A. Michelson and E. Morley. On the Relative Motion of the Earth and the Luminiferous Ether. // American Journal of Science - Third series - Vol. XXXIV, No. 203. - Nov. 1887.

      <<<      340   >>>

  333  334  335  336  337  338  339  340 341  342  343  344  345 

means 0*02 wave-length. The rotation in the observations at noon was contrary to, and in the evening observations, with, that of the hands of a watch.

Noon Observations.

16.

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

13.

14.

15.

16*

July 8.......

44*7

44-0

43*5

39*7

35*2

S4-7

34-3

32*5

28-2

26*2

23*8

23*2

20-3

18-7

17*5

16*8

13T

July 9.......

57-t

57*3

58*2

59*2

58*7

60*2

60-8

62*0

61-5

633

65*8

67*3

69-7

70*7

j. 73*0

70*2

72-2

July 11.....

27-3

23*5

22-0

19*3

19-2

193

18-7

18-8

16-2

14*3

13-3

12*8

13*3

12*3

I 10-2

7-3

6*5

Mean!.......

43*1

41-6

41*2

39*4

37-7

38*1

37-9

37-8

353

34*6

at'3

34*4

34*4

33-9

33*6

31-4

30*8

Mean in w. 1.

862

*832

*824

*788

■754

*762

*758

'756

706

692

*686

*688

688

678

672

628

616

*706

692

*686

688

*688

678

672

*628

:616

Final mean.

784

762

1 '755

738

721

720

715

692

661

P. M. Observations.

July 8.......

61*2

63*3

63'3

68-2

67-7

69-3

70-3

69*8

69*0

713

71*3

70-5

71-2

71-2

70*5

72*5

75'7

July 9.......

26-0

26-0

28-2

29-2

31*5

32-0

313

31-7

33-0

&V8

36-5

37-3

38-8

41-0

42'7

43*7

44-0

July 12......

66*8

66*5

66-0

643

62-2

61-0

613

59-7

58-2

55"7

53-7

54*7

55*0

58-2

58-5

57-0

56*0

Mean.......

51-3

51*9

52*5

53-9

53-8

54*1

54-3

53-7

53*4

54-3

53*b

54-2! 55'0

56-8

572

57*7

58-6

Mean in w. 1.

1-026

r038il*050ir078

1*076

1-082

1-086

1-074

1-068

1-086

1*076

1-084

1*100

1*136

1-144

1-154

1*172

T068

1-086| 1*076! 1-084

1-100

1-136

1-144

1-154

1-172

Final mean.

1*047

1-06211-063! 1-081

1-088

1-109

1-115

1-114

1-120

The results of the observations are expressed graphically in fig. 6. The upper is the curve for the observations at noon, and the lower that for the evening observations. The dotted curves represent one-eighth of the theoretical displacements. It, seems fair to conclude from the figure that if there is any dis-

6.

placement due to the relative motion of the earth and the luminiferous ether, this cannot be much greater than 0*01 of the distance between the fringes.

Considering the motion of the earth in its orbit only, this

V

displacement should be 2D^ra=2DxlO_. The distance D was

about eleven meters, or 2xl07 wave-lengths of yellow light; hence the displacement to be expected was 0*4 fringe. The actual displacement was certainly less than the twentieth part of this, and probably less than the fortieth part. But since the displacement is proportional to the square of the velocity, the relative velocity of the earth and the ether is probably less than one sixth the earths orbital velocity, and certainly less than one-fourth.

In what precedes, only the orbital motion of the earth is considered. If this is combined with the motion of the solar system, concerning which but little is known with certainty, the result would have to be modified ; and it is just possible that the resultant velocity at the time of the observations was small though the chances are much against it. The experiment will therefore be repeated at intervals of three months, and thus all uncertainty will be avoided.

It appears, from all that precedes, reasonably certain that if there be any relative motion between the earth and the luminiferous ether, it must be small; quite small enough entirely to refute Fresnels explanation of aberration. Stokes has given a theory of aberration which assumes the ether at the earths surface to be at rest with regard to the latter, and only requires in addition that the relative velocity have a potential; but Lorentz shows that these conditions are incompatible. Lorentz then proposes a modification which combines some ideas of Stokes and Fresnel, and assumes the existence of a potential, together with Fresnels coefficient. If now it were legitimate to conclude from the present work that the ether is at rest with regard to the earths surface, according to Lorentz there could not be a velocity potential, and his own theory also fails.

Supplement.

It is obvious from what has gone before that it would be hopeless to attempt to solve the question of the motion of the solar system by observations of optical phenomena at the surface of the earth. But it is not impossible that at even moderate distances above the level of the sea, at the top of an isolated mountain peak, for instance, the relative motion might be perceptible in an apparatus like that used in these experiments. Perhaps if the experiment should ever be tried in these circumstances, the cover should be of glass, or should be removed.

It may be worth while to notice another method for multiplying the square of the aberration sufficiently to bring it within the range of observation, which has presented itself during the



Hosted by uCoz