Re: Are *observed* SR effects real?
- From: BURT <macromitch@xxxxxxxxx>
- Date: Sat, 5 Jul 2008 19:55:57 -0700 (PDT)
On Jul 5, 3:13 am, mluttg...@xxxxxxxxxx wrote:
Are *observed* SR effects real?
Luttgens:
Two persons, A and B, are both 1.60 m tall when their
height is mesured in the same room.
After some jogging, the distance between A and B is
x meters, and A will claim that B measure 0.80 m, whereas
B will observe that A measures 0.80 m. Of course, both
are right, but this doesn't change the intrinsic height of
A and B, i.e. 1.60 m.
Similarly, Kat considers that Dirk Vdm measured
only 2.5 years on his clock, aginst 5 years on her clock,
and Vdm claims that Kat travelled during 5 years, but
measured 5 * sqrt(1-0.866^2) =~ 2.5 years on her clock.
SRists don't realize that such observational differences
represent a mere perspective effect, but not an intrinsic
modification of clock rates. They claim that Kat's time has
been physically 'dilated' by a factor 2 because of her
motion wrt the Earth, even if other observers wrt
to which Kat would be moving at othir velocities would
find other 'dilation' factors.
They nevertheless believe that such 'time dilation' is
a permanent effect, which is of course stupid, as it is
simply an observational artefact.
Their belief that clock rates are physically and
*permanently* affected by motion is not different from
that of primitive people, who think that distances
physically affect the height of observed persons.
But those primitive people, unless they were very stupid,
don't believe that the perspective effect is permanent.
PD:
False dichotomy. Both of the alternatives you
present, which you assume to be the only ones
available, are incorrect.
SR does not say that there is something physical
that happens to the clock that alters the way
they work. Nor does SR say anything about
this being a permanent affect.
However, SR does not dismiss it as a perspective
effect or an illusion, either.
You have falsely presumed that if it is not one,
then it must be the other.
What is in fact the case is that physics is
about measurement and a theoretical structure
that allows you to predict what will be *measured*.
It does absolutely no good to have a theory
that tells you that what is going on is one thing,
but that that's not what you'll measure.
The interesting thing about SR is that it
emphasized (not revealed nor added, but
emphasized) that there are certain assumptions
that are built into the *definition* of
measurements. For example, simultaneity of two
events is intrinsic to the *meaning* of
measured length. So if simultaneity is
frame-dependent, then so is length, as length
is *defined*. It does absolutely no good, then,
to insist that length should be a frame-independent
quantity, as it is impossible to define length
as a *measurable* quantity that separates it
from simultaneity.
So then insisting that length be frame-independent
in some underlying reality is to either
a) say that the underlying reality is
unmeasurable, or
b) define length in a self-contradictory way,
making it a one-word oxymoron.
Luttgens:
You wrote: "SR does not say that there is
something physical that happens to the clock
that alters the way they work. Nor does SR
say anything about this being a permanent affect."
I agree, but some 'experts' claim that the
effect is permanent, cf. their interpretation
of the H&K experiment.
PD:
I'm not sure I understand what you think the
interpretation is. In the H&K experiment, when
the airborne clock landed, it was indeed behind
the ground-bound clock. However, when the
two clocks were then compared side-by-side,
they were "ticking" at the same rate.
So the "behindness" did not go away when the
clock landed, but the rate change did.
So is that "permanent" or not?
Luttgens:
Airborne clocks would have been *observed*
to tick slower than ground clocks in the H&K
experiment, but, as you rightly pointed out,
SR does not say that there is something
physical that happens to the clock that alters
the way they work. Nor does SR say anything
about this being a permanent effect.
Btw, the H&K experiment doesn't allow to
conclude that time 'dilation' physically
and permanently affects airborne clocks.
The authors themselves recognized:
1) that "real" cesium beam clocks generally
show systematic rate differences, which in
extreme cases may amount to time differences
as large as 1 microsecond per day
2) that the relative rates for cesium beam
clocks do not remain precisely constant.
3) the number of measured values is too small
for a good statistical analysis.
No Flat Atoms. No Flat Physics.
.
- References:
- Are *observed* SR effects real?
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- Are *observed* SR effects real?
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