Without rigid bodies Relativity cannot exist

How can special relativity exist if there are no rigid bodies throughout the universe? We need breadth to have the Michelson Morley experiment. We can't do it if there is no breadth and no rigid bodies. The present concept of our Universe is that it consists of only point particles. Though assemblies of point particles make rigid bodies, those are not perfect rigid bodies. Because particles vibrate in rigid bodies depending on the temperature. 

The same can be said about straight lines. For ages, we assumed that light travel in straight lines. Wave theory of light, uncertainty principals and quantum physics has proven it is not so. According to General Relativity, light does not travel in strait lines. Even straight lines do not exist in reality. Nevertheless, Special Relativity is built on straight lines and rigid frames.