On the relative motion of the earth and the luminiferous æther

by Albert A. Michelson; Edward Williams Morley

. If now the whole apparatus be turned through

, the difference will be in the opposite direction, hence the displacement of the interference-fringes should be

. Considering only the velocity of the earth in its orbit, this would be

. If, as was the case in the first experiment,

waves of yellow light, the displacement to be expected would be