that it's not measurable.


In one case there is
relative motion, in the other case there is no relative motion.

How can there be no relative motion between the calorimeter and the
center of mass of the particles? I assume that the particles are
moving toward the calorimeter....right?

No, not right. In this case, the colliding particles are moving toward
each other with the same momentum magnitude (compared to the front
steps of the lab). The center of mass of the colliding particles is at
rest relative to the front steps of the lab. The calorimeter in this
case has no motion relative to the center of mass of the colliding
particles.

The calorimeter is fixed wrt you and the colliding particles (from the
opposite directions I assume) are moving toward it including the
center of mass. So there is relative motion between the center of mass
and the calorimeter.

Sorry, no. You seem to be having trouble now understanding what a
center of mass is. You do know that two particles that are both moving
can have a center of mass that is not moving, don't you?



If you put two billiard balls at opposite ends of a billiards table
and roll them at each other at the same speed, the center of mass of
the two balls is *stationary* relative to the billiard table corner
pocket.

Now how can that be???? The center of mass of each billiard ball is
moving toward the billard table corner pocket.

No, they are moving towards each other, not toward the corner pocket.
Your ability to read is pitiful. Moreover, the center of mass of the
two-ball system isn't anywhere near the center of mass of either ball.
You do know what a center of mass is, don't you?




It would help enormously if you would study a little basic physicis
first so you would know what a center of mass of a system is and how
it behaves, especially before attempting to formulate a new
fundamental theory of physics. Especially since you will likely have
to do a calculation in the new theory about the behavior of the center
of mass of a system. Einstein certainly knew what the center of mass
of a system was when he generated his theory of relativity.

ROTFLOL....I am way ahead of you in knowledge of real
physics....Possibility 20 year ahead of you.


But you don't know what a center of mass is. And you don't know what
the relative velocity between your keyboard and your head is.
Hmmmm...
Twenty years ahead....
Hmmmm....


The
distribution of the particles serves as the markings of a ruler. When
you compare the length of a rod against markings of a ruler in two
cases --- when the rod is moving relative to the ruler markings and
when the rod is not moving relative to the ruler markings --- then you
are measuring the effect of relative motion on the length of that rod.
I don't know how to make it any plainer to you, Ken. Simply denying
what you still do not understand accomplishes nothing.

What you said is wrong you ignored the fact that all objects are in a
state of absolute motion.

It doesn't matter if they have absolute motion. Their *relative*
motion is zero. This happens all the time. You are quite certain, no
doubt, that you have absolute motion even as you sit there reading
your screen. Then you would say that the refrigerator also has
absolute motion. But you and your refrigerator are at rest *relative*
to each other.

I wouldn't say that the refrigerator are at rest relative to each
other. I would say that the refrigerator and I are in the same state
of absolute motion.

Yes, that's YOUR notation. You invent all sorts of words and phrases
without knowing what physics terms mean.

What is the value of the relative motion between you and your
refrigerator right now? (you should be able to answer this with a
number.)

Yes they are in the same state of absolute motion.
Obviously the center of mass of the billard balls and the corner
pockets are not in the same state of absolute motion.


You are wrong. Tell me, Ken, where is the center of mass of the two
billiard ball system as the two balls come toward each other? Where is
it? You do know what a center of mass is, don't you?



The case that I mentioned is not wrong, and it is not a thought
experiment. It is a *real* experiment (a couple of real experiments,
in fact) with measurements taken and published in experimental papers.

But they are based on wrong assumptions.

Experiments do not change their results based on assumptions. They are
not right or not right based on assumptions. Experiments tell you how
nature behaves. Period. You have a weird idea of what experiments do.

Furthermore if length contraction is real
and measurable then the rod need to re-expand when rejoins with the
observer. So where is the SR equation for rod expansion?

Length contraction is indeed real and measurable. And when a moving
rod that is measured to be one length when moving (and you *can* do
that, as I've just pointed out to you), and it is brought to rest
relative to the observer, then repeating the measurement when it is at
rest will show a longer length than when it was moving -- so yes,
that's correct.

No that's not correct. There is no experiment that measures the
physical length of a moving rod.

I just told you one about calorimeters. I realize you don't understand
it.


The SR equation for rod expansion is not often mentioned in coffee-
table books of the sort you have read, which is why you probably
haven't seen it. But it's not that complicated.
Sometimes you'll see the SR equation for rod contraction written
something like this:
L' = L / gamma
where L is the length measured when it is at rest and L' is the length
measured when it is moving.
Since gamma is always a number bigger than 1, then (by SR) L' is
always smaller than L.

Here you use the word measure for L'. L' is never measured. It is
predicted.

That's not the case. L' is *measured* AND predicted. Predicting the
value with the equation and then *measuring* the value without
reliance on the equation is the only way to know whether the equation
works or not. This is what experiment does. You make a *prediction* of
a quantity with an equation. Then in an experiment you *measure* the
quantity *without* using the equation. Then you see if the
*prediction* matches the *measurement*, and then this tells you
whether the equation can be trusted. You didn't know this? This is so
basic to science that 3rd graders learn it. You miss that day in
school?


Or conversely, L is always larger than L'. L'
being smaller than L means that a moving rod is contracted compared to
a stationary rod. L being larger than L' means that a stationary rod
is expanded compared to a moving rod. You see? It's the same formula
for both expansion and contraction -- just read in one direction it's
a contraction, and read in the opposite direction it's an expansion.

Ah....but that would mean that L is in a preferred frame.

Not so.

Why??Because
it is always longer than L'.
In real life, L can be longer or shorter than L'.

Where's your *experimental evidence* of what is true in real life?




The contraction of the rod does not result from a physical process
that either compresses the rod or re-expands the rod. The contraction
of the rod is real.

ROTFLOL....this is so stupid.

Sorry, but that's exactly what SR says. And that is exactly confirmed
by experiment, even if you cannot imagine how that is possible.

So?? What SR says is wrong.

Not if it is confirmed by experiment.

The correct interpretation is that the
length of a physical rod remain unchanged in all frames....it does not
experience compression or re-expansion. However, the light path length
of a moving rod can be shorter or longer than the light path length of
the observer's rod.....the observer declares that the light path
length of his rod is the physical length of his rod.



I know that in your head, the *only* way to produce a real and
measurable contraction is if there is a physical process or force that
compresses the rod. But it's not the only way. The fact that you don't
understand the other way doesn't mean it doesn't exist.

There is no experiment that measures length contraction.


I just told you one. Now you can say it doesn't exist because you
don't understand it, but of course that would be a completely stupid
statement.
.

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