The Ghost In The Machine wrote:
In sci.physics.relativity, EjP

wrote
on Wed, 01 Sep 2004 14:12:53 -0500
:

The Ghost In The Machine wrote:

In sci.physics.relativity, EjP

wrote
on Tue, 31 Aug 2004 15:35:23 -0500
:


Androcles wrote:



"The Ghost In The Machine" wrote in
message ...
| In sci.physics.relativity, EjP
|
| wrote
| on Mon, 30 Aug 2004 17:09:56 -0500
| :
| The Ghost In The Machine wrote:
| This is probably a dumb question, but I'm curious, and
| this looks extremely simple to perform, at least for a
| well-equipped lab. Also, Androcles has stipulated that
| he has seen evidence, using a computer simulation and
| stellar observations, that c' = c+v, and I'd like at
| least have someone verify that SR would preclude that,
| using the experiment below. :-)
|
|
| Androcles is a retard, who is at least a century
| out of touch with experimental data.

Once again you get no answer. :-)

|
| I'm also probably out of touch with the data; mostly
| because my field is commercial computer software.
|
|
| A disc with teeth spins on a shaft, as vibrationless
| as possible. The teeth are reflective. A light beam
| is angled tangent to the spinning disc, and it, together
| with a companion beam reflected off a stationary mirror,
| are reflected into an interferometer.
|
|
| The idea is good in principle, but why do this when you
| can Compton scatter photons off of charged particle
| beams, which are moving at a large fraction of the speed of
| light? This is done all the time.
|
| -E
|
| Is it? That sounds even more interesting. :-) I do have a
| picture of a particle beam -- it's in one of my physics
| books.
|
| The idea certainly sounds extremely straightforward,

Really? I wonder how you'd locate a photon as it crosses the start line,
then again locate the same photon as it crosses the finish line.


Gawd, it's lucky most people are smarter than you! Otherwise, we'd
still be trying to work out the best shape for the wheel.


The Wheel Coloring Committee is still working on that; we'll
probably have to await the burning down of the deciduous
forests before funding can be assured, though... :-)

I think their last prototype had 8 sides, though.



Heisenberg's Uncertainty Principle might have something to say about
that.

It does. To get a short laser pulse, you need a large bandwidth. This
is well-known to - well - people who actually know something. I'd tell
you to read up on mode-locked lasers, but I know it would be a
waste of time.


I've no practical experience, but from a theoretical
standpoint, the fewer cycles one squeezes into a packet,
the higher the frequency of the modulating signal --
a square wave (in, say, an AM-style system), and the
"wider" the sidebands go in the frequency graph.


Right. In this case (and many others) there's no real
difference between the Heisenberg Uncertainty Principle
and plain old Fourier theory.


EjP is a retard who hasn't even begun to think through the problems.
Androcles.



Electron bunches are typically measured in picoseconds. Picosecond
lasers are pretty common now as well. Since the math is beyond you,
I'll tell you that in 1 picosecond, light travels 300 microns.
There's no need to track individual photons when you can localize
the entire bunch so well.


Say one has a 15m "racetrack". At the one end is the
picosecond laser and a timing control/recorder device.
At the other end is a particle beam moving at a significant
fraction of the speed of light -- say 2/3c to make the
math easy.

If c'=c+v, the expected transit time for that racetrack
would be 50 ns to the particle beam, 30 ns back (assuming
the beam is shooting into the track).

If c'=c, admittedly, one will have to deal with a frequency shift.
But the time would be 50 ns there, 50 ns back.

Since many modern computers have a clockspeed of less
than 0.5 ns (more than 2 GHz) this shouldn't be too hard
to measure, though it might depend on how often the laser
fires (the "duty cycle").


Measuring transit times to .5ns is quite easy for anyone
with even the most basic lab equipment. After that it
gets a bit harder, but someone with some perseverence
can get down to better than 100 ps.



Darned obvious test -- a lot easier and more obvious than a
few stellar observations (though the stellar observations
have their purpose). Of course one could also use a CW
laser and a "chopper", presumably, in a pinch, if one can
slice the beam fine enough. (I'll admit to wondering if
modern laser diodes have enough control to generate 5-10
ns pulses. That would be more than enough to show the
effect in this case, if there's enough power in the laser
to get photons back in the measurement/timing device.)


But really this is beside the point. The fact is without
special relativity, NOTHING about Compton Scattering
makes any sence: the spectrum, the distribution, the
kinematic cutoff. It would be like trying to explain
an automobile engine if Androcles were claiming gasoline
doesn't burn.


True (AFAIK, anyway).

However, this does not meet Androcles' requirement,
technically; he wants the light *source* to travel
at a near-lightspeed velocity.

First of all, don't waste a lot of brain cells on
what Androcles wants. He'll figure out some reason
to reject any experimental proof you give him.
Worry only about satisfying your own curiosity.
To that end, you might want to start by
aquainting yourself with the body of
experimental evidence supporting SR:
http://math.ucr.edu/home/baez/physic...periments.html

Secondly, high energy particles radiatively
decaying *are* a high velocity light source.
You can find a number of first generation
experiments listed he
http://math.ucr.edu/home/baez/physic...source%20tests
(N.B. the moving mirror test is also there).
In particular, the positronium decay measurement
should be *exactly* what he's asking for - IF
he were sane.

Of course, since then, the fact has become
implicit in the operation of high energy
physics experiments, just like the laws
of thermodynamics are implicit in automobile
manufacture, and Maxwell's Equations are
implicit in the design of an FM radio.
Ford and Sony don't waste a lot of energy
convincing the Androcleses of the world
that the science is sound.

I realize a lot of this stuff is kind of
"out there" to most people, but to those of
us who use this physics every day, these
discussions are like someone living in a
remote jungle abstractly debating the
feasibility of electric lighting. It would
be kind of entertaining, but it would only
hold your interest so long.

-E





However, there's
a simple way around that, too, and it's probably
been done: the beam merely need hit the air. The
particles going at near lightspeed should collide
with the air molecules (which are moving at a few
hundred or so m/s in their own right), causing
many mildly interesting effects.

I'm not sure it will be 2/3 c, but it should introduce
enough "jitter", assuming c'=c+v (which it doesn't
anyway, so the effect will manifest as a frequency
shift instead of a speed diff), or perhaps "spread"
is a better term, to show up in a spectroscope. One
can of course move the spectroscope around the beam,
in this case.

(OK, Andro, if you're still with us :-) . What's wrong
with *this* experiment?)


I'm not sure what hazards there would be in shooting a
charged particle beam into atmosphere; presumably the
effects can be minimalized by encasing the beam in
an apparatus not unlike a large vacuum-tube or CRT,
transparent to the laser light.

I'd be surprised if this hasn't already been done.


Laser beams are bounced off of charged particle beams
all the time. It all part of that "spooky hi-tech
world" that people like Androcles are unaware of.


I'm not all that aware of the details myself. :-) (Not
my field.) However, it's a very obvious test, even if
it does use reflected rather than emitted light -- and
really, what is a mirror anyway but a method by which
one can absorb and reemit a photon? Of course, there
are some interesting issues regarding mirrors as well,
apparently -- but I for one have no clue as to why
the actual emitter has to be moving trans-relativistically,
as opposed to having the beam reflect off something
moving trans-relativistically, not unlike a baseball
bat being used to bunt or hit one out of the park,
depending on how the ballplayer moves the bat as the ball
traveling nearby impinges thereon.


-E


-E



and
| one could probably even get a neutron beam with a little
| work, and scatter light off that -- whether that would
| be useful or not or show different results from a
| charged particle beam, I can't say.
|
| *picks up a copy of "How to Miss The Obvious", by I. M. Blind* :-)
|
| --
| #191,
| It's still legal to go .sigless.