What fundamental physical constraint inherent to the cylinder format caused fidelity inequality across a recording?

Answer

Playback speed and groove pitch varied from the outer edge to the inner edge.

Because the sound groove circled the surface, the beginning of the recording (outer grooves) played back at a different speed and groove density than the end (inner grooves), resulting in unequal fidelity.

What fundamental physical constraint inherent to the cylinder format caused fidelity inequality across a recording?
inventiontechnologyaudiosound recordingCylinder