Why Does the Michelson-Morley Experiment Use T1-T2 Even After Rotation?

[KIRIT PUROHIT]

Pl. guide me for the doubts that i have in MME

In this experiment suppose L1 = L2 Then in this case will there be in any change in time difference T1-T2 calculated before and after rotation of the apparatus?

Another query is first we find T1-T2 now if first path is parallel to ether wind then T1>T2 & so T1-T2 is ok. But after rotating through 90 now T1 < T2 so why we do not write T2-T1?

 

[Andrew Mason]

Pl. guide me for the doubts that i have in MME

In this experiment suppose L1 = L2 Then in this case will there be in any change in time difference T1-T2 calculated before and after rotation of the apparatus?

The hypothesis was that there should be a difference due to the speed of light being dependent upon the speed of the source relative to the medium (the ether). L1 and L2 were perpendicular to each other so as the Earth changed its position relative to the ether, there should be a difference between times taken for light to travel the two paths. As it turned out, there was a null result. No time difference was observed.

Another query is first we find T1-T2 now if first path is parallel to ether wind then T1>T2 & so T1-T2 is ok. But after rotating through 90 now T1 < T2 so why we do not write T2-T1?

But you would not know which direction the ether wind is travelling, so you would not know how either path is oriented to the ether wind. All you are interested in is measuring the magnitude of the time difference.

AM