From the book - Introduction to special relativity, Robert Resnick, I learnt that it was assumed at that time that speed of light is c in ether frame. And so, there was a need to find out ether frame. I am assuming that ether frame is an inertial frame . Speed of light in vacuum could have been measured from different inertial frames and it could have been known that Galilean transformation doesn't work in this case. This itself will lead to the search of another transformation. Now, even if we get the ether frame , what we will know is speed of light in ether frame as well as in all other inertial frames is c, which is not a new information. So, was the ether frame being searched for the purpose of getting an absolute frame? Or, was ether being searched for the purpose of getting a medium in which speed of light is c?