Re: Evidence for Lorentz Contraction?
- From: Darwin123 <drosen0000@xxxxxxxxx>
- Date: Fri, 3 Apr 2009 10:19:02 -0700 (PDT)
On Apr 2, 10:52 pm, maxwell <s...@xxxxxxx> wrote:
On Apr 1, 7:14 pm, Darwin123 <drosen0...@xxxxxxxxx> wrote:ANY intermediate theory? If that is what you mean, there has never
On Apr 1, 6:49 pm, maxwell <s...@xxxxxxx> wrote:
On Mar 30, 3:33 pm, Darwin123 <drosen0...@xxxxxxxxx> wrote:
On Mar 29, 3:26 pm, maxwell <s...@xxxxxxx> wrote:
Can anyone provide a peer-reviewed reference to any experiment that
demonstrates the reality of the Lorentz contraction of a real physical
object & not just a CALCULATED length between two events?
If not, then SRT is only about redefining TIME and length contraction
is just a mere consequence of using light as the 'measuring stick'.
Relativity is used all the time in various experiments. These
experiments are seldom done to "prove" relativity. Relativity is used
as a means of finding something else. Experiments with "relativistic
electron diffraction" have always shown the validity of the Lorentz
contraction. Because if the wavelength of the electron waves didn't
obey the Lorentz contraction, there would be no agreement with theory
at all. Therefore, I submit the following two experiments in electron
diffraction as proof that the Lorentz contraction formula is accurate
(at least with respect to electron waves).
1) A. N. Aleinik, A. N. Baldin, et. al., “Experimental Observation
of Parametric X-Ray Radiation Directed Along the Propagation Velocity
of Relativistic Electrons in a Tungsten Crystal,” JETP LETTERS Vol. 80
No. 6, pp 393-397 (2004).
Abstract:
Parametric X-ray radiation (PXR) due to dynamic diffraction of
relativistic electrons is experimentally observed at small angles to
the propagation velocity of electrons in a tungsten crystal. The
specific features of the experimental method are described, and
forward PXR reflections from two crystallographic planes of tungsten
are reliably measured.
© 2004 MAIK “Nauka/Interperiodica2)
2) NURMAGAMBETOV S. B and VOROBIEV S. A., “Planar channelling and
diffraction of relativistic electrons in thin crystals,” Journal de
physique Vol. 47 No. 7 pp. 1227-1232 (1986).
Abstract
“The calculated results have been used to analyse the experimental
data obtained by measuring the angular distributions of 5.1 MeV
electrons incident along the (110) planes of Si crystal. On the one
hand, experimental and theoretical investigations indicate a
possibility of preferential population of the transverse motion
states, and, on the other hand, make it possible to separate the
channelling effects from those of electron diffraction.”
Experiments using electron diffraction implicitly rely on the
wavelength of the electrons being certain lengths relative to the
spacing of the crystallographic planes. The wavelength is effected by
Lorentz contraction just as any length is effected by length
contraction. At relativistic energies, the wavelength has to be
consistent with relativity. That is, given the velocity of the
electron particle the wavelength of the corresponding electron wave
has to be consistent with the Lorentz contraction.
If there is no length contraction as described in SR, then the
model for diffraction using relativistic principles can't work.
I do not consider an assumption based on an interpretation as a
demonstration of direct measurement.
It is DISAPPOINTING to see (once again) that when I ask for direct
evidence I get NO response.
It is not a real question. You haven't told us why these
measurments aren't direct. In fact, you haven't told us what a "direct
measurement" is. I hypothesize that you will dismiss any and all
experimental results that anyone finds as "indirect measurements".
The question that you asked is based on a tautology. Any
experiment where length contraction is involved is automatically in
your mind an "indirect experiment." You are dissappointed because you
want to be disappointed.
If I am incorrect, you will set forth a protocol or list of
conditions which define "direct measurement of length."
...
OK. Any technique that does not involve an intermediate theory >will constitute evidence.
been a direct experiment nor will there ever be a direct experiment
for a hypothesis. There is always some assumptions made in analyzing
data.
Consider as an example measuring the length of the stick with a
ruler. You are also assuming that the stick doesn't move between the
time you look at the marking at one end of the stick, and the marking
at the other end of the stick. If the stick is moving rapidly, you
will need some protocol to compensate for the time delay of your eyes.
You are assuming that the time delay due to the speed of light is
negligible. You are also assuming that the air between your eyes and
the ruler has the same optical properties as the air between your eyes
and the piece of rope. This is not always true, so you may need some
more measurements.
In the case, the assumption that the "stick is motionless" can't be
made. Restricting the experiment makes no sense, since relativity is a
theory that concerns relative motion. You also can't make the
assumption that the speed of light is negligible, since has been
measured. The differences between Newton and Einstein are significant
only when the distances are large enough so the delay is significant.
However, there is an even worse tautology embedded in your definition
of "direct experiment."
You would have made more sense if you had said, " Any technique
that doesn't use relativity theory." If relativity was intimately used
in filtering the experimental data, then the experiment would be
circular. However, even this stipulation is a little too tight. In
order to falsify relativity, one needs to compare the experimental
results with calculated results made using relativity, as applied to a
separate set of data. At some point you need to compare a calculated
prediction from the theory with experimental results. You can't
compare experimental with calculated results unless you do a
theoretical calculations at least once.
To test a theory, you have to basically compare the experimental
results of two separate experiments. One experiment is usually planned
after the theory in question has been proposed. The other experiment
is independent of the theory in question. This experiment is often
performed previous to the theory or hypothesis being test.
In the case of the diffraction experiments that I mentioned, there
are actually two sets of measurements. The distance between the
crystallographic planes have been measured in these crystals many
times with techniques that don't involve relativity. Xray diffraction,
low energy electron diffraction, and low energy neutron diffraction
are all perfectly suitable methods for finding the distances between
crystallographic planes. None of the measurements that I described use
relativity. In fact, density measurements combined with group theory
could probably be used to estimate these distances without any
diffraction at all. I didn't think to look up the experiments
analyzing the distances between planes. The distances between
crystallographic planes, in the frame where the crystal is stationary,
is well known.
However, these scientists were using relativistic electrons. The
electrons were traveling so fast relative to the crystal that their
inertial mass, in the frame of the crystal, was about five times their
rest mass. The wavelengths are very short. The reason that electrons
diffract in a certain way depends on the wavelength of the electrons
relative to the stationary crystallographic spacing. So to get
identifiable diffraction points they had to compare the know spacing
of the planes with the wavelength of the electrons, calculated by the
Lorentz contraction.
Yes, the investigators assumed that the laws of diffraction were
correct. The laws of diffraction are a "theory". However, they are no
more theoretical than the assumption that the air in your room doesn't
refract light. To me, a diffraction experiment with crystals is just
as "direct" as placing a ruler next to the wave. The crystal is
effectively a "ruler."
Diffraction experiments are as close as anyone is ever going to
get with "direct measurements" of the Lorentz contraction. Those "barn
door" thought experiments will never be done with real barn doors.
Basically, a diffraction experiment is a good analog to a barn door.
The barn is the space between crystallographic planes. Do you really
need the experiment done with real barns?
.
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