Re: Are *observed* SR effects real?

On Jul 23, 5:06 pm, PD <TheDraperFam...@xxxxxxxxx> wrote:
On Jul 23, 8:48 am, mluttg...@xxxxxxxxxx wrote:





On Jul 23, 1:36 pm, PD <TheDraperFam...@xxxxxxxxx> wrote:

On Jul 23, 6:19 am, mluttg...@xxxxxxxxxx wrote:

You have been contradicting yourself!
You agreed that the domain of applicability of SR is limited
to 'inertial' frames.

Please pay attention to what I actually said. What I said is that
there are many frames that are not *absolutely* inertial, but in which
the non-inertial effects are much smaller than the effect being
measured and are therefore negligible (where "negligible" literally
means "can be neglected").

Iow, you agree with what I wote:

"Claiming that nothing changes physically when the Earth moves
wrt the plane is wrong, because the Earth is gravitationally
linked with the Sun (neglecting the Galaxy, and even the whole
Universe), and you should know that SR cannot be applied
in gravitational fields."

No, I don't agree with it. Please read what I wrote about the
equivalence principle, which is one of the underlying bases of GR.

I wrote: "you should know that SR cannot be applied
in gravitational fields", and suddenly, you jump
to GR! Does that imply that SR also applies (nothing
coming from SRists can surprise me, even bad faith)!

Let's settle this first before continuing.

Marcel Luttgens



The curvature of the train tracks can be neglected because the effect
of that curvature is small compared to the size of the disagreement
about simultaneity being considered.

Not when the train velocity is big, for instance 0.5 c.

Who said it was that big? You have no distance and time benchmarks in
the scenario I put forward that would allow you to derive or assume
this speed. Relativistic effects are present at quite ordinary speeds,
and are measurable if you have sufficient precision. The clocks in the
H&K experiment, for example, traveled at speeds much, much, much
smaller than even one percent of c.







Moreover, the *gedanken* is designed to be an idealized situation and
not a real experiment. Where the verification of these principles has
occurred in *real* experiments, the design of the experiment has
rendered those noninertial effects truly negligible. If you want to
deal with real experiments only, I'm happy to start referring to, and
discussing the details of, a real experiment, but the explanation of
length contraction and time dilation will be much longer and much more
complicated.

Now I agree with you, your plan is not physically realistic, but
corresponds to an idealized situation. It can be used as a
useful tool, even if the train velocity is too high to neglect
non-inertial effects.
What I didn't accept from SR specialist is their propensity
for neglecting the physical reality.

They don't neglect physical reality. Do not confuse a gedanken, which
is a *teaching* exercise, with an experiment. If you think that SR
gained acceptance on the basis of gedankens, then you have a very slim
grasp of the history of science surrounding relativity. Real
experimental tests of special relativity, which have little in common
with gedankens in physical circumstances (though the *principles* are
the same) are very much embedded in physical reality and all that
implies.

It might help if you dove a little deeper into what is actually known
about SR, including some full experimental details.

But barring that, you said we could continue. Let's recap where we
are:
1. Physical length is determined by a procedure that is dependent on
simultaneity.
2. If two observers disagree on which length-determining marks or
events are simultaneous, then they will naturally disagree on the
physical length of the object. Nothing physical happens to the object
in this process. On the other hand, it is not an optical illusion or
optical delay effect, either, because all optical delays are accounted
for.
3. Two observers do (in reality) disagree on which events are
simultaneous. This has been discovered in documented experiment,
though the train gedanken certainly is not proof of that.
4. However, each observer understands why the other observer sees non-
simultaneous events to be simultaneous, and simultaneous events to be
non-simultaneous. This is wholly consistent with the laws of physics
(in the gedanken, the laws happen to be the laws of electrodynamics,
sometimes written as Maxwell's equations), and those laws are the same
in both reference frames.
5. Because both accounts of which events are simultaneous and not
simultaneous are consistent with a common set of physical laws, there
is no way to determine which one is "right". And in fact, the
difference between the two observers' accounts is wholly due to the
relative velocity between them, and the relative velocity is the same,
regardless of which observer you choose.
6. We therefore conclude that simultaneity has no MEASURABLE
determination other than what is determined in each frame, and this
means that it is a frame-dependent conclusion. What is simultaneous in
Stan's frame is not simultaneous in Tom's frame, and what is
simultaneous in Tom's frame is not simultaneous in Stan's frame.
7. Because length is determined by simultaneous marks, the length
between those marks is also frame-dependent. This is why the length of
the train is 600 m in Stan's frame (marked by yellow and green
simultaneous flashes), and 800 m in Tom's frame (marked by yellow and
red simultaneous flashes). This also accounts for why Stan measures
the distance between the poles where the yellow and red non-
simultaneous flashes occurred to be 1067 m. (This is the answer to the
question you answered incorrectly earlier).

Do you have any questions about how length contraction arises? If not,
we can move on to time dilation. In preparation for this, let me ask
you a simple and suggestive question: In length measurement, we found
that it was important to mark the location of two events at *same
time*; in time measurement, can you guess what should be held the same
when measuring the duration between two events?

PD- Hide quoted text -

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