Hello exchemist. long time no see.

How are you going to gain or lose momentum when the distance travelled in both directions is the same and the movement of the aether is constant? Evidentaly the M-M experiment did show some movement of the aether just not what they expected. There experiment was predicting the earth's movement around the sun which is much slower then the suns movement around the galaxy and then even slower then the galaxy's movement through the universe!

If you have a water wave travelling in still water, at speed w, and reflecting off a wall a distance d away, the time taken for it to get out and back , T =

**2d/w. **
If there is a current of speed c towards the wall, the speed of a wave travelling with the current will be w+c and that when it is going against the current will be w-c.

If it travels the same distance d, hits the reflecting wall and comes back, the time it takes to get to the wall is d/(w+c). The time for the return journey is d/(w-c). So the total time T for out and back is now d/(w+c) + d/(w-c) =

**2dw/(w² - c²).** You can see that when c=0, i.e. still water, this becomes 2d/w, as it should. BUT, as c increases, the denominator gets smaller, so

** T gets larger**. Indeed when c=w, the denominator vanishes and the time becomes infinite. This makes sense when you think about it because the time taken to get back increases faster than the outward time and when c=w the wave can't get back at all

The above is the principle Michelson and Morley would have used.

Asking about momentum is a distraction. A wave does not have a mean momentum. It is a travelling disturbance, not a material object. What is the mass of a wave, after all? It does not make sense.