Physics

Sound propagates through the compression and rarefaction of air molecules—a longitudinal process where particles oscillate parallel to the wave's direction of travel. Transverse waves require a medium with rigidity or shear strength to resist sideways displacement; air molecules can't support that kind of perpendicular motion because they're free to move in all directions. The key insight is that a medium's ability to transmit a wave type depends on its physical properties: gases lack the structural resistance needed for transverse waves, so sound must travel as a longitudinal wave instead.

Sound propagates through the compression and rarefaction of air molecules—a longitudinal process where particles oscillate parallel to the wave's direction of travel. Transverse waves require a medium with rigidity or shear strength to resist sideways displacement; air molecules can't support that kind of perpendicular motion because they're free to move in all directions. The key insight is that a medium's ability to transmit a wave type depends on its physical properties: gases lack the structural resistance needed for transverse waves, so sound must travel as a longitudinal wave instead.