I don&#x27;t see how the exact structure could be important. No matter what it exactly looks like you would probably introduce a preferred reference frame, the frame in which the space quanta are at rest. Or looking at it the other way round, you would observe different lengths when you measure those space quanta from different reference frames no matter what the exact structure is but that contradicts the assumption that they are fundamental and have observer independent properties.<p>Relativity does not allow for fundamental lengths because you can mix space and time by going to a different reference frame. You could maybe say that you have quanta of spacetime with some proper length, quanta that look like separation in space to some observers and like separation in time to others, but no idea if that makes any sense and it probably has not less problems than quanta of space.<p>Quantum physics and special relativity fit nicely together, the standard model and its parts are relativistic quantum field theories. The problems arise when one tries to combine general relativity and quantum physics. When someone says quantum physics and relativity are incompatible he pretty surly means general relativity not special relativity.