It proved the absence of Ether medium.

1. SEMINAR PRESENTATION

2. Michelson–Morley experiment
Figure 1. Michelson and Morley's interferometric setup,
mounted on a stone slab that floats in an annular trough
of mercury.

3. DATE AND TIME OF THE EXPERIMENT
The Michelson–Morley experiment was performed between April and July 1887 by Albert A.
Michelson and Edward W. Morley.
At what is now Case Western Reserve University in Cleveland, Ohio, and published in
November of the same year.

4. When we say that the speed of the light is 2.997925*108 m/sec, it is not clear that what
reference frame should be implied with respect to which we can measure the speed of the
Light.
It seemed inconceivable to 19th century physicists that the light and other
electromagnetic waves, in contrast to all other kinds of waves, could be propagated
without a medium.
That is why it seemed to be a logical step to postulate such a medium, called the
ETHER.

5. Physics theories of the late 19th century assumed that light must also require a medium, the
"luminiferous ether”, to transmit its wave motions.
 Because light can travel through a vacuum, it was assumed that even a vacuum must be filled with ether.
Because the speed of light is so great, and because material bodies pass through the ether without obvious
friction or drag.
Earth orbits around the Sun at a speed of around 30 km/s (18.64 mi/s), or 108,000 km/h (67,000 mph).
The Earth is in motion, so two main possibilities were considered.
(1) The ether is stationary and only partially dragged by Earth (proposed by Augustin-Jean Fresnel in
1818)
(2) the ether is completely dragged by Earth and thus shares its motion at Earth's surface (proposed by
Sir George Stokes, 1st Baronet in 1844.

6. Figure 2. A depiction of the concept of the "ether wind"

7. 1881 and 1887 experiments
Michelson experiment (1881)

8. Michelson's 1881 interferometer. Although ultimately it proved incapable of distinguishing between differing theories
of ether-dragging, its construction provided important lessons for the design of Michelson and Morley's 1887
instrument.
The device he designed, later known as a Michelson interferometer, sent yellow light from a sodium flame (for
alignment), or white light (for the actual observations) through a half-silvered mirror that was used to split it into two
beams traveling at right angles to one another.
After leaving the splitter, the beams traveled out to the ends of long arms where they were reflected back into the
middle by small mirrors.
 They then recombined on the far side of the splitter in an eyepiece, producing a pattern of constructive and
destructive interference whose transverse displacement would depend on the relative time it takes light to transit the
longitudinal vs. the transverse arms.
 Michelson expected that the Earth's motion would produce a fringe shift equal to 0.04 fringes.

9. Figure 5. This figure illustrates the folded light path used in the
Michelson–Morley interferometer that enabled a path length of 11 m.
 a is the light source, an oil lamp. b is a beam splitter. c is a compensating
plate, d, d' and e are mirrors. e' is a fine adjustment mirror. f is a telescope.

10. In 1885, Michelson began a collaboration with Edward Morley, spending considerable time
and money to confirm with higher accuracy Fizeau's 1851 experiment on Fresnel's drag
coefficient.
 In 1886, Michelson and Morley successfully confirmed Fresnel's drag coefficient – this
result was also considered as a confirmation of the stationary ether concept.

11. Figure 6. Fringe pattern produced with a Michelson interferometer using white
light. As configured here, the central fringe is white rather than black.
Michelson and Morley and other early experimentalists using interferometric techniques in
an attempt to measure the properties of the luminiferous ether.
They used (partially) monochromatic light only for initially setting up their equipment,
always switching to white light for the actual measurements. The reason is that measurements
were recorded visually.
Purely monochromatic light would result in a uniform fringe pattern.
THE ADVANTAGES OF WHITE LIGHT, WHICH PRODUCED A DISTINCTIVE COLORED FRINGE PATTERN,
FAR OUTWEIGHED THE DIFFICULTIES OF ALIGNING THE APPARATUS DUE TO ITS LOW COHERENCE
LENGTH.

13. Let us compute the phase difference between beams 1 and 2.This difference can arise from two causes, the different
path lengths traveled, l1 and l2, and the different speeds of travel with respect to the instrument because of the “ether
wind” v.
The time for beam 1 to travel from M to M1 and back is
t1 = (l1/c-v) + (l1/c+v) = l1(2c/c2-v2) =2l1/c (1/1-v2
/c2) ------------------------ (1)
The transit time is given by
∆t= t2-t1 = (2/c) [(l2/ (1-v2/c2)1/2)-(l1/ (1-v2/c2)]………………………………(2)
If the instrument is rotated through 900 then the time difference is ∆t1 will be
∆t1 = (2/c) [(l2/ (1-v2/c2))-(l1/ (1-v2/c2)1/2]
Now if ∆N represents the number of Fringes
∆N= (∆t1-∆t)/T= [(l1+l2)/ƛ] [v2/c2] -------------------------------------------- (3)
Where (l1+ l2) is optical path length of about 22 m.In their experiment the arms were of equal length, that is,
l1= l2=l, so that ∆N=(2l/ƛ)(v2/c2) ,where we choose=5.5×10-7m and v/c = 10-4m,then
∆N=0.4

14. EXPERIMENTAL OBSERVATION:-
The fringes were observed under a continuous rotation of the apparatus and a shift as small as 1/100 of a fringe definitely
could have been detected.
Observations were made day and night (as earth spins about its axis) and during all seasons of the year (as the earth
rotates about the sun), but the expected fringe shift was not observed.
Indeed, the experimental conclusion was that there was no fringe shift at all.
OBSERVE
R
YEAR PLACE L
METERS
FRINGE
SHIFT
PREDICTE
D BY
ETHER
THEORY
UPPER
LIMIT OF
OBSERVED
FRINGE
SHIFT
Michelson 1881 Potsdam 1.2 0.04 0.02
Michelson
and Morley
1887 Cleveland 11.0 0.40 0.01
Morley and
Miller
1902-1904 Cleveland 32.2 1.13 0.015
Miller 1921 Mt.Wilson 32.0 1.12 0.08
Miller 1923-1924 Cleveland 32.0 1.12 0.030
Miller(sunli
ght)
1924 Cleveland 32.0 1.12 0.014
Tomascheck
(starlight)
1924 Heidelber
g
8.6 0.3 0.02
Miller 1925-1926 Mt.Wilson 32.0 1.12 0.088
Kennedy 1926 Pasadena
and
2.0 0.07 0.002

15. OBSERVER YEAR PLACE L METER FRINGE
SHIFT
PREDICTE
D BY
ETHER
THEORY
UPPER
LIMIT OF
OBSERVED
FRINGE
SHIFT
ILLINGWO
RTH,PICCA
RD AND
STAHEL
1927 Mt.Rigi 2.8 0.13 0.006
MICHELSO
N et all
1929 Mt.Wilson 25.9 0.9 0.010
Joos 1930 Jena 21.0 0.75 0.002
CONCLUSION :- This null-result is well established.
There is No ether medium

16. BIBLIOGRAPHY :
 INTRODUCTION TO SPECIAL RELATIVITY : ROBERT RESNICK
WIKIPEDIA
MY RESPECTED PROFESSORS
THANKS…