Here's why:
* S-waves are shear waves, meaning they cause particles in the medium to move perpendicular to the direction of wave propagation.
* Liquids and gases cannot support shear stress, as their molecules are not rigidly bound together.
* P-waves (primary waves), on the other hand, are compressional waves that can travel through all states of matter. They cause particles to move back and forth in the same direction as the wave travels.
