Science and Technology news... :: View topic - when push comes to shove, the only way Special Relativity ca

RustyJames · Guest

On Oct 10, 10:40 am, PD <TheDraperFam...@gmail.com> wrote:
[quote]On Oct 10, 12:25 pm, strich.9...@gmail.com wrote:

On Oct 10, 12:55 pm, PD <TheDraperFam...@gmail.com> wrote:

That is not what happens. In any given inertial reference frame, the
length has a constant value. At the *same* time in a different
inertial reference frame, the length has a different constant value.

Let us summarize:
For a single object: Dirk>s finger
1) Different frame, different length
2) One frame, one constant length

Dirk>s appendage will always measure 10cm in his own frame, no matter
how hard he cries.

Well, unless something happens to compress the finger or lop it off,
like with an axe. And by "his own frame", I assume you mean the
inertial reference frame in which he is at rest.

You agree with everything so far? (A simple yes or no will suffice)

I>m not sure that>s true that a simple yes or no will suffice. You get
muddled up over the most basic of things.
[/quote]
yes these statements are true from our frame of refrance on what I
stated not from the internal frame though

Guest

On Oct 10, 1:40 pm, PD <TheDraperFam...@gmail.com> wrote:
[quote]On Oct 10, 12:25 pm, strich.9...@gmail.com wrote:

On Oct 10, 12:55 pm, PD <TheDraperFam...@gmail.com> wrote:

That is not what happens. In any given inertial reference frame, the
length has a constant value. At the *same* time in a different
inertial reference frame, the length has a different constant value.

Let us summarize:
For a single object: Dirk>s finger
1) Different frame, different length
2) One frame, one constant length

Dirk>s appendage will always measure 10cm in his own frame, no matter
how hard he cries.

Well, unless something happens to compress the finger or lop it off,
like with an axe. And by "his own frame", I assume you mean the
inertial reference frame in which he is at rest.

[/quote]
So it>s agreed. Dirk>s appendage is 10cm in his own frame.

Let us proceed...

Another person by the name of Doug was also unfortunately born into
the same situation. Doug measures his appendage at exactly 10cm.
Dirk and Doug decide to compare notes and place their appendages side
by side. They are exactly equal at 10cm.

Dirk then flies off to the Waffler Galaxy at constant velocity of
0.995c. He peers into his telescope and laughs, measuring Doug>s
appendage at 1cm. Dirk gets scared for a second and hastily checks
his own appendage and is happy to know it is still 10cm. Meanwhile,
Doug peers into his telescope and measures Dirk>s appendage at 1cm.
He double checks his own and measures 10cm.

PD will say all 4 measurements are valid. But, would anybody deny
that Dirk>s and Doug>s appendages are still equal in length?

Uncle Ben · Guest

On Oct 10, 1:11 pm, strich.9...@gmail.com wrote:
[quote]On Oct 10, 1:07 pm, Uncle Ben <b...@greenba.com> wrote:

On Oct 10, 1:01 pm, strich.9...@gmail.com wrote:

On Oct 10, 12:52 pm, Uncle Ben <b...@greenba.com> wrote:

On Oct 9, 2:48 pm, strich.9...@gmail.com wrote:

The premise was simple...

Clocks E and M in inertial frames E and M are at rest with respect to
one another. The rate of clock E in frame E (E1) is by definition
equal to the clock rate of M in frame M (M1), or E1=M1. Let clock M
now move with respect to E, with relative constant velocity v. It is
easily shown that the new rate of the moving clock M in frame M (M2)
is equal to its old rate (M1), or M2=M1. It is also easily shown that
the new rate of clock E in frame E (E2) is equal to its old rate (E1),
or E2=E1.

The obvious conclusion is that M2=E2. This disproves Special
Relativity (SR) since time becomes constant in any inertial frame..

Relativity physicists scramble for a 'scientific' defense. The
defenses are:

1) "It does not take into account the Lorentz transformation
equations". The LTE however assumes beforehand that SR is already
correct.
2) "It disagrees with experiment." The experiment being the so-called
Muon experiment, which assumed that the premise of time dilation is
correct in its interpretation of the result.
3) The last resort is to invoke General Relativity. This is like
proving a theorem A by invoking corollary A, which had followed from
the same theorem.

When all these circular defenses are exposed, the relativists resort
to the their last options:
1) Ad hominems
2) Non-sequiturs
3) Other 'trolling' techniques

One would think that a supposedly solid theory as Einstein>s Theories
of Relativity could mount up a better defense than that typically
employed by highly paid lawyers defending a losing client.

Thanks.

Of course Special Relativity cannot be proven mathematically or
experimentally. The same can be said of any theory in physical
science. "Mathematical" is obviously insufficient, since SR claims
something about physical reality. Mathematicians don>t deal with
physical reality, only logic. "Experimentally" because no amount of
experiments can ever prove a theory correct; experiments can only
support or subvert physical theories.

What can be said of SR is that no experiment has yet shown it to be
false. In physics, it doesn>t get any better than that.

Uncle Ben- Hide quoted text -

- Show quoted text -

It is not falsifiable, hence it has not been falsified.- Hide quoted text -

- Show quoted text -

The second postulate can certainly be falsified, and it has been
attempted.- Hide quoted text -

- Show quoted text -

Give me one example (of an attempt)- Hide quoted text -

- Show quoted text -
[/quote]
Certainly:

Filipas and Fox, Phys. Rev. 135 no. 4B (1964), pg B1071.

Measured the speed of gamma rays from the decay of fast ð0 (~0.2 c) in
an experiment specifically designed to avoid extinction effects. Their
results are in complete disagreement with the assumption c+v, and are
consistent with SR. k < 0.5 with a confidence level of 99.9%.

Uncle Ben

RustyJames · Guest

On Oct 10, 11:00 am, strich.9...@gmail.com wrote:
[quote]On Oct 10, 1:40 pm, PD <TheDraperFam...@gmail.com> wrote:

On Oct 10, 12:25 pm, strich.9...@gmail.com wrote:

On Oct 10, 12:55 pm, PD <TheDraperFam...@gmail.com> wrote:

That is not what happens. In any given inertial reference frame, the
length has a constant value. At the *same* time in a different
inertial reference frame, the length has a different constant value.

Let us summarize:
For a single object: Dirk>s finger
1) Different frame, different length
2) One frame, one constant length

Dirk>s appendage will always measure 10cm in his own frame, no matter
how hard he cries.

Well, unless something happens to compress the finger or lop it off,
like with an axe. And by "his own frame", I assume you mean the
inertial reference frame in which he is at rest.

So it>s agreed. Dirk>s appendage is 10cm in his own frame.

Let us proceed...

Another person by the name of Doug was also unfortunately born into
the same situation. Doug measures his appendage at exactly 10cm.
Dirk and Doug decide to compare notes and place their appendages side
by side. They are exactly equal at 10cm.

Dirk then flies off to the Waffler Galaxy at constant velocity of
0.995c. He peers into his telescope and laughs, measuring Doug>s
appendage at 1cm. Dirk gets scared for a second and hastily checks
his own appendage and is happy to know it is still 10cm. Meanwhile,
Doug peers into his telescope and measures Dirk>s appendage at 1cm.
He double checks his own and measures 10cm.

PD will say all 4 measurements are valid. But, would anybody deny
that Dirk>s and Doug>s appendages are still equal in length?- Hide quoted text -

- Show quoted text -
[/quote]
as long as they were varified from each ones frame of refrance

PD · Guest

On Oct 10, 1:00 pm, strich.9...@gmail.com wrote:
[quote]On Oct 10, 1:40 pm, PD <TheDraperFam...@gmail.com> wrote:

On Oct 10, 12:25 pm, strich.9...@gmail.com wrote:

On Oct 10, 12:55 pm, PD <TheDraperFam...@gmail.com> wrote:

That is not what happens. In any given inertial reference frame, the
length has a constant value. At the *same* time in a different
inertial reference frame, the length has a different constant value.

Let us summarize:
For a single object: Dirk>s finger
1) Different frame, different length
2) One frame, one constant length

Dirk>s appendage will always measure 10cm in his own frame, no matter
how hard he cries.

Well, unless something happens to compress the finger or lop it off,
like with an axe. And by "his own frame", I assume you mean the
inertial reference frame in which he is at rest.

So it>s agreed. Dirk>s appendage is 10cm in his own frame.

Let us proceed...

Another person by the name of Doug was also unfortunately born into
the same situation. Doug measures his appendage at exactly 10cm.
Dirk and Doug decide to compare notes and place their appendages side
by side. They are exactly equal at 10cm.

Dirk then flies off to the Waffler Galaxy at constant velocity of
0.995c. He peers into his telescope and laughs, measuring Doug>s
appendage at 1cm. Dirk gets scared for a second and hastily checks
his own appendage and is happy to know it is still 10cm. Meanwhile,
Doug peers into his telescope and measures Dirk>s appendage at 1cm.
He double checks his own and measures 10cm.
[/quote]
Yes, exactly.

[quote]
PD will say all 4 measurements are valid.
[/quote]
Yes.

[quote] But, would anybody deny
that Dirk>s and Doug>s appendages are still equal in length?
[/quote]
Some people would, some people wouldn>t, depending on what they meant
in the sloppy and casual use of the word "length" with regard to the
appendage.

If one means by "length" the lengths that are measured in the rest
frames of the fingers, then of course the two lengths are the same.

If one means by "length" the length that is measured in any single
reference frame, then, no, the two lengths are not the same, as you
noted above.

Such is the risk of being careless with terms. In colloquial usage,
there is no distinction made, and that>s where you get into trouble.
Back in Galileo>s day, centuries ago, people were just used to
referring to "the speed" of an object, as though it were just obvious
there is one and only one speed of a given object at a given time.
Galileo made it clear that you had to be more careful and ask "speed
with respect to what?" Some folks -- like Spaceman -- still have
problems with that, as you can see. A hundred years ago, people were
just used to referring to "the length" of an object, as though it were
obvious there is only one true length of an object. Einstein and
others made it clear that you had to be more careful and ask "in which
frame of reference?". Some folks -- like Spaceman -- think that if it
worked fine to be sloppy and casual about those terms for thousands of
years, that we shouldn>t let some fool physicist change that.

PD

Sue... · Guest

On Oct 9, 8:38 pm, Uncle Al <Uncle...@hate.spam.net> wrote:
[quote]strich.9...@gmail.com wrote:

The premise was simple...

Clocks E and M in inertial frames E and M are at rest with respect to

[snip crap]

http://cc3d.free.fr/Relativity/Relat1.html
Special Relativity for yard apes

http://www.edu-observatory.org/physics-faq/Relativity/SR/experiments....[/quote]

[quote] Experimental constraints on Special Relativity
[/quote]
Indeed...

<<Domain of Applicability

The domain of applicability of a physical theory is the set of
physical situations in which the theory is valid. For SR this is
basically measurements of distance, time, momentum, energy, etc. in
inertial frames (coordinates); calculus can be used to apply SR in
accelerated systems, as can the more advanced mathematics of
differential geometry. A more technical definition is that SR is valid
only in flat Lorentz manifolds topologically equivalent to R4.

In particular, any experiment in which the effects of gravitation are
important is outside the domain of SR. Because SR is the local limit
of General Relativity it is possible to compute how large an error is
made when one applies SR to a situation that is approximately but not
exactly inertial, such as the common case of experimental apparatus
supported against gravity on the Earth>s surface. In many cases (e.g.
most optical and elementary-particle experiments on the rotating
Earth>s surface) these errors are vastly smaller than the experimental
resolution, and SR can be accurately applied. >>

That is what the OP says.

Or as Einstein said:

<<The weakness of the principle of inertia lies in this, that it
involves an argument in a circle: a mass moves without acceleration if
it is sufficiently far from other bodies; we know that it is
sufficiently far from other bodies only by the fact that it moves
without acceleration. >>

http://www.mathpages.com/rr/s4-07/4-07.htm

Sue...

PD · Guest

On Oct 10, 1:00 pm, strich.9...@gmail.com wrote:
[quote]On Oct 10, 1:40 pm, PD <TheDraperFam...@gmail.com> wrote:

On Oct 10, 12:25 pm, strich.9...@gmail.com wrote:

On Oct 10, 12:55 pm, PD <TheDraperFam...@gmail.com> wrote:

That is not what happens. In any given inertial reference frame, the
length has a constant value. At the *same* time in a different
inertial reference frame, the length has a different constant value.

Let us summarize:
For a single object: Dirk>s finger
1) Different frame, different length
2) One frame, one constant length

Dirk>s appendage will always measure 10cm in his own frame, no matter
how hard he cries.

Well, unless something happens to compress the finger or lop it off,
like with an axe. And by "his own frame", I assume you mean the
inertial reference frame in which he is at rest.

So it>s agreed. Dirk>s appendage is 10cm in his own frame.

Let us proceed...

Another person by the name of Doug was also unfortunately born into
the same situation. Doug measures his appendage at exactly 10cm.
Dirk and Doug decide to compare notes and place their appendages side
by side. They are exactly equal at 10cm.

Dirk then flies off to the Waffler Galaxy at constant velocity of
0.995c. He peers into his telescope and laughs, measuring Doug>s
appendage at 1cm. Dirk gets scared for a second and hastily checks
his own appendage and is happy to know it is still 10cm. Meanwhile,
Doug peers into his telescope and measures Dirk>s appendage at 1cm.
He double checks his own and measures 10cm.

PD will say all 4 measurements are valid. But, would anybody deny
that Dirk>s and Doug>s appendages are still equal in length?
[/quote]
Just as a side comment, however, I>d like to commend you for at least
getting to the questions that get to the root of some common
misconceptions. Misconceptions are not anything to judge anyone by;
the ability to get at them, confront them, and remove them is what
gets judged.

So far you>ve managed to come up against several key things:
- the role of experiment vs logic in science, and how theories are
validated;
- the difference between logic and common-sense intuition;
- the recognition that there are some physical properties that are
frame-dependent and others that are frame-independent;
- that casual usage of terms can obfuscate the frame-dependence of
some physical quantities;
- that the acceptance of relativity had less to do with arguments and
thought-experiments and plausible assumptions than with experimental
test and confirmation, even though you hear more in magazines about
the colorful character than you do about the experimentalists who did
a ton of work.

These are not insignificant dealings. Those who come to physics from
outside the sciences are *usually* confused about these things.

PD

glird · Guest

On Oct 9, 6:13 pm, PD wrote:

[quote]It>s quite possible that [some people] don>t know what a
reference frame is, or what synchronization means, or both.
[/quote]
It is certain that relativists think that clocks whose indications
differ by -vx/c^2 seconds ARE "synchronous"
even though it is totally obvious that they are not!

glird

Guest

On Oct 10, 2:13 pm, PD <TheDraperFam...@gmail.com> wrote:
[quote]On Oct 10, 1:00 pm, strich.9...@gmail.com wrote:

On Oct 10, 1:40 pm, PD <TheDraperFam...@gmail.com> wrote:

On Oct 10, 12:25 pm, strich.9...@gmail.com wrote:

On Oct 10, 12:55 pm, PD <TheDraperFam...@gmail.com> wrote:

That is not what happens. In any given inertial reference frame, the
length has a constant value. At the *same* time in a different
inertial reference frame, the length has a different constant value.

Let us summarize:
For a single object: Dirk>s finger
1) Different frame, different length
2) One frame, one constant length

Dirk>s appendage will always measure 10cm in his own frame, no matter
how hard he cries.

Well, unless something happens to compress the finger or lop it off,
like with an axe. And by "his own frame", I assume you mean the
inertial reference frame in which he is at rest.

So it>s agreed. Dirk>s appendage is 10cm in his own frame.

Let us proceed...

Another person by the name of Doug was also unfortunately born into
the same situation. Doug measures his appendage at exactly 10cm.
Dirk and Doug decide to compare notes and place their appendages side
by side. They are exactly equal at 10cm.

Dirk then flies off to the Waffler Galaxy at constant velocity of
0.995c. He peers into his telescope and laughs, measuring Doug>s
appendage at 1cm. Dirk gets scared for a second and hastily checks
his own appendage and is happy to know it is still 10cm. Meanwhile,
Doug peers into his telescope and measures Dirk>s appendage at 1cm.
He double checks his own and measures 10cm.

Yes, exactly.

PD will say all 4 measurements are valid.

Yes.

But, would anybody deny
that Dirk>s and Doug>s appendages are still equal in length?

Some people would, some people wouldn>t...
[/quote]
Thus Dirk would swear his appendage is constant at 10cm
Doug would pledge that his appendage is constant at 10cm

Thus we can compare the two appendages anytime, by using their 'at
rest' measurements. Though Dirk may be going at 0.995c to the left,
and Doug may be going 0.1c to the front, we can always say that their
fingers are equal based on the 'at rest' measurements.

Everybody agrees?

PD · Guest

On Oct 10, 1:39 pm, strich.9...@gmail.com wrote:
[quote]On Oct 10, 2:13 pm, PD <TheDraperFam...@gmail.com> wrote:

On Oct 10, 1:00 pm, strich.9...@gmail.com wrote:

On Oct 10, 1:40 pm, PD <TheDraperFam...@gmail.com> wrote:

On Oct 10, 12:25 pm, strich.9...@gmail.com wrote:

On Oct 10, 12:55 pm, PD <TheDraperFam...@gmail.com> wrote:

That is not what happens. In any given inertial reference frame, the
length has a constant value. At the *same* time in a different
inertial reference frame, the length has a different constant value.

Let us summarize:
For a single object: Dirk>s finger
1) Different frame, different length
2) One frame, one constant length

Dirk>s appendage will always measure 10cm in his own frame, no matter
how hard he cries.

Well, unless something happens to compress the finger or lop it off,
like with an axe. And by "his own frame", I assume you mean the
inertial reference frame in which he is at rest.

So it>s agreed. Dirk>s appendage is 10cm in his own frame.

Let us proceed...

Another person by the name of Doug was also unfortunately born into
the same situation. Doug measures his appendage at exactly 10cm.
Dirk and Doug decide to compare notes and place their appendages side
by side. They are exactly equal at 10cm.

Dirk then flies off to the Waffler Galaxy at constant velocity of
0.995c. He peers into his telescope and laughs, measuring Doug>s
appendage at 1cm. Dirk gets scared for a second and hastily checks
his own appendage and is happy to know it is still 10cm. Meanwhile,
Doug peers into his telescope and measures Dirk>s appendage at 1cm.
He double checks his own and measures 10cm.

Yes, exactly.

PD will say all 4 measurements are valid.

Yes.

But, would anybody deny
that Dirk>s and Doug>s appendages are still equal in length?

Some people would, some people wouldn>t...

Thus Dirk would swear his appendage is constant at 10cm
[/quote]
He would *measure* it to be 10cm in the reference frame in which the
appendage is at rest, yes. Physics is more about what will be
*measured* and doesn>t get metaphysical about what "is".

[quote]Doug would pledge that his appendage is constant at 10cm

Thus we can compare the two appendages anytime, by using their 'at
rest' measurements. Though Dirk may be going at 0.995c to the left,
and Doug may be going 0.1c to the front, we can always say that their
fingers are equal based on the 'at rest' measurements.

Everybody agrees?
[/quote]
That>s fine. Keep in mind, though that relativistic length contraction
is about what gets measured for two objects in relative motion, from a
*single* reference frame, not in two different reference frames.

PD

Guest

On Oct 10, 2:53 pm, PD <TheDraperFam...@gmail.com> wrote:
[quote]On Oct 10, 1:39 pm, strich.9...@gmail.com wrote:

On Oct 10, 2:13 pm, PD <TheDraperFam...@gmail.com> wrote:

On Oct 10, 1:00 pm, strich.9...@gmail.com wrote:

On Oct 10, 1:40 pm, PD <TheDraperFam...@gmail.com> wrote:

On Oct 10, 12:25 pm, strich.9...@gmail.com wrote:

On Oct 10, 12:55 pm, PD <TheDraperFam...@gmail.com> wrote:

That is not what happens. In any given inertial reference frame, the
length has a constant value. At the *same* time in a different
inertial reference frame, the length has a different constant value.

Let us summarize:
For a single object: Dirk>s finger
1) Different frame, different length
2) One frame, one constant length

Dirk>s appendage will always measure 10cm in his own frame, no matter
how hard he cries.

Well, unless something happens to compress the finger or lop it off,
like with an axe. And by "his own frame", I assume you mean the
inertial reference frame in which he is at rest.

So it>s agreed. Dirk>s appendage is 10cm in his own frame.

Let us proceed...

Another person by the name of Doug was also unfortunately born into
the same situation. Doug measures his appendage at exactly 10cm.
Dirk and Doug decide to compare notes and place their appendages side
by side. They are exactly equal at 10cm.

Dirk then flies off to the Waffler Galaxy at constant velocity of
0.995c. He peers into his telescope and laughs, measuring Doug>s
appendage at 1cm. Dirk gets scared for a second and hastily checks
his own appendage and is happy to know it is still 10cm. Meanwhile,
Doug peers into his telescope and measures Dirk>s appendage at 1cm.
He double checks his own and measures 10cm.

Yes, exactly.

PD will say all 4 measurements are valid.

Yes.

But, would anybody deny
that Dirk>s and Doug>s appendages are still equal in length?

Some people would, some people wouldn>t...

Thus Dirk would swear his appendage is constant at 10cm

He would *measure* it to be 10cm in the reference frame in which the
appendage is at rest, yes. Physics is more about what will be
*measured* and doesn>t get metaphysical about what "is".

Doug would pledge that his appendage is constant at 10cm

Thus we can compare the two appendages anytime, by using their 'at
rest' measurements. Though Dirk may be going at 0.995c to the left,
and Doug may be going 0.1c to the front, we can always say that their
fingers are equal based on the 'at rest' measurements.

Everybody agrees?

That>s fine. Keep in mind, though that relativistic length contraction
is about what gets measured for two objects in relative motion, from a
*single* reference frame, not in two different reference frames.

PD- Hide quoted text -

- Show quoted text -
[/quote]
Good. So Dirk and Doug keep exchanging text messages confirming that
their appendages are 10cm, and henceforth equal, and continue to be
equal.

In other words, when DirK and DouG were together, K1=G1=10cm.
When DirK and DouG are away and moving with some relative velocity v,
K2=G2=10cm.

________________________________________
*K1 measurement taken by Dirk of his finger in his rest frame, with
Doug
G1 measurement taken by Doug of his finger in his rest frame, with
Dirk
K2 measurement taken by Dirk of his finger in his rest frame, moving
wrt Doug
G2 measurement taken by Doug of his finger in his rest frame, moving
wrt Dirk

glird · Guest

On Oct 9, 7:03 pm, PD wrote:
[quote]
the way theories are tested is:[/quote]
1. Assume the premises of the theory are correct -- for the moment. >

The three premises of SR are
1. Poincare>s principle that the equations of Physics should hold good
in all systems.
2. That the speed of light in 'empty space" is a universal constant.
3. That clocks of any system must be set to measure that speed as a
constant, regardless of the speed of that system relative either to
"empty space" or as plotted by any other system.
Although these premises are allowable, they should be understood
before proceeding any further.

< 2. Follow the consequences of those premises until they produce a
set of quantitative and qualitative predictions about measurable
phenomena that would be observed under various sets of conditions. >

The trouble is that Einstein did NOT follow the consequences of
those premises until they produced a set of quantitative and
qualitative predictions - the Lorentz transformation equations - about
measurable phenomena that would be observed under various sets of
conditions.

< So far, relativity wins over any other competing theory that has
been put forward *so far*. >

Confirmation of the predictions of a set of equations that a given
theory never reached does not mean the given theory won anything.
Indeed, if the equations contradict the theory – as the LT do wrt STR
– their confirmation proves that the theory is false!

[quote]This is precisely how science works.
[/quote]
That may be how mathematical physicists – who wrote the junk now
drowning our economy – work; but it isn>t how science works. If it
IS, we should cancel any funding for their projects.

<If you don>t like it, then you>re not really interested in science,
and you might be well served to find a hobby you enjoy more. >

Good idea! How about Metaphysics, which studies the nature of the
things and mechanisms that Physics merely measures?

glird

PD · Guest

On Oct 10, 2:02 pm, strich.9...@gmail.com wrote:
[quote]On Oct 10, 2:53 pm, PD <TheDraperFam...@gmail.com> wrote:

On Oct 10, 1:39 pm, strich.9...@gmail.com wrote:

On Oct 10, 2:13 pm, PD <TheDraperFam...@gmail.com> wrote:

On Oct 10, 1:00 pm, strich.9...@gmail.com wrote:

On Oct 10, 1:40 pm, PD <TheDraperFam...@gmail.com> wrote:

On Oct 10, 12:25 pm, strich.9...@gmail.com wrote:

On Oct 10, 12:55 pm, PD <TheDraperFam...@gmail.com> wrote:

That is not what happens. In any given inertial reference frame, the
length has a constant value. At the *same* time in a different
inertial reference frame, the length has a different constant value.

Let us summarize:
For a single object: Dirk>s finger
1) Different frame, different length
2) One frame, one constant length

Dirk>s appendage will always measure 10cm in his own frame, no matter
how hard he cries.

Well, unless something happens to compress the finger or lop it off,
like with an axe. And by "his own frame", I assume you mean the
inertial reference frame in which he is at rest.

So it>s agreed. Dirk>s appendage is 10cm in his own frame.

Let us proceed...

Another person by the name of Doug was also unfortunately born into
the same situation. Doug measures his appendage at exactly 10cm.
Dirk and Doug decide to compare notes and place their appendages side
by side. They are exactly equal at 10cm.

Dirk then flies off to the Waffler Galaxy at constant velocity of
0.995c. He peers into his telescope and laughs, measuring Doug>s
appendage at 1cm. Dirk gets scared for a second and hastily checks
his own appendage and is happy to know it is still 10cm. Meanwhile,
Doug peers into his telescope and measures Dirk>s appendage at 1cm.
He double checks his own and measures 10cm.

Yes, exactly.

PD will say all 4 measurements are valid.

Yes.

But, would anybody deny
that Dirk>s and Doug>s appendages are still equal in length?

Some people would, some people wouldn>t...

Thus Dirk would swear his appendage is constant at 10cm

He would *measure* it to be 10cm in the reference frame in which the
appendage is at rest, yes. Physics is more about what will be
*measured* and doesn>t get metaphysical about what "is".

Doug would pledge that his appendage is constant at 10cm

Thus we can compare the two appendages anytime, by using their 'at
rest' measurements. Though Dirk may be going at 0.995c to the left,
and Doug may be going 0.1c to the front, we can always say that their
fingers are equal based on the 'at rest' measurements.

Everybody agrees?

That>s fine. Keep in mind, though that relativistic length contraction
is about what gets measured for two objects in relative motion, from a
*single* reference frame, not in two different reference frames.

PD- Hide quoted text -

- Show quoted text -

Good. So Dirk and Doug keep exchanging text messages confirming that
their appendages are 10cm, and henceforth equal, and continue to be
equal.

In other words, when DirK and DouG were together, K1=G1=10cm.
When DirK and DouG are away and moving with some relative velocity v,
K2=G2=10cm.

________________________________________
*K1 measurement taken by Dirk of his finger in his rest frame, with
Doug
G1 measurement taken by Doug of his finger in his rest frame, with
Dirk
K2 measurement taken by Dirk of his finger in his rest frame, moving
wrt Doug
G2 measurement taken by Doug of his finger in his rest frame, moving
wrt Dirk
[/quote]
You may want to add K3: measurement taken by Doug of Dirk>s finger,
moving wrt to Doug
G3: measurement taken by Dirk of Doug>s finger, moving wrt to Dirk.

Length contraction in relativity is a comparison of G2 with K3, or K2
with G3, knowing full well that K1 = G1.

PD

PD · Guest

On Oct 10, 2:20 pm, "Spaceman" <space...@yourclockmalfunctioned.duh>
wrote:
[quote]
Again PD proves he has MSS (Multiple Standards Syndrome)
Poor thing.
He refuses to stop worshipping his rubber ruler.
:)
[/quote]
I already talked about this. In case you missed it, I said:

Such is the risk of being careless with terms. In colloquial usage,
there is no distinction made, and that>s where you get into trouble.
Back in Galileo>s day, centuries ago, people were just used to
referring to "the speed" of an object, as though it were just obvious
there is one and only one speed of a given object at a given time.
Galileo made it clear that you had to be more careful and ask "speed
with respect to what?" Some folks -- like Spaceman -- still have
problems with that, as you can see. A hundred years ago, people were
just used to referring to "the length" of an object, as though it
were
obvious there is only one true length of an object. Einstein and
others made it clear that you had to be more careful and ask "in
which
frame of reference?". Some folks -- like Spaceman -- think that if it
worked fine to be sloppy and casual about those terms for thousands
of
years, that we shouldn>t let some fool physicist change that.

PD · Guest

On Oct 10, 2:22 pm, glird <gl...@aol.com> wrote:
[quote]On Oct 9, 7:03 pm, PD wrote:

<the way theories are tested is:
1. Assume the premises of the theory are correct -- for the moment.

The three premises of SR are
1. Poincare>s principle that the equations of Physics should hold good
in all systems.
2. That the speed of light in 'empty space" is a universal constant.
3. That clocks of any system must be set to measure that speed as a
constant, regardless of the speed of that system relative either to
"empty space" or as plotted by any other system.
[/quote]
The first two are ok. The third is a bit off.

[quote] Although these premises are allowable, they should be understood
before proceeding any further.

2. Follow the consequences of those premises until they produce a
set of quantitative and qualitative predictions about measurable
phenomena that would be observed under various sets of conditions.

The trouble is that Einstein did NOT follow the consequences of
those premises until they produced a set of quantitative and
qualitative predictions - the Lorentz transformation equations - about
measurable phenomena that would be observed under various sets of
conditions.
[/quote]
Sure he did. Have you not read his papers?

[quote]
So far, relativity wins over any other competing theory that has
been put forward *so far*.

Confirmation of the predictions of a set of equations that a given
theory never reached does not mean the given theory won anything.
Indeed, if the equations contradict the theory – as the LT do wrt STR
– their confirmation proves that the theory is false!
[/quote]
Would you like blue cheese or thousand island with that?

[quote]
This is precisely how science works.

That may be how mathematical physicists – who wrote the junk now
drowning our economy – work; but it isn>t how science works. If it
IS, we should cancel any funding for their projects.
[/quote]
I>m sorry you don>t care for the scientific method.

[quote]
If you don>t like it, then you>re not really interested in science,
and you might be well served to find a hobby you enjoy more.

Good idea! How about Metaphysics, which studies the nature of the
things and mechanisms that Physics merely measures?
[/quote]
Excellent. Then I take it that you will recognize that you>re in the
wrong place and will instead take your interests to alt.metaphysics,
which is obviously a better match for you, rather than your trying to
retitle this newsgroup to conform to your wishes.

PD


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