Hi All, MMX has been discussed a lot but I could not find solution to my problem. So, I had to start a new thread on this subject! Sorry it is lengthy, you can just read the last paragraph (below red text) for short form. I was going through details of the calculations and have problem at one step on the vertical calculation. Before going in to that step, I will detail the general approach of my understanding so far. I am trying to use same symbolism as in Special Relativity (with primes), please bear with me. For any diagram, I am using what is in Wikipedia: http://en.wikipedia.org/wiki/Michelson–Morley_experiment#Light_path_analysis_and_consequences Situation A when there is 100% aether drag: t'/t = 1 for both horizontal and vertical. Method 1: velocity relative to local aether is zero. Method 2: If distant static aether is used as reference, speed of light will be affected by same extent and compensate the L changes which will result in t'/t = 1.So, anyway we will expect a null result if there were full aether drag. So far I have no problem. Situation B when there is 0% aether drag: Horizontal L'/L = t'/t = gamma^2 (not yet including length contraction) (still no problem). Vertical: Only here I have problem understanding how it can be L'/L = t'/t = gamma. We know that the mirrors will have the increased distance of L' = L*gamma (always). But, my thinking is that the light will not be following the mirrors. It will just stay with static aether and move straight up/down (in earlier Situation A it went to the mirror only because it was dragged there by the aether). So, the light path will not be same as the hardware distances. This will give only L'/L = t'/t = 1 (or same calculation arrived by Michelson first as Tt = 2L/c). In such case, the beam will hit the top mirror vt distance behind and hit the inclined mirror at 2vt distance behind (compared to static earth expected positions). Basically the confusion is how the light can follow same path whether aether drag is there or not? It will be great if where I am mistaking is pointed out. Thanks all and sorry for the lengthy description.