Re: michelson morley experiment

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

vern@xxxxxxxxxxxx wrote:
I believe this is an important issue and one that I have been
considering in relation to the laser experiments done by H. Webster
Kehr. Tom, would you agree that if you have a stationary laser on the
surface of the Earth pointing at a stationary target on the surface of
the Earth, that irrespective of the motion of the Earth at
approximately 370 kilometers per second linearly towards the
constellation Leo, as evidenced by the CMBR, the laser beam would still
be pointed directly at the target in order to hit it and the laser beam
does not leave the laser at an angle?

In the frame of the earth surface at the location of the laser, the
light leaves the laser straight down its centerline.

Then why do telescopes have to be "tilted" to account for stellar
aberration? i.e. the line of the telescope has to be at a very slight
angle to the line of the light.



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.


I don't understand.

If the light path of the laser is at right angles to the 400 km per
second motion of the earth, then over a distance of 1 km, the laser
takes 1/300000 seconds to reach the target, during which time the
target has moved by (1/300000) * 400 km - which is .001333 km -
equals 130 cm. (or 1cm over 10 metres as you say).

If the light path of the laser is parallel to the direction of motion
(which it could be after 8 hours) then the target hasn't moved so a
difference of 1 cm would be seen on the "strike point" at the target.

I'm sure you're right coz I know next to nothing about physics but why
doesn't the "strike point" move?

Darkknight.
.

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