Re: michelson morley experiment


<vern@xxxxxxxxxxxx> wrote in message
news:1145381562.771348.149250@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Harry wrote:
"darkknight" <darkknight.21@xxxxxxxxx> wrote in message
news:00a642502jeogh7fkdipbsfpaopcphusaa@xxxxxxxxxx
On Mon, 17 Apr 2006 11:07:55 +1200, darkknight
<darkknight.21@xxxxxxxxx> wrote:

On Sun, 16 Apr 2006 21:38:49 GMT, Tom Roberts
<tjroberts137@xxxxxxxxxxxxx> wrote:

Insofar as the non-inertial motions of the earth can be neglected
during
the flight time of the light, the image at the target will remain
motionless, 24 hours a day 365 days a year (assuming true stability
in
mounting and the optical path). Indeed, since the non-inertial
motions
of the earth are so steady, they will be accounted for during setup,
and
it's really the variation in them that matters (e.g. the beating
between
rotational and orbital motion).

That 370 km/s is roughly 0.001 times the speed of light, and the
angle
relative to the CMBR dipole=0 frame varies diurnally -- people would
notice if light danced around by that milliradian as the earth
turned:
surveying over just 10 meters would be off by a cm! This does not
happen.

[snip]

Well, upon further thought, I guess the explanation could be that the
motion of the source affects the angle of the "laser beam" so that it
has a "sideways" component the equivalent of the 1 cm movement of the
target. This would allow the laser beam to leave the laser "straight
down its centre line" regardless of the movement of the laser.

Almost correct: the speed of light remains constant, so that the
components
don't add up vectorially. But it's even more straightforward: the light
inside the laser follows a certain angle to start with (90 degrees in
the
rocket's rest frame, but not in the stationary frame), and the light
doesn't
change angle when it leaves the laser.

The posts above were not about the speed of light or about rockets.
The scenario was a laser experiment on the surface of the Earth in
which the laser is positioned perpendicular to the essentially linear
movement of the solar system through the galaxy at around 40 degrees
latitude and approximately 300 feet between source and target.

You may here above replace "rocket" by "Earth", that doesn't matter for SRT.
What matters is that one may choose (pretend to be) any approx. inertial
frame (solar, CMBR) as "stationary" frame. Note that for MMX the Earth's
surface isn't approximately an inertial frame, except for very short time
intervals.

A laser
pulse is sent every hour for 24 hours and the strikes marked on the
target. Since the target moves approximately four inches during the
transit time of the laser beam after the pulse is fired and before it
strikes the target, the plot of the strikes on the target over the 24
hour period should be an ellipse with the center representing where the
laser is actually aimed. The result of the experiment is that the
strikes are always in the same place instead producing the elliptical
pattern.

I've worked out such things in the past, and it always worked out perfectly.
Here you give insufficient detail, thus I don't know what you overlook - but
probably you overlooked the Lorentz contraction.

Harald


.

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