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. . .
Michelson's 1913 experiment
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to decide whether a moving mirror acts as an elastic wall
or a new moving source
or does not influence the speed of light
by Thomas-t
. . . . . . . . . . . . . . . .
Oct 1998
.
. . .
The following arrangement was devised for the purpose of deciding the question experimentally.
. . .
Light from source S falls on a semi-mirror A.
The reflected pencil goes to a revolving mirror D, thence to the concave mirror E
to the mirror C revolving about the same axis,
whence it proceeds to the plain mirror B and it reflected back to A.
. . .
The transmitted pencil pursues the same path in the opposite direction (CED)
and at mirror A meets the first pencil, producing interference fringes
which are observed by means of telescope T.
. . .
After hitting the surface of moving mirror the speed of photon might be:
. . . . . . . . . . . . .
V= c + p * v
where c is the speed of light,,
v is the speed of moving mirror and parameter p= 0, 1, 2
parameter p= 2 : the case of "elastic wall"
parameter p= 1 : the case of "new moving source"
parameter p= 0 : the case of "does not influence"
The experiment was tried under the following conditions:
. . .
The revolving mirrors were mounted on the shaft of an electric motor. The speed could be varied from zero to 1800 revolutions per minute, but results of experiments were reduced to 1000 r.p.m. Wave-length (lambda) was 600 nm.
The formulas to calculate displacements: (*)
List of experiments
| . .
No. of experiment . . |
. . .
Displacements . . . |
. . .
Weight . . . |
| 1. . . . . . . . . |
3.8 |
1 |
| 2. . . . . . . . . |
3.1 |
1 |
| 3. . . . . . . . . |
3.2 |
1 |
| 4. . . . . . . . . |
4.3 |
2 |
| 5. . . . . . . . . |
3.8 |
2 |
| 6. . . . . . . . . |
3.93 |
3 |
| 7. . . . . . . . . |
3.83 |
4 |
. . . . . . .
Weighed result of experiments : 3.81
. . . . . . .
Calculated displacement ( p=0 ) : 3.76
. .
It appears that within the limit of experiment (say 2 per cent) the velocity
of moving mirror is without influence on the velocity of light
reflected from its surface.
Remarks:
- Source: Journal Optical Society of America
-
The original title of Michelson's 1913 paper :
EFFECT OF REFLECTION FROM A MOVING MIRROR
ON THE VELOCITY OF LIGHT
BY A. A. MICHELSON
RYERSON PHYSICAL LABORATORY
UNIVERSITY OF CHICAGO
-
I managed the original text a little bit shorter and dropped some less
important details and cross-references.
But on the whole I tried to use Michelson's original sentences.
I also changed names of some
parameters as they seemed disturbing. The new ones are: s, ds, c, p, n.
For case p=0 I used the phrase does not influence, what means
that moving mirror does not influence the speed of light.
. . .
In the original papper Michelson used this notion: undulatory theory of light.
In my opinion usage of this phrase is not correct here. It suggests
that his experiment can decide whether light consists of waves or consists of photons - but this task
is beyond its power. Furthermore usage of this phrase nowadays needs a plentiful explanation.
In those days the aether theory (light ought to have a carrier medium) was well known.
Michelson very likely thought that the undulatory theory of light
and the theory of aether together are a trivial interpretation.
Special Relativity also has interpretation. Its II. postullate says that speed of light is
always c in every inertia frame. If we choose mirror E (or the instrument or the table, e.t.c. )
as a reference frame then this theory also gives the right result. (But we are allowed to choose
a moving mirror C or D as reference frame too, and then we will have three
different speeds of light in the same instrument at the same time. It is a problem if the light is
a real physical entity.)
(*) And here is the math how to get formulas:
----- o O o ----- .
. . .
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Physics,
Relativity,
Cosmology
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Question,
remark,
opinion
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. .
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. .
. . .
. . . and one step
forward, I hope !
Thomas-t
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